ACCT 370-EXCEL3

Comcast-10K.xlsx

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Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Jun. 30, 2020
Document And Entity Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	001-32871
Entity Registrant Name	COMCAST CORPORATION
Entity Tax Identification Number	27-0000798
Entity Incorporation, State or Country Code	PA
Entity Address, Address Line One	One Comcast Center
Entity Address, City or Town	Philadelphia
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	19103-2838
City Area Code	215
Local Phone Number	286-1700
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float		$ 176,648
Documents Incorporated by Reference	Comcast Corporation – Part III – The registrant’s definitive Proxy Statement for its annual meeting of shareholders.
Document Fiscal Period Focus	FY
Amendment Flag	false
Document Fiscal Year Focus	2020
Entity Central Index Key	0001166691
Class A Common Stock [Member]
Document And Entity Information [Line Items]
Title of 12(b) Security	Class A Common Stock, $0.01 par value
Trading Symbol	CMCSA
Security Exchange Name	NASDAQ
Entity Common Stock, Shares Outstanding	4,571,211,797
0.250% Notes due 2027 [Member]
Document And Entity Information [Line Items]
Title of 12(b) Security	0.250% Notes due 2027
Trading Symbol	CMCS27
Security Exchange Name	NASDAQ
1.500% Notes due 2029 [Member]
Document And Entity Information [Line Items]
Title of 12(b) Security	1.500% Notes due 2029
Trading Symbol	CMCS29
Security Exchange Name	NASDAQ
0.750% Notes due 2032 [Member]
Document And Entity Information [Line Items]
Title of 12(b) Security	0.750% Notes due 2032
Trading Symbol	CMCS32
Security Exchange Name	NASDAQ
1.875% Notes due 2036 [Member]
Document And Entity Information [Line Items]
Title of 12(b) Security	1.875% Notes due 2036
Trading Symbol	CMCS36
Security Exchange Name	NASDAQ
1.250% Notes due 2040 [Member]
Document And Entity Information [Line Items]
Title of 12(b) Security	1.250% Notes due 2040
Trading Symbol	CMCS40
Security Exchange Name	NASDAQ
9.455% Guaranteed Notes due 2022 [Member]
Document And Entity Information [Line Items]
Title of 12(b) Security	9.455% Guaranteed Notes due 2022
Trading Symbol	CMCSA/22
Security Exchange Name	NYSE
5.50% Notes due 2029[Member]
Document And Entity Information [Line Items]
Title of 12(b) Security	5.50% Notes due 2029
Trading Symbol	CCGBP29
Security Exchange Name	NYSE
2.0% Exchangeable Subordinated Debentures due 2029 [Member]
Document And Entity Information [Line Items]
Title of 12(b) Security	2.0% Exchangeable Subordinated Debentures due 2029
Trading Symbol	CCZ
Security Exchange Name	NYSE
Class B Common Stock [Member]
Document And Entity Information [Line Items]
Entity Common Stock, Shares Outstanding	9,444,375

Consolidated Statement of Incom

Consolidated Statement of Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
Revenue	$ 103,564	$ 108,942	$ 94,507
Costs and Expenses:
Programming and production	33,121	34,440	29,692
Other operating and administrative	33,109	32,807	28,094
Advertising, marketing and promotion	6,741	7,617	7,036
Depreciation	8,320	8,663	8,281
Amortization	4,780	4,290	2,736
Other operating gains	0	0	(341)
Total costs and expenses	86,071	87,817	75,498
Operating income (loss)	17,493	21,125	19,009
Interest expense	(4,588)	(4,567)	(3,542)
Investment and other income (loss), net	1,160	438	(225)
Income before income taxes	14,065	16,996	15,242
Income tax (expense) benefit	(3,364)	(3,673)	(3,380)
Net income	10,701	13,323	11,862
Less: Net income attributable to noncontrolling interests and redeemable subsidiary preferred stock	167	266	131
Net income attributable to Comcast Corporation	$ 10,534	$ 13,057	$ 11,731
Basic earnings per common share attributable to Comcast Corporation shareholders (in dollars per share)	$ 2.30	$ 2.87	$ 2.56
Diluted earnings per common share attributable to Comcast Corporation shareholders (in dollars per share)	$ 2.28	$ 2.83	$ 2.53

Consolidated Statement of Compr

Consolidated Statement of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 10,701	$ 13,323	$ 11,862
Currency translation adjustments, net of deferred taxes of $(331), $(66) and $9	1,213	1,375	(916)
Cash flow hedges:
Deferred gains (losses), net of deferred taxes of $26, $(4) and $(3)	(101)	19	50
Realized (gains) losses reclassified to net income, net of deferred taxes of $31, $(10) and $(4)	(147)	65	(6)
Employee benefit obligations and other, net of deferred taxes of $20, $16 and $(3)	(68)	(57)	8
Comprehensive income	11,598	14,725	10,998
Less: Net income attributable to noncontrolling interests and redeemable subsidiary preferred stock	167	266	131
Less: Other comprehensive income (loss) attributable to noncontrolling interests	60	(13)	(41)
Comprehensive income attributable to Comcast Corporation	$ 11,371	$ 14,472	$ 10,908

Consolidated Statement of Com_2

Consolidated Statement of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Currency translation adjustments, deferred taxes	$ (331)	$ (66)	$ 9
Deferred gains (losses) on cash flow hedges, deferred taxes	26	(4)	(3)
Realized (gains) losses on cash flow hedges, deferred taxes	31	(10)	(4)
Employee benefit obligations and other, deferred taxes	$ 20	$ 16	$ (3)

Consolidated Statement of Cash

Consolidated Statement of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating Activities
Net income	$ 10,701	$ 13,323	$ 11,862
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and other operating gains	13,100	12,953	10,676
Share-based compensation	1,193	1,021	826
Noncash interest expense (income), net	697	417	364
Net (gain) loss on investment activity and other	(970)	(20)	576
Deferred income taxes	(550)	563	290
Changes in operating assets and liabilities, net of effects of acquisitions and divestitures:
Current and noncurrent receivables, net	(20)	(57)	(802)
Film and television costs, net	(244)	(929)	(395)
Accounts payable and accrued expenses related to trade creditors	(266)	(347)	(394)
Other operating assets and liabilities	1,096	(1,227)	1,294
Net cash provided by operating activities	24,737	25,697	24,297
Investing Activities
Capital expenditures	(9,179)	(9,953)	(9,774)
Cash paid for intangible assets	(2,455)	(2,475)	(1,935)
Construction of Universal Beijing Resort	(1,498)	(1,116)	(460)
Purchase of spectrum	(459)	0	0
Acquisitions, net of cash acquired	(233)	(370)	(38,219)
Proceeds from sales of businesses and investments	2,339	886	141
Purchases of investments	(812)	(1,899)	(1,257)
Other	250	86	650
Net cash provided by (used in) investing activities	(12,047)	(14,841)	(50,854)
Financing Activities
Proceeds from (repayments of) short-term borrowings, net	0	(1,288)	379
Proceeds from borrowings	18,644	5,479	44,781
Proceeds from collateralized obligation	0	5,175	0
Repurchases and repayments of debt	(18,777)	(14,354)	(8,798)
Repurchases of common stock under repurchase program and employee plans	(534)	(504)	(5,320)
Dividends paid	(4,140)	(3,735)	(3,352)
Other	(1,706)	46	(550)
Net cash provided by (used in) financing activities	(6,513)	(9,181)	27,140
Impact of foreign currency on cash, cash equivalents and restricted cash	2	5	(245)
Increase (decrease) in cash, cash equivalents and restricted cash	6,179	1,680	338
Cash, cash equivalents and restricted cash, beginning of year	5,589	3,909	3,571
Cash, cash equivalents and restricted cash, end of year	$ 11,768	$ 5,589	$ 3,909

Consolidated Balance Sheet

Consolidated Balance Sheet - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Current Assets:
Cash and cash equivalents	$ 11,740	$ 5,500
Receivables, net	11,466	11,292
Programming rights	0
Programming rights		3,877
Other current assets	3,535	4,723
Total current assets	26,741	25,392
Film and television costs	13,340
Film and television costs		8,933
Investments	7,820	6,989
Investment securing collateralized obligation	447	694
Property and equipment, net	51,995	48,322
Goodwill	70,669	68,725
Franchise rights	59,365	59,365
Other intangible assets, net	35,389	36,128
Other noncurrent assets, net	8,103	8,866
Total assets	273,869	263,414
Current Liabilities:
Accounts payable and accrued expenses related to trade creditors	11,364	10,826
Accrued participations and residuals	1,706	1,730
Deferred revenue	2,963	2,768
Accrued expenses and other current liabilities	9,617	10,516
Current portion of long-term debt	3,146	4,452
Total current liabilities	28,796	30,292
Long-term debt, less current portion	100,614	97,765
Collateralized obligation	5,168	5,166
Deferred income taxes	28,051	28,180
Other noncurrent liabilities	18,222	16,765
Commitments and contingencies
Redeemable noncontrolling interests and redeemable subsidiary preferred stock	1,280	1,372
Equity:
Preferred stock	0	0
Additional paid-in capital	39,464	38,447
Retained earnings	56,438	50,695
Treasury stock	(7,517)	(7,517)
Accumulated other comprehensive income (loss)	1,884	1,047
Total Comcast Corporation shareholders’ equity	90,323	82,726
Noncontrolling interests	1,415	1,148
Total equity	91,738	83,874
Total liabilities and equity	273,869	263,414
Class A Common Stock [Member]
Equity:
Common stock	54	54
Class B Common Stock [Member]
Equity:
Common stock	$ 0	$ 0

Consolidated Balance Sheet (Par

Consolidated Balance Sheet (Parenthetical) - $ / shares	Dec. 31, 2020	Dec. 31, 2019
Preferred stock, shares authorized (in shares)	20,000,000	20,000,000
Preferred stock, shares issued (in shares)	0	0
Treasury stock (in shares)	872,791,028	872,791,028
Class A Common Stock [Member]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	7,500,000,000	7,500,000,000
Common stock, shares issued (in shares)	5,444,002,825	5,416,381,298
Common stock, shares outstanding (in shares)	4,571,211,797	4,543,590,270
Class B Common Stock [Member]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	75,000,000	75,000,000
Common stock, shares issued (in shares)	9,444,375	9,444,375
Common stock, shares outstanding (in shares)	9,444,375	9,444,375

Consolidated Statement of Chang

Consolidated Statement of Changes in Equity - USD ($) $ in Millions	Total	Redeemable Noncontrolling Interests And Redeemable Subsidiary Preferred Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Retained Earnings [Member]Cumulative Effect, Period of Adoption, Adjustment [Member]	Treasury Stock at Cost [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Other Comprehensive Income (Loss) [Member]Cumulative Effect, Period of Adoption, Adjustment [Member]	Noncontrolling Interests [Member]	Class A Common Stock [Member]Common Stock [Member]	Class B Common Stock [Member]Common Stock [Member]
Beginning balance at Dec. 31, 2017		$ 1,357
Increase (Decrease) in Temporary Equity [Roll Forward]
Contributions from (distributions to) noncontrolling interests, net		(56)
Other		(43)
Net income (loss)		58
Ending balance at Dec. 31, 2018		1,316
Beginning balance at Dec. 31, 2017			$ 37,497	$ 38,202	$ (43)		$ 379	$ 76	$ 843	$ 55	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock compensation plans			607
Repurchases of common stock under repurchase program and employee plans			(920)	(4,408)						(1)
Employee stock purchase plans			214
Dividends declared				(3,499)
Other comprehensive income (loss)							(823)		(41)
Contributions from (distributions to) noncontrolling interests, net									294
Other			63	0					(280)
Net income (loss)	$ 11,731			11,731
Net income (loss)									73
Ending balance at Dec. 31, 2018	$ 72,502		37,461	41,983	0	$ (7,517)	(368)	0	889	54	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends declared per common share (in dollars per share)	$ 0.76
Contributions from (distributions to) noncontrolling interests, net		(62)
Other		(38)
Net income (loss)		156
Ending balance at Dec. 31, 2019	$ 1,372	1,372
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock compensation plans			783
Repurchases of common stock under repurchase program and employee plans			(34)	(485)						0
Employee stock purchase plans			222
Dividends declared				(3,860)
Other comprehensive income (loss)							1,415		(13)
Contributions from (distributions to) noncontrolling interests, net									176
Other			15	0					(14)
Net income (loss)	13,057			13,057
Net income (loss)									110
Ending balance at Dec. 31, 2019	$ 83,874		38,447	50,695	$ (124)	(7,517)	1,047	$ 0	1,148	54	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends declared per common share (in dollars per share)	$ 0.84
Contributions from (distributions to) noncontrolling interests, net		(51)
Other		(190)
Net income (loss)		149
Ending balance at Dec. 31, 2020	$ 1,280	$ 1,280
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock compensation plans			920
Repurchases of common stock under repurchase program and employee plans			(143)	(407)						0
Employee stock purchase plans			255
Dividends declared				(4,250)
Other comprehensive income (loss)							837		60
Contributions from (distributions to) noncontrolling interests, net									192
Other			(15)	(10)					(3)
Net income (loss)	10,534			10,534
Net income (loss)									18
Ending balance at Dec. 31, 2020	$ 91,738		$ 39,464	$ 56,438		$ (7,517)	$ 1,884		$ 1,415	$ 54	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends declared per common share (in dollars per share)	$ 0.92

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Note 1: Summary of Significant Accounting Policies Basis of Presentation The accompanying consolidated financial statements include all entities in which we have a controlling voting interest and variable interest entities (“VIEs”) required to be consolidated including Universal Beijing Resort (see Note 7). We translate assets and liabilities of our foreign operations where the functional currency is the local currency into U.S. dollars at the exchange rate as of the balance sheet date and translate revenue and expenses using average monthly exchange rates. The related translation adjustments are recorded as a component of accumulated other comprehensive income (loss) in our consolidated balance sheet. Any foreign currency transaction gains or losses are included in our consolidated statement of income in investment and other income (loss), net. For disclosures containing future amounts where the functional currency is the local currency, we translate the amounts into U.S. dollars at the exchange rates as of the balance sheet date. Accounting Policies Our consolidated financial statements are prepared in accordance with GAAP, which require us to select accounting policies, including in certain cases industry-specific policies, and make estimates that affect the reported amount of assets, liabilities, revenue and expenses, and the related disclosure of contingent assets and contingent liabilities. Actual results could differ from these estimates. The following accounting policies are specific to the industries in which we operate: • capitalization and amortization of film and television costs (see Note 4) • costs for connecting customers to our cable systems (see Note 10) Information on other accounting policies and methods that we use in the preparation of our consolidated financial statements are included, where applicable, in their respective footnotes that follow. The collateralized obligation related to our investment in Hulu is discussed in Note 9 and our other long-term debt is discussed in Note 6. Below is a discussion of accounting policies and methods used in our consolidated financial statements that are not presented within other footnotes. Advertising Expenses Advertising costs are expensed as incurred. Derivative Financial Instruments We use derivative financial instruments to manage our exposure to the risks associated with fluctuations in interest rates, foreign exchange rates and equity prices. Our objective is to manage the financial and operational exposure arising from these risks by offsetting gains and losses on the underlying exposures with gains and losses on the derivatives used to economically hedge them. Our derivative financial instruments are recorded in our consolidated balance sheet at fair value. We designate certain derivative instruments as cash flow hedges of forecasted foreign currency denominated transactions, including cash flows associated with non-functional currency debt and non-functional currency revenue and expenses. Changes in the fair value of derivative instruments accounted for as cash flow hedges are recorded as a component of accumulated other comprehensive income (loss) until the hedged items affect earnings. For derivatives not designated as cash flow hedges, changes in fair value are recognized in earnings. Refer to Note 6 for further information on derivative instruments related to debt. The impact of our remaining derivative financial instruments was not material to our consolidated financial statements in any of the periods presented. Fair Value Measurements The accounting guidance related to fair value measurements establishes a hierarchy based on the types of inputs used for the various valuation techniques. The levels of the hierarchy are described below. • Level 1: Values are determined using quoted market prices for identical financial instruments in an active market. • Level 2: Values are determined using quoted prices for similar instruments in active markets; quoted prices for identical or similar instruments in markets that are not active; and model-derived valuations in which all significant inputs and significant value drivers are observable in active markets. • Level 3: Values are determined using models that use significant inputs that are primarily unobservable, discounted cash flow methodologies or similar techniques, as well as instruments for which the determination of fair value requires significant management judgment or estimation.

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2020
Segment Reporting [Abstract]
Segment Information	Note 2: Segment Information We are a global media and technology company with three primary businesses: Comcast Cable, NBCUniversal and Sky. We present our operations for (1) Comcast Cable in one reportable business segment, referred to as Cable Communications; (2) NBCUniversal in four reportable business segments: Cable Networks, Broadcast Television, Filmed Entertainment and Theme Parks; and (3) Sky in one reportable business segment. See Note 3 for a description of the various products and services within each reportable segment. Our other business interests consist primarily of the operations of Comcast Spectacor, which owns the Philadelphia Flyers and the Wells Fargo Center arena in Philadelphia, Pennsylvania, and other business initiatives, such as Peacock, our new direct-to-consumer streaming service that features NBCUniversal content. Our financial data by reportable segment is presented in the tables below. We do not present a measure of total assets for our reportable business segments as this information is not used by management to allocate resources and capital. (in millions) Revenue Adjusted EBITDA (b) Depreciation and Amortization Capital Cash Paid for 2020 Cable Communications $ 60,051 $ 25,270 $ 7,753 $ 6,605 $ 1,333 NBCUniversal Cable Networks 10,849 4,616 771 34 24 Broadcast Television 10,244 1,934 163 82 15 Filmed Entertainment 5,276 785 95 13 17 Theme Parks 1,846 (541) 771 1,171 56 Headquarters and Other 121 (521) 478 185 139 Eliminations (a) (254) (4) — — — NBCUniversal 28,082 6,269 2,278 1,485 251 Sky 18,594 1,954 3,034 959 741 Corporate and Other 366 (2,447) 35 130 130 Eliminations (a) (3,529) (220) — — — Comcast Consolidated $ 103,564 $ 30,826 $ 13,100 $ 9,179 $ 2,455 (in millions) Revenue Adjusted EBITDA (b) Depreciation and Capital Cash Paid for 2019 Cable Communications $ 58,082 $ 23,266 $ 7,994 $ 6,909 $ 1,426 NBCUniversal Cable Networks 11,513 4,444 735 41 17 Broadcast Television 10,261 1,730 157 161 15 Filmed Entertainment 6,493 833 79 21 22 Theme Parks 5,933 2,455 696 1,605 60 Headquarters and Other 83 (689) 462 244 171 Eliminations (a) (316) (1) — — — NBCUniversal 33,967 8,772 2,129 2,072 285 Sky 19,219 3,099 2,699 768 707 Corporate and Other 333 (880) 131 204 57 Eliminations (a) (2,659) 1 — — — Comcast Consolidated $ 108,942 $ 34,258 $ 12,953 $ 9,953 $ 2,475 (in millions) Revenue Adjusted EBITDA (b) Depreciation and Capital Cash Paid for 2018 Cable Communications $ 56,033 $ 21,681 $ 8,262 $ 7,723 $ 1,346 NBCUniversal Cable Networks 11,773 4,428 738 42 23 Broadcast Television 11,439 1,657 146 204 81 Filmed Entertainment 7,152 734 145 35 25 Theme Parks 5,683 2,455 660 1,143 173 Headquarters and Other 63 (680) 419 306 146 Eliminations (a) (349) 4 — — — NBCUniversal 35,761 8,598 2,108 1,730 448 Sky 4,587 692 539 222 137 Corporate and Other 513 (779) 108 99 4 Eliminations (a) (2,387) (27) — — — Comcast Consolidated $ 94,507 $ 30,165 $ 11,017 $ 9,774 $ 1,935 (a) Included in Eliminations are transactions that our segments enter into with one another. Our segments generally report transactions with one another as if they were stand-alone businesses in accordance with GAAP, and these transactions are eliminated in consolidation. When multiple segments enter into transactions to provide products and services to third parties, revenue is generally allocated to our segments based on relative value. The most significant transactions between our segments include distribution revenue at Cable Networks for the sale of programming to Cable Communications; content licensing revenue in our NBCUniversal segments (Broadcast Television, Filmed Entertainment and Cable Networks) for the license of owned content to Peacock and Sky, and for licenses of owned content to other NBCUniversal segments; advertising revenue at Cable Communications, Cable Networks and Broadcast Television; and distribution revenue at Broadcast Television for fees received under retransmission consent agreements from Cable Communications. For segment reporting purposes, we account for intercompany content licenses as follows: • Revenue for licenses of content from NBCUniversal segments to Peacock and Sky are generally recognized at a point in time, consistent with the recognition of transactions with third parties, when the content is delivered and made available for use. The costs of these licenses at Peacock and Sky are recognized as the content is used over the license period. The difference in timing of recognition between segments results in an Adjusted EBITDA impact in eliminations as the profits on these transactions are deferred in our consolidated results and recognized as the content is used over the license period. • Revenue for licenses of content between NBCUniversal segments is recognized over time to correspond with the amortization of the costs of the licensed content as the content is used over the license period. (b) We use Adjusted EBITDA as the measure of profit or loss for our operating segments. From time to time we may report the impact of certain events, gains, losses or other charges related to our operating segments (such as certain costs incurred in response to COVID-19, including severance charges), within Corporate and Other. Our reconciliation of the aggregate amount of Adjusted EBITDA for our reportable segments to consolidated income before income taxes is presented in the table below. Year ended December 31 (in millions) 2020 2019 2018 Adjusted EBITDA $ 30,826 $ 34,258 $ 30,165 Adjustment for legal settlement (177) — (125) Adjustment for Sky transaction-related costs (56) (180) (355) Depreciation (8,320) (8,663) (8,281) Amortization (4,780) (4,290) (2,736) Other operating gains — — 341 Interest expense (4,588) (4,567) (3,542) Investment and other income (loss), net 1,160 438 (225) Income before income taxes $ 14,065 $ 16,996 $ 15,242

