Comcast (CMCSA) 10-K 31 Jan 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Jun. 30, 2017
Document And Entity Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Trading Symbol	cmcsa
Entity Registrant Name	COMCAST CORP
Entity Central Index Key	1,166,691
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Public Float		$ 181,936
Entity Current Reporting Status	Yes
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
NBCUniversal Media LLC [Member]
Document And Entity Information [Line Items]
Entity Registrant Name	NBCUniversal Media, LLC
Entity Central Index Key	902,739
Entity Filer Category	Non-accelerated Filer
Entity Public Float		$ 0
Entity Current Reporting Status	Yes
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Class A Common Stock [Member]
Document And Entity Information [Line Items]
Entity Common Stock, Shares Outstanding	4,635,063,642
Class B Common Stock [Member]
Document And Entity Information [Line Items]
Entity Common Stock, Shares Outstanding	9,444,375

Consolidated Balance Sheet

Consolidated Balance Sheet - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Current Assets:
Cash and cash equivalents	$ 3,428	$ 3,301
Receivables, net	8,546	7,955
Programming rights	1,613	1,250
Deposits	9	1,772
Other current assets	2,464	2,083
Total current assets	16,060	16,361
Film and television costs	7,076	7,252
Investments	6,931	5,247
Property and equipment, net	38,470	36,253
Franchise rights	59,364	59,364
Goodwill	36,780	35,980
Other intangible assets, net	18,779	17,274
Other noncurrent assets, net	3,489	2,769
Total assets	186,949	180,500
Current Liabilities:
Accounts payable and accrued expenses related to trade creditors	6,926	6,915
Accrued participations and residuals	1,683	1,726
Deferred revenue	1,552	1,132
Accrued expenses and other current liabilities	6,266	6,282
Current portion of long-term debt	5,134	5,480
Total current liabilities	21,561	21,535
Long-term debt, less current portion	59,422	55,566
Deferred income taxes	24,256	34,854
Other noncurrent liabilities	10,904	10,925
Commitments and contingencies
Redeemable noncontrolling interests	1,357	1,446
Equity:
Preferred stock—authorized, 20,000,000 shares; issued, zero	0	0
Common stock	55	56
Additional paid-in capital	37,497	38,230
Retained earnings	38,192	23,076
Treasury stock, 872,791,028 Class A common shares	(7,517)	(7,517)
Accumulated other comprehensive income (loss)	379	98
Total Comcast Corporation shareholders’ equity	68,606	53,943
Noncontrolling interests	843	2,231
Total equity	69,449	56,174
Total liabilities and equity	186,949	180,500
NBCUniversal Media LLC [Member]
Current Assets:
Cash and cash equivalents	2,347	1,966
Receivables, net	6,682	6,302
Programming rights	1,606	1,241
Other current assets	1,038	938
Total current assets	11,673	10,447
Film and television costs	7,071	7,245
Investments	1,816	1,263
Property and equipment, net	11,346	10,511
Goodwill	23,989	23,323
Intangible assets, net	13,306	13,777
Other noncurrent assets, net	1,872	1,688
Total assets	71,073	68,254
Current Liabilities:
Accounts payable and accrued expenses related to trade creditors	1,663	1,647
Accrued participations and residuals	1,683	1,726
Program obligations	745	807
Deferred revenue	1,438	1,016
Accrued expenses and other current liabilities	2,044	1,888
Note payable to Comcast	1,831	2,703
Current portion of long-term debt	198	127
Total current liabilities	9,602	9,914
Long-term debt, less current portion	12,275	11,461
Accrued participations, residuals and program obligations	1,490	1,202
Other noncurrent liabilities	4,109	4,130
Commitments and contingencies
Redeemable noncontrolling interests	409	530
Equity:
Member’s capital	42,295	39,036
Accumulated other comprehensive income (loss)	(20)	(135)
Total NBCUniversal member’s equity	42,275	38,901
Noncontrolling interests	913	2,116
Total equity	43,188	41,017
Total liabilities and equity	71,073	68,254
Class A Common Stock [Member]
Equity:
Common stock	55	56
Class B Common Stock [Member]
Equity:
Common stock	$ 0	$ 0

Consolidated Balance Sheet (Par

Consolidated Balance Sheet (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Preferred stock, shares authorized (in shares)	20,000,000	20,000,000
Preferred stock, shares issued (in shares)	0	0
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)	5,507,854,670	5,614,950,039
Common stock, shares outstanding (in shares)	4,635,063,642	4,742,159,011
Treasury stock (in shares)	872,791,028	872,791,028
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 Incom

Consolidated Statement of Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue	$ 84,526	$ 80,403	$ 74,510
Costs and Expenses:
Programming and production	25,384	24,463	22,550
Other operating and administrative	25,013	23,416	21,325
Advertising, marketing and promotion	6,317	6,107	5,957
Depreciation	7,914	7,464	6,781
Amortization	2,353	2,094	1,899
Other operating gains	(442)	0	0
Total costs and expenses	66,539	63,544	58,512
Operating income	17,987	16,859	15,998
Other Income (Expense):
Interest expense	(3,086)	(2,942)	(2,702)
Investment income (loss), net	253	213	81
Equity in net income (losses) of investees, net	107	(104)	(325)
Other income (expense), net	61	327	320
Total other income (expense)	(2,665)	(2,506)	(2,626)
Income before income taxes	15,322	14,353	13,372
Income tax benefit (expense)	7,578	(5,308)	(4,959)
Net income	22,900	9,045	8,413
Net (income) loss attributable to noncontrolling interests and redeemable subsidiary preferred stock	(186)	(350)	(250)
Net income attributable to Comcast Corporation	$ 22,714	$ 8,695	$ 8,163
Basic earnings per common share attributable to Comcast Corporation shareholders (in dollars per share)	$ 4.82	$ 1.80	$ 1.64
Diluted earnings per common share attributable to Comcast Corporation shareholders (in dollars per share)	4.75	1.78	1.62
Dividends declared per common share (in dollars per share)	$ 0.63	$ 0.55	$ 0.50
NBCUniversal Media LLC [Member]
Revenue	$ 32,997	$ 31,593	$ 28,462
Costs and Expenses:
Programming and production	14,304	14,540	13,418
Other operating and administrative	7,709	7,059	5,891
Advertising, marketing and promotion	2,799	2,767	2,795
Depreciation	994	861	669
Amortization	1,047	944	870
Other operating gains	(337)	0	0
Total costs and expenses	26,516	26,171	23,643
Operating income	6,481	5,422	4,819
Other Income (Expense):
Interest expense	(727)	(595)	(495)
Investment income (loss), net	46	30	5
Equity in net income (losses) of investees, net	(201)	(99)	(376)
Other income (expense), net	11	93	(102)
Total other income (expense)	(871)	(571)	(968)
Income before income taxes	5,610	4,851	3,851
Income tax benefit (expense)	(392)	(305)	(227)
Net income	5,218	4,546	3,624
Net (income) loss attributable to noncontrolling interests	(134)	(311)	(210)
Net income attributable to Comcast Corporation	$ 5,084	$ 4,235	$ 3,414

Consolidated Statement of Compr

Consolidated Statement of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net income	$ 22,900	$ 9,045	$ 8,413
Unrealized gains (losses) on marketable securities, net of deferred taxes	(42)	0	1
Deferred gains (losses) on cash flow hedges, net of deferred taxes	60	(60)	(106)
Amounts reclassified to net income:
Realized (gains) losses on marketable securities, net of deferred taxes	(1)	(1)	(1)
Realized (gains) losses on cash flow hedges, net of deferred taxes	(37)	92	64
Employee benefit obligations, net of deferred taxes	41	213	74
Currency translation adjustments, net of deferred taxes	147	102	(89)
Comprehensive income	23,068	9,391	8,356
Net (income) loss attributable to noncontrolling interests and redeemable subsidiary preferred stock	(186)	(350)	(250)
Other comprehensive (income) loss attributable to noncontrolling interests	(81)	(74)	29
Comprehensive income attributable to Parent	22,801	8,967	8,135
NBCUniversal Media LLC [Member]
Net income	5,218	4,546	3,624
Unrealized gains (losses) on marketable securities, net of deferred taxes	(233)	0	0
Deferred gains (losses) on cash flow hedges, net of deferred taxes	(13)	24	(21)
Amounts reclassified to net income:
Employee benefit obligations, net of deferred taxes	112	15	60
Currency translation adjustments, net of deferred taxes	189	112	(121)
Comprehensive income	5,273	4,697	3,542
Net (income) loss attributable to noncontrolling interests	(134)	(311)	(210)
Other comprehensive (income) loss attributable to noncontrolling interests	(81)	(74)	29
Comprehensive income attributable to Parent	$ 5,058	$ 4,312	$ 3,361

Consolidated Statement of Comp6

Consolidated Statement of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Unrealized gains (losses) on marketable securities, deferred taxes	$ 25	$ (1)	$ (1)
Deferred gains (losses) on cash flow hedges, deferred taxes	(35)	35	62
Realized (gains) losses on marketable securities, deferred taxes	1	1	1
Realized (gains) losses on cash flow hedges, deferred taxes	22	(54)	(38)
Employee benefit obligations, deferred taxes	(24)	(125)	(43)
Currency translation adjustments, deferred taxes	$ (40)	$ (14)	$ 34

Consolidated Statement of Cash

Consolidated Statement of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Activities
Net income	$ 22,900	$ 9,045	$ 8,413
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and other operating gains	9,825	9,558	8,680
Share-based compensation	751	640	567
Noncash interest expense (income), net	272	230	205
Equity in net (income) losses of investees, net	(107)	104	325
Cash received from investees	95	85	168
Net (gain) loss on investment activity and other	(182)	(169)	(318)
Deferred income taxes	(10,655)	1,444	958
Changes in operating assets and liabilities, net of effects of acquisitions and divestitures:
Current and noncurrent receivables, net	(888)	(782)	(708)
Film and television costs, net	(197)	(495)	(299)
Accounts payable and accrued expenses related to trade creditors	181	374	384
Other operating assets and liabilities	(592)	(209)	1,110
Net cash provided by operating activities	21,403	19,825	19,485
Investing Activities
Capital expenditures	(9,550)	(9,135)	(8,499)
Cash paid for intangible assets	(1,747)	(1,686)	(1,370)
Acquisitions and construction of real estate properties	(418)	(428)	(178)
Acquisitions, net of cash acquired	(532)	(3,929)	(1,786)
Proceeds from sales of businesses and investments	150	218	433
Purchases of investments	(2,292)	(1,697)	(784)
Deposits	0	(1,749)	(18)
Other	685	21	238
Net cash provided by (used in) investing activities	(13,704)	(18,385)	(11,964)
Financing Activities
Proceeds from (repayments of) short-term borrowings, net	(1,905)	1,790	135
Proceeds from borrowings	11,466	9,231	5,486
Repurchases and repayments of debt	(6,364)	(3,052)	(4,378)
Repurchases of common stock under repurchase program and employee plans	(5,435)	(5,352)	(7,175)
Dividends paid	(2,883)	(2,601)	(2,437)
Purchase of Universal Studios Japan noncontrolling interests	(2,299)	0	0
Issuances of common stock	0	23	36
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock	(252)	(253)	(232)
Other	100	(220)	(571)
Net cash provided by (used in) financing activities	(7,572)	(434)	(9,136)
Increase (decrease) in cash and cash equivalents	127	1,006	(1,615)
Cash and cash equivalents, beginning of year	3,301	2,295	3,910
Cash and cash equivalents, end of year	3,428	3,301	2,295
NBCUniversal Media LLC [Member]
Operating Activities
Net income	5,218	4,546	3,624
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and other operating gains	1,704	1,805	1,539
Equity in net (income) losses of investees, net	201	99	376
Cash received from investees	85	68	60
Net (gain) loss on investment activity and other	142	(80)	56
Deferred income taxes	2	89	(11)
Changes in operating assets and liabilities, net of effects of acquisitions and divestitures:
Current and noncurrent receivables, net	(615)	(635)	(718)
Film and television costs, net	(199)	(502)	(304)
Accounts payable and accrued expenses related to trade creditors	(43)	51	97
Other operating assets and liabilities	581	(544)	585
Net cash provided by operating activities	7,076	4,897	5,304
Investing Activities
Capital expenditures	(1,502)	(1,452)	(1,386)
Cash paid for intangible assets	(295)	(283)	(211)
Acquisitions, net of cash acquired	(140)	(205)	(1,522)
Proceeds from sales of businesses and investments	45	109	218
Purchases of investments	(490)	(290)	(649)
Other	506	(123)	150
Net cash provided by (used in) investing activities	(1,876)	(2,244)	(3,400)
Financing Activities
Proceeds from borrowings	3,948	0	0
Repurchases and repayments of debt	(3,498)	(1,565)	(1,022)
Proceeds from (repayments of) borrowings from Comcast, net	(872)	928	854
Purchase of Universal Studios Japan noncontrolling interests	(2,299)	0	0
Distributions to member	(1,968)	(1,606)	(1,385)
Distributions to noncontrolling interests	(209)	(210)	(189)
Other	79	356	0
Net cash provided by (used in) financing activities	(4,819)	(2,097)	(1,742)
Increase (decrease) in cash and cash equivalents	381	556	162
Cash and cash equivalents, beginning of year	1,966	1,410	1,248
Cash and cash equivalents, end of year	$ 2,347	$ 1,966	$ 1,410