Revenue

Revenue	12 Months Ended
	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Revenue	Note 3: Revenue Year ended December 31 (in millions) 2020 2019 2018 Residential: High-speed internet $ 20,599 $ 18,752 $ 17,144 Video 21,937 22,270 22,455 Voice 3,532 3,879 3,960 Wireless 1,574 1,167 890 Business services 8,191 7,795 7,129 Advertising 2,594 2,465 2,795 Other 1,624 1,754 1,660 Total Cable Communications 60,051 58,082 56,033 Distribution 6,437 6,790 6,826 Advertising 3,155 3,478 3,587 Content licensing and other 1,257 1,245 1,360 Total Cable Networks 10,849 11,513 11,773 Advertising 5,027 5,712 7,010 Content licensing 2,640 2,157 2,182 Distribution and other 2,577 2,392 2,247 Total Broadcast Television 10,244 10,261 11,439 Theatrical 421 1,469 2,111 Content licensing 3,342 3,045 2,899 Home entertainment 944 957 1,048 Other 569 1,022 1,094 Total Filmed Entertainment 5,276 6,493 7,152 Total Theme Parks 1,846 5,933 5,683 Headquarters and Other 121 83 63 Eliminations (a) (254) (316) (349) Total NBCUniversal 28,082 33,967 35,761 Direct-to-consumer 15,223 15,538 3,632 Content 1,373 1,432 304 Advertising 1,998 2,249 651 Total Sky 18,594 19,219 4,587 Corporate and Other 366 333 513 Eliminations (a) (3,529) (2,659) (2,387) Total revenue $ 103,564 $ 108,942 $ 94,507 (a) Included in Eliminations are transactions that our segments enter into with one another. See Note 2 for a description of these transactions. We operate primarily in the United States but also in select international markets. The table below summarizes revenue by geographic location. Year ended December 31 (in millions) 2020 2019 2018 United States $ 80,327 $ 82,952 $ 82,233 Europe 20,460 21,553 7,721 Other 2,777 4,437 4,553 Total revenue $ 103,564 $ 108,942 $ 94,507 Cable Communications Segment Revenue is generated from the sale of our high-speed internet, video, voice, wireless and other services to residential customers in the United States under the Xfinity brand, which we market individually and as bundled services at a discounted rate. We also provide these and other services to business customers and sell advertising. Residential We recognize revenue as the services are provided on a monthly basis. Subscription rates and related charges vary according to the services and features customers receive. Revenue from customers that purchase bundled services at a discounted rate is allocated between the separate services based on the respective stand-alone selling prices. The stand-alone selling prices are determined based on the current prices at which we separately sell the services. Significant judgment is used to determine performance obligations that should be accounted for separately and the allocation of revenue when services are combined in a bundle. Customers are typically billed in advance and pay on a monthly basis. Installation fees are deferred and recognized as revenue over the period of benefit to the customer, which is less than a year. While a portion of our customers are subject to contracts for their services, which are typically 1 to 2 years in length, based on our evaluation of the terms of these contracts, we recognize revenue for these services on a basis that is consistent with our customers that are not subject to contracts. Our services generally involve customer premise equipment, such as set-top boxes, cable modems and wireless gateways. The timing and pattern of recognition for customer premise equipment revenue are consistent with those of our services. We recognize revenue from the sale of wireless handsets at the point of sale. Sales commissions are expensed as incurred, as the related period of benefit is less than a year. We also have arrangements to sell certain DTC streaming services to our customers. We have concluded we are generally the sales agent in these arrangements and we record net commission revenue as earned, which is generally as customers are billed on a monthly basis, within high-speed internet revenues. Under the terms of cable franchise agreements, we are generally required to pay the cable franchising authority an amount based on gross video revenue. We generally pass these and other similar fees through to our customers and classify these fees in the respective Cable Communications services revenue, with the corresponding costs included in other operating and administrative expenses. Business Services Revenue is generated from subscribers to a variety of our products and services which are offered to businesses. Our service offerings for small business locations primarily include high-speed internet services, as well as voice and video services, that are similar to those provided to residential customers, and include certain other features specific to businesses. We also offer Ethernet network services that connect multiple locations and other services to meet the needs of medium-sized customers and larger enterprises, and we provide cellular backhaul services to mobile network operators. We recognize revenue as the services are provided on a monthly basis. Substantially all of our customers are initially under contracts, with terms typically ranging from 2 years for small and medium-sized businesses to up to 5 years for larger enterprises. At any given time, the amount of future revenue to be earned related to fixed pricing under existing agreements is equal to approximately half of our annual business services revenue, of which the substantial majority will be recognized within 2 years. Customers with contracts may only discontinue service in accordance with the terms of their contracts. We receive payments based on a billing schedule established in our contracts, which is typically on a monthly basis. Installation revenue and sales commissions are generally deferred and recognized over the respective contract terms. Advertising Revenue is generated from the sale of advertising and technology, tools and solutions relating to advertising businesses. As part of distribution agreements with cable networks, we generally receive an allocation of scheduled advertising time that we sell to local, regional and national advertisers. In most cases, the available advertising units are sold by our sales force. We also represent the advertising sales efforts of other multichannel video providers in some markets. Since we are acting as the principal in these arrangements, we record the advertising that is sold in advertising revenue and the fees paid to multichannel video providers in other operating and administrative expenses. In some cases, we work with representation firms as an extension of our sales force to sell a portion of the advertising units allocated to us and record the revenue net of agency commissions. In addition, we generate revenue from the sale of advertising on digital platforms. We enter into advertising arrangements with customers and have determined that a contract exists once all terms and conditions are agreed upon, typically when the number of advertising units is specifically identified and the timing of airing is scheduled. Advertisements are generally aired or viewed within one year once all terms and conditions are agreed upon. Revenue from these arrangements is recognized in the period in which advertisements are aired or viewed. Payment terms vary by contract, although terms generally require payment within 30 to 60 days from when advertisements are aired or viewed. In addition, we also provide technology, tools, data-driven services and marketplace solutions to customers in the media industry, which allows advertisers to more effectively engage with their target audiences. Revenue earned in this manner is recognized when services are provided. NBCUniversal Segments Distribution Cable Networks generates revenue from the distribution of our national, regional and international cable network programming to traditional and virtual multichannel video providers. Broadcast Television generates revenue from the fees received under retransmission consent agreements for our NBC and Telemundo owned local broadcast television stations and associated fees received from NBC-affiliated local broadcast television stations. These arrangements are accounted for as licenses of functional intellectual property and revenue is recognized as programming is provided on a monthly basis, generally under multiyear agreements. Monthly fees received under distribution agreements with multichannel video providers are generally based on the number of subscribers. Payment terms and conditions vary by contract type, although terms generally include payment within 60 days. Advertising Cable Networks and Broadcast Television generate revenue from the sale of advertising on our cable and broadcast networks, our owned local broadcast television stations and various digital properties. We enter into advertising arrangements with customers and have determined that a contract exists once all terms and conditions are agreed upon, typically when the number of advertising units is specifically identified and the timing of airing is scheduled. Advertisements are generally aired or viewed within one year once all terms are agreed upon. Revenue is recognized, net of agency commissions, in the period in which advertisements are aired or viewed and payment occurs thereafter, with payment generally required within 30 days. In some instances, we guarantee audience ratings for the advertisements. To the extent there is a shortfall in contracts where the ratings were guaranteed, a portion of the revenue is deferred until the shortfall is settled, typically by providing additional advertising units generally within one year of the original airing. Theatrical Filmed Entertainment generates revenue from the worldwide theatrical release of produced and acquired films for exhibition in movie theaters. Our arrangements with exhibitors generally entitle us to a percentage of ticket sales. We recognize revenue as the films are viewed and exhibited in theaters and payment generally occurs within 30 days after exhibition. Content Licensing Cable Networks’, Broadcast Television’s and Filmed Entertainment’s production studios generate revenue from the licensing of our owned film and television content in the United States and internationally to cable, broadcast and premium networks and to DTC streaming service providers. Our agreements generally include fixed pricing and span multiple years. For example, following a film’s theatrical release, Filmed Entertainment may license the exhibition rights of a film to different customers over multiple successive distribution windows. We recognize revenue when the content is delivered and available for use by the licensee. When the term of an existing agreement is renewed or extended, we recognize revenue at the later of when the content is available or when the renewal or extension period begins. Payment terms and conditions vary by contract type, although payments are generally collected over the license term. The amount of future revenue to be earned related to fixed pricing under existing agreements at any given time equals approximately 1 to 2 years of annual Filmed Entertainment content licensing revenue, which is the segment with the largest portion of this future revenue. The majority of this revenue will be recognized within 2 years. This amount may fluctuate from period to period depending on the timing of the releases and the availability of content under existing agreements and may not represent the total revenue expected to be recognized as it does not include revenue from future agreements or from variable pricing or optional purchases under existing agreements. For our agreements that include variable pricing, such as pricing based on the number of subscribers to a DTC streaming service sold by our customers, we generally recognize revenue as our customers sell to their subscribers. Home Entertainment Filmed Entertainment generates revenue from the sale of our produced and acquired films on DVDs and through digital distribution services. Cable Networks and Broadcast Television also generate revenue from the sale of owned programming on DVDs and through digital distribution services, which is reported in other revenue. We generally recognize revenue from DVD sales, net of estimated returns and customer incentives, on the date that DVDs are delivered to and made available for sale by retailers. Payment terms generally include payment within 60 to 90 days from delivery to the retailer. Theme Parks Theme Parks generates revenue primarily from guest spending at our Universal theme parks in Orlando, Florida; Hollywood, California; and Osaka, Japan. Guest spending includes ticket sales and in-park spending on food, beverages and merchandise. We recognize revenue from ticket sales when the tickets are used, generally within a year from the date of purchase. For annual passes, we generally recognize revenue on a straight-line basis over the period the pass is available to be used. We recognize revenue from in-park spending at the point of sale. Sky Segment Direct-to-Consumer Revenue is generated from subscribers to our video services from both residential and business customers, primarily in the United Kingdom, Italy and Germany. We also provide high-speed internet, voice and wireless phone services in select countries. Generally, all of our residential customers are initially under contracts, with terms typically ranging from rolling monthly to 18 months, depending on the product and territory, and may only discontinue service in accordance with the terms of their contracts. Subscription rates and related charges vary according to the services and features customers receive and the types of equipment they use. Our video, high-speed internet, voice and wireless phone services generally may be purchased individually or in bundles. We recognize revenue from video, high-speed internet, voice and wireless phone services as the services are provided on a monthly basis. At any given time, the amount of future revenue to be earned related to existing agreements is equal to less than half of our annual direct-to-consumer revenue, which generally will be recognized within 18 months. Content Revenue is generated from the distribution of our television channels on third-party platforms and the licensing of owned and acquired programming to third-party video providers. See the NBCUniversal segment discussion of distribution and content licensing revenue above for accounting policies for these types of arrangements. Advertising Revenue is generated from advertising and sponsorships across our owned television channels and where we represent the sales efforts of third-party channels. We also generate revenue from the sale of advertising on digital platforms and various technology, tools and solutions relating to our advertising business. Revenue is recognized when the advertising is aired or viewed. Since we are acting as the principal in the arrangements where we represent the sales efforts of third parties, we record the advertising that is sold in advertising revenue and the fees paid to the third-party channels in other operating and administrative expenses. Consolidated Balance Sheet The following table summarizes our accounts receivable: December 31 (in millions) 2020 2019 Receivables, gross $ 12,273 $ 11,711 Less: Allowance for doubtful accounts 807 419 Receivables, net $ 11,466 $ 11,292 The following table presents changes in our allowance for doubtful accounts: (in millions) Beginning Balance Additions Charged to Costs and Expenses and Other Accounts Deductions from Reserves Ending Balance 2020 $ 419 $ 912 $ 524 $ 807 2019 $ 352 $ 769 $ 702 $ 419 2018 $ 288 $ 616 $ 552 $ 352 The following table summarizes our other balances that are not separately presented in our consolidated balance sheet that relate to the recognition of revenue and collection of the related cash, as well as the deferred costs associated with our contracts with customers: December 31 (in millions) 2020 2019 Noncurrent receivables, net (included in other noncurrent assets, net) $ 1,091 $ 1,337 Contract acquisition and fulfillment costs (included in other noncurrent assets, net) $ 1,060 $ 1,083 Noncurrent deferred revenue (included in other noncurrent liabilities) $ 750 $ 618

Programming and Production Cost

Programming and Production Costs	12 Months Ended
	Dec. 31, 2020
Other Industries [Abstract]
Programming and Production Costs	Note 4: Programming and Production Costs Year ended December 31 (in millions) 2020 Video distribution programming $ 12,684 Film and television content: Owned (a) 7,973 Licensed, including sports rights 11,264 Other 1,200 Total programming and production costs $ 33,121 (a) Amount includes amortization of owned content of $6.6 billion as well as participations and residuals expense. Video Distribution Programming Expenses We incur programming expenses related to the license of rights to distribute the third-party programmed channels, platforms and related content included in video services we sell to end consumers. Programming is generally acquired under multiyear distribution agreements, with fees typically based on the number of customers that receive the programming and the extent of distribution. Programming arrangements are accounted for as executory contracts with expenses generally recognized based on the rates in the agreements and the arrangements are not subject to impairment. Film and Television Content We incur costs related to the production of owned content and the license of the rights to use content owned by third parties and sports rights on our owned networks and platforms, which are described as owned and licensed content, respectively. We adopted new accounting guidance related to film and television content in the first quarter of 2020 (see Note 8), and accordingly, amounts presented below for 2020 and the policy discussion reflect the updated accounting guidance, and amounts presented for 2019 reflect the accounting guidance in effect at that time. Under the new accounting guidance, we have determined that the predominant monetization strategy for the substantial majority of our content is on an individual basis. Capitalized Film and Television Costs 2020 2019 December 31 (in millions) Film and Television Costs Film Costs Television Costs Total Owned: Released, less amortization $ 3,815 $ 1,551 $ 2,810 $ 4,361 Completed, not released 139 187 — 187 In production and in development 2,755 1,314 1,162 2,476 6,709 3,052 3,972 7,024 Licensed, including sports advances 6,631 5,786 13,340 12,810 Less: Current portion of licensed programming rights — 3,877 Film and television costs $ 13,340 $ 8,933 The table below summarizes estimated future amortization expense for the capitalized film and television costs recorded in our consolidated balance sheet as of December 31, 2020. (in millions) Owned Licensed Completed, not released: 2021 $ 69 Released and licensed content: 2021 $ 1,445 $ 4,722 2022 $ 543 $ 820 2023 $ 336 $ 470 We have future minimum commitments for sports rights and licensed content that are not recognized in our consolidated balance sheet as of December 31, 2020 totaling $38.5 billion and $4.5 billion, respectively. Capitalization and Recognition of Film and Television Content We capitalize costs for owned film and television content, including direct costs, production overhead, print costs, development costs and interest, as well as acquired libraries. Amortization for owned content predominantly monetized on an individual basis and accrued costs associated with participations and residual payments are recorded using the individual film forecast computation method, which recognizes the costs in the same ratio as the associated ultimate revenue. Estimates of ultimate revenue and total costs are based on anticipated release patterns and distribution strategies, public acceptance and historical results for similar productions. Amortization for content predominantly monetized with other owned or licensed content is recorded based on estimated usage. In determining the method of amortization and estimated life of an acquired film or television library, we generally use the method and the life that most closely follow the undiscounted cash flows over the estimated life of the asset. We do not capitalize costs related to the distribution of a film in movie theaters or the licensing or sale of a film or television production, which primarily include costs associated with marketing and distribution. We may enter into cofinancing arrangements with third parties to jointly finance or distribute certain of our film productions. Cofinancing arrangements can take various forms, but in most cases involve the grant of an economic interest in a film to an investor who owns an undivided copyright interest in the film. The number of investors and the terms of these arrangements can vary, although investors generally assume the full risks and rewards for the portion of the film acquired in these arrangements. We account for the proceeds received from the investor under these arrangements as a reduction of our capitalized film costs and the investor’s interest in the profit or loss of the film is recorded as either a charge or a benefit, respectively, in programming and production costs. The investor’s interest in the profit or loss of a film is recorded each period using the individual film forecast computation method. We capitalize the costs of licensed content when the license period begins, the content is made available for use and the costs of the licenses are known. Licensed content is amortized as the associated programs are broadcast. Owned and licensed content are presented as noncurrent assets in film and television costs. We present amortization of owned and licensed content and accrued costs associated with participation and residual payments in programming and production costs. When an event or a change in circumstance occurs that was known or knowable as of the balance sheet date and that indicates the fair value of either owned or licensed content is less than the unamortized costs in the balance sheet, we determine the fair value and record an impairment charge to the extent the unamortized costs exceed the fair value. Owned content is assessed either individually or in identified film groups, for content predominantly monetized on an individual basis or with other content, respectively. The substantial majority of our owned content is evaluated for impairment on an individual title basis. Licensed content that is not part of a film group is generally assessed in packages, channels or dayparts. A daypart is an aggregation of programs broadcast during a particular time of day or programs of a similar type. Licensed content is tested for impairment primarily on a channel, network or platform basis, with the exception of our broadcast networks and owned local broadcast television stations, which are tested on a daypart basis. Estimated fair values of owned and licensed content are generally based on Level 3 inputs including analysis of market participant estimates of future cash flows. We record charges related to impairments or content that is substantively abandoned to programming and production costs. Impairments of capitalized film and television costs were not material in any of the periods presented.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	Note 5: Income Taxes Income Before Income Taxes Year ended December 31 (in millions) 2020 2019 2018 Domestic $ 16,211 $ 16,646 $ 14,387 Foreign (2,146) 350 855 $ 14,065 $ 16,996 $ 15,242 Components of Income Tax (Expense) Benefit Year ended December 31 (in millions) 2020 2019 2018 Current (Expense) Benefit: Federal $ (2,824) $ (2,085) $ (2,026) State (836) (425) (639) Foreign (254) (600) (425) (3,914) (3,110) (3,090) Deferred (Expense) Benefit: Federal 111 (902) (546) State 71 15 167 Foreign 368 324 89 550 (563) (290) Income tax (expense) benefit $ (3,364) $ (3,673) $ (3,380) Our income tax (expense) benefit differs from the federal statutory amount because of the effect of the items detailed in the table below. Year ended December 31 (in millions) 2020 2019 2018 Federal tax at statutory rate $ (2,954) $ (3,569) $ (3,201) State income taxes, net of federal benefit (265) (306) (212) Foreign income taxed at different rates (24) (126) (147) Adjustments to uncertain and effectively settled tax positions, net (344) (3) (144) Federal research and development credits 164 124 22 Excess tax benefits recognized on share-based compensation 150 196 75 Other (91) 11 227 Income tax (expense) benefit $ (3,364) $ (3,673) $ (3,380) We base our provision for income taxes on our current period income, changes in our deferred income tax assets and liabilities, income tax rates, changes in estimates of our uncertain tax positions, tax planning opportunities available in the jurisdictions in which we operate and excess tax benefits or deficiencies that arise when the tax consequences of share-based compensation differ from amounts previously recognized in the statement of income. We recognize deferred tax assets and liabilities when there are temporary differences between the financial reporting basis and tax basis of our assets and liabilities and for the expected benefits of using net operating loss carryforwards. When a change in the tax rate or tax law has an impact on deferred taxes, we apply the change based on the years in which the temporary differences are expected to reverse. We record the change in our consolidated financial statements in the period of enactment. The determination of the income tax consequences of a business combination includes identifying the tax basis of assets and liabilities acquired and any contingencies associated with uncertain tax positions assumed or resulting from the business combination. Deferred tax assets and liabilities related to temporary differences of an acquired entity are recorded as of the date of the business combination and are based on our estimate of the ultimate tax basis that will be accepted by the various tax authorities. We record liabilities for contingencies associated with prior tax returns filed by the acquired entity based on criteria set forth in the appropriate accounting guidance. We adjust the deferred tax accounts and the liabilities periodically to reflect any revised estimated tax basis and any estimated settlements with the various tax authorities. The effects of these adjustments are recorded to income tax (expense) benefit. From time to time, we engage in transactions in which the tax consequences may be subject to uncertainty. In these cases, we evaluate our tax position using the recognition threshold and the measurement attribute in accordance with the accounting guidance related to uncertain tax positions. Examples of these transactions include business acquisitions and dispositions, including consideration paid or received in connection with these transactions, certain financing transactions, and the allocation of income among state and local tax jurisdictions. Significant judgment is required in assessing and estimating the tax consequences of these transactions. We determine whether it is more likely than not that a tax position will be sustained on examination, including the resolution of any related appeals or litigation processes, based on the technical merits of the position. A tax position that meets the more-likely-than-not recognition threshold is measured to determine the amount of benefit to be recognized in our consolidated financial statements. We classify interest and penalties, if any, associated with our uncertain tax positions as a component of income tax (expense) benefit. Components of Net Deferred Tax Liability December 31 (in millions) 2020 2019 Deferred Tax Assets: Net operating loss and other loss carryforwards $ 2,609 $ 2,017 Nondeductible accruals and other 3,253 2,779 Less: Valuation allowance 2,312 1,906 3,550 2,890 Deferred Tax Liabilities: Differences between book and tax basis of property and equipment and intangible assets 29,829 29,387 Differences between book and tax basis of investments 405 702 Differences between book and tax basis of long-term debt 680 751 Differences between book and tax basis of foreign subsidiaries and undistributed foreign earnings 468 143 31,382 30,983 Net deferred tax liability $ 27,832 $ 28,093 The following table presents changes in our valuation allowance for deferred tax assets: (in millions) Beginning Balance Additions Charged to Income Tax Expense and Other Accounts Deductions from Reserves Ending Balance 2020 $ 1,906 $ 430 $ 24 $ 2,312 2019 $ 632 $ 1,403 $ 129 $ 1,906 2018 $ 377 $ 367 $ 112 $ 632 Changes in our net deferred tax liability in 2020 that were not recorded as deferred income tax benefit (expense) are primarily related to an increase of $330 million associated with items included in other comprehensive income (loss). As of December 31, 2020, we had federal net operating loss carryforwards of $196 million, and various state net operating loss carryforwards, the majority of which expire in periods through 2040. As of December 31, 2020, we also had foreign net operating loss carryforwards of $7.6 billion related to the foreign operations of Sky and NBCUniversal, the majority of which can be carried forward indefinitely. The determination of the realization of the state and foreign net operating loss carryforwards is dependent on our subsidiaries’ taxable income or loss, apportionment percentages, redetermination from taxing authorities, and state and foreign laws that can change from year to year and impact the amount of such carryforwards. We recognize a valuation allowance if we determine it is more likely than not that some portion, or all, of a deferred tax asset will not be realized. As of December 31, 2020 and 2019, our valuation allowance was primarily related to foreign and state net operating loss carryforwards. Uncertain Tax Positions Reconciliation of Unrecognized Tax Benefits (in millions) 2020 2019 2018 Gross unrecognized tax benefits, January 1 $ 1,422 $ 1,543 $ 1,497 Additions based on tax positions related to the current year 436 230 229 Additions based on tax positions related to prior years 152 133 125 Additions from acquired subsidiaries — 1 130 Reductions for tax positions of prior years (31) (344) (346) Reductions due to expiration of statutes of limitations (76) (117) (75) Settlements with tax authorities (24) (24) (17) Gross unrecognized tax benefits, December 31 $ 1,879 $ 1,422 $ 1,543 Our gross unrecognized tax benefits include both amounts related to positions for which we have recorded liabilities for potential payment obligations and those for which tax has been assessed and paid. The amounts exclude the federal benefits on state tax positions that were recorded to deferred income taxes. If we were to recognize our gross unrecognized tax benefits in the future, $1.4 billion would impact our effective tax rate and the remaining amount would increase our deferred income tax liability. The amount and timing of the recognition of any such tax benefit is dependent on the completion of examinations of our tax filings by the various tax authorities and the expiration of statutes of limitations. It is reasonably possible that certain tax contests could be resolved within the next 12 months that may result in a decrease in our effective tax rate. As of December 31, 2020 and 2019, accrued interest and penalties associated with our liability for uncertain tax positions were not material.