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]	Treasury Stock at Cost [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interest [Member]	NBCUniversal Media LLC [Member]	NBCUniversal Media LLC [Member]Redeemable Noncontrolling Interest [Member]	NBCUniversal Media LLC [Member]Member's Capital [Member]	NBCUniversal Media LLC [Member]Accumulated Other Comprehensive Income (Loss) [Member]	NBCUniversal Media LLC [Member]Noncontrolling Interest [Member]	Class A Common Stock [Member]Common Stock [Member]	Class A Special Common Stock [Member]Common Stock [Member]	Class B Common Stock [Member]Common Stock [Member]
Beginning Balance at Dec. 31, 2014	$ 53,068		$ 38,776	$ 21,539	$ (7,517)	$ (146)	$ 357						$ 50	$ 9	$ 0
Beginning Balance at Dec. 31, 2014								$ 30,637		$ 30,529	$ (159)	$ 267
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock compensation plans	768		768
Repurchases of common stock under repurchase program and employee plans	(7,181)		(1,373)	(5,806)										(2)
Employee stock purchase plans	136		136
Dividends declared / Distributions to member	(2,483)			(2,483)				(1,385)		(1,385)
Other comprehensive income (loss)	(57)					(28)	(29)	(82)			(53)	(29)
Acquisition of Universal Studios Japan	1,440						1,440	1,429		(11)		1,440
Contributions from (distributions to) noncontrolling interests, net	(146)						(146)	(159)				(159)
Contribution from member								252		252
Reclassification of Class A Special common stock	0												7	(7)
Other	106		183				(77)	31		35		(4)
Net income (loss)	8,327			8,163			164	3,580		3,414		166
Ending Balance at Dec. 31, 2015	53,978		38,490	21,413	(7,517)	(174)	1,709						57	0	0
Ending Balance at Dec. 31, 2015								34,303		32,834	(212)	1,681
Beginning Balance at Dec. 31, 2014		$ 1,066							$ 330
Increase (Decrease) in Temporary Equity [Roll Forward]
Contributions from (distributions to) noncontrolling interests, net		11							(30)
Other		58							28
Net income (loss)		86							44
Ending Balance at Dec. 31, 2015		1,221							372
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock compensation plans	770		770
Repurchases of common stock under repurchase program and employee plans	(5,376)		(999)	(4,376)									(1)
Employee stock purchase plans	156		156
Dividends declared / Distributions to member	(2,656)			(2,656)				(1,606)		(1,606)
Other comprehensive income (loss)	346					272	74	151			77	74
Contributions from (distributions to) noncontrolling interests, net	(134)						(134)	(148)				(148)
Contribution from member								3,655		3,566		89
Other	138		(187)				325	165		7		158
Net income (loss)	8,952			8,695			257	4,497		4,235		262
Ending Balance at Dec. 31, 2016	56,174		38,230	23,076	(7,517)	98	2,231						56	0	0
Ending Balance at Dec. 31, 2016								41,017		39,036	(135)	2,116
Increase (Decrease) in Temporary Equity [Roll Forward]
Contributions from (distributions to) noncontrolling interests, net		(16)							(59)
Other		148							168
Net income (loss)		93							49
Ending Balance at Dec. 31, 2016	1,446	1,446						530	530
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock compensation plans	554		554
Repurchases of common stock under repurchase program and employee plans	(5,456)		(832)	(4,623)									(1)
Employee stock purchase plans	190		190
Dividends declared / Distributions to member	(2,975)			(2,975)				(1,968)		(1,968)
Other comprehensive income (loss)	168					87	81	55			(26)	81
Contributions from (distributions to) noncontrolling interests, net	(108)						(108)	(120)				(120)
Contribution from member								662		662
Purchase of Universal Studios Japan noncontrolling interests	(2,238)		(696)			194	(1,736)	(2,299)		(704)	141	(1,736)
Other	313		51				262	651		185		466
Net income (loss)	22,827			22,714			113	5,190		5,084		106
Ending Balance at Dec. 31, 2017	69,449		$ 37,497	$ 38,192	$ (7,517)	$ 379	$ 843						$ 55	$ 0	$ 0
Ending Balance at Dec. 31, 2017								43,188		$ 42,295	$ (20)	$ 913
Increase (Decrease) in Temporary Equity [Roll Forward]
Contributions from (distributions to) noncontrolling interests, net		(39)							(65)
Other		(123)							(84)
Net income (loss)		73							28
Ending Balance at Dec. 31, 2017	$ 1,357	$ 1,357						$ 409	$ 409

Business and Basis of Presentat

Business and Basis of Presentation	12 Months Ended
	Dec. 31, 2017
Business And Basis Of Presentation [Line Items]
Business and Basis of Presentation	Note 1: Business and Basis of Presentation We are a global media and technology company with two primary businesses, Comcast Cable and NBCUniversal. We were incorporated under the laws of Pennsylvania in December 2001. Through our predecessors, we have developed, managed and operated cable systems since 1963. We present our operations for Comcast Cable in one reportable business segment, referred to as Cable Communications, and our operations for NBCUniversal in four reportable business segments: Cable Networks, Broadcast Television, Filmed Entertainment and Theme Parks (collectively, the “NBCUniversal segments”). See Note 17 for additional information on our reportable business segments. Our Cable Communications segment primarily manages and operates cable systems that serve residential and business customers in the United States and sells advertising. As of December 31, 2017 , our cable systems had 29.3 million total customer relationships, including 27.2 million residential and 2.2 million business customer relationships, and served 22.4 million video customers, 25.9 million high-speed Internet customers and 11.6 million voice customers. Our Cable Networks segment consists primarily of a diversified portfolio of cable television networks. Our cable networks are comprised of our national cable networks that provide a variety of entertainment, news and information, and sports content; our regional sports and news networks; our international cable networks; our cable television studio production operations; and our various digital properties. Our Broadcast Television segment consists primarily of the NBC and Telemundo broadcast networks, our NBC and Telemundo owned local broadcast television stations, the NBC Universo national cable network, our broadcast television studio production operations; and our various digital properties. Our Filmed Entertainment segment primarily produces, acquires, markets and distributes filmed entertainment worldwide. Our films are produced primarily under the Universal Pictures, Illumination, DreamWorks Animation and Focus Features names. See Note 5 for additional information on the DreamWorks Animation acquisition. Our Theme Parks segment consists primarily of our Universal theme parks in Orlando, Florida; Hollywood, California; and Osaka, Japan. See Note 5 for additional information on the Universal Studios Japan transactions. Our other business interests, which are included in Corporate and Other, consist primarily of Comcast Spectacor, which owns the Philadelphia Flyers and the Wells Fargo Center arena in Philadelphia, Pennsylvania and operates arena management-related businesses, and our wireless phone service, which commenced operations in 2017. 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 in accordance with generally accepted accounting principles in the United States (“GAAP”). We translate assets and liabilities of our foreign operations where the functional currency is the local currency, primarily the Japanese yen, euro and British pound, 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. Stock Split On January 24, 2017, our Board of Directors approved a two -for-one stock split in the form of a 100% stock dividend that was distributed on February 17, 2017 to shareholders of record as of February 8, 2017. The stock split was in the form of one additional share for every share held and was payable in shares of Class A common stock for both the existing Class A common stock and Class B common stock. All share-based data, including the number of shares outstanding and per share amounts, have been adjusted to reflect the stock split for all periods presented. Reclassifications Reclassifications have been made to our consolidated financial statements for the prior periods to conform to classifications used in 2017 .
NBCUniversal Media LLC [Member]
Business And Basis Of Presentation [Line Items]
Business and Basis of Presentation	Note 1: Business and Basis of Presentation Unless indicated otherwise, throughout these notes to the consolidated financial statements, we refer to NBCUniversal and its consolidated subsidiaries as “we,” “us” and “our.” We are one of the world’s leading media and entertainment companies that develops, produces and distributes entertainment, news and information, sports, and other content for global audiences, and owns and operates theme parks worldwide. We present our operations as the following four reportable business segments: Cable Networks, Broadcast Television, Filmed Entertainment and Theme Parks. See Note 15 for additional information on our reportable business segments. Our Cable Networks segment consists primarily of a diversified portfolio of cable television networks. Our cable networks are comprised of our national cable networks that provide a variety of entertainment, news and information, and sports content; our regional sports and news networks; our international cable networks; our cable television studio production operations; and our various digital properties. Our Broadcast Television segment consists primarily of the NBC and Telemundo broadcast networks, our NBC and Telemundo owned local broadcast television stations, the NBC Universo national cable network, our broadcast television studio production operations; and our various digital properties. Our Filmed Entertainment segment primarily produces, acquires, markets and distributes filmed entertainment worldwide. Our films are produced primarily under the Universal Pictures, Illumination, DreamWorks Animation and Focus Features names. See Note 4 for additional information on the DreamWorks Animation acquisition. Our Theme Parks segment consists primarily of our Universal theme parks in Orlando, Florida; Hollywood, California; and Osaka, Japan. See Note 4 for additional information on the Universal Studios Japan transactions. 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 in accordance with generally accepted accounting principles in the United States (“GAAP”). Transactions between NBCUniversal and both Comcast and Comcast’s consolidated subsidiaries are reflected in these consolidated financial statements and disclosed as related party transactions when material. We translate assets and liabilities of our foreign operations where the functional currency is the local currency, primarily the Japanese yen, euro and British pound, 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.

Accounting Policies

Accounting Policies	12 Months Ended
	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounting Policies	Note 2: 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. We believe that the judgments and related estimates for the following items are critical in the preparation of our consolidated financial statements: • valuation and impairment testing of cable franchise rights (see Note 9) • film and television costs (see Note 6) In addition, the following accounting policies are specific to the industries in which we operate: • capitalization and amortization of film and television costs (see Note 6) • installation revenue and costs for connecting customers to our cable systems (see revenue recognition below and Note 8) 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. Below is a discussion of accounting policies and methods used in our consolidated financial statements that are not presented within other footnotes. Revenue Recognition Cable Communications Segment Our Cable Communications segment generates revenue primarily from residential and business customers that subscribe to our video, high-speed Internet, voice, and security and automation services (“cable services”), and from the sale of advertising. We recognize revenue from cable services as each service is provided. Customers are typically billed in advance on a monthly basis based on the services and features they receive and the type of equipment they use. Since installation revenue obtained from the connection of customers to our cable systems is less than the related direct selling costs, we recognize revenue as connections are completed. We manage credit risk by screening applicants through the use of internal customer information, identification verification tools and credit bureau data. If a customer’s account is delinquent, various measures are used to collect outstanding amounts, including termination of the customer’s cable services. As part of our distribution agreements with cable networks, we generally receive an allocation of scheduled advertising time on cable networks that we sell through our advertising business to local, regional and national advertisers. We recognize advertising revenue when the advertising is aired or viewed. In most cases, the available advertising units are sold by our sales force. 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. 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 revenue and the fees paid to representation firms and multichannel video providers in other operating and administrative expenses. Under the terms of our cable franchise agreements, we are generally required to pay to the cable franchising authority an amount based on our gross video revenue. We pass these fees through to our cable services customers and classify the fees as a component of revenue with the corresponding costs included in other operating and administrative expenses. Cable Networks and Broadcast Television Segments Our Cable Networks segment generates revenue primarily from the distribution of our cable network programming to traditional and virtual multichannel video providers; from the sale of advertising on our cable networks and digital properties; from the licensing of our owned programming, including programming from our cable television studio production operations, to cable and broadcast networks and subscription video on demand services; and from the sale of our owned programming on standard-definition digital video discs and Blu-ray discs (together, “DVDs”) and through digital distribution services such as iTunes. Our Broadcast Television segment generates revenue primarily from the sale of advertising on our broadcast networks, owned local broadcast television stations and digital properties; from the licensing of our owned programming by our broadcast television studio production operations to various distribution platforms, including to cable and broadcast networks as well as to subscription video on demand services; from the fees received under retransmission consent agreements and associated fees received from NBC-affiliated local broadcast television stations; and from the sale of our owned programming on DVDs and through digital distribution services. We recognize revenue from distributors as programming is provided, generally under multiyear distribution agreements. From time to time, the distribution agreements expire while programming continues to be provided to the distributor based on interim arrangements while the parties negotiate new contract terms. Revenue recognition is generally limited to current payments being made by the distributor, typically under the prior contract terms, until a new contract is negotiated, sometimes with effective dates that affect prior periods. Differences between actual amounts determined upon resolution of negotiations and amounts recorded during these interim arrangements are recorded in the period of resolution. Advertising revenue for our Cable Networks and Broadcast Television segments is recognized in the period in which the advertising is aired or viewed. In some instances, we guarantee audience ratings for the advertising. To the extent there is a shortfall in the ratings that were guaranteed, a portion of the revenue is deferred until the shortfall is settled, primarily by providing additional advertising units. We recognize revenue from the licensing of our owned programming, including programming produced by our studios for third parties, when the content is made available for use by the licensee and when certain other conditions are met. When license fees include advertising time, we recognize the component of revenue associated with the advertisements when they are aired or viewed. Filmed Entertainment Segment Our Filmed Entertainment segment generates revenue primarily from the worldwide distribution of our produced and acquired films for exhibition in movie theaters, from the licensing of produced and acquired films through various distribution platforms, and from the sale of produced and acquired films on DVDs and through digital distribution services. Our Filmed Entertainment segment also generates revenue from Fandango, our movie ticketing and entertainment business, the sale of consumer products, the production and licensing of live stage plays, and the distribution of filmed entertainment produced by third parties. We recognize revenue from the distribution of films to movie theaters when the films are exhibited. We recognize revenue from the licensing of a film when the film is made available for use by the licensee, and when certain other conditions are met. We recognize revenue from the sale of DVDs, net of estimated returns and customer incentives, on the date that the DVDs are delivered to and made available for sale by retailers. Theme Parks Segment Our Theme Parks segment generates revenue primarily from ticket sales and guest spending at our Universal theme parks. We recognize revenue from advance theme park ticket sales when the tickets are used. For annual passes, we recognize revenue on a straight-line basis over the period following the activation date. Cable Communications Programming Expenses Cable Communications programming expenses are the fees we pay to license the programming we distribute to our video customers. Programming is generally acquired under multiyear distribution agreements, with rates typically based on the number of customers that receive the programming, channel positioning and the extent of distribution. From time to time, these contracts expire and programming continues to be provided under interim arrangements while the parties negotiate new contract terms, sometimes with effective dates that affect prior periods. While payments are typically made under the prior contract’s terms, the amount of programming expenses recorded during the interim arrangement is based on our estimate of the ultimate contract terms expected to be negotiated. Differences between actual amounts determined upon resolution of negotiations and amounts recorded during these interim arrangements are recorded in the period of resolution. When our Cable Communications segment receives incentives from a cable network for the licensing of its programming, we defer a portion of these incentives, which are included in other current and noncurrent liabilities, and recognize them over the term of the contract as a reduction to programming expenses. Advertising Expenses Advertising costs are expensed as incurred. Cash Equivalents The carrying amounts of our cash equivalents approximate their fair values. Our cash equivalents consist primarily of money market funds and U.S. government obligations, as well as commercial paper and certificates of deposit with maturities of three months or less when purchased. 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. The impact of our derivative financial instruments on our consolidated financial statements was not material 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 (market approach, income approach and cost approach). 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 financial instruments and valuation models whose inputs are observable • Level 3: Values are determined using pricing 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 We use these levels of hierarchy to measure the fair value of certain financial instruments on a recurring basis, such as for investments; on a non-recurring basis, such as for acquisitions and impairment testing; for disclosure purposes, such as for long-term debt and redeemable subsidiary preferred stock; and for other applications, as discussed in their respective footnotes. Our assessment of the significance of a particular input to the fair value measurement requires judgment and may affect the valuation and classification within the fair value hierarchy. Asset Retirement Obligations 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 any 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 retirements recorded in our consolidated financial statements.
NBCUniversal Media LLC [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounting Policies	Note 2: 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. We believe that the judgments and related estimates for the following items are critical in the preparation of our consolidated financial statements: • revenue recognition (see below) • film and television costs (see Note 6) • goodwill and intangible assets (see Note 9) In addition, the following accounting policy is specific to the industries in which we operate: • capitalization and amortization of film and television costs (see Note 6) 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. Below is a discussion of accounting policies and methods used in our consolidated financial statements that are not presented within other footnotes. Revenue Recognition Cable Networks and Broadcast Television Segments Our Cable Networks segment generates revenue primarily from the distribution of our cable network programming to traditional and virtual multichannel video providers; from the sale of advertising on our cable networks and digital properties; from the licensing of our owned programming, including programming from our cable television studio production operations, to cable and broadcast networks and subscription video on demand services; and from the sale of our owned programming on standard-definition digital video discs and Blu-ray discs (together, “DVDs”) and through digital distribution services such as iTunes. Our Broadcast Television segment generates revenue primarily from the sale of advertising on our broadcast networks, owned local broadcast television stations and digital properties; from the licensing of our owned programming by our broadcast television studio production operations to various distribution platforms, including to cable and broadcast networks as well as to subscription video on demand services; from the fees received under retransmission consent agreements and associated fees received from NBC-affiliated local broadcast television stations; and from the sale of our owned programming on DVDs and through digital distribution services. We recognize revenue from distributors as programming is provided, generally under multiyear distribution agreements. From time to time, the distribution agreements expire while programming continues to be provided to the distributor based on interim arrangements while the parties negotiate new contract terms. Revenue recognition is generally limited to current payments being made by the distributor, typically under the prior contract terms, until a new contract is negotiated, sometimes with effective dates that affect prior periods. Differences between actual amounts determined upon resolution of negotiations and amounts recorded during these interim arrangements are recorded in the period of resolution. Advertising revenue for our Cable Networks and Broadcast Television segments is recognized in the period in which the advertising is aired or viewed. In some instances, we guarantee audience ratings for the advertising. To the extent there is a shortfall in the ratings that were guaranteed, a portion of the revenue is deferred until the shortfall is settled, primarily by providing additional advertising units. We recognize revenue from the licensing of our owned programming, including programming produced by our studios for third parties, when the content is made available for use by the licensee and when certain other conditions are met. When license fees include advertising time, we recognize the component of revenue associated with the advertisements when they are aired or viewed. Filmed Entertainment Segment Our Filmed Entertainment segment generates revenue primarily from the worldwide distribution of our produced and acquired films for exhibition in movie theaters, from the licensing of produced and acquired films through various distribution platforms, and from the sale of produced and acquired films on DVDs and through digital distribution services. Our Filmed Entertainment segment also generates revenue from Fandango, our movie ticketing and entertainment business, the sale of consumer products, the production and licensing of live stage plays, and the distribution of filmed entertainment produced by third parties. We recognize revenue from the distribution of films to movie theaters when the films are exhibited. We recognize revenue from the licensing of a film when the film is made available for use by the licensee, and when certain other conditions are met. We recognize revenue from the sale of DVDs, net of estimated returns and customer incentives, on the date that the DVDs are delivered to and made available for sale by retailers. Theme Parks Segment Our Theme Parks segment generates revenue primarily from ticket sales and guest spending at our Universal theme parks. We recognize revenue from advance theme park ticket sales when the tickets are used. For annual passes, we recognize revenue on a straight-line basis over the period following the activation date. Advertising Expenses Advertising costs are expensed as incurred. Cash Equivalents The carrying amounts of our cash equivalents approximate their fair values. Our cash equivalents consist primarily of money market funds and U.S. government obligations, as well as commercial paper and certificates of deposit with maturities of three months or less when purchased. Derivative Financial Instruments We use derivative financial instruments to manage our exposure to the risks associated with fluctuations in foreign exchange rates and interest rates. 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. The impact of our derivative financial instruments on our consolidated financial statements was not material 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 (market approach, income approach and cost approach). 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 financial instruments and valuation models whose inputs are observable • Level 3: Values are determined using pricing 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 We use these levels of hierarchy to measure the fair value of certain financial instruments on a recurring basis, such as for investments; on a non-recurring basis, such as for acquisitions and impairment testing; for disclosure purposes, such as long-term debt; and for other applications, as discussed in their respective footnotes. Our assessment of the significance of a particular input to the fair value measurement requires judgment and may affect the valuation and classification within the fair value hierarchy.