Long-Term Debt

Long-Term Debt	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Long-Term Debt	Note 6: Long-Term Debt Long-Term Debt Outstanding December 31 (in millions) Weighted-Average Weighted-Average Interest Rate as of December 31, 2019 2020 (b) 2019 (b) Term loans 2.07 % 1.87 % 7,641 8,078 Senior notes with maturities of 5 years or less, at face value 3.41 % 3.29 % 19,190 26,378 Senior notes with maturities between 5 and 10 years, at face value 3.47 % 3.74 % 23,114 21,683 Senior notes with maturities greater than 10 years, at face value 4.03 % 4.54 % 54,203 46,653 Other, including finance lease obligations 1,261 1,098 Debt issuance costs, premiums, discounts, fair value adjustments for acquisition accounting and hedged positions, net (a) (1,649) (1,673) Total debt 3.60 % (a) 3.78 % (a) 103,760 102,217 Less: Current portion 3,146 4,452 Long-term debt $ 100,614 $ 97,765 (a) Includes the effects of our derivative financial instruments. (b) As of December 31, 2020, included in our outstanding debt were foreign currency denominated borrowings with principal amounts of £4.7 billion, €7.3 billion, ¥238.5 billion and ¥16.4 billion RMB. As of December 31, 2019, included in our outstanding debt were foreign currency denominated borrowings with principal amounts of £4.9 billion, €4.9 billion, ¥267 billion and ¥9 billion RMB. Our senior notes are unsubordinated and unsecured obligations and are subject to parent and/or subsidiary guarantees. As of December 31, 2020 and 2019, our debt had an estimated fair value of $125.6 billion and $115.8 billion, respectively. The estimated fair value of our publicly traded debt was primarily based on Level 1 inputs that use quoted market value for the debt. The estimated fair value of debt for which there are no quoted market prices was based on Level 2 inputs that use interest rates available to us for debt with similar terms and remaining maturities. Principal Maturities of Debt (in millions) 2021 $ 3,133 2022 $ 4,028 2023 $ 3,925 2024 $ 6,746 2025 $ 6,953 Thereafter $ 80,624 We use cross-currency swaps as cash flow hedges for foreign currency denominated debt obligations when those obligations are denominated in a currency other than the functional currency. Cross-currency swaps effectively convert foreign currency denominated debt to debt denominated in the functional currency, which hedge currency exchange risks associated with foreign currency denominated cash flows such as interest and principal debt repayments. As of December 31, 2020 and 2019, we had cross-currency swaps designated as cash flow hedges on $1.7 billion and $3.7 billion of our foreign currency denominated debt, respectively. As of December 31, 2020 and 2019, the aggregate estimated fair values of cross-currency swaps designated as cash flow hedges were a net liability of $45 million and a net asset of $373 million, respectively. We are also exposed to foreign exchange risk on the consolidation of our foreign operations. We have foreign currency denominated debt and cross-currency swaps designated as hedges of our net investments in certain of these subsidiaries. Transaction gains and losses resulting from currency movements on debt and changes in fair value of cross-currency swaps designated as net investment hedges are recorded within the currency translation adjustments component of accumulated other comprehensive income (loss). As of December 31, 2020 and 2019, the amount of our net investment in foreign subsidiaries hedged using foreign currency denominated debt was $10.3 billion and $9.2 billion, respectively, and the amount of our net investment in foreign subsidiaries hedged using cross-currency swaps was $4.0 billion and $4.8 billion, respectively. As of December 31, 2020 and 2019, the aggregate estimated fair value of these cross-currency swaps was a net liability of $376 million and $373 million, respectively. The amount of pre-tax gains (losses) related to net investment hedges recognized in the cumulative translation adjustments component of other comprehensive income (loss) were losses of $686 million in 2020, gains of $343 million in 2019 and losses of $3 million in 2018. Revolving Credit Facilities and Commercial Paper Programs As of December 31, 2020, we had $9.2 billion of revolving credit facilities due 2022 with a syndicate of banks that may be used for general corporate purposes. In June 2019, we amended the terms of our revolving credit facilities to extend their expiration dates from May 26, 2021 to May 26, 2022. We may increase the commitment under the revolving credit facilities up to a total of $12 billion, as well as extend the expiration dates to no later than 2023, subject to approval of the lenders. The interest rates on the revolving credit facilities consist of a base rate plus a borrowing margin that is determined based on Comcast’s credit rating. As of December 31, 2020, the borrowing margin for borrowings based on the London Interbank Offered Rate was 1.00%. Our revolving credit facilities require that we maintain certain financial ratios based on debt and EBITDA, as defined in the revolving credit facilities. We were in compliance with all financial covenants for all periods presented. Our commercial paper programs are supported by our revolving credit facility and provides a lower cost source of borrowing to fund short-term working capital requirements. As of December 31, 2020 and 2019, we had no borrowings outstanding under our commercial paper programs or revolving credit facilities. As of December 31, 2020, amounts available under our revolving credit facilities, net of amounts outstanding under our commercial paper programs and outstanding letters of credit and bank guarantees, totaled $9.2 billion. Letters of Credit and Bank Guarantees As of December 31, 2020, we and certain of our subsidiaries had undrawn irrevocable standby letters of credit and bank guarantees totaling $320 million to cover potential fundings under various agreements.

Significant Transactions

Significant Transactions	12 Months Ended
	Dec. 31, 2020
Business Combinations [Abstract]
Significant Transactions	Note 7: Significant Transactions Sky Transaction In the fourth quarter of 2018, we acquired Sky for £17.28 per Sky share and total cash consideration of £30.2 billion (approximately $39.4 billion using the exchange rates on the purchase dates). We financed the acquisition through a combination of fixed and floating rate senior notes, the issuance of term loans and cash on hand. Acquisition-Related Costs As a result of the Sky transaction, we incurred expenses in 2018 related to legal, accounting, valuation and other professional services, which are reflected in other operating and administrative expenses. We also incurred certain financing costs associated with our borrowings, which are reflected in interest expense. The table below presents the amounts related to these expenses included in our consolidated statement of income. The amounts below do not reflect the costs of any integration activities or costs related to synergies that may be achieved as a result of the acquisition. (in millions) Year ended December 31, 2018 Other operating and administrative expenses $ 339 Interest expense $ 63 Unaudited Pro Forma Information The following unaudited pro forma information has been presented as if the Sky transaction occurred on January 1, 2017. This information is based on historical results of operations, adjusted for allocation of purchase price and other acquisition accounting adjustments, and is not necessarily indicative of what the results would have been had we operated the business since January 1, 2017. For pro forma purposes, 2018 earnings were adjusted to exclude acquisition-related costs noted above. No pro forma adjustments have been made for cost savings or synergies that have been or may be achieved by the combined businesses. The years ended December 31, 2020 and 2019 are not presented as Sky is included in the consolidated results for those periods. Year ended December 31 (in millions, except per share data) 2018 Revenue $ 109,518 Net income attributable to Comcast Corporation $ 12,176 Basic earnings per common share attributable to Comcast Corporation shareholders $ 2.66 Diluted earnings per common share attributable to Comcast Corporation shareholders $ 2.62 Universal Beijing Resort In 2018, we entered into an agreement with a consortium of Chinese state-owned companies to build and operate Universal Beijing Resort, a theme park and resort in Beijing, China. We own a 30% interest in Universal Beijing Resort and the construction is being funded through a combination of debt financing and equity contributions from the investors in accordance with their equity interests. The debt financing, which is being provided by a syndicate of Chinese financial institutions, contains certain covenants and a maximum borrowing limit of ¥26.6 billion RMB (approximately $4 billion). The debt financing is secured by the assets of Universal Beijing Resort and the equity interests of the investors. As of December 31, 2020, Universal Beijing Resort had $2.5 billion principal amount of a term loan outstanding under the debt financing agreement. We have concluded that Universal Beijing Resort is a variable interest entity based on its governance structure, and we consolidate it because we have the power to direct activities that most significantly impact its economic performance. There are no liquidity arrangements, guarantees or other financial commitments between us and Universal Beijing Resort, and therefore our maximum risk of financial loss is our 30% interest. Universal Beijing Resort’s results of operations are reported in our Theme Parks segment. Our consolidated statement of cash flows includes the costs of construction and related borrowings in the “construction of Universal Beijing Resort” and “proceeds from borrowings” captions, respectively, and equity contributions from the noncontrolling interests are included in other financing activities. In March 2018, Universal Beijing Resort received initial equity investments through a combination of cash and noncash contributions from the investors. As of December 31, 2020, our consolidated balance sheet included assets, primarily property and equipment, and liabilities, including the term loan, of Universal Beijing Resort totaling $5.1 billion and $3.6 billion, respectively.

Recent Accounting Pronouncement

Recent Accounting Pronouncements	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Recent Accounting Pronouncements	Note 8: Recent Accounting Pronouncements Film and Television Content In March 2019, the Financial Accounting Standards Board (“FASB”) updated the accounting guidance related to film and television content. The updated guidance aligned the accounting for production costs of owned episodic television series with those of films, allowing for costs to be capitalized in excess of amounts of revenue contracted for each episode. The guidance also updated certain presentation and disclosure requirements for capitalized film and television content, and when content is predominantly monetized with other owned or licensed content the guidance requires impairment testing for capitalized film and television content to be performed at a film group level and amortization to be based on usage. We adopted the updated guidance on January 1, 2020 on a prospective basis and as a result, prior period amounts were not adjusted. Following the adoption, we now present all capitalized film and television content, including licensed content and sports advances previously classified as current programming rights, as noncurrent film and television costs in the consolidated balance sheet. The adoption of the updated accounting guidance did not have a material impact on our consolidated results of operations or financial position. See Note 4 for further information. Credit Losses In June 2016, the FASB updated the accounting guidance related to the measurement of credit losses on financial instruments, including trade receivables and loans. The updated guidance requires the recognition of credit losses on financial instruments based on an estimate of expected losses, replacing the incurred loss model in the prior guidance. We adopted the updated guidance on January 1, 2020 on a prospective basis, recording $124 million, net of tax, as a cumulative effect adjustment to retained earnings and as a result, prior period amounts were not adjusted. The adoption of the updated accounting guidance did not have a material impact on our consolidated results of operations or financial position for any periods presented.

Investments

Investments	12 Months Ended
	Dec. 31, 2020
Investments [Abstract]
Investments	Note 9: Investments Investment and Other Income (Loss), Net Year ended December 31 (in millions) 2020 2019 2018 Equity in net income (losses) of investees, net $ (113) $ (505) $ (364) Realized and unrealized gains (losses) on equity securities, net 1,014 656 (187) Other income (loss), net 259 287 326 Investment and other income (loss), net $ 1,160 $ 438 $ (225) The amount of unrealized gains (losses) recognized in 2020, 2019 and 2018 that related to marketable and nonmarketable equity securities still held as of the end of each reporting period was $339 million, $237 million and $(200) million, respectively. Investments December 31 (in millions) 2020 2019 Equity method $ 6,006 $ 5,347 Marketable equity securities 460 353 Nonmarketable equity securities 1,950 1,896 Other investments 143 1,796 Total investments 8,559 9,392 Less: Current investments 292 1,709 Less: Investment securing collateralized obligation 447 694 Noncurrent investments $ 7,820 $ 6,989 Equity Method We use the equity method to account for investments in which we have the ability to exercise significant influence over the investee’s operating and financial policies, or in which we hold a partnership or limited liability company interest in an entity with specific ownership accounts, unless we have virtually no influence over the investee’s operating and financial policies. Equity method investments are recorded at cost and are adjusted to recognize (1) our share, based on percentage ownership or other contractual basis, of the investee’s net income or loss after the date of investment, (2) amortization of the recorded investment that exceeds our share of the book value of the investee’s net assets, (3) additional contributions made and dividends received, and (4) impairments resulting from other-than-temporary declines in fair value. For some investments, we record our share of the investee’s net income or loss one quarter in arrears due to the timing of our receipt of such information. Gains or losses on the sale of equity method investments are recorded to other income (loss), net. If an equity method investee were to issue additional securities that would change our proportionate share of the entity, we would recognize the change, if any, as a gain or loss to other income (loss), net. Atairos On January 1, 2016, we established Atairos Group, Inc., a strategic company focused on investing in and operating companies in a range of industries and business sectors, both domestically and internationally. Atairos is controlled by management companies led by our former CFO through interests that carry all of the voting rights. We are the only third-party investor in Atairos. In November 2020, we amended our agreement with Atairos, which primarily extended the investment term of the agreement from up to 12 years to up to 16.5 years, extended the period in which capital can be recycled to the full investment period and decreased our commitment to fund Atairos from up to $5 billion to up to $4.5 billion in the aggregate at any one time, subject to certain offsets, with the maximum amount of annual capital calls reduced to $400 million, plus certain amounts previously distributed. In addition, we have separately committed to fund Atairos $45 million annually for a management fee, subject to certain adjustments. The management company investors have committed to fund from $50 million to $100 million, with at least $40 million to be funded by our former CFO, subject to his continued role with Atairos. Our economic interests do not carry voting rights and obligate us to absorb approximately 99% of any losses and they provide us the right to receive approximately 86% of any residual returns in Atairos, in either case on a cumulative basis. We have concluded that Atairos is a VIE, that we do not have the power to direct the activities that most significantly impact the economic performance of Atairos as we have no voting rights and only certain consent rights, and that we are not a related party with our former CFO or the management companies. We therefore do not consolidate Atairos and account for our investment as an equity method investment. Atairos may pledge our remaining unfunded capital commitment as security to lenders in connection with certain financing arrangements. This has no effect on our funding commitments. There are no other liquidity arrangements, guarantees or other financial commitments between Comcast and Atairos, and therefore our maximum risk of financial loss is our investment balance and our remaining unfunded capital commitment of $1.3 billion as of December 31, 2020. Atairos follows investment company accounting and records its investments at their fair values each reporting period with the net gains or losses reflected in its statement of operations. We recognize our share of these gains and losses in equity in net income (losses) of investees, net. In 2020, 2019 and 2018, we made cash capital contributions totaling $383 million, $571 million and $282 million, respectively, to Atairos. As of December 31, 2020 and 2019, our investment was $3.9 billion and $3.2 billion, respectively. In April 2018, we sold a controlling interest in our arena management-related businesses to Atairos and received as consideration additional equity interests in Atairos. In connection with the sale of the businesses, we recognized a pre-tax gain of $200 million in other operating gains. Hulu and Collateralized Obligation In May 2019, we entered into a series of agreements (the “Hulu Transaction”) with The Walt Disney Company and certain of its subsidiaries, whereby we relinquished our board seats and substantially all voting rights associated with our investment in Hulu, and Disney assumed full operational control. We also acquired our proportionate share of the approximate 10% interest in Hulu previously held by AT&T for approximately $477 million, increasing our ownership interest to approximately 33% from approximately 30%. Following the Hulu Transaction, future capital calls are limited to $1.5 billion in the aggregate each year, with any excess funding requirements funded with member loans. We have the right, but not the obligation, to fund our proportionate share of these capital calls, and if we elect not to fund our share of future equity capital calls, our ownership interest will be diluted, subject to an ownership floor of 21%. The Hulu Transaction agreements include put and call provisions regarding our ownership interest in Hulu, pursuant to which, as early as January 2024, we can require Disney to buy, and Disney can require us to sell our interest, in either case, for fair value at that future time subject to a minimum equity value of $27.5 billion for 100% of the equity of Hulu. The minimum total equity value and ownership floor guarantee minimum proceeds of approximately $5.8 billion upon exercise of the put or call. In connection with the Hulu Transaction, we agreed to extend certain licenses of NBCUniversal content until late 2024. We can terminate most of our content license agreements with Hulu beginning in 2022, and beginning in 2020, we have the right to modify certain content licenses that are currently exclusive to Hulu, so that we can exhibit the content on our platforms in return for reducing the license fee. In August 2019, we entered into a financing arrangement with a syndicate of banks whereby we received proceeds of $5.2 billion under a term loan facility due March 2024. The principal amount of the term loan is secured by the proceeds guaranteed by Disney under the put/call provisions related to our investment in Hulu. The proceeds from the put/call provisions are available only for the repayment of the term loan and are not available to us unless and until the bank lenders are fully paid under the term loan provisions. The bank lenders have no rights to proceeds from the put/call provisions in excess of amounts owed under the term loan. As a result of this transaction, we now present our investment in Hulu and the term loan separately in our consolidated balance sheet in the captions “investment securing collateralized obligation” and “collateralized obligation”, respectively. The recorded value of our investment reflects our historical cost in applying the equity method, and as a result, is less than its fair value. As of December 31, 2020, our collateralized obligation had both a carrying value and estimated fair value of $5.2 billion. The estimated fair value was based on Level 2 inputs that use interest rates for debt with similar terms and remaining maturities. Marketable Equity Securities We classify investments with readily determinable fair values that are not accounted for under the equity method as marketable equity securities. The changes in fair value of our marketable equity securities between measurement dates are recorded in realized and unrealized gains (losses) on equity securities, net. The fair values of our marketable equity securities are based on Level 1 inputs that use quoted market prices. Nonmarketable Equity Securities We classify investments without readily determinable fair values that are not accounted for under the equity method as nonmarketable equity securities. The accounting guidance requires nonmarketable equity securities to be recorded at cost and adjusted to fair value at each reporting period. However, the guidance allows for a measurement alternative, which is to record the investments at cost, less impairment, if any, and subsequently adjust for observable price changes of identical or similar investments of the same issuer. We apply the measurement alternative, adjusting the investments for observable price changes of identical or similar investments of the same issuer, to a majority of our nonmarketable equity securities. When an observable event occurs, we estimate the fair values of our nonmarketable equity securities primarily based on Level 2 inputs that are derived from observable price changes of similar securities adjusted for insignificant differences in rights and obligations. The changes in value are recorded in realized and unrealized gains (losses) on equity securities, net. Other Investments AirTouch During the second quarter of 2020, Verizon Americas, Inc., formerly known as AirTouch Communications, Inc. (“AirTouch”), redeemed the two series of preferred stock held by the Company and we received cash payments totaling $1.7 billion. As of December 31, 2019, our investment in AirTouch was $1.6 billion, and was included in other current assets. During the second quarter of 2020, we redeemed and repurchased the related three series of preferred shares issued by one of our consolidated subsidiaries and made cash payments totaling $1.8 billion. As of December 31, 2019, the two series of redeemable subsidiary preferred shares and the one series of nonredeemable subsidiary preferred shares were recorded at $1.7 billion and $100 million, respectively, and were included in other current liabilities and in noncontrolling interests, respectively, in our consolidated balance sheet. Impairment Testing of Investments We review our investment portfolio, other than our marketable equity securities, each reporting period to determine whether there are identified events or circumstances that would indicate there is a decline in the fair value. For our nonpublic investments, if there are no identified events or circumstances that would have a significant adverse effect on the fair value of the investment, then the fair value is not estimated. For our equity method investments and held to maturity investments, if an investment is deemed to have experienced an other-than-temporary decline below its cost basis, we reduce the carrying amount of the investment to its quoted or estimated fair value, as applicable, and establish a new cost basis for the investment. For our nonmarketable equity securities, we record the impairment to realized and unrealized gains (losses) on equity securities, net. For our equity method investments and our held to maturity investments, we record the impairment to other income (loss), net.

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Property and Equipment	Note 10: Property and Equipment December 31 (in millions) Weighted-Average 2020 2019 Distribution systems 11 years $ 40,861 $ 40,639 Customer premise equipment 6 years 26,323 26,065 Buildings, theme park infrastructure and leasehold improvements 31 years 15,885 15,104 Other equipment 9 years 14,371 13,025 Construction in process N/A 7,095 5,245 Land N/A 1,848 1,483 Property and equipment, at cost 106,383 101,561 Less: Accumulated depreciation 54,388 53,239 Property and equipment, net $ 51,995 $ 48,322 Property and equipment are stated at cost. We capitalize improvements that extend asset lives and expense repairs and maintenance costs as incurred. We record depreciation using the straight-line method over the asset’s estimated useful life. For assets that are sold or retired, we remove the applicable cost and accumulated depreciation and, unless the gain or loss on disposition is presented separately, we recognize it as a component of depreciation expense. Capital expenditures for the construction of Universal Beijing Resort are presented separately in our consolidated statement of cash flows. Cable Communications capitalizes the costs associated with the construction of and improvements to our cable transmission and distribution facilities, including scalable infrastructure and line extensions; costs associated with acquiring and deploying new customer premise equipment; and costs associated with installation of our services, including the customer’s connection to our network, in accordance with the accounting guidance related to cable television companies. Costs capitalized include all direct costs for labor and materials, as well as various indirect costs. Costs incurred in connection with subsequent disconnects, and reconnects of previously deployed customer premise equipment, are expensed as they are incurred. We evaluate the recoverability of our property and equipment whenever events or substantive changes in circumstances indicate that the carrying amount may not be recoverable. The evaluation is based on the cash flows generated by the underlying asset groups, including estimated future operating results, trends or other determinants of fair value. If the total of the expected future undiscounted cash flows were less than the carrying amount of the asset group, we would recognize an impairment charge to the extent the carrying amount of the asset group exceeded its estimated fair value. Unless presented separately, the impairment charge is included as a component of depreciation expense. Certain of our cable franchise agreements and lease agreements contain provisions requiring us to restore facilities or remove property in the event that the franchise or lease agreement is not renewed. We expect to continually renew our cable franchise agreements and therefore cannot reasonably estimate liabilities associated with such agreements. A remote possibility exists that franchise agreements could be terminated unexpectedly, which could result in us incurring significant expense in complying with restoration or removal provisions. We do not have any material liabilities related to asset retirement obligations recorded in our consolidated financial statements.

Goodwill and Intangible Assets

Goodwill and Intangible Assets	12 Months Ended
	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	Note 11: Goodwill and Intangible Assets Goodwill NBCUniversal (in millions) Cable Cable Broadcast Filmed Theme Sky Corporate Total Balance, December 31, 2018 $ 12,784 $ 13,407 $ 843 $ 3,184 $ 6,684 $ 29,250 $ 2 $ 66,154 Acquisitions 86 162 14 — — 17 — 279 Dispositions — — — — — (12) — (12) Adjustments (a) 2,166 490 199 138 — (1,616) 2 1,379 Foreign currency translation 38 8 3 (1) 55 822 — 925 Balance, December 31, 2019 15,074 14,067 1,059 3,321 6,739 28,461 4 68,725 Acquisitions 122 — — 27 — — — 149 Dispositions — — — — — — (4) (4) Adjustments (5) (85) — — — (8) 2 (96) Foreign currency translation 73 12 3 (4) 314 1,497 — 1,895 Balance, December 31, 2020 $ 15,264 $ 13,994 $ 1,062 $ 3,344 $ 7,053 $ 29,950 $ 2 $ 70,669 (a) Adjustments in 2019 primarily included 1) measurement period adjustments resulting from finalization of acquisition accounting for Sky and 2) the final assignment of goodwill resulting from the Sky transaction to our reporting units. Goodwill is calculated as the excess of the consideration transferred over the identifiable net assets acquired in a business combination and represents the future economic benefits expected to arise from anticipated synergies and intangible assets acquired that do not qualify for separate recognition, including increased footprint, assembled workforce, noncontractual relationships and other agreements. We assess the recoverability of our goodwill annually, or more frequently whenever events or substantive changes in circumstances indicate that the carrying amount of a reporting unit may exceed its fair value. We test goodwill for impairment at the reporting unit level. To determine our reporting units, we evaluate the components one level below the segment level and we aggregate the components if they have similar economic characteristics. We evaluate the determination of our reporting units used to test for impairment periodically or whenever events or substantive changes in circumstances occur. The assessment of recoverability may first consider qualitative factors to determine whether the existence of events or circumstances leads to a determination that it is more likely than not that the fair value of a reporting unit is less than its carrying amount. A quantitative assessment is performed if the qualitative assessment results in a more-likely-than-not determination or if a qualitative assessment is not performed. The quantitative assessment considers whether the carrying amount of a reporting unit exceeds its fair value, in which case an impairment charge is recorded to the extent the reporting unit’s carrying value exceeds its fair value. Unless presented separately, the impairment charge is included as a component of amortization expense. We have not recognized any material impairment charges. Intangible Assets 2020 2019 December 31 (in millions) Weighted-Average Gross Carrying Amount Accumulated Amortization Gross Carrying Amount Accumulated Amortization Indefinite-Lived Intangible Assets: Franchise rights N/A $ 59,365 $ 59,365 Trade names N/A — 8,809 FCC licenses N/A 2,804 2,337 Finite-Lived Intangible Assets: Customer relationships 14 years 22,197 $ (8,914) 22,884 $ (8,295) Software 5 years 17,819 (9,518) 15,357 (7,287) Other agreements and rights 28 years 12,394 (1,393) 3,958 (1,635) Total $ 114,579 $ (19,825) $ 112,710 $ (17,217) Indefinite-Lived Intangible Assets Indefinite-lived intangible assets consist primarily of our cable franchise rights. Our cable franchise rights represent the values we attributed to agreements with state and local authorities that allow access to homes and businesses in cable service areas acquired in business combinations. We do not amortize our cable franchise rights because we have determined that they meet the definition of indefinite-lived intangible assets since there are no legal, regulatory, contractual, competitive, economic or other factors which limit the period over which these rights will contribute to our cash flows. We reassess this determination periodically or whenever events or substantive changes in circumstances occur. The purchase of spectrum rights is presented separately in our consolidated statement of cash flows. We assess the recoverability of our cable franchise rights and other indefinite-lived intangible assets annually, or more frequently whenever events or substantive changes in circumstances indicate that the assets might be impaired. Our three Cable Communications divisions represent the unit of account we use to test for impairment of our cable franchise rights. We evaluate the unit of account used to test for impairment of our cable franchise rights and other indefinite-lived intangible assets periodically or whenever events or substantive changes in circumstances occur to ensure impairment testing is performed at an appropriate level. The assessment of recoverability may first consider qualitative factors to determine whether it is more likely than not that the fair value of an indefinite-lived intangible asset is less than its carrying amount. A quantitative assessment is performed if the qualitative assessment results in a more-likely-than-not determination or if a qualitative assessment is not performed. When performing a quantitative assessment, we estimate the fair value of our cable franchise rights and other indefinite-lived intangible assets primarily based on a discounted cash flow analysis that involves significant judgment. When analyzing the fair values indicated under the discounted cash flow models, we also consider multiples of Adjusted EBITDA generated by the underlying assets, current market transactions and profitability information. If the fair value of our cable franchise rights or other indefinite-lived intangible assets were less than the carrying amount, we would recognize an impairment charge for the difference between the estimated fair value and the carrying value of the assets. Unless presented separately, the impairment charge is included as a component of amortization expense. We did not recognize any material impairment charges in any of the periods presented. Finite-Lived Intangible Assets Estimated Amortization Expense of Finite-Lived Intangible Assets (in millions) 2021 $ 4,589 2022 $ 4,087 2023 $ 3,472 2024 $ 2,774 2025 $ 2,412 Finite-lived intangible assets are subject to amortization and consist primarily of customer relationships acquired in business combinations, software, trade names and intellectual property rights. Our finite-lived intangible assets are amortized primarily on a straight-line basis over their estimated useful life or the term of the associated agreement. We capitalize direct development costs associated with internal-use software, including external direct costs of material and services and payroll costs for employees devoting time to these software projects. We also capitalize costs associated with the purchase of software licenses. We generally amortize them on a straight-line basis over a period not to exceed five years. We expense maintenance and training costs, as well as costs incurred during the preliminary stage of a project, as they are incurred. We capitalize initial operating system software costs and amortize them over the life of the associated hardware.

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2020
Retirement Benefits [Abstract]
Employee Benefit Plans	Note 12: Employee Benefit Plans Deferred Compensation Plans Year ended December 31 (in millions) 2020 2019 2018 Benefit obligation $ 3,648 $ 3,273 $ 2,885 Interest expense $ 293 $ 285 $ 222 We maintain unfunded, nonqualified deferred compensation plans for certain members of management and nonemployee directors. The amount of compensation deferred by each participant is based on participant elections. Participant accounts are credited with income primarily based on a fixed annual rate. Participants are eligible to receive distributions from their account based on elected deferral periods that are consistent with the plans and applicable tax law. We have purchased life insurance policies to recover a portion of the future payments related to our deferred compensation plans. As of December 31, 2020 and 2019, the cash surrender value of these policies, which is recorded to other noncurrent assets, net, was $481 million and $423 million, respectively. Pension and Postretirement Benefit Plans We sponsor several 401(k) defined contribution retirement plans that allow eligible employees to contribute a portion of their compensation through payroll deductions in accordance with specified plan guidelines. We make contributions to the plans that include matching a percentage of the employees’ contributions up to certain limits. In 2020, 2019 and 2018, expenses related to these plans totaled $599 million, $573 million and $546 million, respectively. We participate in various multiemployer benefit plans, including pension and postretirement benefit plans, that cover some of our employees and temporary employees who are represented by labor unions. We also participate in other multiemployer benefit plans that provide health and welfare and retirement savings benefits to active and retired participants. If we cease to be obligated to make contributions or were to otherwise withdraw from participation in any of these plans, applicable law would require us to fund our allocable share of the unfunded vested benefits, which is known as a withdrawal liability. In addition, actions taken by other participating employers may lead to adverse changes in the financial condition of one of these plans, which could result in an increase in our withdrawal liability. In 2020, 2019 and 2018, the total contributions we made to multiemployer benefit plans were not material.

Equity

Equity	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Equity	Note 13: Equity Common Stock In the aggregate, holders of our Class A common stock have 66 2 / 3 % of the voting power of our common stock and holders of our Class B common stock have 33 1 / 3 % of the voting power of our common stock, which percentage is generally non-dilutable under the terms of our articles of incorporation. Each share of our Class B common stock is entitled to 15 votes. The number of votes held by each share of our Class A common stock depends on the number of shares of Class A and Class B common stock outstanding at any given time. The 33 1 / 3 % aggregate voting power of our Class B common stock cannot be diluted by additional issuances of any other class of common stock. Our Class B common stock is convertible, share for share, into Class A common stock, subject to certain restrictions. Shares of Common Stock Outstanding (in millions) Class A Class B Balance, December 31, 2017 4,635 9 Stock compensation plans 15 — Repurchases and retirements of common stock (140) — Employee stock purchase plans 7 — Balance, December 31, 2018 4,517 9 Stock compensation plans 21 — Employee stock purchase plans 6 — Balance, December 31, 2019 4,544 9 Stock compensation plans 20 — Employee stock purchase plans 7 — Balance, December 31, 2020 4,571 9 Weighted-Average Common Shares Outstanding Year ended December 31 (in millions) 2020 2019 2018 Weighted-average number of common shares outstanding – basic 4,574 4,548 4,584 Effect of dilutive securities 50 62 56 Weighted-average number of common shares outstanding – diluted 4,624 4,610 4,640 Weighted-average common shares outstanding used in calculating diluted earnings per common share attributable to Comcast Corporation shareholders (“diluted EPS”) considers the impact of potentially dilutive securities using the treasury stock method. Our potentially dilutive securities include potential common shares related to our stock options and our restricted share units (“RSUs”). Diluted EPS excludes the impact of potential common shares related to our stock options in periods in which the combination of the option exercise price and the associated unrecognized compensation expense is greater than the average market price of our common stock. The amount of potential common shares related to our share-based compensation plans that were excluded from diluted EPS because their effect would have been antidilutive was not material in any of the periods presented. Accumulated Other Comprehensive Income (Loss) December 31 (in millions) 2020 2019 Cumulative translation adjustments $ 1,790 $ 637 Deferred gains (losses) on cash flow hedges (109) 139 Unrecognized gains (losses) on employee benefit obligations and other 203 271 Accumulated other comprehensive income (loss), net of deferred taxes $ 1,884 $ 1,047

Share-Based Compensation

Share-Based Compensation	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Share-Based Compensation	Note 14: Share-Based Compensation The tables below provide information on our share-based compensation. Recognized Share-Based Compensation Expense Year ended December 31 (in millions) 2020 2019 2018 Restricted share units $ 628 $ 564 $ 402 Stock options 294 231 205 Employee stock purchase plans 38 30 32 Total $ 960 $ 825 $ 639 Our share-based compensation plans consist primarily of awards of RSUs and stock options to certain employees and directors as part of our approach to long-term incentive compensation. Awards generally vest over a period of 5 years and, in the case of stock options, have a 10 year term. Additionally, through our employee stock purchase plans, employees are able to purchase shares of our common stock at a discount through payroll deductions. As of December 31, 2020, all of our stock options outstanding were net settled stock options, which result in fewer shares being issued and no cash proceeds being received by us when the options are exercised. Stock Options and Restricted Share Units As of December 31, 2020, unless otherwise stated (in millions, except per share data) Stock RSUs Awards granted during 2020 61 18 Weighted-average exercise price of awards granted during 2020 $ 42.42 Stock options outstanding and nonvested RSUs 210 49 Weighted-average exercise price of stock options outstanding $ 35.94 Weighted-average fair value at grant date of nonvested RSUs $ 38.87 The cost associated with our share-based compensation is based on an award’s estimated fair value at the date of grant and is recognized over the period in which any related services are provided. RSUs are valued based on the closing price of our common stock on the date of grant and are discounted for the lack of dividends, if any, during the vesting period. We use the Black-Scholes option pricing model to estimate the fair value of stock option awards. The table below presents the weighted-average fair value on the date of grant of RSUs and stock options awarded under our various plans and the related weighted-average valuation assumptions. Year ended December 31 2020 2019 2018 RSUs fair value $ 41.71 $ 40.42 $ 35.56 Stock options fair value $ 6.61 $ 7.91 $ 7.14 Stock Option Valuation Assumptions: Dividend yield 2.2 % 2.1 % 2.1 % Expected volatility 21.0 % 22.0 % 22.0 % Risk-free interest rate 1.0 % 2.5 % 2.7 % Expected option life (in years) 6.0 6.0 6.0 As of December 31, 2020, we had unrecognized pretax compensation expense of $1.2 billion related to nonvested RSUs and unrecognized pretax compensation expense of $560 million related to nonvested stock options that will be recognized over a weighted-average period of approximately 1.5 years and 1.7 years, respectively. In 2020, 2019, and 2018, we recognized $150 million, $196 million and $75 million, respectively, as a reduction to income tax expense as a result of excess tax benefits associated with our share-based compensation plans.

Supplemental Financial Informat

Supplemental Financial Information	12 Months Ended
	Dec. 31, 2020
Supplemental Financial Information [Abstract]
Supplemental Financial Information	Note 15: Supplemental Financial Information Cash Payments for Interest and Income Taxes Year ended December 31 (in millions) 2020 2019 2018 Interest $ 3,878 $ 4,254 $ 2,897 Income taxes $ 3,183 $ 3,231 $ 2,355 Noncash Activities During 2020: • we acquired $1.9 billion of property and equipment and intangible assets that were accrued but unpaid • we recorded a liability of $1.1 billion for a quarterly cash dividend of $0.23 per common share paid in January 2021 During 2019: • we acquired $1.9 billion of property and equipment and intangible assets that were accrued but unpaid • we recorded a liability of $956 million for a quarterly cash dividend of $0.21 per common share paid in January 2020 During 2018: • we acquired $2.1 billion of property and equipment and intangible assets that were accrued but unpaid • we recorded a liability of $860 million for a quarterly cash dividend of $0.19 per common share paid in January 2019 • we received noncash contributions from noncontrolling interests totaling $391 million related to Universal Beijing Resort (see Note 7) Cash, Cash Equivalents and Restricted Cash The following table provides a reconciliation of cash, cash equivalents and restricted cash reported in the consolidated balance sheet to the total of the amounts reported in our consolidated statement of cash flows. December 31 (in millions) 2020 2019 Cash and cash equivalents $ 11,740 $ 5,500 Restricted cash included in other current assets 14 42 Restricted cash included in other noncurrent assets, net 14 47 Cash, cash equivalents and restricted cash, end of year $ 11,768 $ 5,589

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 16: Commitments and Contingencies Sports Rights and Licensed Content Our most significant fixed-price purchase obligations relate to long-term commitments for sports rights and licensed content. Refer to Note 4 for additional information. Leases Our leases consist primarily of real estate, vehicles and other equipment. We determine if an arrangement is a lease at inception. Lease assets and liabilities are recognized upon commencement of the lease based on the present value of the future minimum lease payments over the lease term. The lease term includes options to extend the lease when it is reasonably certain that we will exercise that option. We generally utilize our incremental borrowing rate based on information available at the commencement of the lease in determining the present value of future payments. The lease asset also includes any lease payments made and initial direct costs incurred and excludes lease incentives. Lease assets and liabilities are not recorded for leases with an initial term of one year or less. Lease expense for operating leases recorded in the balance sheet is included in operating costs and expenses and is based on the future minimum lease payments recognized on a straight-line basis over the term of the lease plus any variable lease costs. Operating lease expenses, inclusive of short-term and variable lease expenses, recognized in our consolidated statement of income for both the periods ended December 31, 2020 and 2019 was $1.1 billion. These amounts do not include lease costs associated with production activities or other amounts capitalized in our consolidated balance sheet, which are not material. The table below summarizes the operating lease assets and liabilities recorded in our consolidated balance sheet. Consolidated Balance Sheet (in millions) December 31, December 31, Other noncurrent assets, net $ 3,784 $ 4,038 Accrued expenses and other current liabilities $ 718 $ 715 Other noncurrent liabilities $ 3,740 $ 3,891 The table below summarizes our future minimum lease commitments for operating leases as of December 31, 2020. (in millions) December 31, 2021 $ 873 2022 778 2023 683 2024 560 2025 444 Thereafter 2,043 Total future minimum lease payments 5,381 Less: imputed interest 923 Total liability $ 4,458 The weighted-average remaining lease terms for operating leases and the weighted-average discount rates used to calculate our operating lease liabilities as of December 31, 2020 were 9 years and 3.58%, respectively, and as of December 31, 2019 were 10 years and 3.74%, respectively. In 2020 and 2019, cash payments for operating leases recorded in the consolidated balance sheet were $936 million and $914 million, respectively. Lease assets and liabilities associated with leases entered into during the year were not material. Our 2018 rent expense for operating leases using the accounting guidance in effect at that time was $779 million. Contractual Obligation We are party to a contractual obligation that involves an interest held by a third party in the revenue of certain theme parks. The arrangement provides the counterparty with the right to periodic payments associated with current period revenue which are recorded as an operating expense, and beginning in June 2017, the option to require NBCUniversal to purchase the interest for cash in an amount based on a contractual formula. The contractual formula is based on an average of specified historical theme park revenue at the time of exercise, which amount could be significantly higher than our carrying value. As of December 31, 2020, our carrying value was $1.1 billion, and the estimated value of the contractual obligation was $1.7 billion based on inputs to the contractual formula as of that date. Redeemable Subsidiary Preferred Stock NBCUniversal Enterprise is a holding company that we control and consolidate whose principal assets are its indirect interests in NBCUniversal. The holders of the Series A cumulative preferred stock of NBCUniversal Enterprise have the right to cause NBCUniversal Enterprise to redeem their shares at a price equal to the $725 million aggregate liquidation preference plus accrued but unpaid dividends for a 30 day period beginning March 19, 2020 and thereafter on every third anniversary of such date (each such date, a “put date”). The NBCUniversal Enterprise preferred stock pays dividends at a fixed rate of 5.25% per year. Shares of preferred stock can be called for redemption by NBCUniversal Enterprise at a price equal to the liquidation preference plus accrued but unpaid dividends one year following the put date applicable to such shares. Because certain of these redemption provisions are outside of our control, the NBCUniversal Enterprise preferred stock is presented outside of equity under the caption “redeemable noncontrolling interests and redeemable subsidiary preferred stock” in our consolidated balance sheet. Its initial value was based on the liquidation preference of the preferred stock and is adjusted for accrued but unpaid dividends. As of December 31, 2020 and 2019, the fair value of the NBCUniversal Enterprise redeemable subsidiary preferred stock was $731 million and $749 million, respectively. The estimated fair values are based on Level 2 inputs that use pricing models whose inputs are derived primarily from or corroborated by observable market data through correlation or other means for substantially the full term of the financial instrument. Contingencies We are subject to legal proceedings and claims that arise in the ordinary course of our business. While the amount of ultimate liability with respect to such actions is not expected to materially affect our results of operations, cash flows or financial position, any litigation resulting from any such legal proceedings or claims could be time-consuming and injure our reputation.