Recent Accounting Pronouncement

Recent Accounting Pronouncements	12 Months Ended
	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Recent Accounting Pronouncements	Note 3: Recent Accounting Pronouncements Revenue Recognition In May 2014, the Financial Accounting Standards Board (“FASB”) updated the accounting guidance related to revenue recognition. The updated accounting guidance provides a single, contract-based revenue recognition model to help improve financial reporting by providing clearer guidance on when an entity should recognize revenue and by reducing the number of standards to which an entity has to refer. The updated guidance also requires additional disclosures regarding the nature, timing and uncertainty of our revenue transactions. We will adopt the updated accounting guidance in the first quarter of 2018 using the full retrospective method, which requires the adjustment of all prior periods presented to reflect the impacts of the updated guidance. The adoption of the new standard will not have a material impact to our consolidated financial position or results of operations. A summary of the changes that will be implemented in 2018 in connection with the new standard are presented below. Changes to Presentation of Revenue and Related Costs with No Impact to the Timing of Recognition • Revenue from our residential video services in our Cable Communications segment will decrease with corresponding increases to high-speed Internet and voice revenue due to a change in the allocation of revenue among our cable services included in a bundle that our residential customers purchase at a discount. • Revenue from franchise and other regulatory fees, which was previously presented in other revenue, will be presented with the corresponding cable services in our Cable Communications segment. This will result in increases to video, voice and business services revenue. • Customer late fees in our Cable Communications segment will now be presented in other and in business services revenue. These fees were previously presented as a reduction to other operating and administrative expenses. • Certain costs, including costs related to the fulfillment of contracts with customers, in our Cable Communications segment will be presented as other assets and the related costs will be recognized over time in operating costs and expenses, which are comprised of total costs and expenses, excluding depreciation and amortization expense and other operating gains. These amounts were previously presented as intangible assets, and the expenses were previously presented in amortization expense. The payments related to these assets will be presented in net cash provided by operating activities rather than in cash paid for intangible assets in our consolidated statement of cash flows. The table below presents the expected effects upon adoption these changes in presentation would have had on our Cable Communications segment revenue, operating costs and expenses and depreciation and amortization expense in 2017 and 2016. Year ended December 31 (in millions) 2017 2016 As Reported Effects of Adoption (a) Upon Adoption (a) As Reported Effects of Adoption (a) Upon Adoption (a) Cable Communications segment Revenue $ 52,519 $ 482 $ 53,001 $ 50,048 $ 471 $ 50,519 Operating costs and expenses $ 31,349 $ 619 $ 31,968 $ 29,939 $ 602 $ 30,541 Depreciation and amortization expense $ 8,143 $ (137 ) $ 8,006 $ 7,670 $ (131 ) $ 7,539 (a) Certain other immaterial changes in presentation and the impacts due to changes in timing of revenue recognition and related costs described below were excluded from the table. The final effects of the adoption will differ from the amounts presented above. Changes to the Timing of Recognition of Revenue and Related Costs • Installation revenue and commission expenses in our Cable Communications segment will be recognized as revenue and costs, respectively, over a period of time. These amounts were previously recognized immediately. • Content licensing revenue associated with renewals or extensions of existing program licensing agreements in our Cable Networks, Broadcast Television and Filmed Entertainment segments will be recognized as revenue when the licensed content becomes available under the renewal or extension. These renewals or extensions were previously recognized as revenue when the agreement was executed. Financial Assets and Financial Liabilities In January 2016, the FASB updated the accounting guidance related to the recognition and measurement of financial assets and financial liabilities. The updated accounting guidance, among other things, requires that all nonconsolidated equity investments, except those accounted for under the equity method, be measured at fair value and that the changes in fair value be recognized in net income. The updated guidance is effective for us as of January 1, 2018. With certain exceptions, the updated accounting guidance requires a cumulative effect adjustment to beginning retained earnings in the year the guidance is adopted. If we had adopted the provisions of the updated guidance as of January 1, 2017 for our equity investments classified as available-for-sale securities, primarily our investment in Snap Inc. (see Note 7), net income attributable to Comcast Corporation would have decreased by $44 million in 2017. If we had adopted the provisions of the updated guidance as of January 1, 2017 for our equity investments classified as cost method investments, the impact on our net income attributable to Comcast Corporation would not have been material. Leases In February 2016, the FASB updated the accounting guidance related to leases. The updated accounting guidance requires lessees to recognize a right-of-use asset and a lease liability on the balance sheet for all leases with the exception of short-term leases. The asset and liability are initially measured based on the present value of committed lease payments. For a lessee, the recognition, measurement and presentation of expenses and cash flows arising from a lease do not significantly change from previous guidance. For a lessor, the accounting applied is also largely unchanged from previous guidance. The updated guidance is effective for us as of January 1, 2019 and early adoption is permitted. The updated accounting guidance must be adopted using a modified retrospective approach for leases that exist or are entered into after the beginning of the earliest comparative period in the financial statements. We are currently in the process of determining the impact that the updated accounting guidance will have on our consolidated financial statements. See Note 16 for a summary of our undiscounted minimum rental commitments under operating leases as of December 31, 2017. Share-Based Compensation In March 2016, the FASB updated the accounting guidance that affects several aspects of the accounting for share-based compensation. The most significant change for us relates to the presentation of the income and withholding tax consequences of share-based compensation in our consolidated financial statements. Among the changes, the updated guidance requires that the excess income tax benefits or deficiencies that arise when the tax consequences of share-based compensation differ from amounts previously recognized in the statement of income be recognized as income tax benefit or expense in the statement of income rather than as additional paid-in capital in the balance sheet. The guidance also states that excess income tax benefits should not be presented separately from other income taxes in the statement of cash flows and, thus, should be classified as an operating activity rather than a financing activity as they were under the prior guidance. In addition, the updated guidance requires that, when an employer withholds shares upon exercise of options or the vesting of restricted stock for the purpose of meeting withholding tax requirements, the cash paid for withholding taxes be classified as a financing activity. We include these amounts in the caption “repurchases of common stock under repurchase program and employee plans” in our consolidated statement of cash flows. We previously recorded these amounts as operating activities. We adopted the updated guidance as of January 1, 2017 and as required, we prospectively adopted the provisions that relate to the recognition of the excess income tax benefits or deficiencies in our consolidated statement of income. The excess tax benefits resulted in an increase to income tax benefit in 2017 of $297 million and our diluted earnings per common share attributable to Comcast Corporation shareholders in 2017 increased by $0.04 . As required by the updated guidance, the prior year periods in our consolidated statement of income were not adjusted as a result of these provisions. In addition, we retrospectively adopted the provisions of this guidance related to changes to the statement of cash flows for all periods presented. This resulted in increases to net cash provided by operating activities and decreases to net cash provided by (used in) financing activities of $732 million , $585 million and $707 million in 2017, 2016 and 2015, respectively.
NBCUniversal Media LLC [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Recent Accounting Pronouncements	Note 3: Recent Accounting Pronouncements Revenue Recognition In May 2014, the Financial Accounting Standards Board (“FASB”) updated the accounting guidance related to revenue recognition. The updated accounting guidance provides a single, contract-based revenue recognition model to help improve financial reporting by providing clearer guidance on when an entity should recognize revenue and by reducing the number of standards to which an entity has to refer. The updated guidance also requires additional disclosures regarding the nature, timing and uncertainty of our revenue transactions. We will adopt the updated accounting guidance in the first quarter of 2018 using the full retrospective method, which requires the adjustment of all prior periods presented to reflect the impacts of the updated guidance. The adoption of the new standard will not have a material impact to our consolidated financial position or results of operations. However, we do expect that the new standard will impact the timing of the recognition of content licensing revenue associated with renewals or extensions of existing program licensing agreements in our Cable Networks, Broadcast Television and Filmed Entertainment segments, which will be recognized as revenue when the licensed content becomes available under the renewal or extension. These renewals or extensions were previously recognized as revenue when the agreement was executed. Financial Assets and Financial Liabilities In January 2016, the FASB updated the accounting guidance related to the recognition and measurement of financial assets and financial liabilities. The updated accounting guidance, among other things, requires that all nonconsolidated equity investments, except those accounted for under the equity method, be measured at fair value and that the changes in fair value be recognized in net income. The updated guidance is effective for us as of January 1, 2018. With certain exceptions, the updated accounting guidance requires a cumulative effect adjustment to beginning retained earnings in the year the guidance is adopted. If we had adopted the provisions of the updated guidance as of January 1, 2017 for our equity investments classified as available-for-sale securities, primarily our investment in Snap Inc. (see Note 7), net income attributable to NBCUniversal would have decreased by $233 million in 2017. If we had adopted the provisions of the updated guidance as of January 1, 2017 for our cost method investments, the impact on our net income attributable to NBCUniversal would not have been material. Leases In February 2016, the FASB updated the accounting guidance related to leases. The updated accounting guidance requires lessees to recognize a right-of-use asset and a lease liability on the balance sheet for all leases with the exception of short-term leases. The asset and liability are initially measured based on the present value of committed lease payments. For a lessee, the recognition, measurement and presentation of expenses and cash flows arising from a lease do not significantly change from previous guidance. For a lessor, the accounting applied is also largely unchanged from previous guidance. The updated guidance is effective for us as of January 1, 2019 and early adoption is permitted. The updated accounting guidance must be adopted using a modified retrospective approach for leases that exist or are entered into after the beginning of the earliest comparative period in the financial statements. We are currently in the process of determining the impact that the updated accounting guidance will have on our consolidated financial statements. See Note 14 for a summary of our undiscounted minimum rental commitments under operating leases as of December 31, 2017.

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Earnings Per Share	Note 4: Earnings Per Share Computation of Diluted EPS 2017 2016 2015 Year ended December 31 Net Income Shares Per Share Net Income Shares Per Share Net Income Shares Per Share Basic EPS attributable to Comcast Corporation shareholders $ 22,714 4,708 $ 4.82 $ 8,695 4,819 $ 1.80 $ 8,163 4,972 $ 1.64 Effect of dilutive securities: Assumed exercise or issuance of shares relating to stock plans 78 56 63 Diluted EPS attributable to Comcast Corporation shareholders $ 22,714 4,786 $ 4.75 $ 8,695 4,875 $ 1.78 $ 8,163 5,035 $ 1.62 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.