Quarterly Financial Information

Quarterly Financial Information (Unaudited)	12 Months Ended
	Dec. 31, 2020
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information (Unaudited)	Note 17: Quarterly Financial Information (Unaudited) (in millions, except per share data) First Second Third Fourth Total 2020 Revenue $ 26,609 $ 23,715 $ 25,532 $ 27,708 $ 103,564 Operating income $ 4,852 $ 4,647 $ 4,076 $ 3,918 $ 17,493 Net income attributable to Comcast Corporation $ 2,147 $ 2,988 $ 2,019 $ 3,380 $ 10,534 Basic earnings per common share attributable to Comcast Corporation shareholders $ 0.47 $ 0.65 $ 0.44 $ 0.74 $ 2.30 Diluted earnings per common share attributable to Comcast Corporation shareholders $ 0.46 $ 0.65 $ 0.44 $ 0.73 $ 2.28 Dividends declared per common share $ 0.23 $ 0.23 $ 0.23 $ 0.23 $ 0.92 2019 Revenue $ 26,859 $ 26,858 $ 26,827 $ 28,398 $ 108,942 Operating income $ 5,182 $ 5,356 $ 5,340 $ 5,247 $ 21,125 Net income attributable to Comcast Corporation $ 3,553 $ 3,125 $ 3,217 $ 3,162 $ 13,057 Basic earnings per common share attributable to Comcast Corporation shareholders $ 0.78 $ 0.69 $ 0.71 $ 0.69 $ 2.87 Diluted earnings per common share attributable to Comcast Corporation shareholders $ 0.77 $ 0.68 $ 0.70 $ 0.68 $ 2.83 Dividends declared per common share $ 0.21 $ 0.21 $ 0.21 $ 0.21 $ 0.84 Minor differences may exist due to rounding.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Basis of Presentation	The accompanying consolidated financial statements include all entities in which we have a controlling voting interest and variable interest entities (“VIEs”) required to be consolidated including Universal Beijing Resort (see Note 7).
Foreign Currency Translation	We translate assets and liabilities of our foreign operations where the functional currency is the local currency into U.S. dollars at the exchange rate as of the balance sheet date and translate revenue and expenses using average monthly exchange rates. The related translation adjustments are recorded as a component of accumulated other comprehensive income (loss) in our consolidated balance sheet. Any foreign currency transaction gains or losses are included in our consolidated statement of income in investment and other income (loss), net. For disclosures containing future amounts where the functional currency is the local currency, we translate the amounts into U.S. dollars at the exchange rates as of the balance sheet date.
Use of Estimates	Our consolidated financial statements are prepared in accordance with GAAP, which require us to select accounting policies, including in certain cases industry-specific policies, and make estimates that affect the reported amount of assets, liabilities, revenue and expenses, and the related disclosure of contingent assets and contingent liabilities. Actual results could differ from these estimates. The following accounting policies are specific to the industries in which we operate: • capitalization and amortization of film and television costs (see Note 4) • costs for connecting customers to our cable systems (see Note 10)
Advertising Cost	Advertising costs are expensed as incurred.
Derivative Financial Instruments	We use derivative financial instruments to manage our exposure to the risks associated with fluctuations in interest rates, foreign exchange rates and equity prices. Our objective is to manage the financial and operational exposure arising from these risks by offsetting gains and losses on the underlying exposures with gains and losses on the derivatives used to economically hedge them. Our derivative financial instruments are recorded in our consolidated balance sheet at fair value. We designate certain derivative instruments as cash flow hedges of forecasted foreign currency denominated transactions, including cash flows associated with non-functional currency debt and non-functional currency revenue and expenses. Changes in the fair value of derivative instruments accounted for as cash flow hedges are recorded as a component of accumulated other comprehensive income (loss) until the hedged items affect earnings. For derivatives not designated as cash flow hedges, changes in fair value are recognized in earnings.
Fair Value Measurements	The accounting guidance related to fair value measurements establishes a hierarchy based on the types of inputs used for the various valuation techniques. The levels of the hierarchy are described below. • Level 1: Values are determined using quoted market prices for identical financial instruments in an active market. • Level 2: Values are determined using quoted prices for similar instruments in active markets; quoted prices for identical or similar instruments in markets that are not active; and model-derived valuations in which all significant inputs and significant value drivers are observable in active markets. • Level 3: Values are determined using models that use significant inputs that are primarily unobservable, discounted cash flow methodologies or similar techniques, as well as instruments for which the determination of fair value requires significant management judgment or estimation.
Revenue Recognition	Cable Communications Segment Revenue is generated from the sale of our high-speed internet, video, voice, wireless and other services to residential customers in the United States under the Xfinity brand, which we market individually and as bundled services at a discounted rate. We also provide these and other services to business customers and sell advertising. Residential We recognize revenue as the services are provided on a monthly basis. Subscription rates and related charges vary according to the services and features customers receive. Revenue from customers that purchase bundled services at a discounted rate is allocated between the separate services based on the respective stand-alone selling prices. The stand-alone selling prices are determined based on the current prices at which we separately sell the services. Significant judgment is used to determine performance obligations that should be accounted for separately and the allocation of revenue when services are combined in a bundle. Customers are typically billed in advance and pay on a monthly basis. Installation fees are deferred and recognized as revenue over the period of benefit to the customer, which is less than a year. While a portion of our customers are subject to contracts for their services, which are typically 1 to 2 years in length, based on our evaluation of the terms of these contracts, we recognize revenue for these services on a basis that is consistent with our customers that are not subject to contracts. Our services generally involve customer premise equipment, such as set-top boxes, cable modems and wireless gateways. The timing and pattern of recognition for customer premise equipment revenue are consistent with those of our services. We recognize revenue from the sale of wireless handsets at the point of sale. Sales commissions are expensed as incurred, as the related period of benefit is less than a year. We also have arrangements to sell certain DTC streaming services to our customers. We have concluded we are generally the sales agent in these arrangements and we record net commission revenue as earned, which is generally as customers are billed on a monthly basis, within high-speed internet revenues. Under the terms of cable franchise agreements, we are generally required to pay the cable franchising authority an amount based on gross video revenue. We generally pass these and other similar fees through to our customers and classify these fees in the respective Cable Communications services revenue, with the corresponding costs included in other operating and administrative expenses. Business Services Revenue is generated from subscribers to a variety of our products and services which are offered to businesses. Our service offerings for small business locations primarily include high-speed internet services, as well as voice and video services, that are similar to those provided to residential customers, and include certain other features specific to businesses. We also offer Ethernet network services that connect multiple locations and other services to meet the needs of medium-sized customers and larger enterprises, and we provide cellular backhaul services to mobile network operators. We recognize revenue as the services are provided on a monthly basis. Substantially all of our customers are initially under contracts, with terms typically ranging from 2 years for small and medium-sized businesses to up to 5 years for larger enterprises. At any given time, the amount of future revenue to be earned related to fixed pricing under existing agreements is equal to approximately half of our annual business services revenue, of which the substantial majority will be recognized within 2 years. Customers with contracts may only discontinue service in accordance with the terms of their contracts. We receive payments based on a billing schedule established in our contracts, which is typically on a monthly basis. Installation revenue and sales commissions are generally deferred and recognized over the respective contract terms. Advertising Revenue is generated from the sale of advertising and technology, tools and solutions relating to advertising businesses. As part of distribution agreements with cable networks, we generally receive an allocation of scheduled advertising time that we sell to local, regional and national advertisers. In most cases, the available advertising units are sold by our sales force. We also represent the advertising sales efforts of other multichannel video providers in some markets. Since we are acting as the principal in these arrangements, we record the advertising that is sold in advertising revenue and the fees paid to multichannel video providers in other operating and administrative expenses. In some cases, we work with representation firms as an extension of our sales force to sell a portion of the advertising units allocated to us and record the revenue net of agency commissions. In addition, we generate revenue from the sale of advertising on digital platforms. We enter into advertising arrangements with customers and have determined that a contract exists once all terms and conditions are agreed upon, typically when the number of advertising units is specifically identified and the timing of airing is scheduled. Advertisements are generally aired or viewed within one year once all terms and conditions are agreed upon. Revenue from these arrangements is recognized in the period in which advertisements are aired or viewed. Payment terms vary by contract, although terms generally require payment within 30 to 60 days from when advertisements are aired or viewed. In addition, we also provide technology, tools, data-driven services and marketplace solutions to customers in the media industry, which allows advertisers to more effectively engage with their target audiences. Revenue earned in this manner is recognized when services are provided. NBCUniversal Segments Distribution Cable Networks generates revenue from the distribution of our national, regional and international cable network programming to traditional and virtual multichannel video providers. Broadcast Television generates revenue from the fees received under retransmission consent agreements for our NBC and Telemundo owned local broadcast television stations and associated fees received from NBC-affiliated local broadcast television stations. These arrangements are accounted for as licenses of functional intellectual property and revenue is recognized as programming is provided on a monthly basis, generally under multiyear agreements. Monthly fees received under distribution agreements with multichannel video providers are generally based on the number of subscribers. Payment terms and conditions vary by contract type, although terms generally include payment within 60 days. Advertising Cable Networks and Broadcast Television generate revenue from the sale of advertising on our cable and broadcast networks, our owned local broadcast television stations and various digital properties. We enter into advertising arrangements with customers and have determined that a contract exists once all terms and conditions are agreed upon, typically when the number of advertising units is specifically identified and the timing of airing is scheduled. Advertisements are generally aired or viewed within one year once all terms are agreed upon. Revenue is recognized, net of agency commissions, in the period in which advertisements are aired or viewed and payment occurs thereafter, with payment generally required within 30 days. In some instances, we guarantee audience ratings for the advertisements. To the extent there is a shortfall in contracts where the ratings were guaranteed, a portion of the revenue is deferred until the shortfall is settled, typically by providing additional advertising units generally within one year of the original airing. Theatrical Filmed Entertainment generates revenue from the worldwide theatrical release of produced and acquired films for exhibition in movie theaters. Our arrangements with exhibitors generally entitle us to a percentage of ticket sales. We recognize revenue as the films are viewed and exhibited in theaters and payment generally occurs within 30 days after exhibition. Content Licensing Cable Networks’, Broadcast Television’s and Filmed Entertainment’s production studios generate revenue from the licensing of our owned film and television content in the United States and internationally to cable, broadcast and premium networks and to DTC streaming service providers. Our agreements generally include fixed pricing and span multiple years. For example, following a film’s theatrical release, Filmed Entertainment may license the exhibition rights of a film to different customers over multiple successive distribution windows. We recognize revenue when the content is delivered and available for use by the licensee. When the term of an existing agreement is renewed or extended, we recognize revenue at the later of when the content is available or when the renewal or extension period begins. Payment terms and conditions vary by contract type, although payments are generally collected over the license term. The amount of future revenue to be earned related to fixed pricing under existing agreements at any given time equals approximately 1 to 2 years of annual Filmed Entertainment content licensing revenue, which is the segment with the largest portion of this future revenue. The majority of this revenue will be recognized within 2 years. This amount may fluctuate from period to period depending on the timing of the releases and the availability of content under existing agreements and may not represent the total revenue expected to be recognized as it does not include revenue from future agreements or from variable pricing or optional purchases under existing agreements. For our agreements that include variable pricing, such as pricing based on the number of subscribers to a DTC streaming service sold by our customers, we generally recognize revenue as our customers sell to their subscribers. Home Entertainment Filmed Entertainment generates revenue from the sale of our produced and acquired films on DVDs and through digital distribution services. Cable Networks and Broadcast Television also generate revenue from the sale of owned programming on DVDs and through digital distribution services, which is reported in other revenue. We generally recognize revenue from DVD sales, net of estimated returns and customer incentives, on the date that DVDs are delivered to and made available for sale by retailers. Payment terms generally include payment within 60 to 90 days from delivery to the retailer. Theme Parks Theme Parks generates revenue primarily from guest spending at our Universal theme parks in Orlando, Florida; Hollywood, California; and Osaka, Japan. Guest spending includes ticket sales and in-park spending on food, beverages and merchandise. We recognize revenue from ticket sales when the tickets are used, generally within a year from the date of purchase. For annual passes, we generally recognize revenue on a straight-line basis over the period the pass is available to be used. We recognize revenue from in-park spending at the point of sale. Sky Segment Direct-to-Consumer Revenue is generated from subscribers to our video services from both residential and business customers, primarily in the United Kingdom, Italy and Germany. We also provide high-speed internet, voice and wireless phone services in select countries. Generally, all of our residential customers are initially under contracts, with terms typically ranging from rolling monthly to 18 months, depending on the product and territory, and may only discontinue service in accordance with the terms of their contracts. Subscription rates and related charges vary according to the services and features customers receive and the types of equipment they use. Our video, high-speed internet, voice and wireless phone services generally may be purchased individually or in bundles. We recognize revenue from video, high-speed internet, voice and wireless phone services as the services are provided on a monthly basis. At any given time, the amount of future revenue to be earned related to existing agreements is equal to less than half of our annual direct-to-consumer revenue, which generally will be recognized within 18 months. Content Revenue is generated from the distribution of our television channels on third-party platforms and the licensing of owned and acquired programming to third-party video providers. See the NBCUniversal segment discussion of distribution and content licensing revenue above for accounting policies for these types of arrangements. Advertising Revenue is generated from advertising and sponsorships across our owned television channels and where we represent the sales efforts of third-party channels. We also generate revenue from the sale of advertising on digital platforms and various technology, tools and solutions relating to our advertising business. Revenue is recognized when the advertising is aired or viewed. Since we are acting as the principal in the arrangements where we represent the sales efforts of third parties, we record the advertising that is sold in advertising revenue and the fees paid to the third-party channels in other operating and administrative expenses.
Film and Television Costs	Video Distribution Programming Expenses We incur programming expenses related to the license of rights to distribute the third-party programmed channels, platforms and related content included in video services we sell to end consumers. Programming is generally acquired under multiyear distribution agreements, with fees typically based on the number of customers that receive the programming and the extent of distribution. Programming arrangements are accounted for as executory contracts with expenses generally recognized based on the rates in the agreements and the arrangements are not subject to impairment. Film and Television Content We incur costs related to the production of owned content and the license of the rights to use content owned by third parties and sports rights on our owned networks and platforms, which are described as owned and licensed content, respectively. We adopted new accounting guidance related to film and television content in the first quarter of 2020 (see Note 8), and accordingly, amounts presented below for 2020 and the policy discussion reflect the updated accounting guidance, and amounts presented for 2019 reflect the accounting guidance in effect at that time. Under the new accounting guidance, we have determined that the predominant monetization strategy for the substantial majority of our content is on an individual basis. We capitalize costs for owned film and television content, including direct costs, production overhead, print costs, development costs and interest, as well as acquired libraries. Amortization for owned content predominantly monetized on an individual basis and accrued costs associated with participations and residual payments are recorded using the individual film forecast computation method, which recognizes the costs in the same ratio as the associated ultimate revenue. Estimates of ultimate revenue and total costs are based on anticipated release patterns and distribution strategies, public acceptance and historical results for similar productions. Amortization for content predominantly monetized with other owned or licensed content is recorded based on estimated usage. In determining the method of amortization and estimated life of an acquired film or television library, we generally use the method and the life that most closely follow the undiscounted cash flows over the estimated life of the asset. We do not capitalize costs related to the distribution of a film in movie theaters or the licensing or sale of a film or television production, which primarily include costs associated with marketing and distribution. We may enter into cofinancing arrangements with third parties to jointly finance or distribute certain of our film productions. Cofinancing arrangements can take various forms, but in most cases involve the grant of an economic interest in a film to an investor who owns an undivided copyright interest in the film. The number of investors and the terms of these arrangements can vary, although investors generally assume the full risks and rewards for the portion of the film acquired in these arrangements. We account for the proceeds received from the investor under these arrangements as a reduction of our capitalized film costs and the investor’s interest in the profit or loss of the film is recorded as either a charge or a benefit, respectively, in programming and production costs. The investor’s interest in the profit or loss of a film is recorded each period using the individual film forecast computation method.
Entertainment Entities	We capitalize the costs of licensed content when the license period begins, the content is made available for use and the costs of the licenses are known. Licensed content is amortized as the associated programs are broadcast.
Film Costs and Entertainment Entities	Owned and licensed content are presented as noncurrent assets in film and television costs. We present amortization of owned and licensed content and accrued costs associated with participation and residual payments in programming and production costs. When an event or a change in circumstance occurs that was known or knowable as of the balance sheet date and that indicates the fair value of either owned or licensed content is less than the unamortized costs in the balance sheet, we determine the fair value and record an impairment charge to the extent the unamortized costs exceed the fair value. Owned content is assessed either individually or in identified film groups, for content predominantly monetized on an individual basis or with other content, respectively. The substantial majority of our owned content is evaluated for impairment on an individual title basis. Licensed content that is not part of a film group is generally assessed in packages, channels or dayparts. A daypart is an aggregation of programs broadcast during a particular time of day or programs of a similar type. Licensed content is tested for impairment primarily on a channel, network or platform basis, with the exception of our broadcast networks and owned local broadcast television stations, which are tested on a daypart basis. Estimated fair values of owned and licensed content are generally based on Level 3 inputs including analysis of market participant estimates of future cash flows. We record charges related to impairments or content that is substantively abandoned to programming and production costs. Impairments of capitalized film and television costs were not material in any of the periods presented.
Income Taxes	We base our provision for income taxes on our current period income, changes in our deferred income tax assets and liabilities, income tax rates, changes in estimates of our uncertain tax positions, tax planning opportunities available in the jurisdictions in which we operate and excess tax benefits or deficiencies that arise when the tax consequences of share-based compensation differ from amounts previously recognized in the statement of income. We recognize deferred tax assets and liabilities when there are temporary differences between the financial reporting basis and tax basis of our assets and liabilities and for the expected benefits of using net operating loss carryforwards. When a change in the tax rate or tax law has an impact on deferred taxes, we apply the change based on the years in which the temporary differences are expected to reverse. We record the change in our consolidated financial statements in the period of enactment. The determination of the income tax consequences of a business combination includes identifying the tax basis of assets and liabilities acquired and any contingencies associated with uncertain tax positions assumed or resulting from the business combination. Deferred tax assets and liabilities related to temporary differences of an acquired entity are recorded as of the date of the business combination and are based on our estimate of the ultimate tax basis that will be accepted by the various tax authorities. We record liabilities for contingencies associated with prior tax returns filed by the acquired entity based on criteria set forth in the appropriate accounting guidance. We adjust the deferred tax accounts and the liabilities periodically to reflect any revised estimated tax basis and any estimated settlements with the various tax authorities. The effects of these adjustments are recorded to income tax (expense) benefit. From time to time, we engage in transactions in which the tax consequences may be subject to uncertainty. In these cases, we evaluate our tax position using the recognition threshold and the measurement attribute in accordance with the accounting guidance related to uncertain tax positions. Examples of these transactions include business acquisitions and dispositions, including consideration paid or received in connection with these transactions, certain financing transactions, and the allocation of income among state and local tax jurisdictions. Significant judgment is required in assessing and estimating the tax consequences of these transactions. We determine whether it is more likely than not that a tax position will be sustained on examination, including the resolution of any related appeals or litigation processes, based on the technical merits of the position. A tax position that meets the more-likely-than-not recognition threshold is measured to determine the amount of benefit to be recognized in our consolidated financial statements. We classify interest and penalties, if any, associated with our uncertain tax positions as a component of income tax (expense) benefit.
Recent Accounting Pronouncements	Film and Television Content In March 2019, the Financial Accounting Standards Board (“FASB”) updated the accounting guidance related to film and television content. The updated guidance aligned the accounting for production costs of owned episodic television series with those of films, allowing for costs to be capitalized in excess of amounts of revenue contracted for each episode. The guidance also updated certain presentation and disclosure requirements for capitalized film and television content, and when content is predominantly monetized with other owned or licensed content the guidance requires impairment testing for capitalized film and television content to be performed at a film group level and amortization to be based on usage. We adopted the updated guidance on January 1, 2020 on a prospective basis and as a result, prior period amounts were not adjusted. Following the adoption, we now present all capitalized film and television content, including licensed content and sports advances previously classified as current programming rights, as noncurrent film and television costs in the consolidated balance sheet. The adoption of the updated accounting guidance did not have a material impact on our consolidated results of operations or financial position. See Note 4 for further information. Credit Losses In June 2016, the FASB updated the accounting guidance related to the measurement of credit losses on financial instruments, including trade receivables and loans. The updated guidance requires the recognition of credit losses on financial instruments based on an estimate of expected losses, replacing the incurred loss model in the prior guidance. We adopted the updated guidance on January 1, 2020 on a prospective basis, recording $124 million, net of tax, as a cumulative effect adjustment to retained earnings and as a result, prior period amounts were not adjusted. The adoption of the updated accounting guidance did not have a material impact on our consolidated results of operations or financial position for any periods presented.
Investments	Equity Method We use the equity method to account for investments in which we have the ability to exercise significant influence over the investee’s operating and financial policies, or in which we hold a partnership or limited liability company interest in an entity with specific ownership accounts, unless we have virtually no influence over the investee’s operating and financial policies. Equity method investments are recorded at cost and are adjusted to recognize (1) our share, based on percentage ownership or other contractual basis, of the investee’s net income or loss after the date of investment, (2) amortization of the recorded investment that exceeds our share of the book value of the investee’s net assets, (3) additional contributions made and dividends received, and (4) impairments resulting from other-than-temporary declines in fair value. For some investments, we record our share of the investee’s net income or loss one quarter in arrears due to the timing of our receipt of such information. Gains or losses on the sale of equity method investments are recorded to other income (loss), net. If an equity method investee were to issue additional securities that would change our proportionate share of the entity, we would recognize the change, if any, as a gain or loss to other income (loss), net. Marketable Equity Securities We classify investments with readily determinable fair values that are not accounted for under the equity method as marketable equity securities. The changes in fair value of our marketable equity securities between measurement dates are recorded in realized and unrealized gains (losses) on equity securities, net. The fair values of our marketable equity securities are based on Level 1 inputs that use quoted market prices. Nonmarketable Equity Securities We classify investments without readily determinable fair values that are not accounted for under the equity method as nonmarketable equity securities. The accounting guidance requires nonmarketable equity securities to be recorded at cost and adjusted to fair value at each reporting period. However, the guidance allows for a measurement alternative, which is to record the investments at cost, less impairment, if any, and subsequently adjust for observable price changes of identical or similar investments of the same issuer. We apply the measurement alternative, adjusting the investments for observable price changes of identical or similar investments of the same issuer, to a majority of our nonmarketable equity securities. When an observable event occurs, we estimate the fair values of our nonmarketable equity securities primarily based on Level 2 inputs that are derived from observable price changes of similar securities adjusted for insignificant differences in rights and obligations. The changes in value are recorded in realized and unrealized gains (losses) on equity securities, net.
Impairment Testing of Investments	Impairment Testing of Investments We review our investment portfolio, other than our marketable equity securities, each reporting period to determine whether there are identified events or circumstances that would indicate there is a decline in the fair value. For our nonpublic investments, if there are no identified events or circumstances that would have a significant adverse effect on the fair value of the investment, then the fair value is not estimated. For our equity method investments and held to maturity investments, if an investment is deemed to have experienced an other-than-temporary decline below its cost basis, we reduce the carrying amount of the investment to its quoted or estimated fair value, as applicable, and establish a new cost basis for the investment. For our nonmarketable equity securities, we record the impairment to realized and unrealized gains (losses) on equity securities, net. For our equity method investments and our held to maturity investments, we record the impairment to other income (loss), net.
Property and Equipment	Property and equipment are stated at cost. We capitalize improvements that extend asset lives and expense repairs and maintenance costs as incurred. We record depreciation using the straight-line method over the asset’s estimated useful life. For assets that are sold or retired, we remove the applicable cost and accumulated depreciation and, unless the gain or loss on disposition is presented separately, we recognize it as a component of depreciation expense. Capital expenditures for the construction of Universal Beijing Resort are presented separately in our consolidated statement of cash flows. Cable Communications capitalizes the costs associated with the construction of and improvements to our cable transmission and distribution facilities, including scalable infrastructure and line extensions; costs associated with acquiring and deploying new customer premise equipment; and costs associated with installation of our services, including the customer’s connection to our network, in accordance with the accounting guidance related to cable television companies. Costs capitalized include all direct costs for labor and materials, as well as various indirect costs. Costs incurred in connection with subsequent disconnects, and reconnects of previously deployed customer premise equipment, are expensed as they are incurred. We evaluate the recoverability of our property and equipment whenever events or substantive changes in circumstances indicate that the carrying amount may not be recoverable. The evaluation is based on the cash flows generated by the underlying asset groups, including estimated future operating results, trends or other determinants of fair value. If the total of the expected future undiscounted cash flows were less than the carrying amount of the asset group, we would recognize an impairment charge to the extent the carrying amount of the asset group exceeded its estimated fair value. Unless presented separately, the impairment charge is included as a component of depreciation expense.
Goodwill	Goodwill is calculated as the excess of the consideration transferred over the identifiable net assets acquired in a business combination and represents the future economic benefits expected to arise from anticipated synergies and intangible assets acquired that do not qualify for separate recognition, including increased footprint, assembled workforce, noncontractual relationships and other agreements. We assess the recoverability of our goodwill annually, or more frequently whenever events or substantive changes in circumstances indicate that the carrying amount of a reporting unit may exceed its fair value. We test goodwill for impairment at the reporting unit level. To determine our reporting units, we evaluate the components one level below the segment level and we aggregate the components if they have similar economic characteristics. We evaluate the determination of our reporting units used to test for impairment periodically or whenever events or substantive changes in circumstances occur. The assessment of recoverability may first consider qualitative factors to determine whether the existence of events or circumstances leads to a determination that it is more likely than not that the fair value of a reporting unit is less than its carrying amount. A quantitative assessment is performed if the qualitative assessment results in a more-likely-than-not determination or if a qualitative assessment is not performed. The quantitative assessment considers whether the carrying amount of a reporting unit exceeds its fair value, in which case an impairment charge is recorded to the extent the reporting unit’s carrying value exceeds its fair value. Unless presented separately, the impairment charge is included as a component of amortization expense. We have not recognized any material impairment charges.
Indefinite-Lived Intangible Assets	Indefinite-lived intangible assets consist primarily of our cable franchise rights. Our cable franchise rights represent the values we attributed to agreements with state and local authorities that allow access to homes and businesses in cable service areas acquired in business combinations. We do not amortize our cable franchise rights because we have determined that they meet the definition of indefinite-lived intangible assets since there are no legal, regulatory, contractual, competitive, economic or other factors which limit the period over which these rights will contribute to our cash flows. We reassess this determination periodically or whenever events or substantive changes in circumstances occur. The purchase of spectrum rights is presented separately in our consolidated statement of cash flows.
Finite-Lived Intangible Assets	Finite-lived intangible assets are subject to amortization and consist primarily of customer relationships acquired in business combinations, software, trade names and intellectual property rights. Our finite-lived intangible assets are amortized primarily on a straight-line basis over their estimated useful life or the term of the associated agreement. We capitalize direct development costs associated with internal-use software, including external direct costs of material and services and payroll costs for employees devoting time to these software projects. We also capitalize costs associated with the purchase of software licenses. We generally amortize them on a straight-line basis over a period not to exceed five years. We expense maintenance and training costs, as well as costs incurred during the preliminary stage of a project, as they are incurred. We capitalize initial operating system software costs and amortize them over the life of the associated hardware.
Postretirement and Pension Benefits	We sponsor several 401(k) defined contribution retirement plans that allow eligible employees to contribute a portion of their compensation through payroll deductions in accordance with specified plan guidelines. We make contributions to the plans that include matching a percentage of the employees’ contributions up to certain limits.We participate in various multiemployer benefit plans, including pension and postretirement benefit plans, that cover some of our employees and temporary employees who are represented by labor unions. We also participate in other multiemployer benefit plans that provide health and welfare and retirement savings benefits to active and retired participants. If we cease to be obligated to make contributions or were to otherwise withdraw from participation in any of these plans, applicable law would require us to fund our allocable share of the unfunded vested benefits, which is known as a withdrawal liability. In addition, actions taken by other participating employers may lead to adverse changes in the financial condition of one of these plans, which could result in an increase in our withdrawal liability.
Share-Based Compensation	The cost associated with our share-based compensation is based on an award’s estimated fair value at the date of grant and is recognized over the period in which any related services are provided. RSUs are valued based on the closing price of our common stock on the date of grant and are discounted for the lack of dividends, if any, during the vesting period. We use the Black-Scholes option pricing model to estimate the fair value of stock option awards.
Leases	Our leases consist primarily of real estate, vehicles and other equipment. We determine if an arrangement is a lease at inception. Lease assets and liabilities are recognized upon commencement of the lease based on the present value of the future minimum lease payments over the lease term. The lease term includes options to extend the lease when it is reasonably certain that we will exercise that option. We generally utilize our incremental borrowing rate based on information available at the commencement of the lease in determining the present value of future payments. The lease asset also includes any lease payments made and initial direct costs incurred and excludes lease incentives. Lease assets and liabilities are not recorded for leases with an initial term of one year or less. Lease expense for operating leases recorded in the balance sheet is included in operating costs and expenses and is based on the future minimum lease payments recognized on a straight-line basis over the term of the lease plus any variable lease costs. Operating lease expenses, inclusive of short-term and variable lease expenses, recognized in our consolidated statement of income for both the periods ended December 31, 2020 and 2019 was $1.1 billion. These amounts do not include lease costs associated with production activities or other amounts capitalized in our consolidated balance sheet, which are not material.
Earnings Per Share	Weighted-average common shares outstanding used in calculating diluted earnings per common share attributable to Comcast Corporation shareholders (“diluted EPS”) considers the impact of potentially dilutive securities using the treasury stock method. Our potentially dilutive securities include potential common shares related to our stock options and our restricted share units (“RSUs”). Diluted EPS excludes the impact of potential common shares related to our stock options in periods in which the combination of the option exercise price and the associated unrecognized compensation expense is greater than the average market price of our common stock. The amount of potential common shares related to our share-based compensation plans that were excluded from diluted EPS because their effect would have been antidilutive was not material in any of the periods presented.