Significant Transactions

Significant Transactions	12 Months Ended
	Dec. 31, 2017
Business Acquisition [Line Items]
Significant Transactions	Note 5: Significant Transactions 2017 FCC Spectrum Auction On April 13, 2017, the Federal Communications Commission announced the results of its spectrum auction. In the auction, NBCUniversal relinquished its spectrum rights in the New York, Philadelphia and Chicago designated market areas (“DMAs”) where NBC and Telemundo had overlapping spectrum. NBCUniversal received proceeds of $482 million in July 2017, which were recorded in other investing activities in our consolidated statement of cash flows. NBCUniversal recognized a pretax gain of $337 million in other operating gains in 2017. NBC and Telemundo stations will share broadcast signals in these DMAs. In connection with the auction, we also acquired the rights to $1.7 billion of spectrum in the second quarter of 2017, which were recorded to other intangible assets, net. We had previously made a deposit of $1.8 billion to participate in the auction in 2016 and received a refund for amounts in excess of the purchase price in 2017. Universal Studios Japan On April 6, 2017, we acquired the remaining interests in Universal Studios Japan that we did not already own for $2.3 billion . The acquisition was funded through cash on hand and borrowings under our commercial paper program. Because we maintained control of Universal Studios Japan, the difference between the consideration transferred and the recorded value of the noncontrolling interests, as well as the related tax and accumulated other comprehensive income impacts, were recorded to additional paid-in capital. 2016 DreamWorks Animation On August 22, 2016, we acquired all of the outstanding stock of DreamWorks Animation for $ 3.8 billion . DreamWorks Animation’s stockholders received $ 41 in cash for each share of DreamWorks Animation common stock. DreamWorks Animation creates animated feature films, television series and specials, live entertainment, and related consumer products. The results of operations for DreamWorks Animation are reported in our Filmed Entertainment segment following the acquisition date. Allocation of Purchase Price The transaction was accounted for under the acquisition method of accounting and, accordingly, the assets and liabilities are to be recorded at their fair market values as of the acquisition date. We recorded the acquired assets and liabilities of DreamWorks Animation at their estimated fair values based on valuation analyses. In valuing acquired assets and liabilities, fair value estimates were primarily based on Level 3 inputs, including future expected cash flows, market rate assumptions and discount rates. The fair value of the assumed debt was primarily based on quoted market values. The fair value of the liability related to a tax receivable agreement that DreamWorks Animation had previously entered into with one of its former stockholders (the “tax receivable agreement”) was based on the contractual settlement provisions in the agreement. Further, we recorded deferred income taxes based on the tax basis of the acquired net assets and the valuation allowances based on the expected use of net operating loss carryforwards. The goodwill is not deductible for tax purposes. In 2017, we updated the allocation of purchase price for DreamWorks Animation based on final valuation analyses, which primarily resulted in increases to noncontrolling interests, intangible assets and goodwill, and decreases to working capital and deferred income tax assets. The changes did not have a material impact on our consolidated financial statements. The table below presents the allocation of the purchase price to the assets and liabilities of DreamWorks Animation. Allocation of Purchase Price (in millions) Film and television costs $ 838 Intangible assets 396 Working capital 156 Debt (381 ) Tax receivable agreement (146 ) Deferred income taxes 291 Other noncurrent assets (liabilities) 170 Identifiable net assets (liabilities) acquired 1,324 Noncontrolling interests (337 ) Goodwill (see Note 9) 2,786 Cash consideration transferred $ 3,773 The tax receivable agreement was settled immediately following the acquisition and the payment was recorded as an operating activity in our consolidated statement of cash flows in 2016. We also repaid all of the assumed debt of DreamWorks Animation in 2016. Revenue and net income attributable to the acquisition of DreamWorks Animation were not material for 2017 or 2016. 2015 Universal Studios Japan On November 13, 2015, NBCUniversal acquired a 51% economic interest in Universal Studios Japan for $1.5 billion . Universal Studios Japan is a consolidated subsidiary of NBCUniversal, and its operations are reported in our Theme Parks segment. The acquisition was funded through cash on hand and borrowings under our commercial paper program. In our allocation of purchase price for this acquisition, we recorded goodwill of $5.1 billion , long-term debt of $3.3 billion and noncontrolling interests of $1.4 billion . Time Warner Cable Merger and Related Divestiture Transactions On April 24, 2015, we and Time Warner Cable Inc. terminated our planned merger, and we terminated our related agreement with Charter Communications, Inc. to spin off, exchange and sell certain cable systems. In connection with these proposed transactions, we incurred incremental transaction-related expenses of $198 million in 2015, which was primarily in other operating and administrative expenses.
NBCUniversal Media LLC [Member]
Business Acquisition [Line Items]
Significant Transactions	Note 4: Significant Transactions 2017 FCC Spectrum Auction On April 13, 2017, the Federal Communications Commission announced the results of its spectrum auction. In the auction, we relinquished our spectrum rights in the New York, Philadelphia and Chicago designated market areas (“DMAs”) where NBC and Telemundo had overlapping spectrum. We received proceeds of $ 482 million in July 2017, which were recorded in other investing activities in our consolidated statement of cash flows. We recognized a pretax gain of $337 million in other operating gains in 2017. NBC and Telemundo stations will share broadcast signals in these DMAs. Universal Studios Japan On April 6, 2017, we acquired the remaining interests in Universal Studios Japan that we did not already own for $ 2.3 billion . The acquisition was funded through borrowings under our revolving credit agreement with Comcast. Because we maintained control of Universal Studios Japan, the difference between the consideration transferred and the recorded value of the noncontrolling interests, as well as the related accumulated other comprehensive income impacts, were recorded to additional paid-in capital. 2016 DreamWorks Animation On August 22, 2016, Comcast acquired all of the outstanding stock of DreamWorks Animation for $ 3.8 billion . DreamWorks Animation’s stockholders received $ 41 in cash for each share of DreamWorks Animation common stock. DreamWorks Animation creates animated feature films, television series and specials, live entertainment, and related consumer products. Following the acquisition, Comcast converted DreamWorks Animation to a limited liability company and contributed its equity to us as a capital contribution. The net assets contributed to us excluded deferred income taxes and other tax-related items recorded by Comcast. The results of operations for DreamWorks Animation are reported in our Filmed Entertainment segment following the acquisition date and are presented as if the initial equity contribution occurred on the date of Comcast’s acquisition. Allocation of Purchase Price The transaction was accounted for under the acquisition method of accounting and, accordingly, the assets and liabilities are to be recorded at their fair market values as of the acquisition date. We recorded the acquired assets and liabilities of DreamWorks Animation at their estimated fair values based on valuation analyses. In valuing acquired assets and liabilities, fair value estimates were primarily based on Level 3 inputs including future expected cash flows, market rate assumptions and discount rates. The fair value of the assumed debt was primarily based on quoted market values. The fair value of the liability related to a tax receivable agreement that DreamWorks Animation had previously entered into with one of its former stockholders (the “tax receivable agreement”) was based on the contractual settlement provisions in the agreement. In 2017, we updated the allocation of purchase price for DreamWorks Animation based on final valuation analyses, which primarily resulted in increases to noncontrolling interests, intangible assets and goodwill, and a decrease to working capital. The changes did not have a material impact on our consolidated financial statements. The table below presents the allocation of the purchase price to the assets and liabilities of DreamWorks Animation. Allocation of Purchase Price (in millions) Film and television costs $ 838 Intangible assets 396 Working capital 156 Debt (381 ) Tax receivable agreement (a) (146 ) Other noncurrent assets (liabilities) and other (b) 461 Identifiable net assets (liabilities) acquired 1,324 Noncontrolling interests (337 ) Goodwill (see Note 9) 2,786 Cash consideration transferred by Comcast $ 3,773 (a) The tax receivable agreement was settled immediately following the acquisition and the payment was recorded as an operating activity in our consolidated statement of cash flows in 2016. Comcast made a separate cash capital contribution of $146 million to fund the settlement, which was recorded as a financing activity in our consolidated statement of cash flows. (b) Other included $279 million recorded to member’s capital that represented deferred income tax assets and other tax-related items recorded by Comcast but excluded from the net assets contributed to us. Revenue and net income attributable to the acquisition of DreamWorks Animation were not material for 2017 or 2016. 2015 Universal Studios Japan On November 13, 2015, we acquired a 51% economic interest in Universal Studios Japan for $1.5 billion . Universal Studios Japan is a consolidated subsidiary and its operations are reported in our Theme Parks segment. The acquisition was funded through cash on hand and borrowings under our commercial paper program. In our allocation of purchase price for this acquisition, we recorded goodwill of $5.1 billion , long-term debt of $3.3 billion and noncontrolling interests of $1.4 billion .

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2017
NBCUniversal Media LLC [Member]
Related Party Transaction [Line Items]
Related Party Transactions	Note 5: Related Party Transactions In the ordinary course of our business, we enter into transactions with Comcast. We generate revenue from Comcast primarily from the distribution of our cable network programming, the fees received under retransmission consent agreements in our Broadcast Television segment and, to a lesser extent, the sale of advertising and our owned programming, and we incur expenses primarily related to advertising and various support services provided by Comcast to us. In September 2016, as part of the Comcast cash management process, we and Comcast amended and restated our revolving credit agreements to increase the amount that we can borrow from Comcast and that Comcast can borrow from us from $3 billion to $5 billion and to extend the maturity date to 2026. Depending on the receivable or payable position, amounts owed by us to Comcast or to us by Comcast under the revolving credit agreements are presented under the captions “note payable to Comcast” and “note receivable from Comcast,” respectively, in our consolidated balance sheet and are presented as current since the amounts include daily borrowings and repayments throughout the year based on our working capital needs. The revolving credit agreements bear interest at floating rates equal to the interest rate calculation under Comcast’s revolving credit facility. The interest rate on Comcast’s revolving credit facility consists of a base rate plus a borrowing margin that is determined based on Comcast’s credit rating. As of December 31, 2017 , the borrowing margin for London Interbank Offered Rate-based borrowings was 1.00% . Comcast is also the counterparty to one of our contractual obligations. As of both December 31, 2017 and 2016 , the carrying value of the liability associated with this contractual obligation was $383 million . The following tables present transactions with Comcast and its consolidated subsidiaries that are included in our consolidated financial statements. Consolidated Balance Sheet December 31 (in millions) 2017 2016 Transactions with Comcast and Consolidated Subsidiaries Receivables, net $ 326 $ 285 Accounts payable and accrued expenses related to trade creditors $ 54 $ 55 Accrued expenses and other current liabilities $ 50 $ 4 Note payable to Comcast $ 1,831 $ 2,703 Long-term debt (see Note 10) $ 610 $ — Other noncurrent liabilities $ 389 $ 389 Consolidated Statement of Income Year ended December 31 (in millions) 2017 2016 2015 Transactions with Comcast and Consolidated Subsidiaries Revenue $ 1,837 $ 1,742 $ 1,349 Total costs and expenses $ (214 ) $ (220 ) $ (246 ) Other income (expense) $ (250 ) $ (69 ) $ (37 ) Distributions to NBCUniversal Holdings In addition to the transaction amounts presented in the table above, we make distributions to NBCUniversal Holdings on a periodic basis to enable its owners to meet their obligations to pay taxes on taxable income generated by our businesses. We also make quarterly distributions to NBCUniversal Holdings to enable it to make its required quarterly payments to NBCUniversal Enterprise at an initial annual rate of 8.25% on the $9.4 billion aggregate liquidation preference of its preferred units. On March 1, 2018, and thereafter on every fifth anniversary of such date, this rate will reset to 7.44% plus the yield on actively traded United States Treasury securities having a 5 year maturity. These distributions are presented under the caption “distributions to member” in our consolidated statement of cash flows. Share-Based Compensation Comcast maintains share-based compensation plans that consist primarily of awards of restricted share units (“RSUs”) and stock options to certain employees and directors as part of its approach to long-term incentive compensation. Additionally, through its employee stock purchase plans, employees are able to purchase shares of Comcast common stock at a discount through payroll deductions. The cost associated with Comcast’s 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 Comcast common stock on the date of grant and are discounted for the lack of dividends, if any, during the vesting period. Stock options are valued using the Black-Scholes option pricing model. Certain of our employees participate in these plans and the expense associated with their participation is settled in cash with Comcast. In 2017, 2016 and 2015, we recognized share-based compensation expense of $ 133 million, $ 99 million, and $ 94 million, respectively. As of December 31, 2017, we had unrecognized pretax compensation expense of $ 245 million related to nonvested Comcast RSUs and unrecognized pretax compensation expense of $ 32 million related to nonvested Comcast stock options that will be recognized over a weighted-average period of approximately 1.8 years and 1.4 years, respectively.

Film and Television Costs

Film and Television Costs	12 Months Ended
	Dec. 31, 2017
Film And Television Cost [Line Items]
Film and Television Costs	Note 6: Film and Television Costs December 31 (in millions) 2017 2016 Film Costs: Released, less amortization $ 1,724 $ 1,750 Completed, not released 50 50 In production and in development 1,149 1,310 2,923 3,110 Television Costs: Released, less amortization 2,259 1,953 In production and in development 818 853 3,077 2,806 Programming rights, less amortization 2,689 2,586 8,689 8,502 Less: Current portion of programming rights 1,613 1,250 Film and television costs $ 7,076 $ 7,252 Based on our current estimates of the total remaining revenue from all sources (“ultimate revenue”), in 2018 we expect to amortize approximately $1.7 billion of film and television costs associated with our original film and television productions that have been released, or are completed and have not been released. Through 2020, we expect to amortize approximately 86% of unamortized film and television costs for our released productions, excluding amounts allocated to acquired libraries. As of December 31, 2017 , acquired film and television libraries, which are included within the “released, less amortization” captions in the table above, had remaining unamortized costs of $475 million . These costs are generally amortized over a period not to exceed 20 years, and approximately 44% of these costs are expected to be amortized through 2020. Capitalization of Film and Television Costs We capitalize film and television production costs, including direct costs, production overhead, print costs, development costs and interest. We amortize capitalized film and television production costs, including acquired libraries, and accrue costs associated with participation and residual payments to programming and production expenses. We generally record the amortization and the accrued costs using the individual film forecast computation method, which amortizes the costs in the same ratio as the associated ultimate revenue. Estimates of ultimate revenue and total costs are based on anticipated release patterns, public acceptance and historical results for similar productions. Unamortized film and television production costs, including acquired libraries, are stated at the lower of unamortized cost or fair value. 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. 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. 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 a film is less than its unamortized costs, we determine the fair value of the film and record an impairment charge for the amount by which the unamortized capitalized costs exceed the film’s fair value. The estimated fair value of a production is based on Level 3 inputs that primarily use an analysis of future expected cash flows. Adjustments to capitalized film production costs were not material in any of the periods presented. 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. 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 a third-party investor under these arrangements as a reduction to our capitalized film costs. Under these arrangements, the investor owns an undivided copyright interest in the film, and therefore in each period we record either a charge or a benefit to programming and production expenses to reflect the estimate of the third-party investor’s interest in the profit or loss of the film. The estimate of the third-party investor’s interest in the profit or loss of a film is determined using the ratio of actual revenue earned to date to the ultimate revenue expected to be recognized over the film’s useful life. We capitalize the costs of programming content that we license but do not own, including rights to multiyear, live-event sports programming, at the earlier of when payments are made for the programming or when the license period begins and the content is made available for use. We amortize capitalized programming costs as the associated programs are broadcast. We generally amortize multiyear, live-event sports programming rights using the ratio of the current period revenue to the estimated ultimate revenue or under the terms of the contract. Programming costs are recorded at the lower of unamortized cost or net realizable value on a program by program, package, channel or daypart basis. A daypart is an aggregation of programs broadcast during a particular time of day or programs of a similar type. Programming acquired by our Cable Networks segment is primarily tested on a channel basis for impairment, whereas programming acquired by our Broadcast Television segment is tested on a daypart basis. If we determine that the estimates of future cash flows are insufficient or if there is no plan to broadcast certain programming, we recognize an impairment charge to programming and production expenses.
NBCUniversal Media LLC [Member]
Film And Television Cost [Line Items]
Film and Television Costs	Note 6: Film and Television Costs December 31 (in millions) 2017 2016 Film Costs: Released, less amortization $ 1,724 $ 1,750 Completed, not released 50 50 In production and in development 1,149 1,310 2,923 3,110 Television Costs: Released, less amortization 2,259 1,953 In production and in development 818 853 3,077 2,806 Programming rights, less amortization 2,677 2,570 8,677 8,486 Less: Current portion of programming rights 1,606 1,241 Film and television costs $ 7,071 $ 7,245 Based on our current estimates of the total remaining revenue from all sources (“ultimate revenue”), in 2018 we expect to amortize approximately $1.7 billion of film and television costs associated with our original film and television productions that have been released, or are completed and have not been released. Through 2020, we expect to amortize approximately 86% of unamortized film and television costs for our released productions, excluding amounts allocated to acquired libraries. As of December 31, 2017 , acquired film and television libraries, which are included within the “released, less amortization” captions in the table above, had remaining unamortized costs of $475 million . These costs are generally amortized over a period not to exceed 20 years, and approximately 44% of these costs are expected to be amortized through 2020. Capitalization of Film and Television Costs We capitalize film and television production costs, including direct costs, production overhead, print costs, development costs and interest. We amortize capitalized film and television production costs, including acquired libraries, and accrue costs associated with participation and residual payments to programming and production expenses. We generally record the amortization and the accrued costs using the individual film forecast computation method, which amortizes the costs in the same ratio as the associated ultimate revenue. Estimates of ultimate revenue and total costs are based on anticipated release patterns, public acceptance and historical results for similar productions. Unamortized film and television production costs, including acquired libraries, are stated at the lower of unamortized cost or fair value. 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. 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. 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 a film is less than its unamortized costs, we determine the fair value of the film and record an impairment charge for the amount by which the unamortized capitalized costs exceed the film’s fair value. The estimated fair value of a production is based on Level 3 inputs that primarily use an analysis of future expected cash flows. Adjustments to capitalized film production costs were not material in any of the periods presented. 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. 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 a third-party investor under these arrangements as a reduction to our capitalized film costs. Under these arrangements, the investor owns an undivided copyright interest in the film, and therefore in each period we record either a charge or a benefit to programming and production expenses to reflect the estimate of the third-party investor’s interest in the profit or loss of the film. The estimate of the third-party investor’s interest in the profit or loss of a film is determined using the ratio of actual revenue earned to date to the ultimate revenue expected to be recognized over the film’s useful life. We capitalize the costs of programming content that we license but do not own, including rights to multiyear, live-event sports programming, at the earlier of when payments are made for the programming or when the license period begins and the content is made available for use. We amortize capitalized programming costs as the associated programs are broadcast. We generally amortize multiyear, live-event sports programming rights using the ratio of the current period revenue to the estimated ultimate revenue or under the terms of the contract. Programming costs are recorded at the lower of unamortized cost or net realizable value on a program by program, package, channel or daypart basis. A daypart is an aggregation of programs broadcast during a particular time of day or programs of a similar type. Programming acquired by our Cable Networks segment is primarily tested on a channel basis for impairment, whereas programming acquired by our Broadcast Television segment is tested on a daypart basis. If we determine that the estimates of future cash flows are insufficient or if there is no plan to broadcast certain programming, we recognize an impairment charge to programming and production expenses.