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2020
Segment Reporting [Abstract]
Financial Data by Business Segment	Our financial data by reportable segment is presented in the tables below. We do not present a measure of total assets for our reportable business segments as this information is not used by management to allocate resources and capital. (in millions) Revenue Adjusted EBITDA (b) Depreciation and Amortization Capital Cash Paid for 2020 Cable Communications $ 60,051 $ 25,270 $ 7,753 $ 6,605 $ 1,333 NBCUniversal Cable Networks 10,849 4,616 771 34 24 Broadcast Television 10,244 1,934 163 82 15 Filmed Entertainment 5,276 785 95 13 17 Theme Parks 1,846 (541) 771 1,171 56 Headquarters and Other 121 (521) 478 185 139 Eliminations (a) (254) (4) — — — NBCUniversal 28,082 6,269 2,278 1,485 251 Sky 18,594 1,954 3,034 959 741 Corporate and Other 366 (2,447) 35 130 130 Eliminations (a) (3,529) (220) — — — Comcast Consolidated $ 103,564 $ 30,826 $ 13,100 $ 9,179 $ 2,455 (in millions) Revenue Adjusted EBITDA (b) Depreciation and Capital Cash Paid for 2019 Cable Communications $ 58,082 $ 23,266 $ 7,994 $ 6,909 $ 1,426 NBCUniversal Cable Networks 11,513 4,444 735 41 17 Broadcast Television 10,261 1,730 157 161 15 Filmed Entertainment 6,493 833 79 21 22 Theme Parks 5,933 2,455 696 1,605 60 Headquarters and Other 83 (689) 462 244 171 Eliminations (a) (316) (1) — — — NBCUniversal 33,967 8,772 2,129 2,072 285 Sky 19,219 3,099 2,699 768 707 Corporate and Other 333 (880) 131 204 57 Eliminations (a) (2,659) 1 — — — Comcast Consolidated $ 108,942 $ 34,258 $ 12,953 $ 9,953 $ 2,475 (in millions) Revenue Adjusted EBITDA (b) Depreciation and Capital Cash Paid for 2018 Cable Communications $ 56,033 $ 21,681 $ 8,262 $ 7,723 $ 1,346 NBCUniversal Cable Networks 11,773 4,428 738 42 23 Broadcast Television 11,439 1,657 146 204 81 Filmed Entertainment 7,152 734 145 35 25 Theme Parks 5,683 2,455 660 1,143 173 Headquarters and Other 63 (680) 419 306 146 Eliminations (a) (349) 4 — — — NBCUniversal 35,761 8,598 2,108 1,730 448 Sky 4,587 692 539 222 137 Corporate and Other 513 (779) 108 99 4 Eliminations (a) (2,387) (27) — — — Comcast Consolidated $ 94,507 $ 30,165 $ 11,017 $ 9,774 $ 1,935 (a) Included in Eliminations are transactions that our segments enter into with one another. Our segments generally report transactions with one another as if they were stand-alone businesses in accordance with GAAP, and these transactions are eliminated in consolidation. When multiple segments enter into transactions to provide products and services to third parties, revenue is generally allocated to our segments based on relative value. The most significant transactions between our segments include distribution revenue at Cable Networks for the sale of programming to Cable Communications; content licensing revenue in our NBCUniversal segments (Broadcast Television, Filmed Entertainment and Cable Networks) for the license of owned content to Peacock and Sky, and for licenses of owned content to other NBCUniversal segments; advertising revenue at Cable Communications, Cable Networks and Broadcast Television; and distribution revenue at Broadcast Television for fees received under retransmission consent agreements from Cable Communications. For segment reporting purposes, we account for intercompany content licenses as follows: • Revenue for licenses of content from NBCUniversal segments to Peacock and Sky are generally recognized at a point in time, consistent with the recognition of transactions with third parties, when the content is delivered and made available for use. The costs of these licenses at Peacock and Sky are recognized as the content is used over the license period. The difference in timing of recognition between segments results in an Adjusted EBITDA impact in eliminations as the profits on these transactions are deferred in our consolidated results and recognized as the content is used over the license period. • Revenue for licenses of content between NBCUniversal segments is recognized over time to correspond with the amortization of the costs of the licensed content as the content is used over the license period. (b) We use Adjusted EBITDA as the measure of profit or loss for our operating segments. From time to time we may report the impact of certain events, gains, losses or other charges related to our operating segments (such as certain costs incurred in response to COVID-19, including severance charges), within Corporate and Other. Our reconciliation of the aggregate amount of Adjusted EBITDA for our reportable segments to consolidated income before income taxes is presented in the table below. Year ended December 31 (in millions) 2020 2019 2018 Adjusted EBITDA $ 30,826 $ 34,258 $ 30,165 Adjustment for legal settlement (177) — (125) Adjustment for Sky transaction-related costs (56) (180) (355) Depreciation (8,320) (8,663) (8,281) Amortization (4,780) (4,290) (2,736) Other operating gains — — 341 Interest expense (4,588) (4,567) (3,542) Investment and other income (loss), net 1,160 438 (225) Income before income taxes $ 14,065 $ 16,996 $ 15,242
Reconciliation of Adjusted EBITDA from Segments to Consolidated	Our reconciliation of the aggregate amount of Adjusted EBITDA for our reportable segments to consolidated income before income taxes is presented in the table below. Year ended December 31 (in millions) 2020 2019 2018 Adjusted EBITDA $ 30,826 $ 34,258 $ 30,165 Adjustment for legal settlement (177) — (125) Adjustment for Sky transaction-related costs (56) (180) (355) Depreciation (8,320) (8,663) (8,281) Amortization (4,780) (4,290) (2,736) Other operating gains — — 341 Interest expense (4,588) (4,567) (3,542) Investment and other income (loss), net 1,160 438 (225) Income before income taxes $ 14,065 $ 16,996 $ 15,242

Revenue (Tables)

Revenue (Tables)	12 Months Ended
	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Disaggregation of revenue	Year ended December 31 (in millions) 2020 2019 2018 Residential: High-speed internet $ 20,599 $ 18,752 $ 17,144 Video 21,937 22,270 22,455 Voice 3,532 3,879 3,960 Wireless 1,574 1,167 890 Business services 8,191 7,795 7,129 Advertising 2,594 2,465 2,795 Other 1,624 1,754 1,660 Total Cable Communications 60,051 58,082 56,033 Distribution 6,437 6,790 6,826 Advertising 3,155 3,478 3,587 Content licensing and other 1,257 1,245 1,360 Total Cable Networks 10,849 11,513 11,773 Advertising 5,027 5,712 7,010 Content licensing 2,640 2,157 2,182 Distribution and other 2,577 2,392 2,247 Total Broadcast Television 10,244 10,261 11,439 Theatrical 421 1,469 2,111 Content licensing 3,342 3,045 2,899 Home entertainment 944 957 1,048 Other 569 1,022 1,094 Total Filmed Entertainment 5,276 6,493 7,152 Total Theme Parks 1,846 5,933 5,683 Headquarters and Other 121 83 63 Eliminations (a) (254) (316) (349) Total NBCUniversal 28,082 33,967 35,761 Direct-to-consumer 15,223 15,538 3,632 Content 1,373 1,432 304 Advertising 1,998 2,249 651 Total Sky 18,594 19,219 4,587 Corporate and Other 366 333 513 Eliminations (a) (3,529) (2,659) (2,387) Total revenue $ 103,564 $ 108,942 $ 94,507 (a) Included in Eliminations are transactions that our segments enter into with one another. See Note 2 for a description of these transactions. We operate primarily in the United States but also in select international markets. The table below summarizes revenue by geographic location. Year ended December 31 (in millions) 2020 2019 2018 United States $ 80,327 $ 82,952 $ 82,233 Europe 20,460 21,553 7,721 Other 2,777 4,437 4,553 Total revenue $ 103,564 $ 108,942 $ 94,507
Schedule of receivables, net	The following table summarizes our accounts receivable: December 31 (in millions) 2020 2019 Receivables, gross $ 12,273 $ 11,711 Less: Allowance for doubtful accounts 807 419 Receivables, net $ 11,466 $ 11,292
Changes in the allowance for doubtful accounts	The following table presents changes in our allowance for doubtful accounts: (in millions) Beginning Balance Additions Charged to Costs and Expenses and Other Accounts Deductions from Reserves Ending Balance 2020 $ 419 $ 912 $ 524 $ 807 2019 $ 352 $ 769 $ 702 $ 419 2018 $ 288 $ 616 $ 552 $ 352
Other balance sheet accounts	The following table summarizes our other balances that are not separately presented in our consolidated balance sheet that relate to the recognition of revenue and collection of the related cash, as well as the deferred costs associated with our contracts with customers: December 31 (in millions) 2020 2019 Noncurrent receivables, net (included in other noncurrent assets, net) $ 1,091 $ 1,337 Contract acquisition and fulfillment costs (included in other noncurrent assets, net) $ 1,060 $ 1,083 Noncurrent deferred revenue (included in other noncurrent liabilities) $ 750 $ 618

Programming and Production Co_2

Programming and Production Costs (Tables)	12 Months Ended
	Dec. 31, 2020
Other Industries [Abstract]
Programming and Production Expense	Year ended December 31 (in millions) 2020 Video distribution programming $ 12,684 Film and television content: Owned (a) 7,973 Licensed, including sports rights 11,264 Other 1,200 Total programming and production costs $ 33,121 (a) Amount includes amortization of owned content of $6.6 billion as well as participations and residuals expense.
Capitalized Film and Television Costs and Programming Rights	Capitalized Film and Television Costs 2020 2019 December 31 (in millions) Film and Television Costs Film Costs Television Costs Total Owned: Released, less amortization $ 3,815 $ 1,551 $ 2,810 $ 4,361 Completed, not released 139 187 — 187 In production and in development 2,755 1,314 1,162 2,476 6,709 3,052 3,972 7,024 Licensed, including sports advances 6,631 5,786 13,340 12,810 Less: Current portion of licensed programming rights — 3,877 Film and television costs $ 13,340 $ 8,933
Estimated Future Amortization Expense for Capitalized Film and Television Costs and Programming Rights	The table below summarizes estimated future amortization expense for the capitalized film and television costs recorded in our consolidated balance sheet as of December 31, 2020. (in millions) Owned Licensed Completed, not released: 2021 $ 69 Released and licensed content: 2021 $ 1,445 $ 4,722 2022 $ 543 $ 820 2023 $ 336 $ 470

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Schedule of income before income taxes	Income Before Income Taxes Year ended December 31 (in millions) 2020 2019 2018 Domestic $ 16,211 $ 16,646 $ 14,387 Foreign (2,146) 350 855 $ 14,065 $ 16,996 $ 15,242
Schedule for the components of income tax expense	Components of Income Tax (Expense) Benefit Year ended December 31 (in millions) 2020 2019 2018 Current (Expense) Benefit: Federal $ (2,824) $ (2,085) $ (2,026) State (836) (425) (639) Foreign (254) (600) (425) (3,914) (3,110) (3,090) Deferred (Expense) Benefit: Federal 111 (902) (546) State 71 15 167 Foreign 368 324 89 550 (563) (290) Income tax (expense) benefit $ (3,364) $ (3,673) $ (3,380)
Schedule of items that effect income tax expense	Our income tax (expense) benefit differs from the federal statutory amount because of the effect of the items detailed in the table below. Year ended December 31 (in millions) 2020 2019 2018 Federal tax at statutory rate $ (2,954) $ (3,569) $ (3,201) State income taxes, net of federal benefit (265) (306) (212) Foreign income taxed at different rates (24) (126) (147) Adjustments to uncertain and effectively settled tax positions, net (344) (3) (144) Federal research and development credits 164 124 22 Excess tax benefits recognized on share-based compensation 150 196 75 Other (91) 11 227 Income tax (expense) benefit $ (3,364) $ (3,673) $ (3,380)
Schedule of the components of net deferred tax liability	Components of Net Deferred Tax Liability December 31 (in millions) 2020 2019 Deferred Tax Assets: Net operating loss and other loss carryforwards $ 2,609 $ 2,017 Nondeductible accruals and other 3,253 2,779 Less: Valuation allowance 2,312 1,906 3,550 2,890 Deferred Tax Liabilities: Differences between book and tax basis of property and equipment and intangible assets 29,829 29,387 Differences between book and tax basis of investments 405 702 Differences between book and tax basis of long-term debt 680 751 Differences between book and tax basis of foreign subsidiaries and undistributed foreign earnings 468 143 31,382 30,983 Net deferred tax liability $ 27,832 $ 28,093
Schedule of changes in the valuation allowance for deferred tax assets	The following table presents changes in our valuation allowance for deferred tax assets: (in millions) Beginning Balance Additions Charged to Income Tax Expense and Other Accounts Deductions from Reserves Ending Balance 2020 $ 1,906 $ 430 $ 24 $ 2,312 2019 $ 632 $ 1,403 $ 129 $ 1,906 2018 $ 377 $ 367 $ 112 $ 632
Reconciliation of unrecognized tax benefits	Reconciliation of Unrecognized Tax Benefits (in millions) 2020 2019 2018 Gross unrecognized tax benefits, January 1 $ 1,422 $ 1,543 $ 1,497 Additions based on tax positions related to the current year 436 230 229 Additions based on tax positions related to prior years 152 133 125 Additions from acquired subsidiaries — 1 130 Reductions for tax positions of prior years (31) (344) (346) Reductions due to expiration of statutes of limitations (76) (117) (75) Settlements with tax authorities (24) (24) (17) Gross unrecognized tax benefits, December 31 $ 1,879 $ 1,422 $ 1,543

Long-Term Debt (Tables)

Long-Term Debt (Tables)	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Schedule of Long-Term Debt	Long-Term Debt Outstanding December 31 (in millions) Weighted-Average Weighted-Average Interest Rate as of December 31, 2019 2020 (b) 2019 (b) Term loans 2.07 % 1.87 % 7,641 8,078 Senior notes with maturities of 5 years or less, at face value 3.41 % 3.29 % 19,190 26,378 Senior notes with maturities between 5 and 10 years, at face value 3.47 % 3.74 % 23,114 21,683 Senior notes with maturities greater than 10 years, at face value 4.03 % 4.54 % 54,203 46,653 Other, including finance lease obligations 1,261 1,098 Debt issuance costs, premiums, discounts, fair value adjustments for acquisition accounting and hedged positions, net (a) (1,649) (1,673) Total debt 3.60 % (a) 3.78 % (a) 103,760 102,217 Less: Current portion 3,146 4,452 Long-term debt $ 100,614 $ 97,765 (a) Includes the effects of our derivative financial instruments. (b) As of December 31, 2020, included in our outstanding debt were foreign currency denominated borrowings with principal amounts of £4.7 billion, €7.3 billion, ¥238.5 billion and ¥16.4 billion RMB. As of December 31, 2019, included in our outstanding debt were foreign currency denominated borrowings with principal amounts of £4.9 billion, €4.9 billion, ¥267 billion and ¥9 billion RMB.
Debt Maturities	Principal Maturities of Debt (in millions) 2021 $ 3,133 2022 $ 4,028 2023 $ 3,925 2024 $ 6,746 2025 $ 6,953 Thereafter $ 80,624

Significant Transactions (Table

Significant Transactions (Tables)	12 Months Ended
	Dec. 31, 2020
Business Combinations [Abstract]
Amounts Related to Expenses Included in Consolidated Statement of Operations	The amounts below do not reflect the costs of any integration activities or costs related to synergies that may be achieved as a result of the acquisition. (in millions) Year ended December 31, 2018 Other operating and administrative expenses $ 339 Interest expense $ 63
Unaudited Pro Forma Information	The following unaudited pro forma information has been presented as if the Sky transaction occurred on January 1, 2017. This information is based on historical results of operations, adjusted for allocation of purchase price and other acquisition accounting adjustments, and is not necessarily indicative of what the results would have been had we operated the business since January 1, 2017. For pro forma purposes, 2018 earnings were adjusted to exclude acquisition-related costs noted above. No pro forma adjustments have been made for cost savings or synergies that have been or may be achieved by the combined businesses. The years ended December 31, 2020 and 2019 are not presented as Sky is included in the consolidated results for those periods. Year ended December 31 (in millions, except per share data) 2018 Revenue $ 109,518 Net income attributable to Comcast Corporation $ 12,176 Basic earnings per common share attributable to Comcast Corporation shareholders $ 2.66 Diluted earnings per common share attributable to Comcast Corporation shareholders $ 2.62

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2020
Investments [Abstract]
Investment and Other Income (Loss), Net	Investment and Other Income (Loss), Net Year ended December 31 (in millions) 2020 2019 2018 Equity in net income (losses) of investees, net $ (113) $ (505) $ (364) Realized and unrealized gains (losses) on equity securities, net 1,014 656 (187) Other income (loss), net 259 287 326 Investment and other income (loss), net $ 1,160 $ 438 $ (225)
Investment Summary	Investments December 31 (in millions) 2020 2019 Equity method $ 6,006 $ 5,347 Marketable equity securities 460 353 Nonmarketable equity securities 1,950 1,896 Other investments 143 1,796 Total investments 8,559 9,392 Less: Current investments 292 1,709 Less: Investment securing collateralized obligation 447 694 Noncurrent investments $ 7,820 $ 6,989

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Property and Equipment	December 31 (in millions) Weighted-Average 2020 2019 Distribution systems 11 years $ 40,861 $ 40,639 Customer premise equipment 6 years 26,323 26,065 Buildings, theme park infrastructure and leasehold improvements 31 years 15,885 15,104 Other equipment 9 years 14,371 13,025 Construction in process N/A 7,095 5,245 Land N/A 1,848 1,483 Property and equipment, at cost 106,383 101,561 Less: Accumulated depreciation 54,388 53,239 Property and equipment, net $ 51,995 $ 48,322

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill	Goodwill NBCUniversal (in millions) Cable Cable Broadcast Filmed Theme Sky Corporate Total Balance, December 31, 2018 $ 12,784 $ 13,407 $ 843 $ 3,184 $ 6,684 $ 29,250 $ 2 $ 66,154 Acquisitions 86 162 14 — — 17 — 279 Dispositions — — — — — (12) — (12) Adjustments (a) 2,166 490 199 138 — (1,616) 2 1,379 Foreign currency translation 38 8 3 (1) 55 822 — 925 Balance, December 31, 2019 15,074 14,067 1,059 3,321 6,739 28,461 4 68,725 Acquisitions 122 — — 27 — — — 149 Dispositions — — — — — — (4) (4) Adjustments (5) (85) — — — (8) 2 (96) Foreign currency translation 73 12 3 (4) 314 1,497 — 1,895 Balance, December 31, 2020 $ 15,264 $ 13,994 $ 1,062 $ 3,344 $ 7,053 $ 29,950 $ 2 $ 70,669 (a) Adjustments in 2019 primarily included 1) measurement period adjustments resulting from finalization of acquisition accounting for Sky and 2) the final assignment of goodwill resulting from the Sky transaction to our reporting units.
Summary of Intangible Assets	Intangible Assets 2020 2019 December 31 (in millions) Weighted-Average Gross Carrying Amount Accumulated Amortization Gross Carrying Amount Accumulated Amortization Indefinite-Lived Intangible Assets: Franchise rights N/A $ 59,365 $ 59,365 Trade names N/A — 8,809 FCC licenses N/A 2,804 2,337 Finite-Lived Intangible Assets: Customer relationships 14 years 22,197 $ (8,914) 22,884 $ (8,295) Software 5 years 17,819 (9,518) 15,357 (7,287) Other agreements and rights 28 years 12,394 (1,393) 3,958 (1,635) Total $ 114,579 $ (19,825) $ 112,710 $ (17,217)
Amortization of Intangible Assets	Estimated Amortization Expense of Finite-Lived Intangible Assets (in millions) 2021 $ 4,589 2022 $ 4,087 2023 $ 3,472 2024 $ 2,774 2025 $ 2,412

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2020
Retirement Benefits [Abstract]
Deferred Compensation Plans	Year ended December 31 (in millions) 2020 2019 2018 Benefit obligation $ 3,648 $ 3,273 $ 2,885 Interest expense $ 293 $ 285 $ 222

Equity (Tables)

Equity (Tables)	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Schedule of common stock outstanding	Shares of Common Stock Outstanding (in millions) Class A Class B Balance, December 31, 2017 4,635 9 Stock compensation plans 15 — Repurchases and retirements of common stock (140) — Employee stock purchase plans 7 — Balance, December 31, 2018 4,517 9 Stock compensation plans 21 — Employee stock purchase plans 6 — Balance, December 31, 2019 4,544 9 Stock compensation plans 20 — Employee stock purchase plans 7 — Balance, December 31, 2020 4,571 9
Schedule of weighted average common shares outstanding	Weighted-Average Common Shares Outstanding Year ended December 31 (in millions) 2020 2019 2018 Weighted-average number of common shares outstanding – basic 4,574 4,548 4,584 Effect of dilutive securities 50 62 56 Weighted-average number of common shares outstanding – diluted 4,624 4,610 4,640
Schedule of accumulated other comprehensive income (loss)	Accumulated Other Comprehensive Income (Loss) December 31 (in millions) 2020 2019 Cumulative translation adjustments $ 1,790 $ 637 Deferred gains (losses) on cash flow hedges (109) 139 Unrecognized gains (losses) on employee benefit obligations and other 203 271 Accumulated other comprehensive income (loss), net of deferred taxes $ 1,884 $ 1,047

Share-Based Compensation (Table

Share-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Schedule of recognized share-based compensation expense	The tables below provide information on our share-based compensation. Recognized Share-Based Compensation Expense Year ended December 31 (in millions) 2020 2019 2018 Restricted share units $ 628 $ 564 $ 402 Stock options 294 231 205 Employee stock purchase plans 38 30 32 Total $ 960 $ 825 $ 639
Schedule of stock option and restricted share units activity	Stock Options and Restricted Share Units As of December 31, 2020, unless otherwise stated (in millions, except per share data) Stock RSUs Awards granted during 2020 61 18 Weighted-average exercise price of awards granted during 2020 $ 42.42 Stock options outstanding and nonvested RSUs 210 49 Weighted-average exercise price of stock options outstanding $ 35.94 Weighted-average fair value at grant date of nonvested RSUs $ 38.87
Schedule of stock option and restricted share units fair value and significant assumptions	The table below presents the weighted-average fair value on the date of grant of RSUs and stock options awarded under our various plans and the related weighted-average valuation assumptions. Year ended December 31 2020 2019 2018 RSUs fair value $ 41.71 $ 40.42 $ 35.56 Stock options fair value $ 6.61 $ 7.91 $ 7.14 Stock Option Valuation Assumptions: Dividend yield 2.2 % 2.1 % 2.1 % Expected volatility 21.0 % 22.0 % 22.0 % Risk-free interest rate 1.0 % 2.5 % 2.7 % Expected option life (in years) 6.0 6.0 6.0

Supplemental Financial Inform_2

Supplemental Financial Information (Tables)	12 Months Ended
	Dec. 31, 2020
Supplemental Financial Information [Abstract]
Schedule of cash payments for interest and income taxes	Cash Payments for Interest and Income Taxes Year ended December 31 (in millions) 2020 2019 2018 Interest $ 3,878 $ 4,254 $ 2,897 Income taxes $ 3,183 $ 3,231 $ 2,355
Schedule of cash, cash equivalents and restricted cash	The following table provides a reconciliation of cash, cash equivalents and restricted cash reported in the consolidated balance sheet to the total of the amounts reported in our consolidated statement of cash flows. December 31 (in millions) 2020 2019 Cash and cash equivalents $ 11,740 $ 5,500 Restricted cash included in other current assets 14 42 Restricted cash included in other noncurrent assets, net 14 47 Cash, cash equivalents and restricted cash, end of year $ 11,768 $ 5,589

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Summary of operating lease assets and liabilities	The table below summarizes the operating lease assets and liabilities recorded in our consolidated balance sheet. Consolidated Balance Sheet (in millions) December 31, December 31, Other noncurrent assets, net $ 3,784 $ 4,038 Accrued expenses and other current liabilities $ 718 $ 715 Other noncurrent liabilities $ 3,740 $ 3,891
Summary of future minimum rental commitments for operating leases under the new guidance	The table below summarizes our future minimum lease commitments for operating leases as of December 31, 2020. (in millions) December 31, 2021 $ 873 2022 778 2023 683 2024 560 2025 444 Thereafter 2,043 Total future minimum lease payments 5,381 Less: imputed interest 923 Total liability $ 4,458

Quarterly Financial Informati_2

Quarterly Financial Information (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2020
Quarterly Financial Information Disclosure [Abstract]
Schedule of quarterly financial information	(in millions, except per share data) First Second Third Fourth Total 2020 Revenue $ 26,609 $ 23,715 $ 25,532 $ 27,708 $ 103,564 Operating income $ 4,852 $ 4,647 $ 4,076 $ 3,918 $ 17,493 Net income attributable to Comcast Corporation $ 2,147 $ 2,988 $ 2,019 $ 3,380 $ 10,534 Basic earnings per common share attributable to Comcast Corporation shareholders $ 0.47 $ 0.65 $ 0.44 $ 0.74 $ 2.30 Diluted earnings per common share attributable to Comcast Corporation shareholders $ 0.46 $ 0.65 $ 0.44 $ 0.73 $ 2.28 Dividends declared per common share $ 0.23 $ 0.23 $ 0.23 $ 0.23 $ 0.92 2019 Revenue $ 26,859 $ 26,858 $ 26,827 $ 28,398 $ 108,942 Operating income $ 5,182 $ 5,356 $ 5,340 $ 5,247 $ 21,125 Net income attributable to Comcast Corporation $ 3,553 $ 3,125 $ 3,217 $ 3,162 $ 13,057 Basic earnings per common share attributable to Comcast Corporation shareholders $ 0.78 $ 0.69 $ 0.71 $ 0.69 $ 2.87 Diluted earnings per common share attributable to Comcast Corporation shareholders $ 0.77 $ 0.68 $ 0.70 $ 0.68 $ 2.83 Dividends declared per common share $ 0.21 $ 0.21 $ 0.21 $ 0.21 $ 0.84 Minor differences may exist due to rounding.

Segment Information (Narrative)

Segment Information (Narrative) (Details) - Operating Segments [Member]	12 Months Ended
	Dec. 31, 2020segmentbusiness
Segment Reporting Information [Line Items]
Number of primary businesses \| business	3
Cable Communications [Member]
Segment Reporting Information [Line Items]
Number of reportable segments	1
NBCUniversal Segments [Member]
Segment Reporting Information [Line Items]
Number of reportable segments	4
Sky Limited [Member]
Segment Reporting Information [Line Items]
Number of reportable segments	1

Segment Information (Details)

Segment Information (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Financial Data by Business Segment
Revenue	$ 27,708	$ 25,532	$ 23,715	$ 26,609	$ 28,398	$ 26,827	$ 26,858	$ 26,859	$ 103,564	$ 108,942	$ 94,507
Adjusted EBITDA									30,826	34,258	30,165
Depreciation and Amortization									13,100	12,953	11,017
Capital Expenditures									9,179	9,953	9,774
Cash Paid for Intangible Assets									2,455	2,475	1,935
Operating Segments [Member] \| Cable Communications [Member]
Financial Data by Business Segment
Revenue									60,051	58,082	56,033
Adjusted EBITDA									25,270	23,266	21,681
Depreciation and Amortization									7,753	7,994	8,262
Capital Expenditures									6,605	6,909	7,723
Cash Paid for Intangible Assets									1,333	1,426	1,346
Operating Segments [Member] \| NBCUniversal Segments [Member]
Financial Data by Business Segment
Revenue									28,082	33,967	35,761
Adjusted EBITDA									6,269	8,772	8,598
Depreciation and Amortization									2,278	2,129	2,108
Capital Expenditures									1,485	2,072	1,730
Cash Paid for Intangible Assets									251	285	448
Operating Segments [Member] \| Cable Networks [Member]
Financial Data by Business Segment
Revenue									10,849	11,513	11,773
Adjusted EBITDA									4,616	4,444	4,428
Depreciation and Amortization									771	735	738
Capital Expenditures									34	41	42
Cash Paid for Intangible Assets									24	17	23
Operating Segments [Member] \| Broadcast Television [Member]
Financial Data by Business Segment
Revenue									10,244	10,261	11,439
Adjusted EBITDA									1,934	1,730	1,657
Depreciation and Amortization									163	157	146
Capital Expenditures									82	161	204
Cash Paid for Intangible Assets									15	15	81
Operating Segments [Member] \| Filmed Entertainment [Member]
Financial Data by Business Segment
Revenue									5,276	6,493	7,152
Adjusted EBITDA									785	833	734
Depreciation and Amortization									95	79	145
Capital Expenditures									13	21	35
Cash Paid for Intangible Assets									17	22	25
Operating Segments [Member] \| Theme Parks [Member]
Financial Data by Business Segment
Revenue									1,846	5,933	5,683
Adjusted EBITDA									(541)	2,455	2,455
Depreciation and Amortization									771	696	660
Capital Expenditures									1,171	1,605	1,143
Cash Paid for Intangible Assets									56	60	173
Operating Segments [Member] \| Headquarters And Other [Member]
Financial Data by Business Segment
Revenue									121	83	63
Adjusted EBITDA									(521)	(689)	(680)
Depreciation and Amortization									478	462	419
Capital Expenditures									185	244	306
Cash Paid for Intangible Assets									139	171	146
Operating Segments [Member] \| Sky Limited [Member]
Financial Data by Business Segment
Revenue									18,594	19,219	4,587
Adjusted EBITDA									1,954	3,099	692
Depreciation and Amortization									3,034	2,699	539
Capital Expenditures									959	768	222
Cash Paid for Intangible Assets									741	707	137
Operating Segments [Member] \| Corporate and Other [Member]
Financial Data by Business Segment
Revenue									366	333	513
Adjusted EBITDA									(2,447)	(880)	(779)
Depreciation and Amortization									35	131	108
Capital Expenditures									130	204	99
Cash Paid for Intangible Assets									130	57	4
Intersegment Eliminations [Member]
Financial Data by Business Segment
Revenue									(3,529)	(2,659)	(2,387)
Adjusted EBITDA									(220)	1	(27)
Depreciation and Amortization									0	0	0
Capital Expenditures									0	0	0
Cash Paid for Intangible Assets									0	0	0
Intersegment Eliminations [Member] \| NBCUniversal Segments [Member]
Financial Data by Business Segment
Revenue									(254)	(316)	(349)
Adjusted EBITDA									(4)	(1)	4
Depreciation and Amortization									0	0	0
Capital Expenditures									0	0	0
Cash Paid for Intangible Assets									$ 0	$ 0	$ 0

Segment Information (Reconcilia

Segment Information (Reconciliation of Adjusted EBITDA from Segment to Consolidated Statements) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting [Abstract]
Adjusted EBITDA	$ 30,826	$ 34,258	$ 30,165
Adjustment for legal settlement	(177)	0	(125)
Adjustment for Sky transaction-related costs	(56)	(180)	(355)
Depreciation	(8,320)	(8,663)	(8,281)
Amortization	(4,780)	(4,290)	(2,736)
Other operating gains	0	0	341
Interest expense	(4,588)	(4,567)	(3,542)
Investment and other income (loss), net	1,160	438	(225)
Income before income taxes	$ 14,065	$ 16,996	$ 15,242

Revenue (Details)

Revenue (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Revenue	$ 27,708	$ 25,532	$ 23,715	$ 26,609	$ 28,398	$ 26,827	$ 26,858	$ 26,859	$ 103,564	$ 108,942	$ 94,507
Operating Segments [Member] \| Cable Communications [Member]
Disaggregation of Revenue [Line Items]
Revenue									60,051	58,082	56,033
Operating Segments [Member] \| Cable Communications [Member] \| Residential, High-Speed Internet [Member]
Disaggregation of Revenue [Line Items]
Revenue									20,599	18,752	17,144
Operating Segments [Member] \| Cable Communications [Member] \| Residential, Video [Member]
Disaggregation of Revenue [Line Items]
Revenue									21,937	22,270	22,455
Operating Segments [Member] \| Cable Communications [Member] \| Residential, Voice [Member]
Disaggregation of Revenue [Line Items]
Revenue									3,532	3,879	3,960
Operating Segments [Member] \| Cable Communications [Member] \| Residential, Wireless [Member]
Disaggregation of Revenue [Line Items]
Revenue									1,574	1,167	890
Operating Segments [Member] \| Cable Communications [Member] \| Business Services [Member]
Disaggregation of Revenue [Line Items]
Revenue									8,191	7,795	7,129
Operating Segments [Member] \| Cable Communications [Member] \| Other [Member]
Disaggregation of Revenue [Line Items]
Revenue									1,624	1,754	1,660
Operating Segments [Member] \| Cable Communications [Member] \| Advertising [Member]
Disaggregation of Revenue [Line Items]
Revenue									2,594	2,465	2,795
Operating Segments [Member] \| Cable Networks [Member]
Disaggregation of Revenue [Line Items]
Revenue									10,849	11,513	11,773
Operating Segments [Member] \| Cable Networks [Member] \| Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenue									6,437	6,790	6,826
Operating Segments [Member] \| Cable Networks [Member] \| Advertising [Member]
Disaggregation of Revenue [Line Items]
Revenue									3,155	3,478	3,587
Operating Segments [Member] \| Cable Networks [Member] \| Content Licensing And Other [Member]
Disaggregation of Revenue [Line Items]
Revenue									1,257	1,245	1,360
Operating Segments [Member] \| Broadcast Television [Member]
Disaggregation of Revenue [Line Items]
Revenue									10,244	10,261	11,439
Operating Segments [Member] \| Broadcast Television [Member] \| Advertising [Member]
Disaggregation of Revenue [Line Items]
Revenue									5,027	5,712	7,010
Operating Segments [Member] \| Broadcast Television [Member] \| Content Licensing [Member]
Disaggregation of Revenue [Line Items]
Revenue									2,640	2,157	2,182
Operating Segments [Member] \| Broadcast Television [Member] \| Distribution And Other [Member]
Disaggregation of Revenue [Line Items]
Revenue									2,577	2,392	2,247
Operating Segments [Member] \| Filmed Entertainment [Member]
Disaggregation of Revenue [Line Items]
Revenue									5,276	6,493	7,152
Operating Segments [Member] \| Filmed Entertainment [Member] \| Other [Member]
Disaggregation of Revenue [Line Items]
Revenue									569	1,022	1,094
Operating Segments [Member] \| Filmed Entertainment [Member] \| Theatrical [Member]
Disaggregation of Revenue [Line Items]
Revenue									421	1,469	2,111
Operating Segments [Member] \| Filmed Entertainment [Member] \| Content Licensing [Member]
Disaggregation of Revenue [Line Items]
Revenue									3,342	3,045	2,899
Operating Segments [Member] \| Filmed Entertainment [Member] \| Home Entertainment [Member]
Disaggregation of Revenue [Line Items]
Revenue									944	957	1,048
Operating Segments [Member] \| NBCUniversal Segments [Member]
Disaggregation of Revenue [Line Items]
Revenue									28,082	33,967	35,761
Operating Segments [Member] \| Theme Parks [Member]
Disaggregation of Revenue [Line Items]
Revenue									1,846	5,933	5,683
Operating Segments [Member] \| Headquarters And Other [Member]
Disaggregation of Revenue [Line Items]
Revenue									121	83	63
Operating Segments [Member] \| Sky Limited [Member]
Disaggregation of Revenue [Line Items]
Revenue									18,594	19,219	4,587
Operating Segments [Member] \| Sky Limited [Member] \| Direct To Consumer [Member]
Disaggregation of Revenue [Line Items]
Revenue									15,223	15,538	3,632
Operating Segments [Member] \| Sky Limited [Member] \| Content [Member]
Disaggregation of Revenue [Line Items]
Revenue									1,373	1,432	304
Operating Segments [Member] \| Sky Limited [Member] \| Advertising [Member]
Disaggregation of Revenue [Line Items]
Revenue									1,998	2,249	651
Operating Segments [Member] \| Corporate and Other [Member]
Disaggregation of Revenue [Line Items]
Revenue									366	333	513
Intersegment Eliminations [Member]
Disaggregation of Revenue [Line Items]
Revenue									(3,529)	(2,659)	(2,387)
Intersegment Eliminations [Member] \| NBCUniversal Segments [Member]
Disaggregation of Revenue [Line Items]
Revenue									$ (254)	$ (316)	$ (349)

Revenue (Revenue by Geographic

Revenue (Revenue by Geographic Location) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Revenue	$ 27,708	$ 25,532	$ 23,715	$ 26,609	$ 28,398	$ 26,827	$ 26,858	$ 26,859	$ 103,564	$ 108,942	$ 94,507
United States [Member]
Disaggregation of Revenue [Line Items]
Revenue									80,327	82,952	82,233
Europe [Member]
Disaggregation of Revenue [Line Items]
Revenue									20,460	21,553	7,721
Other [Member]
Disaggregation of Revenue [Line Items]
Revenue									$ 2,777	$ 4,437	$ 4,553

Revenue (Narrative) (Details)

Revenue (Narrative) (Details)	12 Months Ended
	Dec. 31, 2020
Cable Communications [Member] \| Residential [Member] \| Minimum [Member]
Revenue [Line Items]
Term of contract	1 year
Cable Communications [Member] \| Residential [Member] \| Maximum [Member]
Revenue [Line Items]
Term of contract	2 years
Cable Communications [Member] \| Business Services [Member]
Revenue [Line Items]
Annual revenue that estimates remaining performance obligations	6 months
Cable Communications [Member] \| Business Services [Member] \| Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue [Line Items]
Timing period of recognition	2 years
Cable Communications [Member] \| Business Services [Member] \| Minimum [Member]
Revenue [Line Items]
Term of contract	2 years
Cable Communications [Member] \| Business Services [Member] \| Maximum [Member]
Revenue [Line Items]
Term of contract	5 years
Cable Communications [Member] \| Advertising [Member] \| Minimum [Member]
Revenue [Line Items]
Expected payment terms	30 days
Cable Communications [Member] \| Advertising [Member] \| Maximum [Member]
Revenue [Line Items]
Expected payment terms	60 days
Cable Networks [Member] \| Advertising [Member]
Revenue [Line Items]
Expected payment terms	30 days
Cable Networks [Member] \| Distribution [Member]
Revenue [Line Items]
Expected payment terms	60 days
Broadcast Television [Member] \| Advertising [Member]
Revenue [Line Items]
Expected payment terms	30 days
Broadcast Television [Member] \| Distribution [Member]
Revenue [Line Items]
Expected payment terms	60 days
Filmed Entertainment [Member] \| Theatrical [Member]
Revenue [Line Items]
Expected payment terms	30 days
Filmed Entertainment [Member] \| Content Licensing [Member] \| Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue [Line Items]
Timing period of recognition	2 years
Filmed Entertainment [Member] \| Content Licensing [Member] \| Minimum [Member]
Revenue [Line Items]
Annual revenue that estimates remaining performance obligations	1 year
Filmed Entertainment [Member] \| Content Licensing [Member] \| Maximum [Member]
Revenue [Line Items]
Annual revenue that estimates remaining performance obligations	2 years
Filmed Entertainment [Member] \| Home Entertainment [Member] \| Minimum [Member]
Revenue [Line Items]
Expected payment terms	60 days
Filmed Entertainment [Member] \| Home Entertainment [Member] \| Maximum [Member]
Revenue [Line Items]
Expected payment terms	90 days
Sky Limited [Member] \| Direct To Consumer [Member]
Revenue [Line Items]
Term of contract	18 months
Sky Limited [Member] \| Direct To Consumer [Member] \| Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue [Line Items]
Timing period of recognition	18 months

Revenue (Condensed Consolidated

Revenue (Condensed Consolidated Balance Sheet) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Receivables, gross	$ 12,273	$ 11,711
Less: Allowance for doubtful accounts	807	419
Receivables, net	11,466	11,292
Noncurrent receivables, net (included in other noncurrent assets, net)	1,091	1,337
Contract acquisition and fulfillment costs (included in other noncurrent assets, net)	1,060	1,083
Noncurrent deferred revenue (included in other noncurrent liabilities)	$ 750	$ 618

Revenue (Changes in the Allowan

Revenue (Changes in the Allowance for Doubtful Accounts) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	$ 419	$ 352	$ 288
Additions Charged to Costs and Expenses and Other Accounts	912	769	616
Deductions from Reserves	524	702	552
Ending Balance	$ 807	$ 419	$ 352

Programming and Production Co_3

Programming and Production Costs (Programming and Production Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Other Industries [Abstract]
Video distribution programming	$ 12,684
Film and television content:
Owned	7,973
Licensed, including sports rights	11,264
Other	1,200
Total programming and production costs	33,121	$ 34,440	$ 29,692
Amortization of owned film and television costs	$ 6,600

Programming and Production Co_4

Programming and Production Costs (Capitalized Film and Television Costs and Programming Rights) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Film and Television Costs
Released, less amortization	$ 3,815
Completed, not released	139
In production and in development	2,755
Film and Television Costs	6,709
Programming rights, less amortization	6,631
Total film and television costs and programming rights	13,340
Less: Current portion of licensed programming rights	0
Film and television costs	$ 13,340
Film Costs
Released, less amortization		$ 1,551
Completed, not released		187
In production and in development		1,314
Film Costs		3,052
Television Costs
Released, less amortization		2,810
Completed, not released		0
In production and in development		1,162
Television Costs		3,972
Total
Released, less amortization		4,361
Completed, not released		187
In production and in development		2,476
Total		7,024
Licensed, including sports advances		5,786
Total film and television costs and programming rights		12,810
Less: Current portion of licensed programming rights		3,877
Film and television costs		$ 8,933

Programming and Production Co_5

Programming and Production Costs (Estimated Future Amortization Expense for Capitalized Film and Television Costs and Programming Rights) (Details) $ in Millions	Dec. 31, 2020USD ($)
Completed, not released:
2021	$ 69
Released and licensed content:
2021	1,445
2022	543
2023	336
Released and licensed content:
2021	4,722
2022	820
2023	$ 470

Programming and Production Co_6

Programming and Production Costs (Narrative) (Details) $ in Billions	Dec. 31, 2020USD ($)
Other Industries [Abstract]
Future minimum commitments for sports rights	$ 38.5
Future minimum commitments for licensed content	$ 4.5

Income Taxes (Income Before Inc

Income Taxes (Income Before Income Taxes) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Domestic	$ 16,211	$ 16,646	$ 14,387
Foreign	(2,146)	350	855
Income before income taxes	$ 14,065	$ 16,996	$ 15,242

Income Taxes (Components of Inc

Income Taxes (Components of Income Tax Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current (Expense) Benefit:
Federal	$ (2,824)	$ (2,085)	$ (2,026)
State	(836)	(425)	(639)
Foreign	(254)	(600)	(425)
Current income tax (expense) benefit	(3,914)	(3,110)	(3,090)
Deferred (Expense) Benefit:
Federal	111	(902)	(546)
State	71	15	167
Foreign	368	324	89
Deferred income tax (expense) benefit	550	(563)	(290)
Income tax (expense) benefit	$ (3,364)	$ (3,673)	$ (3,380)

Income Taxes (Federal Statutory

Income Taxes (Federal Statutory) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Taxes [Line Items]
Federal tax at statutory rate	$ (2,954)	$ (3,569)	$ (3,201)
State income taxes, net of federal benefit	(265)	(306)	(212)
Foreign income taxed at different rates	(24)	(126)	(147)
Excess tax benefits recognized on share-based compensation	150	196	75
Federal research and development credits	164	124	22
Other	(91)	11	227
Income tax (expense) benefit	(3,364)	(3,673)	(3,380)
Adjustments to uncertain and effectively settled tax positions, net [Member]
Income Taxes [Line Items]
Other	$ (344)	$ (3)	$ (144)

Income Taxes (Components of Net

Income Taxes (Components of Net Deferred Tax Liability) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Deferred Tax Assets:
Net operating loss and other loss carryforwards	$ 2,609	$ 2,017
Nondeductible accruals and other	3,253	2,779
Less: Valuation allowance	2,312	1,906	$ 632	$ 377
Total deferred tax assets, net of valuation allowance	3,550	2,890
Deferred Tax Liabilities:
Differences between book and tax basis of property and equipment and intangible assets	29,829	29,387
Differences between book and tax basis of investments	405	702
Differences between book and tax basis of long-term debt	680	751
Differences between book and tax basis of foreign subsidiaries and undistributed foreign earnings	468	143
Total deferred tax liabilities	31,382	30,983
Net deferred tax liability	$ 27,832	$ 28,093

Income Taxes (Changes in the Va

Income Taxes (Changes in the Valuation Allowance for Deferred Tax Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Changes In The Valuation Allowance For Deferred Tax Assets, Valuation Allowance [Roll Forward]
Beginning Balance	$ 1,906	$ 632	$ 377
Additions Charged to Income Tax Expense and Other Accounts	430	1,403	367
Deductions from Reserves	24	129	112
Ending Balance	$ 2,312	$ 1,906	$ 632

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)
Income Taxes [Line Items]
Deferred tax liability attributable to temporary differences in other comprehensive income	$ 330
Unrecognized tax benefits that would impact effective tax rate	1,400
Federal Tax Authority [Member]
Income Taxes [Line Items]
Operating loss carryforwards	196
Foreign Tax Authority [Member]
Income Taxes [Line Items]
Operating loss carryforwards	$ 7,600

Income Taxes (Reconciliation of

Income Taxes (Reconciliation of Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Gross unrecognized tax benefits, January 1	$ 1,422	$ 1,543	$ 1,497
Additions based on tax positions related to the current year	436	230	229
Additions based on tax positions related to prior years	152	133	125
Additions from acquired subsidiaries	0	1	130
Reductions for tax positions of prior years	(31)	(344)	(346)
Reductions due to expiration of statutes of limitations	(76)	(117)	(75)
Settlements with tax authorities	(24)	(24)	(17)
Gross unrecognized tax benefits, December 31	$ 1,879	$ 1,422	$ 1,543

Long-Term Debt (Schedule of Deb

Long-Term Debt (Schedule of Debt Outstanding) (Details) $ in Millions, € in Billions, ¥ in Billions, ¥ in Billions, £ in Billions	Dec. 31, 2020USD ($)	Dec. 31, 2020GBP (£)	Dec. 31, 2020EUR (€)	Dec. 31, 2020JPY (¥)	Dec. 31, 2020CNY (¥)	Dec. 31, 2019USD ($)	Dec. 31, 2019GBP (£)	Dec. 31, 2019EUR (€)	Dec. 31, 2019JPY (¥)	Dec. 31, 2019CNY (¥)
Debt Instrument [Line Items]
Debt issuance costs, premiums, discounts, fair value adjustments for acquisition accounting and hedged positions, net	$ (1,649)					$ (1,673)
Total debt	103,760					102,217
Less: Current portion	3,146					4,452
Long-term debt	$ 100,614					$ 97,765
Interest rate	3.60%	3.60%	3.60%	3.60%	3.60%	3.78%	3.78%	3.78%	3.78%	3.78%
Term Loans [Member]
Debt Instrument [Line Items]
Term loans	$ 7,641					$ 8,078
Interest rate	2.07%	2.07%	2.07%	2.07%	2.07%	1.87%	1.87%	1.87%	1.87%	1.87%
Senior notes with maturities of 5 years or less, at face value [Member]
Debt Instrument [Line Items]
Senior notes	$ 19,190					$ 26,378
Interest rate	3.41%	3.41%	3.41%	3.41%	3.41%	3.29%	3.29%	3.29%	3.29%	3.29%
Senior notes with maturities between 5 and 10 years, at face value [Member]
Debt Instrument [Line Items]
Senior notes	$ 23,114					$ 21,683
Interest rate	3.47%	3.47%	3.47%	3.47%	3.47%	3.74%	3.74%	3.74%	3.74%	3.74%
Senior notes with maturities greater than 10 years, at face value [Member]
Debt Instrument [Line Items]
Senior notes	$ 54,203					$ 46,653
Interest rate	4.03%	4.03%	4.03%	4.03%	4.03%	4.54%	4.54%	4.54%	4.54%	4.54%
Other Including Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Other, including finance lease obligations	$ 1,261					$ 1,098
Foreign Currency Denominated Borrowings [Member]
Debt Instrument [Line Items]
Aggregate principal amount		£ 4.7	€ 7.3	¥ 238.5	¥ 16.4		£ 4.9	€ 4.9	¥ 267	¥ 9