Investments

Investments	12 Months Ended
	Dec. 31, 2017
Fair Value, Equity And Cost Method Investments [Line Items]
Investments	Note 7: Investments December 31 (in millions) 2017 2016 Fair Value Method: Snap $ 430 $ — Other 167 198 597 198 Equity Method: Atairos 2,388 1,601 Hulu 249 225 Other 909 550 3,546 2,376 Cost Method: AirTouch 1,614 1,599 BuzzFeed 400 400 Other 793 771 2,807 2,770 Total investments 6,950 5,344 Less: Current investments 19 97 Noncurrent investments $ 6,931 $ 5,247 Investment Income (Loss), Net Year ended December 31 (in millions) 2017 2016 2015 Gains (losses) on sales of investments, net $ 12 $ 46 $ 12 Investment impairment losses (29 ) (34 ) (59 ) Interest and dividend income 136 123 115 Other, net 134 78 13 Investment income (loss), net $ 253 $ 213 $ 81 Fair Value Method We classify publicly traded investments that are not accounted for under the equity method as available-for-sale (“AFS”) or trading securities. The estimated fair value of our publicly traded investments was primarily based on Level 1 inputs that use quoted market values. For other fair value method investments, the estimated fair value was 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 AFS securities, we record unrealized gains or losses resulting from changes in fair value between measurement dates as a component of other comprehensive income (loss), except when we consider declines in value to be other than temporary. For trading securities, we record unrealized gains or losses resulting from changes in fair value between measurement dates as a component of investment income (loss), net. We recognize realized gains and losses associated with our fair value method investments using the specific identification method. We classify the cash flows related to purchases of and proceeds from the sale of trading securities based on the nature of the securities and the purpose for which they were acquired. Snap In March 2017, we acquired an interest in Snap Inc. for $500 million as part of its initial public offering, which we have classified as an available-for-sale security. Snap is a camera company whose primary product is Snapchat, a camera app that was created to help people communicate through short videos and images. 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 significant partnership or limited liability company interest. Equity method investments are recorded at cost and are adjusted to recognize (1) our proportionate share 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 (expense), 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 (expense), 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 has a term of up to 12 years and is controlled by management companies led by our former CFO through interests that carry all of the voting rights. We are the only investor other than our former CFO and the other management company employees. We have committed to fund Atairos up to $4 billion in the aggregate at any one time, subject to certain offsets, and $40 million annually for a management fee, subject to certain adjustments. The management company investors have committed to fund up 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 86.5% 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. 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 remaining unfunded capital commitment. In 2017 and 2016, we made cash capital contributions totaling $994 million and $1.2 billion , respectively, to Atairos. 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 2017 and 2016 , we recognized our share of Atairos income of $281 million and Atairos losses of $38 million , respectively. In July 2017, we sold a business to a company owned by Atairos and received as consideration an investment in that company, which we account for as an equity method investment. In connection with the sale of the business, we recognized a pretax gain of $105 million in other operating gains in 2017. Hulu In 2017, 2016 and 2015, we made cash capital contributions totaling $300 million , $50 million and $123 million , respectively, to Hulu. In 2017, 2016 and 2015, we recognized our proportionate share of Hulu’s losses of $276 million , $168 million and $106 million , respectively. In August 2016, Time Warner Inc. acquired a 10% interest in Hulu, LLC, which diluted our interest in Hulu from 33% to 30% . For a period not to exceed 3 years , Time Warner may put its shares to Hulu or Hulu may call Time Warner’s shares under certain limited circumstances arising from regulatory review. Given the contingent nature of the put and call options, we recorded a deferred gain of $159 million and a corresponding increase to our investment in Hulu as a result of the dilution. The deferred gain will be recognized in other income (expense), net if and when the options expire unexercised. The Weather Channel In January 2016, following a legal restructuring at The Weather Channel, we and the other investors sold the entity holding The Weather Channel’s product and technology businesses to IBM. Following the close of the transaction, we continue to hold an investment in The Weather Channel cable network through a new holding company. As a result of the sale of our investment, we recognized a pretax gain of $108 million in other income (expense), net. In June and December 2015, The Weather Channel recorded impairment charges related to goodwill. In 2015, we recorded expenses of $333 million that represented NBCUniversal’s proportionate share of these impairment charges in equity in net income (losses) of investees, net. Cost Method We use the cost method to account for investments not accounted for under the fair value method or the equity method. AirTouch We hold two series of preferred stock of Verizon Americas, Inc., formerly known as AirTouch Communications, Inc., a subsidiary of Verizon Communications Inc., which are redeemable in April 2020. As of both December 31, 2017 and 2016 , the estimated fair value of the AirTouch preferred stock was $1.7 billion . The dividend and redemption activity of the AirTouch preferred stock determines the dividend and redemption payments associated with substantially all of the preferred shares issued by one of our consolidated subsidiaries, which is a VIE. The subsidiary has three series of preferred stock outstanding with an aggregate redemption value of $1.75 billion . Substantially all of the AirTouch preferred stock is redeemable in April 2020 at a redemption value of $1.65 billion . As of both December 31, 2017 and 2016 , the two series of redeemable subsidiary preferred shares were recorded at $1.6 billion , and those amounts are included in other noncurrent liabilities. As of both December 31, 2017 and 2016 , the liability related to the redeemable subsidiary preferred shares had an aggregate estimated fair value of $1.7 billion . The estimated fair values of the AirTouch preferred stock and redeemable subsidiary preferred shares 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. The one series of nonredeemable subsidiary preferred shares was recorded at $100 million as of both December 31, 2017 and 2016 , and those amounts are included in noncontrolling interests in our consolidated balance sheet. The carrying amount of the nonredeemable subsidiary preferred shares approximates its fair value. BuzzFeed and Vox Media In September 2015, NBCUniversal acquired an interest in BuzzFeed, Inc. and made an additional investment in Vox Media, Inc. for $200 million each in cash. In November 2016, NBCUniversal made an additional investment of $200 million in Buzzfeed. Impairment Testing of Investments We review our investment portfolio each reporting period to determine whether there are identified events or circumstances that would indicate there is a decline in the fair value that would be considered other than temporary. 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. 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 AFS securities and our cost method investments, we record the impairment to investment income (loss), net. For our equity method investments, we record the impairment to other income (expense), net.
NBCUniversal Media LLC [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Investments	Note 7: Investments December 31 (in millions) 2017 2016 Fair Value Method: Snap $ 430 $ — Other — 6 430 6 Equity Method: Hulu 249 225 Other 441 336 690 561 Cost Method: BuzzFeed 400 400 Other 296 296 696 696 Total investments $ 1,816 $ 1,263 Fair Value Method We classify publicly traded investments that are not accounted for under the equity method as available-for-sale (“AFS”) or trading securities. The estimated fair value of our publicly traded investments was primarily based on Level 1 inputs that use quoted market values. For other fair value method investments, the estimated fair value was 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 AFS securities, we record unrealized gains or losses resulting from changes in fair value between measurement dates as a component of other comprehensive income (loss), except when we consider declines in value to be other than temporary. For trading securities, we record unrealized gains or losses resulting from changes in fair value between measurement dates as a component of investment income (loss), net. We recognize realized gains and losses associated with our fair value method investments using the specific identification method. We classify the cash flows related to purchases of and proceeds from the sale of trading securities based on the nature of the securities and the purpose for which they were acquired. Snap In March 2017, Comcast acquired an interest in Snap Inc. as part of its initial public offering. On March 31, 2017, Comcast contributed its investment in Snap to us as an equity contribution of $662 million , which was recorded in our consolidated statement of equity based on the fair value of the investment as of March 31, 2017. We have classified our investment as an available-for-sale security. Snap is a camera company whose primary product is Snapchat, a camera app that was created to help people communicate through short videos and images. 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 significant partnership or limited liability company interest. Equity method investments are recorded at cost and are adjusted to recognize (1) our proportionate share 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 (expense), 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 (expense), net. Hulu In 2017, 2016 and 2015, we made cash capital contributions totaling $300 million , $50 million and $123 million , respectively, to Hulu. In 2017, 2016 and 2015, we recognized our proportionate share of Hulu’s losses of $276 million , $168 million and $106 million , respectively. In August 2016, Time Warner Inc. acquired a 10% interest in Hulu, LLC, which diluted our interest in Hulu from 33% to 30% . For a period not to exceed 3 years , Time Warner may put its shares to Hulu or Hulu may call Time Warner’s shares under certain limited circumstances arising from regulatory review. Given the contingent nature of the put and call options, we recorded a deferred gain of $159 million and a corresponding increase to our investment in Hulu as a result of the dilution. The deferred gain will be recognized in other income (expense), net if and when the options expire unexercised. The Weather Channel In January 2016, following a legal restructuring at The Weather Channel, we and the other investors sold the entity holding The Weather Channel’s product and technology businesses to IBM. Following the close of the transaction, we continue to hold an investment in The Weather Channel cable network through a new holding company. As a result of the sale of our investment, we recognized a pretax gain of $108 million in other income (expense), net. In June and December 2015, The Weather Channel recorded impairment charges related to goodwill. In 2015, we recorded expenses of $333 million that represented our proportionate share of these impairment charges in equity in net income (losses) of investees, net. Summarized Financial Information The tables below present the summarized combined financial information of our equity method investments. December 31 (in millions) 2017 2016 Current assets $ 2,612 $ 2,105 Noncurrent assets $ 3,690 $ 2,724 Current liabilities $ 2,205 $ 1,921 Noncurrent liabilities $ 3,969 $ 2,853 Year ended December 31 (in millions) 2017 2016 2015 Revenue $ 4,234 $ 4,285 $ 3,944 Operating income (loss) $ (465 ) $ (182 ) $ (1,609 ) Net income (loss) $ (656 ) $ (313 ) $ (1,820 ) Cost Method We use the cost method to account for investments not accounted for under the fair value method or the equity method. In September 2015, we acquired an interest in BuzzFeed, Inc. and made an additional investment in Vox Media, Inc. for $200 million each in cash. In November 2016, we made an additional investment of $200 million in Buzzfeed. Impairment Testing of Investments We review our investment portfolio each reporting period to determine whether there are identified events or circumstances that would indicate there is a decline in the fair value that would be considered other than temporary. 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. 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 AFS securities and our cost method investments, we record the impairment to investment income (loss), net. For our equity method investments, we record the impairment to other income (expense), net.

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and Equipment	Note 8: Property and Equipment December 31 (in millions) Weighted-Average 2017 2016 Cable distribution system 11 years $ 36,046 $ 34,028 Customer premise equipment 6 years 26,392 28,621 Other equipment 9 years 10,518 9,471 Buildings and leasehold improvements 30 years 12,346 10,653 Construction in process N/A 1,752 1,901 Land N/A 1,332 1,273 Property and equipment, at cost 88,386 85,947 Less: Accumulated depreciation 49,916 49,694 Property and equipment, net $ 38,470 $ 36,253 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. In accordance with the accounting guidance related to cable television companies, we capitalize 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. 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 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.
NBCUniversal Media LLC [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment	Note 8: Property and Equipment December 31 (in millions) Weighted-Average 2017 2016 Buildings and leasehold improvements 31 years $ 8,124 $ 7,543 Furniture, fixtures and equipment 11 years 4,843 4,158 Construction in process N/A 1,506 1,176 Land N/A 1,039 984 Property and equipment, at cost 15,512 13,861 Less: Accumulated depreciation 4,166 3,350 Property and equipment, net $ 11,346 $ 10,511 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. 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 and Intangible Assets

Goodwill and Intangible Assets	12 Months Ended
	Dec. 31, 2017
Goodwill And Intangible Assets [Line Items]
Goodwill and Intangible Assets	Note 9: Goodwill and Intangible Assets Goodwill NBCUniversal (in millions) Cable Cable Broadcast Filmed Theme Corporate Total Balance, December 31, 2015 $ 12,389 $ 12,947 $ 806 $ 267 $ 6,344 $ 192 $ 32,945 Acquisitions (a) 82 232 — 2,717 — 1 3,032 Adjustments (b) 174 — — — (250 ) (181 ) (257 ) Foreign currency translation — 4 — 9 247 — 260 Balance, December 31, 2016 12,645 13,183 806 2,993 6,341 12 35,980 Acquisitions 140 241 — 32 — 5 418 Dispositions — — — — — (11 ) (11 ) Adjustments (c) (1 ) 1 — 185 — 1 186 Foreign currency translation — 2 — 2 203 — 207 Balance, December 31, 2017 $ 12,784 $ 13,427 $ 806 $ 3,212 $ 6,544 $ 7 $ 36,780 (a) Acquisitions in 2016 in our Filmed Entertainment segment primarily included the DreamWorks Animation acquisition (see Note 5 for additional information). (b) Adjustments in 2016 primarily included the updated allocation of the purchase price for Universal Studios Japan in our Theme Parks segment and the reclassification of certain operations and businesses from Corporate and Other to our Cable Communications segment. (c) Adjustments in 2017 primarily included the updated allocation of the purchase price for DreamWorks Animation (see Note 5 for additional information). 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 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. As a result of this assessment, our reporting units are the same as our five reportable segments. 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 carrying amount of the reporting unit’s goodwill exceeds its implied fair value. Unless presented separately, the impairment charge is included as a component of amortization expense. We did not recognize any impairment charges in any of the periods presented. Intangible Assets 2017 2016 December 31 (in millions) Weighted-Average Original Useful Life as of December 31, 2017 Gross Carrying Amount Accumulated Amortization Gross Carrying Amount Accumulated Amortization Indefinite-Lived Intangible Assets: Franchise rights N/A $ 59,364 $ 59,364 Trade names N/A 2,981 2,981 FCC licenses (a) N/A 2,238 651 Finite-Lived Intangible Assets: Customer relationships 19 years 13,612 $ (5,819 ) 13,478 $ (5,110 ) Software 4 years 8,258 (4,846 ) 7,017 (3,997 ) Cable franchise renewal costs and contractual operating rights 9 years 1,492 (834 ) 1,460 (800 ) Patents and other technology rights 7 years 259 (221 ) 257 (208 ) Other agreements and rights 16 years 2,724 (1,065 ) 2,443 (898 ) Total $ 90,928 $ (12,785 ) $ 87,651 $ (11,013 ) (a) In 2017, we acquired the rights to spectrum in the FCC Spectrum auction (see Note 5 for additional information). 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. Costs we incur in negotiating and renewing cable franchise agreements are included in other intangible assets and are generally amortized on a straight-line basis over the term of the franchise agreement. 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) 2018 $ 2,283 2019 $ 1,952 2020 $ 1,629 2021 $ 1,225 2022 $ 905 Finite-lived intangible assets are subject to amortization and consist primarily of customer relationships acquired in business combinations, software, cable franchise renewal costs, contractual operating rights 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. We evaluate the recoverability of our finite-lived intangible assets 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 amortization expense.
NBCUniversal Media LLC [Member]
Goodwill And Intangible Assets [Line Items]
Goodwill and Intangible Assets	Note 9: Goodwill and Intangible Assets Goodwill (in millions) Cable Broadcast Filmed Theme Total Balance, December 31, 2015 $ 12,947 $ 806 $ 267 $ 6,344 $ 20,364 Acquisitions (a) 232 — 2,717 — 2,949 Adjustments (b) — — — (250 ) (250 ) Foreign currency translation 4 — 9 247 260 Balance, December 31, 2016 13,183 806 2,993 6,341 23,323 Acquisitions 241 — 32 — 273 Adjustments (c) 1 — 185 — 186 Foreign currency translation 2 — 2 203 207 Balance, December 31, 2017 $ 13,427 $ 806 $ 3,212 $ 6,544 $ 23,989 (a) Acquisitions in 2016 in our Filmed Entertainment segment primarily included the DreamWorks Animation acquisition (see Note 4 for additional information). (b) Adjustments in 2016 included the updated allocation of the purchase price for Universal Studios Japan in our Theme Parks segment. (c) Adjustments in 2017 primarily included the updated allocation of the purchase price for DreamWorks Animation (see Note 4 for additional information). 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 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. As a result of this assessment, our reporting units are the same as our four reportable segments. 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 carrying amount of the reporting unit’s goodwill exceeds its implied fair value. Unless presented separately, the impairment charge is included as a component of amortization expense. We did not recognize any impairment charges in any of the periods presented. Intangible Assets 2017 2016 December 31 (in millions) Weighted-Average Gross Accumulated Gross Accumulated Finite-Lived Intangible Assets: Customer relationships 19 years $ 13,301 $ (5,643 ) $ 13,173 $ (4,952 ) Software 5 years 1,516 (737 ) 1,195 (563 ) Other 16 years 2,580 (1,205 ) 2,345 (1,053 ) Indefinite-Lived Intangible Assets: Trade names N/A 2,981 2,981 FCC licenses N/A 513 651 Total $ 20,891 $ (7,585 ) $ 20,345 $ (6,568 ) Indefinite-Lived Intangible Assets Indefinite-lived intangible assets consist of trade names and FCC licenses. We assess the recoverability of our indefinite-lived intangible assets annually, or more frequently whenever events or substantive changes in circumstances indicate that the assets might be impaired. We evaluate the unit of account used to test for impairment of our 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 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 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) 2018 $ 1,018 2019 $ 1,010 2020 $ 968 2021 $ 866 2022 $ 786 Finite-lived intangible assets are subject to amortization and consist primarily of customer relationships acquired in business combinations, intellectual property rights and software. 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. We evaluate the recoverability of our finite-lived intangible assets 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 amortization expense.

Long-Term Debt

Long-Term Debt	12 Months Ended
	Dec. 31, 2017
Debt Instrument [Line Items]
Long-Term Debt	Note 10: Long-Term Debt Long-Term Debt Outstanding December 31 (in millions) Weighted-Average 2017 2016 Commercial paper 1.84 % $ 903 $ 2,781 Term loans (a) 0.82 % 3,880 3,262 Senior notes with maturities of 5 years or less, at face value 4.18 % 15,680 13,850 Senior notes with maturities between 5 and 10 years, at face value 3.31 % 13,277 12,049 Senior notes with maturities greater than 10 years, at face value (b) 4.74 % 31,838 28,587 Other, including capital lease obligations — 921 842 Debt issuance costs, premiums, discounts and fair value adjustments for hedged positions, net (c) — (1,943 ) (325 ) Total debt 4.04 % (d) 64,556 61,046 Less: Current portion 5,134 5,480 Long-term debt $ 59,422 $ 55,566 (a) The December 31, 2017 and 2016 amounts primarily consist of ¥435 billion and ¥382 billion , respectively, of Universal Studios Japan term loans translated using the exchange rates as of these dates. In May 2017, Universal Studios Japan entered into ¥450 billion of new term loans with a final maturity of March 2022. We used the proceeds from these borrowings to repay in full Universal Studios Japan’s existing yen-denominated term loans and a portion of amounts outstanding under our commercial paper program. (b) The December 31, 2017 and 2016 amounts include £625 million of 5.50% notes due 2029, which translated to $845 million and $771 million , respectively, using the exchange rates as of these dates. (c) The December 31, 2017 amount includes the difference between the principal amount of the new senior notes and the carrying amount of the exchanged senior notes at the time of the senior notes exchange. See below under the heading “Senior Notes Exchange” for additional information on this transaction. (d) Includes the effects of our derivative financial instruments. As of December 31, 2017 and 2016 , our debt had an estimated fair value of $71.7 billion and $66.3 billion , respectively. The estimated fair value of our publicly traded debt was primarily based on Level 1 inputs that use quoted market values 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. See Note 19 for additional information on our cross-guarantee structure. Principal Maturities of Debt (in millions) 2018 $ 5,127 2019 $ 2,367 2020 $ 3,688 2021 $ 3,884 2022 $ 5,879 Thereafter $ 45,554 2017 Debt Borrowings Year ended December 31, 2017 (in millions) Universal Studios Japan term loans maturing 2022 $ 3,948 Comcast 3.15% senior notes due 2028 1,650 NBCUniversal Enterprise floating rate notes due 2021 1,500 Comcast 3.00% senior notes due 2024 1,250 Comcast 3.30% senior notes due 2027 1,250 Comcast 4.45% senior notes due 2047 1,005 Comcast 4.00% senior notes due 2047 850 Other 13 Total $ 11,466 2017 Debt Redemptions and Repayments Year ended December 31, 2017 (in millions) Universal Studios Japan term loans maturing 2020 $ 3,347 Comcast 6.30% senior notes due 2017 1,000 Comcast 6.50% senior notes due 2017 1,000 Comcast 8.875% senior notes due 2017 550 Comcast 5.00% senior notes due 2061 288 Other 179 Total $ 6,364 Senior Notes Exchange In October 2017, we and NBCUniversal completed a debt exchange transaction. We issued $5.5 billion aggregate principal amount of new senior notes in exchange for $3.9 billion aggregate principal amount of certain series of outstanding senior notes that had been issued by us and NBCUniversal, as detailed in the table below. (in millions) Principal Amount Exchanged Principal Amount Issued in Exchange Comcast 6.95% senior notes due 2037 $ 1,212 Comcast 6.45% senior notes due 2037 946 Comcast 6.40% senior notes due 2040 518 NBCUniversal 6.40% senior notes due 2040 442 Comcast 6.40% senior notes due 2038 428 Comcast 6.55% senior notes due 2039 386 Comcast 3.97% senior notes due 2047 $ 2,000 Comcast 4.00% senior notes due 2049 2,000 Comcast 4.05% senior notes due 2052 1,500 Total $ 3,932 $ 5,500 The new senior notes are unsecured, rank equally in right of payment with all of our unsecured and unsubordinated indebtedness, and are fully and unconditionally guaranteed by Comcast Cable Communications, LLC and NBCUniversal. The debt exchange transaction was accounted for as a debt modification, and therefore following the exchange, the book value of our debt was unchanged and the difference between the principal amount of the new senior notes and the carrying amount of the exchanged senior notes will accrue through interest expense over the period to maturity of the new senior notes. Debt Instruments Revolving Bank Credit Facilities As of December 31, 2017 and 2016, we had a $7 billion revolving credit facility due 2021 with a syndicate of banks (“Comcast revolving credit facility”) that may be used for general corporate purposes. We may increase the commitment under the Comcast revolving credit facility up to a total of $10 billion , as well as extend the expiration date to a date no later than 2023, subject to approval of the lenders. In addition, as of December 31, 2017 and 2016, NBCUniversal Enterprise had a $1.5 billion revolving credit facility due 2021 with a syndicate of banks (“NBCUniversal Enterprise revolving credit facility”) that may be used for general corporate purposes. We may increase the commitment under the NBCUniversal Enterprise revolving credit facility up to a total of $2 billion , as well as extend the expiration date to a date 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, 2017, the borrowing margin for borrowings based on the London Interbank Offered Rate was 1.00% . Each of the revolving credit facilities requires that we maintain certain financial ratios based on the respective debt and EBITDA of each entity, as defined in the credit facility. We were in compliance with all financial covenants for all periods presented. There were no amounts outstanding under the Comcast or NBCUniversal Enterprise revolving credit facility as of December 31, 2017 or 2016. As of December 31, 2017 , amounts available under our consolidated revolving credit facilities, net of amounts outstanding under our commercial paper programs and outstanding letters of credit, totaled $7.4 billion , which included $1.5 billion available under the NBCUniversal Enterprise revolving credit facility. Commercial Paper Programs Our commercial paper programs provide a lower-cost source of borrowing to fund our short-term working capital requirements. In June 2017, we increased the Comcast and NBCUniversal Enterprise commercial paper programs to $7.0 billion and $1.5 billion , respectively, to coincide with the borrowing capacities under the Comcast and NBCUniversal Enterprise revolving credit facilities. Letters of Credit As of December 31, 2017 , we and certain of our subsidiaries had undrawn irrevocable standby letters of credit totaling $439 million to cover potential fundings under various agreements.
NBCUniversal Media LLC [Member]
Debt Instrument [Line Items]
Long-Term Debt	Note 10: Long-Term Debt Long-Term Debt Outstanding December 31 (in millions) Weighted-Average 2017 2016 Term loans (a) 0.79 % $ 3,860 $ 3,262 Senior notes with maturities of 5 years or less, at face value 4.76 % 4,000 4,000 Senior notes with maturities between 5 and 10 years, at face value 2.88 % 1,000 1,000 Senior notes with maturities greater than 10 years, at face value 5.50 % 2,759 3,200 Notes due 2049 to Comcast 4.00 % 610 — Other, including capital lease obligations — 276 138 Debt issuance costs, premiums, discounts and fair value adjustments for hedged positions, net — (32 ) (12 ) Total debt 3.49 % 12,473 11,588 Less: Current portion 198 127 Long-term debt $ 12,275 $ 11,461 (a) The December 31, 2017 and 2016 amounts consist of ¥435 billion and ¥382 billion , respectively, of Universal Studios Japan term loans translated using the exchange rates as of these dates. In May 2017, Universal Studios Japan entered into ¥450 billion of new term loans with a final maturity of March 2022. We used the proceeds from these borrowings to repay in full Universal Studios Japan’s existing yen-denominated term loans and a portion of amounts outstanding under our revolving credit agreement with Comcast. As of December 31, 2017 and 2016 , our debt, excluding our revolving credit agreement with Comcast, had an estimated fair value of $13.5 billion and $12.6 billion , respectively. The estimated fair value of our publicly traded debt was primarily based on Level 1 inputs that use quoted market values 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) 2018 $ 200 2019 $ 147 2020 $ 2,268 2021 $ 2,349 2022 $ 2,981 Thereafter $ 4,560 Cross-Guarantee Structure We, Comcast and a 100% owned cable holding company subsidiary of Comcast (“CCCL Parent”) fully and unconditionally guarantee each other’s debt securities, including the $7 billion Comcast revolving credit facility due 2021. As of December 31, 2017 , outstanding debt securities of $49.1 billion of Comcast and CCCL Parent were subject to the cross-guarantee structure. We do not, however, guarantee the obligations of NBCUniversal Enterprise with respect to its $4.8 billion aggregate principal amount of senior notes, $1.5 billion revolving credit facility, commercial paper program, or $725 million liquidation preference of Series A cumulative preferred stock. The Universal Studios Japan term loans are not subject to the cross-guarantee structure, however they have a separate guarantee from Comcast. Senior Notes Exchange In October 2017, we and Comcast completed a debt exchange transaction. Comcast issued $2.0 billion aggregate principal amount of new 3.97% senior notes due 2047, $2.0 billion aggregate principal amount of new 4.00% senior notes due 2049, and $1.5 billion aggregate principal amount of new 4.05% senior notes due 2052 in exchange for $3.9 billion aggregate principal amount of certain series of outstanding senior notes issued by Comcast and us, including $442 million of our 6.40% senior notes due 2040. The new notes are fully and unconditionally guaranteed by us and CCCL Parent. In connection with the exchange transaction, we issued $610 million of 4.00% notes due 2049 to Comcast. The debt exchange transaction was accounted for as a debt extinguishment, and therefore we recorded a charge of $157 million to interest expense upon retirement of the old notes.