Long-Term Debt (Narrative) (Det

Long-Term Debt (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Total fair value of debt	$ 125,600,000,000	$ 115,800,000,000
Cumulative translation gains (losses) related to net investment hedges recorded in other comprehensive income (loss)	(686,000,000)	343,000,000	$ (3,000,000)
Maximum borrowing capacity of revolving credit facilities	9,200,000,000
Potential increase of maximum borrowing capacity of revolving credit facilities	12,000,000,000
Amounts available under revolving credit facilities	9,200,000,000
Unused irrevocable standby letters of credit and bank guarantees	320,000,000
Revolving Credit Facilities [Member]
Debt Instrument [Line Items]
Borrowings outstanding under credit facility	0	0
Commercial Paper [Member]
Debt Instrument [Line Items]
Borrowings outstanding under commercial paper program	$ 0	0
London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Borrowing margin for LIBOR based borrowings	1.00%
Cash Flow Hedging [Member]
Debt Instrument [Line Items]
Amount of foreign currency denominated debt hedged	$ 1,700,000,000	3,700,000,000
Cash Flow Hedging [Member] \| Currency Swap [Member]
Debt Instrument [Line Items]
Amount of net investment in foreign subsidiaries hedged	4,000,000,000	4,800,000,000
Cash Flow Hedging [Member] \| Currency Swap [Member]
Debt Instrument [Line Items]
Aggregate asset (liability) fair value	(45,000,000)	373,000,000
Net Investment Hedging [Member] \| Foreign Currency Denominated Debt [Member]
Debt Instrument [Line Items]
Amount of net investment in foreign subsidiaries hedged	10,300,000,000	9,200,000,000
Net Investment Hedging [Member] \| Currency Swap [Member]
Debt Instrument [Line Items]
Aggregate asset (liability) fair value	$ (376,000,000)	$ (373,000,000)

Long-Term Debt (Debt Maturities

Long-Term Debt (Debt Maturities) (Details) $ in Millions	Dec. 31, 2020USD ($)
Long-term Debt, Fiscal Year Maturity [Abstract]
2021	$ 3,133
2022	4,028
2023	3,925
2024	6,746
2025	6,953
Thereafter	$ 80,624

Significant Transactions (Sky T

Significant Transactions (Sky Transaction) (Details) - 3 months ended Dec. 31, 2018 - Sky Limited [Member] £ / shares in Units, £ in Billions, $ in Billions	GBP (£)£ / shares	USD ($)
Business Acquisition [Line Items]
Shares acquired, share price (in gbp per share)	£ 17.28
Cash consideration	£ 30.2	$ 39.4

Significant Transactions (Acqui

Significant Transactions (Acquisition-Related Costs) (Details) - Sky Limited [Member] $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)
Business Acquisition [Line Items]
Other operating and administrative expenses	$ 339
Interest expense	$ 63

Significant Transactions (Unaud

Significant Transactions (Unaudited Pro Forma Information) (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)$ / shares
Business Combinations [Abstract]
Revenue \| $	$ 109,518
Net income attributable to Comcast Corporation \| $	$ 12,176
Basic earnings per common share attributable to Comcast Corporation shareholders (in dollars per share) \| $ / shares	$ 2.66
Diluted earnings per common share attributable to Comcast Corporation shareholders (in dollars per share) \| $ / shares	$ 2.62

Significant Transactions (Unive

Significant Transactions (Universal Beijing Resort) (Details) $ in Millions, ¥ in Billions	Dec. 31, 2020USD ($)	Dec. 31, 2020CNY (¥)	Dec. 31, 2019USD ($)
Variable Interest Entity [Line Items]
Consolidated variable interest entity's assets included in the balance sheet	$ 273,869		$ 263,414
Universal Beijing Resort [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Ownership percentage in variable interest entity	30.00%	30.00%
Maximum borrowing capacity of variable interest entity	$ 4,000	¥ 26.6
Consolidated variable interest entity's assets included in the balance sheet	5,100
Consolidated variable interest entity's liabilities the balance sheet	3,600
Universal Beijing Resort [Member] \| Universal Beijing Resort Term Loans [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Proceeds from borrowings	$ 2,500

Recent Accounting Pronounceme_2

Recent Accounting Pronouncements (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Jan. 01, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Cumulative effects of adoption of accounting standards	$ (91,738)		$ (83,874)	$ (72,502)
Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effects of adoption of accounting standards	$ (56,438)		(50,695)	(41,983)	$ (38,202)
Cumulative Effect, Period of Adoption, Adjustment [Member] \| Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effects of adoption of accounting standards		$ 124	$ 124	$ 0	$ 43

Investments (Investment and Oth

Investments (Investment and Other Income (Loss), Net) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Investments [Abstract]
Equity in net income (losses) of investees, net	$ (113)	$ (505)	$ (364)
Realized and unrealized gains (losses) on equity securities, net	1,014	656	(187)
Other income (loss), net	259	287	326
Investment and other income (loss), net	1,160	438	(225)
Unrealized gains (losses) recognized	$ 339	$ 237	$ (200)

Investments (Schedule of Invest

Investments (Schedule of Investments) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Investments [Abstract]
Equity method	$ 6,006	$ 5,347
Marketable equity securities	460	353
Nonmarketable equity securities	1,950	1,896
Other investments	143	1,796
Total investments	8,559	9,392
Less: Current investments	292	1,709
Less: Investment securing collateralized obligation	447	694
Noncurrent investments	$ 7,820	$ 6,989

Investments (Equity Method Inve

Investments (Equity Method Investments) (Details) - USD ($)	Jan. 01, 2016	Nov. 30, 2020	Aug. 31, 2019	May 31, 2019	Apr. 30, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Apr. 30, 2019	Feb. 28, 2018
Schedule of Equity Method Investments [Line Items]
Equity method investments						$ 6,006,000,000	$ 5,347,000,000
Proceeds from collateralized obligation			$ 5,200,000,000			0	5,175,000,000	$ 0
Collateralized obligation						5,168,000,000	5,166,000,000
Equity in net income (losses) of investees, net						(113,000,000)	(505,000,000)	(364,000,000)
Investment securing collateralized obligation						447,000,000	694,000,000
Level 2 [Member]
Schedule of Equity Method Investments [Line Items]
Estimated fair value of collateralized obligation						5,200,000,000
Atairos [Member]
Schedule of Equity Method Investments [Line Items]
Pretax gain, sale of business to Atairos					$ 200,000,000
Atairos [Member]
Schedule of Equity Method Investments [Line Items]
Term of agreement	12 years	16 years 6 months
Funding commitment		$ 4,500,000,000								$ 5,000,000,000
Maximum amount of annual capital calls		$ 400,000,000
Management fee funding commitment										45,000,000
Percent of losses	99.00%
Percentage of residual returns	86.00%
Cash capital contributions for equity method investments						383,000,000	571,000,000	$ 282,000,000
Equity method investments						3,900,000,000	$ 3,200,000,000
Atairos [Member] \| Minimum [Member]
Schedule of Equity Method Investments [Line Items]
Funding commitment by management company investors										50,000,000
Atairos [Member] \| Maximum [Member]
Schedule of Equity Method Investments [Line Items]
Funding commitment by management company investors										$ 100,000,000
Atairos [Member] \| Variable Interest Entity, Not Primary Beneficiary [Member]
Schedule of Equity Method Investments [Line Items]
Unfunded capital commitment						$ 1,300,000,000
Hulu [Member]
Schedule of Equity Method Investments [Line Items]
Ownership percentage				33.00%					30.00%
Cash capital contributions for equity method investments				$ 477,000,000
Maximum total capital call in annual period				$ 1,500,000,000
Ownership percentage floor				21.00%
Fair market value assessment floor for put and call option				$ 27,500,000,000
Ownership percentage representing fair market value floor for put and call option				100.00%
Minimum guaranteed proceeds floor for put and call option				$ 5,800,000,000
Hulu [Member] \| AT&T Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Ownership percentage				10.00%
Former CFO [Member] \| Atairos [Member] \| Minimum [Member]
Schedule of Equity Method Investments [Line Items]
Funding commitment by management company investors	$ 40,000,000

Investments (Other Investments)

Investments (Other Investments) (Details) $ in Millions	3 Months Ended
	Jun. 30, 2020USD ($)preferred_stock_series	Dec. 31, 2019USD ($)
Schedule of Other Investments [Line Items]
Cash payments for the redemption of redeemable preferred shares	$ 1,800
Air Touch [Member]
Schedule of Other Investments [Line Items]
Number of series of preferred stock \| preferred_stock_series	3
Redeemable subsidiary preferred shares		$ 1,700
Nonredeemable subsidiary preferred shares		100
Air Touch [Member]
Schedule of Other Investments [Line Items]
Number of series of preferred stock \| preferred_stock_series	2
Cash payments received upon redemption of preferred stock	$ 1,700
Held to maturity investment		$ 1,600

Property and Equipment (Details

Property and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	$ 106,383	$ 101,561
Less: Accumulated depreciation	54,388	53,239
Property and equipment, net	$ 51,995	48,322
Distribution System [Member]
Property, Plant and Equipment [Line Items]
Weighted-Average Original Useful Life	11 years
Property and equipment, at cost	$ 40,861	40,639
Customer Premise Equipment [Member]
Property, Plant and Equipment [Line Items]
Weighted-Average Original Useful Life	6 years
Property and equipment, at cost	$ 26,323	26,065
Buildings, Theme Park Attractions And Leasehold Improvements
Property, Plant and Equipment [Line Items]
Weighted-Average Original Useful Life	31 years
Property and equipment, at cost	$ 15,885	15,104
Other Equipment [Member]
Property, Plant and Equipment [Line Items]
Weighted-Average Original Useful Life	9 years
Property and equipment, at cost	$ 14,371	13,025
Construction in Process [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	7,095	5,245
Land [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	$ 1,848	$ 1,483

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets (Schedule of Change in Goodwill) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Goodwill [Roll Forward]
Balance, beginning of period	$ 68,725	$ 66,154
Acquisitions	149	279
Dispositions	(4)	(12)
Adjustments	(96)	1,379
Foreign currency translation	1,895	925
Balance, end of period	70,669	68,725
Operating Segments [Member] \| Cable Communications [Member]
Goodwill [Roll Forward]
Balance, beginning of period	15,074	12,784
Acquisitions	122	86
Dispositions	0	0
Adjustments	(5)	2,166
Foreign currency translation	73	38
Balance, end of period	15,264	15,074
Operating Segments [Member] \| Cable Networks [Member]
Goodwill [Roll Forward]
Balance, beginning of period	14,067	13,407
Acquisitions	0	162
Dispositions	0	0
Adjustments	(85)	490
Foreign currency translation	12	8
Balance, end of period	13,994	14,067
Operating Segments [Member] \| Broadcast Television [Member]
Goodwill [Roll Forward]
Balance, beginning of period	1,059	843
Acquisitions	0	14
Dispositions	0	0
Adjustments	0	199
Foreign currency translation	3	3
Balance, end of period	1,062	1,059
Operating Segments [Member] \| Filmed Entertainment [Member]
Goodwill [Roll Forward]
Balance, beginning of period	3,321	3,184
Acquisitions	27	0
Dispositions	0	0
Adjustments	0	138
Foreign currency translation	(4)	(1)
Balance, end of period	3,344	3,321
Operating Segments [Member] \| Theme Parks [Member]
Goodwill [Roll Forward]
Balance, beginning of period	6,739	6,684
Acquisitions	0	0
Dispositions	0	0
Adjustments	0	0
Foreign currency translation	314	55
Balance, end of period	7,053	6,739
Operating Segments [Member] \| Sky Limited [Member]
Goodwill [Roll Forward]
Balance, beginning of period	28,461	29,250
Acquisitions	0	17
Dispositions	0	(12)
Adjustments	(8)	(1,616)
Foreign currency translation	1,497	822
Balance, end of period	29,950	28,461
Operating Segments [Member] \| Corporate and Other [Member]
Goodwill [Roll Forward]
Balance, beginning of period	4	2
Acquisitions	0	0
Dispositions	(4)	0
Adjustments	2	2
Foreign currency translation	0	0
Balance, end of period	$ 2	$ 4

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets (Intangible Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Estimated Amortization Expense of Finite-Lived Intangible Assets
Accumulated Amortization	$ (19,825)	$ (17,217)
Total	114,579	112,710
Franchise Rights [Member]
Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	59,365	59,365
Trade Names [Member]
Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	0	8,809
FCC Licenses [Member]
Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 2,804	2,337
Customer Relationships [Member]
Estimated Amortization Expense of Finite-Lived Intangible Assets
Weighted-Average Original Useful Life	14 years
Gross Carrying Amount	$ 22,197	22,884
Accumulated Amortization	$ (8,914)	(8,295)
Software [Member]
Estimated Amortization Expense of Finite-Lived Intangible Assets
Weighted-Average Original Useful Life	5 years
Gross Carrying Amount	$ 17,819	15,357
Accumulated Amortization	$ (9,518)	(7,287)
Other Agreements and Rights [Member]
Estimated Amortization Expense of Finite-Lived Intangible Assets
Weighted-Average Original Useful Life	28 years
Gross Carrying Amount	$ 12,394	3,958
Accumulated Amortization	$ (1,393)	$ (1,635)

Goodwill and Intangible Asset_4

Goodwill and Intangible Assets (Narrative) (Details)	12 Months Ended
	Dec. 31, 2020division
Software [Member]
Segment Reporting Information [Line Items]
Finite-lived intangible asset amortization period (not to exceed)	5 years
Cable Communications [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Number of divisions	3

Goodwill and Intangible Asset_5

Goodwill and Intangible Assets (Amortization of Intangible Assets) (Details) $ in Millions	Dec. 31, 2020USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
2021	$ 4,589
2022	4,087
2023	3,472
2024	2,774
2025	$ 2,412

Employee Benefit Plans (Deferre

Employee Benefit Plans (Deferred Compensation Plans) (Details) - Deferred Compensation Plans [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefit obligation	$ 3,648	$ 3,273	$ 2,885
Interest expense	$ 293	$ 285	$ 222

Employee Benefit Plans (Narrati

Employee Benefit Plans (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Retirement Benefits [Abstract]
Cash surrender value of life insurance policies	$ 481	$ 423
Expenses related to retirement investment plans	$ 599	$ 573	$ 546

Equity (Narrative) (Details)

Equity (Narrative) (Details)	12 Months Ended
	Dec. 31, 2020vote
Equity [Line Items]
Number of votes entitled of each class B common stock	15
Class A Common Stock [Member]
Equity [Line Items]
Voting power	66.67%
Class B Common Stock [Member]
Equity [Line Items]
Voting power	33.33%

Equity (Changes in Common Stock

Equity (Changes in Common Stock) (Details) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Class A Common Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock, shares outstanding at beginning of period (in shares)	4,543,590,270	4,517,000,000	4,635,000,000
Stock compensation plans (in shares)	20,000,000	21,000,000	15,000,000
Repurchases and retirements of common stock (in shares)			(140,000,000)
Employee stock purchase plan (in shares)	7,000,000	6,000,000	7,000,000
Common stock, shares outstanding at end of period (in shares)	4,571,211,797	4,543,590,270	4,517,000,000
Class B Common Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock, shares outstanding at beginning of period (in shares)	9,444,375	9,000,000	9,000,000
Stock compensation plans (in shares)	0	0	0
Repurchases and retirements of common stock (in shares)			0
Employee stock purchase plan (in shares)	0	0	0
Common stock, shares outstanding at end of period (in shares)	9,444,375	9,444,375	9,000,000

Equity (Weighted Average Common

Equity (Weighted Average Common Shares Outstanding) (Details) - shares shares in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Equity [Abstract]
Weighted average number of common shares outstanding – basic (in shares)	4,574	4,548	4,584
Effect of dilutive securities (in shares)	50	62	56
Weighted average number of common shares outstanding – diluted (in shares)	4,624	4,610	4,640

Equity (Components of Accumulat

Equity (Components of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Equity [Abstract]
Cumulative translation adjustments	$ 1,790	$ 637
Deferred gains (losses) on cash flow hedges	(109)	139
Unrecognized gains (losses) on employee benefit obligations and other	203	271
Accumulated other comprehensive income (loss), net of deferred taxes	$ 1,884	$ 1,047

Share-Based Compensation (Recog

Share-Based Compensation (Recognized Share-Based Compensation Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized share-based compensation expense	$ 960	$ 825	$ 639
Restricted share units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized share-based compensation expense	628	564	402
Stock options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized share-based compensation expense	294	231	205
Employee stock purchase plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized share-based compensation expense	$ 38	$ 30	$ 32

Share-Based Compensation (Narra

Share-Based Compensation (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting period in years	5 years
Adjustments to additional paid in capital, income tax benefit from share-based compensation	$ 150	$ 196	$ 75
Restricted share units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized pretax compensation expense on nonvested awards	$ 1,200
Unrecognized pretax compensation expense on nonvested awards, weighted average period of recognition (in years)	1 year 6 months
Stock options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Period from grant date that an equity-based award expires	10 years
Unrecognized pretax compensation expense on nonvested awards	$ 560
Unrecognized pretax compensation expense on nonvested awards, weighted average period of recognition (in years)	1 year 8 months 12 days

Share-Based Compensation (Stock

Share-Based Compensation (Stock Options and Restricted Share Units) (Details) shares in Millions	12 Months Ended
	Dec. 31, 2020$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted (in shares)	61
Weighted-average exercise price of awards granted during the year (in dollars per share) \| $ / shares	$ 42.42
Stock options outstanding (in shares)	210
Weighted-average exercise price of shares outstanding (in dollars per share) \| $ / shares	$ 35.94
Restricted share units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted (in shares)	18
Awards nonvested (in shares)	49
Weighted-average fair value at grant date of nonvested awards (in dollars per share) \| $ / shares	$ 38.87

Share-Based Compensation (Restr

Share-Based Compensation (Restricted Share Units and Stock Option Fair Value) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option fair value (in dollars per share)	$ 6.61	$ 7.91	$ 7.14
Stock Option Valuation Assumptions:
Dividend yield	2.20%	2.10%	2.10%
Expected volatility	21.00%	22.00%	22.00%
Risk-free interest rate	1.00%	2.50%	2.70%
Expected option life	6 years	6 years	6 years
Restricted share units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair value of RSUs (in dollars per share)	$ 41.71	$ 40.42	$ 35.56

Supplemental Financial Inform_3

Supplemental Financial Information (Cash Payments for Interest and Income Taxes) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash Payments for Interest and Income Taxes
Interest	$ 3,878	$ 4,254	$ 2,897
Income taxes	$ 3,183	$ 3,231	$ 2,355

Supplemental Financial Inform_4

Supplemental Financial Information (Noncash Investing and Financing Activities) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Supplemental Financial Information [Line Items]
Property and equipment and intangible assets accrued but not yet paid	$ 1,900	$ 1,900	$ 2,100
Dividends payable	$ 1,100	$ 956	$ 860
Dividends payable (in dollars per share)	$ 0.23	$ 0.21	$ 0.19
Universal Beijing Resort [Member]
Supplemental Financial Information [Line Items]
Assets contributed to variable interest entity			$ 391

Supplemental Financial Inform_5

Supplemental Financial Information (Cash, Cash Equivalents and Restricted Cash) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Supplemental Financial Information [Abstract]
Cash and cash equivalents	$ 11,740	$ 5,500
Restricted cash included in other current assets	14	42
Restricted cash included in other noncurrent assets, net	14	47
Cash, cash equivalents and restricted cash, end of year	$ 11,768	$ 5,589	$ 3,909	$ 3,571

Commitments and Contingencies_2

Commitments and Contingencies (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Commitments And Contingencies [Line Items]
Operating lease expense inclusive of short-term and variable lease expenses	$ 1,100	$ 1,100
Weighted average remaining lease term for operating leases	9 years	10 years
Weighted average discount rate used to calculate operating lease liabilities	3.58%	3.74%
Cash payments for operating leases	$ 936	$ 914
Operating lease assets	3,784	4,038
Operating lease liabilities	4,458
Rent expense for operating leases			$ 779
Carrying value of contractual obligation	1,100
Contractual value of a potential obligation	1,700
NBCUniversal Enterprise [Member]
Commitments And Contingencies [Line Items]
Preferred stock redemption value	$ 725
Redeemable Subsidiary Preferred Stock [Member] \| NBCUniversal Enterprise [Member]
Commitments And Contingencies [Line Items]
Redeemable subsidiary preferred stock, put period	30 days
Redeemable subsidiary preferred stock, dividend rate	5.25%
Redeemable subsidiary preferred stock, call period	1 year
Redeemable Subsidiary Preferred Stock [Member] \| NBCUniversal Enterprise [Member] \| Level 2 [Member]
Commitments And Contingencies [Line Items]
Temporary equity, fair value of redeemable subsidiary preferred stock	$ 731	$ 749

Commitments and Contingencies_3

Commitments and Contingencies (Summary of Operating Lease Assets and Liabilities Recorded in the Consolidated Balance Sheets) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Operating lease assets	$ 3,784	$ 4,038
Operating lease liabilities, current	718	715
Operating lease liabilities, noncurrent	$ 3,740	$ 3,891
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:OtherAssetsNoncurrent	us-gaap:OtherAssetsNoncurrent
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:AccruedLiabilitiesCurrent	us-gaap:AccruedLiabilitiesCurrent
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesNoncurrent	us-gaap:OtherLiabilitiesNoncurrent

Commitments and Contingencies_4

Commitments and Contingencies (Summary of Future Minimum Rental Commitments for Operating Leases Under New Accounting Guidance) (Details) $ in Millions	Dec. 31, 2020USD ($)
Commitments and Contingencies Disclosure [Abstract]
2021	$ 873
2022	778
2023	683
2024	560
2025	444
Thereafter	2,043
Total future minimum lease payments	5,381
Less: imputed interest	(923)
Total liability	$ 4,458

Quarterly Financial Informati_3

Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 27,708	$ 25,532	$ 23,715	$ 26,609	$ 28,398	$ 26,827	$ 26,858	$ 26,859	$ 103,564	$ 108,942	$ 94,507
Operating income	3,918	4,076	4,647	4,852	5,247	5,340	5,356	5,182	17,493	21,125	19,009
Net income attributable to Comcast Corporation	$ 3,380	$ 2,019	$ 2,988	$ 2,147	$ 3,162	$ 3,217	$ 3,125	$ 3,553	$ 10,534	$ 13,057	$ 11,731
Basic earnings per common share attributable to Comcast Corporation shareholders (in dollars per share)	$ 0.74	$ 0.44	$ 0.65	$ 0.47	$ 0.69	$ 0.71	$ 0.69	$ 0.78	$ 2.30	$ 2.87	$ 2.56
Diluted earnings per common share attributable to Comcast Corporation shareholders (in dollars per share)	0.73	0.44	0.65	0.46	0.68	0.70	0.68	0.77	2.28	2.83	2.53
Dividends declared per common share (in dollars per share)	$ 0.23	$ 0.23	$ 0.23	$ 0.23	$ 0.21	$ 0.21	$ 0.21	$ 0.21	$ 0.92	$ 0.84	$ 0.76