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Employee Benefit Plans	Note 11: Employee Benefit Plans Deferred Compensation Plans Year ended December 31 (in millions) 2017 2016 2015 Benefit obligation $ 2,539 $ 2,164 $ 2,038 Interest expense $ 209 $ 178 $ 171 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, except for those in the NBCUniversal plan, are credited with income primarily based on a fixed annual rate. Participants in the NBCUniversal plan designate one or more valuation funds, independently established funds or indices that are used to determine the amount of investment gain or loss in the participant’s account. 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, 2017 and 2016 , the cash surrender value of these policies, which is recorded to other noncurrent assets, was $820 million and $709 million , respectively. Postretirement Benefit Plan Year ended December 31 (in millions) 2017 2016 Benefit obligation $ 425 $ 538 Amounts in accumulated other comprehensive income not yet recognized in benefits expense $ (458 ) $ (372 ) We sponsor a retiree health and welfare benefit plan that provides postretirement benefits to eligible employees. The plan provides to eligible employees who retire from Comcast or its subsidiaries, an annual stipend for reimbursement of certain eligible healthcare costs. The amount of the stipend for an eligible retiree is fixed at a predetermined amount based on the retiree’s years of service and whether the retiree is eligible for Medicare. In December 2016, the plan was amended primarily to reduce the stipend benefits of active employees of Comcast and subsidiaries other than NBCUniversal who retire after December 31, 2017, and in 2017 additional amendments were made to reduce the benefits of NBCUniversal employees who retire after December 31, 2017. The plan amendments reduced our benefit obligation by $361 million and $146 million in 2016 and 2017, respectively. Additionally, under the plan, a small number of employees are also eligible to participate in legacy plan benefits that were previously sponsored by acquired companies. The plan is unfunded and substantially all of our postretirement benefit obligations are recorded to noncurrent liabilities. The expense we recognize for the plan is determined using certain assumptions, including the discount rate. The benefits expense we recognized for the plan was not material in any of the periods presented. Pension Plans NBCUniversal sponsors various nonqualified defined benefit pension plans for domestic employees. Since the future benefits have been frozen since the beginning of 2013, we did not recognize service costs related to the pension plans for any period presented. The benefits expense we recognized for our defined benefit plans was not material in any of the periods presented. In addition to the defined benefit plans it sponsors, NBCUniversal is also obligated to reimburse The General Electric Company (“GE”) for future benefit payments to those participants who were vested in the supplemental pension plan sponsored by GE at the time of the NBCUniversal transaction in 2011. These pension plans are currently unfunded and we recorded a benefit obligation of $338 million and $314 million as of December 31, 2017 and 2016 , respectively, which consists primarily of our obligations to reimburse GE. Retirement Investment 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 2017 , 2016 and 2015 , expenses related to these plans totaled $458 million , $446 million and $416 million , respectively. Multiemployer Benefit Plans 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. We make periodic contributions to these plans in accordance with the terms of applicable collective bargaining agreements and laws but do not sponsor or administer these plans. We do not participate in any multiemployer benefit plans for which we consider our contributions to be individually significant. In 2017 , 2016 and 2015 , the total contributions we made to multiemployer pension plans were $97 million , $84 million and $77 million , respectively. In 2017 , 2016 and 2015 , the total contributions we made to multiemployer postretirement and other benefit plans were $152 million , $136 million and $119 million , respectively. 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. Severance Benefits We provide severance benefits to certain former employees. A liability is recorded when payment is probable, the amount is reasonably estimable, and the obligation relates to rights that have vested or accumulated. In 2017 , 2016 and 2015 , we recorded severance costs of $203 million , $315 million and $181 million , respectively. Severance costs in 2016 included $61 million of severance costs associated with the acquisition of DreamWorks Animation.
NBCUniversal Media LLC [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Employee Benefit Plans	Note 11: Employee Benefit Plans Deferred Compensation Plans Year ended December 31 (in millions) 2017 2016 2015 Benefit obligation $ 621 $ 494 $ 417 Interest expense $ 64 $ 48 $ 28 Certain members of management participate in Comcast’s unfunded, nonqualified deferred compensation plan. 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. Additionally, we maintain unfunded, nonqualified deferred compensation plans for certain members of management. The amount of compensation deferred by each participant is based on participant elections. Participants designate one or more valuation funds, independently established funds or indices that are used to determine the amount of investment gain or loss in the participant’s account. Deferred compensation plan participants are eligible to receive distributions from their account based on elected deferral periods that are consistent with the plans and applicable tax law. Postretirement Benefit Plan Year ended December 31 (in millions) 2017 2016 Benefit obligation $ 51 $ 192 Amounts in accumulated other comprehensive income not yet recognized in benefits expense $ (177 ) $ (42 ) We provide postretirement benefits to eligible employees through a retiree health and welfare benefits plan. The plan provides credit to employees for length of service provided before Comcast’s acquisition of NBCUniversal. The plan provides eligible employees who retire from NBCUniversal with an annual stipend for reimbursement of certain eligible healthcare costs. The amount of the stipend for an eligible retiree is fixed at a predetermined amount based on the retiree’s years of service and whether the retiree is eligible for Medicare. In 2017, the plan was amended primarily to reduce the benefits of active employees who retire after December 31, 2017. The plan amendment reduced the benefit obligation by $146 million in 2017. The plan is unfunded and substantially all of our postretirement benefit obligations are recorded to noncurrent liabilities. The expense we recognize for the plan is determined using certain assumptions, including the discount rate. The benefits expense we recognized for the plan was not material in any of the periods presented. Pension Plans We sponsor various nonqualified defined benefit pension plans for domestic employees. Since the future benefits have been frozen since the beginning of 2013, we did not recognize service costs related to our pension plans in any of the periods presented. The benefits expense we recognized for our defined benefit plans was not material for any period presented. In addition to the defined benefit plans we sponsor, we are also obligated to reimburse The General Electric Company (“GE”) for future benefit payments to those participants who were vested in the supplemental pension plan sponsored by GE at the time of Comcast’s acquisition of NBCUniversal. These pension plans are currently unfunded and we recorded a benefit obligation of $338 million and $314 million as of December 31, 2017 and 2016 , respectively, which consists primarily of our obligations to reimburse GE. Retirement Investment Plans We sponsor several defined contribution retirement plans, including 401(k) 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 2017 , 2016 and 2015 , expenses related to these plans totaled $201 million , $185 million and $174 million , respectively. Multiemployer Benefit Plans 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. We make periodic contributions to these plans in accordance with the terms of applicable collective bargaining agreements and laws but do not sponsor or administer these plans. We do not participate in any multiemployer benefit plans for which we consider our contributions to be individually significant. In 2017 , 2016 and 2015 , the total contributions we made to multiemployer pension plans were $97 million , $84 million and $77 million , respectively. In 2017 , 2016 and 2015 , the total contributions we made to multiemployer postretirement and other benefit plans were $152 million , $136 million and $119 million , respectively. 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. Severance Benefits We provide severance benefits to certain former employees. A liability is recorded when payment is probable, the amount is reasonably estimable, and the obligation relates to rights that have vested or accumulated. In 2017 , 2016 and 2015 , we recorded severance costs of $108 million , $165 million and $113 million , respectively. Severance costs in 2016 included $61 million of severance costs associated with the acquisition of DreamWorks Animation.

Equity

Equity	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Equity	Note 12: 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. See Note 1 for additional information regarding the stock split that occurred in 2017. Class A Special Common Stock Reclassification In December 2015, our shareholders approved a proposal to amend and restate our Amended and Restated Certificate of Incorporation in order to reclassify each issued share of our Class A Special common stock into one share of our Class A common stock. This reclassification became effective as of the close of business on December 11, 2015, at which time our Class A Special common stock was no longer outstanding and ceased trading on the NASDAQ under the symbol CMCSK and instead became listed on the NASDAQ under the symbol CMCSA. There was no impact on basic and diluted EPS or the carrying value of total common stock as presented in our consolidated balance sheet because it was a one -for-one stock exchange. Shares of Common Stock Outstanding (in millions) A A Special B Balance, December 31, 2014 4,272 801 9 Stock compensation plans 25 — — Repurchases and retirements of common stock (125 ) (107 ) — Employee stock purchase plans 5 — — Reclassification of Class A Special common stock 694 (694 ) — Other 4 — — Balance, December 31, 2015 4,875 — 9 Stock compensation plans 23 — — Repurchases and retirements of common stock (161 ) — — Employee stock purchase plans 5 — — Balance, December 31, 2016 4,742 — 9 Stock compensation plans 19 — — Repurchases and retirements of common stock (131 ) — — Employee stock purchase plans 5 — — Balance, December 31, 2017 4,635 — 9 Share Repurchases Effective January 1, 2017, our Board of Directors increased our share repurchase program authorization to a total of $12 billion , which does not have an expiration date. As of December 31, 2017, $7 billion remained under this authorization. Under the authorization, we may repurchase shares in the open market or in private transactions. Share Repurchases Under Share Repurchase Program Authorization Year ended December 31 (in millions) 2017 2016 2015 Cash consideration $ 5,000 $ 5,000 $ 6,750 Shares repurchased 131 161 232 Accumulated Other Comprehensive Income (Loss) December 31 (in millions) 2017 2016 Unrealized gains (losses) on marketable securities $ (43 ) $ — Deferred gains (losses) on cash flow hedges 9 (14 ) Unrecognized gains (losses) on employee benefit obligations 260 219 Cumulative translation adjustments 153 (107 ) Accumulated other comprehensive income (loss), net of deferred taxes $ 379 $ 98

Share-Based Compensation

Share-Based Compensation	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Compensation	Note 13: Share-Based Compensation The tables below provide information on our share-based compensation. Recognized Share-Based Compensation Expense Year ended December 31 (in millions) 2017 2016 2015 Restricted share units $ 349 $ 306 $ 273 Stock options 205 173 157 Employee stock purchase plans 32 28 25 Total $ 586 $ 507 $ 455 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, 2017 , all of our stock options outstanding were net settled stock options. Net settled stock options, as opposed to stock options exercised with a cash payment, 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, 2017, unless otherwise stated (in millions, except per share data) Stock Options RSUs Awards granted during 2017 39 15 Weighted-average exercise price of awards granted during 2017 $ 37.47 Stock options outstanding and nonvested RSUs 191 42 Weighted-average exercise price of stock options outstanding $ 24.98 Weighted-average fair value at grant date of nonvested RSUs $ 30.93 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 2017 2016 2015 RSUs fair value $ 37.77 $ 30.02 $ 29.41 Stock options fair value $ 7.01 $ 5.78 $ 5.89 Stock Option Valuation Assumptions: Dividend yield 1.7 % 1.8 % 1.7 % Expected volatility 20.1 % 23.0 % 23.0 % Risk-free interest rate 2.2 % 1.5 % 1.6 % Expected option life (in years) 6.1 6.1 6.0 As of December 31, 2017 , we had unrecognized pretax compensation expense of $806 million related to nonvested RSUs and unrecognized pretax compensation expense of $404 million related to nonvested stock options that will each be recognized over a weighted-average period of approximately 1.7 years. In 2016 and 2015 , we recorded increases to additional paid-in capital of $233 million and $311 million , respectively, which were the result of excess tax benefits associated with our share-based compensation plans. As a result of the adoption of new accounting guidance related to share-based compensation in 2017 , these tax benefits are now recorded as a reduction to income tax expense (see Note 3).

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Taxes [Line Items]
Income Taxes	Note 14: Income Taxes Components of Income Tax Expense (Benefit) Year ended December 31 (in millions) 2017 2016 2015 Current Expense (Benefit): Federal $ 2,411 $ 3,190 $ 3,210 State 277 480 570 Foreign 389 194 221 3,077 3,864 4,001 Deferred Expense (Benefit): Federal (10,659 ) 1,192 890 State 10 154 66 Foreign (6 ) 98 2 (10,655 ) 1,444 958 Income tax expense (benefit) $ (7,578 ) $ 5,308 $ 4,959 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) 2017 2016 2015 Federal tax at statutory rate $ 5,363 $ 5,024 $ 4,680 State income taxes, net of federal benefit 298 373 326 Foreign income taxes, net of federal credit 70 65 13 Nontaxable income attributable to noncontrolling interests (45 ) (128 ) (69 ) Adjustments to uncertain and effectively settled tax positions, net (62 ) 24 15 Accrued interest on uncertain and effectively settled tax positions, net 3 17 73 Excess tax benefits recognized on share-based compensation (297 ) — — 2017 federal tax reform enactment (12,679 ) — — Other (229 ) (67 ) (79 ) Income tax expense (benefit) $ (7,578 ) $ 5,308 $ 4,959 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, and tax planning opportunities available in the jurisdictions in which we operate. 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). Current and deferred foreign income taxes are incurred primarily by NBCUniversal’s foreign subsidiaries. In 2017 , 2016 and 2015 , NBCUniversal had foreign income before taxes of $1.0 billion , $871 million and $704 million , respectively, on which foreign income tax expense (benefit) was recorded. We generally record U.S. income tax expense (benefit) on our allocable share of our subsidiaries’ income before domestic and foreign taxes, which is reduced by a U.S. tax credit equal to our allocable share of our subsidiaries’ foreign income tax expense (benefit). Federal Tax Reform On December 22, 2017, new federal tax reform legislation was enacted in the United States, resulting in significant changes from previous tax law. The 2017 Tax Act reduces the federal corporate income tax rate to 21% from 35% effective January 1, 2018. The rate change, along with certain immaterial changes in tax basis resulting from the 2017 Tax Act, resulted in a reduction of our net deferred tax liabilities of $12.4 billion and a corresponding deferred income tax benefit in 2017. Our federal income tax expense for periods beginning in 2018 will be based on the new rate. The 2017 Tax Act also changes the taxation of foreign earnings, and companies generally will not be subject to United States federal income taxes upon the receipt of dividends from foreign subsidiaries and will not be permitted foreign tax credits related to such dividends. Beginning in 2018, we will no longer record United States federal income tax on our share of the income of our foreign subsidiaries, nor will we record a benefit for foreign tax credits related to that income. Accordingly, we reversed $382 million of net deferred tax liabilities related to our cumulative undistributed foreign earnings and deferred tax assets for related foreign tax credits, resulting in a corresponding net tax benefit in 2017. Additionally, upon enactment, there is a one-time deemed repatriation tax on undistributed foreign earnings and profits (the “transition tax”). We recognized tax expense of $101 million related to the transition tax in 2017. The 2017 Tax Act also provides for immediate deduction of 100% of the costs of qualified property, including significant portions of our capital expenditures and film and television production costs, that are incurred and the property placed in service during the period from September 27, 2017 to December 31, 2022. This provision will begin to phase down by 20% per year beginning January 1, 2023 and will be completely phased out as of January 1, 2027. The adjustments to deferred tax assets and liabilities and the liability related to the transition tax are provisional amounts estimated based on information available as of December 31, 2017. These amounts are subject to change as we obtain information necessary to complete the calculations. We will recognize any changes to the provisional amounts as we refine our estimates of our cumulative temporary differences, including those related to the immediate deduction for qualified property, and our interpretations of the application of the 2017 Tax Act. We expect to complete our analysis of the provisional items during the second half of 2018. The effects of other provisions of the 2017 Tax Act are not expected to have a material impact on our consolidated financial statements. Components of Net Deferred Tax Liability December 31 (in millions) 2017 2016 (a) Deferred Tax Assets: Net operating loss carryforwards $ 481 $ 544 Nondeductible accruals and other 2,026 3,797 Less: Valuation allowance 377 266 2,130 4,075 Deferred Tax Liabilities: Differences between book and tax basis of property and equipment and intangible assets 25,154 36,957 Differences between book and tax basis of investments 466 498 Differences between book and tax basis of long-term debt 673 571 Differences between book and tax basis of foreign subsidiaries and undistributed foreign earnings 39 862 26,332 38,888 Net deferred tax liability $ 24,202 $ 34,813 (a) Prior year amounts in the table above have been adjusted to appropriately classify certain deferred tax items. These adjustments had no impact on the net deferred tax liability recorded in our consolidated balance sheet. Changes in our net deferred tax liability in 2017 that were not recorded as deferred income tax benefit (expense) are primarily related to an increase of $108 million associated with items included in other comprehensive income (loss), an increase of $51 million related to acquisitions and a decrease of $112 million associated with our purchase of a noncontrolling interest. Our net deferred tax liability includes $15 billion related to cable franchise rights that will remain unchanged unless we recognize an impairment or dispose of a cable franchise or there is a change in the tax law. As of December 31, 2017 , we had federal net operating loss carryforwards of $348 million , and various state net operating loss carryforwards that expire in periods through 2037. As of December 31, 2017 , we also had foreign net operating loss carryforwards of $387 million that are related to the foreign operations of NBCUniversal, the majority of which expire in periods through 2027. 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, 2017 and 2016 , our valuation allowance was primarily related to state and foreign net operating loss carryforwards. Uncertain Tax Positions Our liability for uncertain tax positions as of December 31, 2017 totaled $809 million , which excludes the federal benefits on state tax positions that were recorded as deferred income taxes. Included in our liability for uncertain tax positions was $162 million related to tax positions of NBCUniversal and NBCUniversal Enterprise for which we have been indemnified by GE. We are indemnified by GE for any income tax liability attributable to the NBCUniversal contributed businesses for periods prior to the close of the NBCUniversal transaction in January 2011 and also for any income tax liability attributable to NBCUniversal Enterprise for periods prior to the date of the NBCUniversal redemption transaction in March 2013. Reconciliation of Unrecognized Tax Benefits (in millions) 2017 2016 (a) 2015 (a) Gross unrecognized tax benefits, January 1 $ 1,443 $ 1,441 $ 1,455 Additions based on tax positions related to the current year 121 74 67 Additions based on tax positions related to prior years 319 72 98 Additions from acquired subsidiaries — 13 — Reductions for tax positions of prior years (251 ) (66 ) (101 ) Reductions due to expiration of statutes of limitations (70 ) (44 ) (41 ) Settlements with tax authorities (65 ) (47 ) (37 ) Gross unrecognized tax benefits, December 31 1,497 1,443 1,441 Positions paid (688 ) (340 ) (305 ) Liability for uncertain tax positions $ 809 $ 1,103 $ 1,136 (a) We have updated the presentation of the table above to include amounts related to positions previously paid and have updated prior year amounts to conform. Our liability for uncertain tax positions represents the amounts recorded for potential payment obligations. Our gross unrecognized tax benefits also include amounts related to positions for which tax has been assessed and paid. If we were to recognize our gross unrecognized tax benefits in the future, $ 1.2 billion , which includes amounts indemnified by GE, 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, 2017 and 2016 , our accrued interest associated with our liability for uncertain tax positions was $173 million and $483 million , respectively. As of December 31, 2017 and 2016 , $43 million and $39 million , respectively, of these amounts were related to tax positions of NBCUniversal and NBCUniversal Enterprise for which we have been indemnified by GE. The IRS has completed its examination of our income tax returns for all years through 2014. Various states are examining our state tax returns and the tax years of those tax returns currently under examination vary by state, with most of the periods relating to tax years 2000 and forward.
NBCUniversal Media LLC [Member]
Income Taxes [Line Items]
Income Taxes	Note 12: Income Taxes Components of Income Tax Expense Year ended December 31 (in millions) 2017 2016 2015 Foreign Current income tax expense $ 201 $ 38 $ 81 Deferred income tax expense (7 ) 96 2 Withholding tax expense 187 158 139 U.S. domestic tax expense 11 13 5 Income tax expense $ 392 $ 305 $ 227 We are a limited liability company, and our company is disregarded for U.S. federal income tax purposes as an entity separate from NBCUniversal Holdings, a tax partnership. For U.S federal and state income tax purposes, our income is included in tax returns filed by Comcast and its subsidiaries, and therefore we are not expected to incur any significant current or deferred U.S. domestic income taxes and do not expect any significant impacts from the 2017 federal tax reform legislation. Our tax liability is comprised primarily of withholding tax on foreign licensing activity and income taxes on foreign earnings. As a result of our tax status, the deferred tax assets and liabilities included in our consolidated balance sheet at December 31, 2017 and 2016 were not material. In jurisdictions in which we are subject to 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, and tax planning opportunities available in the jurisdictions in which we operate. 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. We classify interest and penalties, if any, associated with our uncertain tax positions as a component of income tax expense. Uncertain Tax Positions We retain liabilities for uncertain tax positions where we are the tax filer of record. GE and Comcast have indemnified NBCUniversal Holdings and us with respect to our income tax obligations attributable to periods prior to Comcast’s acquisition of NBCUniversal, including indemnification of uncertain tax positions for these periods. The liabilities for uncertain tax positions included in our consolidated balance sheet were not material as of December 31, 2017 and 2016 . Various domestic and foreign tax authorities are examining our tax returns through tax year 2016. The majority of the periods under examination relate to tax years 2009 and forward.

Supplemental Financial Informat

Supplemental Financial Information	12 Months Ended
	Dec. 31, 2017
Supplemental Financial Information [Line Items]
Supplemental Financial Information	Note 15: Supplemental Financial Information Receivables December 31 (in millions) 2017 2016 Receivables, gross $ 9,253 $ 8,622 Less: Allowance for returns and customer incentives 419 417 Less: Allowance for doubtful accounts 288 250 Receivables, net $ 8,546 $ 7,955 In addition to the amounts in the table above, as of December 31, 2017 and 2016 , net noncurrent receivables of $1.3 billion and $939 million , respectively, are included in other noncurrent assets, net that primarily relate to the licensing of our television and film productions to third parties and sales of wireless devices. Cash Payments for Interest and Income Taxes Year ended December 31 (in millions) 2017 2016 2015 Interest $ 2,820 $ 2,565 $ 2,443 Income taxes $ 4,057 $ 3,693 $ 3,726 Noncash Investing and Financing Activities During 2017 : • we acquired $1.2 billion of property and equipment and intangible assets that were accrued but unpaid • we recorded a liability of $732 million for a quarterly cash dividend of $0.1575 per common share paid in January 2018 • we completed a senior notes exchange in the fourth quarter of 2017 (see Note 10 for additional information) During 2016 : • we acquired $1.3 billion of property and equipment and intangible assets that were accrued but unpaid • we recorded a liability of $653 million for a quarterly cash dividend of $0.1375 per common share paid in January 2017 • we recorded a liability of $447 million for capital contributions to Atairos that were accrued in December and paid in January 2017 (see Note 7 for additional information) During 2015 : • we acquired $1.1 billion of property and equipment and intangible assets that were accrued but unpaid • we recorded a liability of $612 million for a quarterly cash dividend of $0.125 per common share paid in January 2016 • we assumed liabilities related to the Universal Studios Japan transaction (see Note 5 for additional information) • we used $517 million of equity securities to settle a portion of our obligations under prepaid forward sale agreements
NBCUniversal Media LLC [Member]
Supplemental Financial Information [Line Items]
Supplemental Financial Information	Note 13: Supplemental Financial Information Receivables December 31 (in millions) 2017 2016 Receivables, gross $ 7,184 $ 6,799 Less: Allowance for returns and customer incentives 414 413 Less: Allowance for doubtful accounts 88 84 Receivables, net $ 6,682 $ 6,302 In addition to the amounts in the table above, as of December 31, 2017 and 2016 , noncurrent receivables of $1.2 billion and $939 million , respectively, are included in other noncurrent assets, net that primarily relate to the licensing of our television and film productions to third parties . Accumulated Other Comprehensive Income (Loss) December 31 (in millions) 2017 2016 Unrealized gains (losses) on marketable securities $ (233 ) $ — Deferred gains (losses) on cash flow hedges 10 23 Unrecognized gains (losses) on employee benefit obligations 126 14 Cumulative translation adjustments 77 (172 ) Accumulated other comprehensive income (loss) $ (20 ) $ (135 ) Cash Payments for Interest and Income Taxes Year ended December 31 (in millions) 2017 2016 2015 Interest $ 517 $ 548 $ 456 Income taxes $ 282 $ 208 $ 182 Noncash Investing and Financing Activities During 2017 : • we acquired $325 million of property and equipment and intangible assets that were accrued but unpaid • Comcast contributed its investment in Snap to us at its fair value, which was a noncash transaction (see Note 7 for additional information) • we and Comcast completed a senior notes exchange in the fourth quarter of 2017 (see Note 10 for additional information) During 2016 : • we acquired $189 million of property and equipment and intangible assets that were accrued but unpaid • Comcast contributed the net assets of DreamWorks Animation to us, which was primarily a noncash transaction (see Note 4 for additional information) During 2015 : • we acquired $287 million of property and equipment and intangible assets that were accrued but unpaid • Comcast contributed the net assets of $252 million related to an acquired business, which was a noncash transaction • we assumed liabilities related to the Universal Studios Japan transaction

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitment And Contingencies [Line Items]
Commitments and Contingencies	Note 16: Commitments and Contingencies Commitments NBCUniversal enters into long-term commitments with third parties in the ordinary course of its business, including commitments to acquire film and television programming, obligations under various creative talent agreements, and various other television-related commitments. Some of NBCUniversal’s employees, including writers, directors, actors, technical and production personnel, and others, as well as some of its on-air and creative talent, are covered by collective bargaining agreements or works councils. As of December 31, 2017 , the total number of NBCUniversal employees covered by collective bargaining agreements was 9,500 full-time equivalent employees. Approximately 63% of these full-time equivalent employees were covered by collective bargaining agreements that have expired or are scheduled to expire during 2018 . We, through Comcast Spectacor, have employment agreements with both players and coaches of the Philadelphia Flyers. Certain of these employment agreements, which provide for payments that are guaranteed regardless of employee injury or termination, are covered by disability insurance if certain conditions are met. The table below summarizes our minimum annual programming and talent commitments and our minimum annual rental commitments under operating leases for office space, equipment and transponder service agreements. Programming and talent commitments include acquired film and television programming, including U.S. broadcast rights to the Olympic Games through 2032, Sunday Night Football through the 2022-23 season , certain NASCAR events through 2024 and other programming commitments, as well as various contracts with creative talent. As of December 31, 2017 (in millions) Programming and Talent Commitments Operating Leases 2018 $ 6,350 $ 559 2019 $ 3,895 $ 512 2020 $ 4,812 $ 457 2021 $ 3,301 $ 391 2022 $ 3,732 $ 326 Thereafter $ 17,416 $ 1,829 The table below presents our rental expense charged to operations. Year ended December 31 (in millions) 2017 2016 2015 Rental expense $ 839 $ 744 $ 608 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, 2017 , our carrying value was $1.1 billion , and the estimated value of the contractual obligation was $1.5 billion based on inputs to the contractual formula as of that date. Contingent Consideration In June 2015, we settled a contingent consideration liability related to the acquisition of NBCUniversal, which was based upon future net tax benefits realized by us that would affect future payments to GE, for a payment of $450 million , which was included as a financing activity in our consolidated statement of cash flows. The settlement resulted in a gain of $240 million , which was recorded to other income (expense), net in our consolidated statement of income. Redeemable Subsidiary Preferred Stock NBCUniversal Enterprise is a holding company that we control and consolidate whose principal assets are its interests in NBCUniversal Holdings. 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 on 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, 2017 and 2016 , the fair value of the NBCUniversal Enterprise redeemable subsidiary preferred stock was $748 million and $741 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 were a defendant in a lawsuit filed in December 2011 by Sprint Communications Company L.P. (“Sprint”) in the United States District Court for the District of Kansas. Sprint’s initial complaint alleged that Comcast Digital Voice and Xfinity Voice infringe 12 Sprint patents covering various aspects of a telecommunications system. In March 2015, Sprint withdrew its allegations of infringement for two of the patents. In December 2016, the Court granted summary judgment for us with respect to non-infringement on one of the patents and granted summary judgment for Sprint on one of the patents as to infringement with respect to some but not all of our accused telecommunications systems but not as to the patent’s validity. In January 2017, the Court entered judgment in favor of us on Sprint’s claims for infringement of two of the patents. In March 2017, Sprint indicated that it would not proceed to trial on three of the patents. Trial with respect to the four remaining patents, including the patent for which the Court granted partial summary judgment to Sprint, was set to begin on October 23, 2017. On October 16, 2017, the parties entered into a settlement agreement which dismisses all claims and resolves the parties’ disputes asserted in the matters described above, as well as in all other outstanding patent litigation matters between the parties, for a payment to Sprint and certain contractual rights. In connection therewith, we recorded a charge of $250 million in 2017. We also are a defendant in several unrelated lawsuits claiming infringement of various patents relating to various aspects of our businesses. In certain of these cases other industry participants are also defendants, and also in certain of these cases we expect that any potential liability would be in part or in whole the responsibility of our equipment and technology vendors under applicable contractual indemnification provisions. In addition, we are subject to other 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.
NBCUniversal Media LLC [Member]
Commitment And Contingencies [Line Items]
Commitments and Contingencies	Note 14: Commitments and Contingencies Commitments We enter into long-term commitments with third parties in the ordinary course of our business, including commitments to acquire film and television programming, obligations under various creative talent agreements, and various other television-related commitments. Some of our employees, including writers, directors, actors, technical and production personnel, and others, as well as some of our on-air and creative talent, are covered by collective bargaining agreements or works councils. As of December 31, 2017 , the total number of employees covered by collective bargaining agreements was 9,500 full-time equivalent employees. Approximately 63% of these full-time equivalent employees were covered by collective bargaining agreements that have expired or are scheduled to expire during 2018 . The table below summarizes our minimum annual programming and talent commitments and our minimum annual rental commitments under operating leases for office space and equipment. Programming and talent commitments include acquired film and television programming, including U.S. broadcast rights to the Olympic Games through 2032, Sunday Night Football through the 2022-23 season , certain NASCAR events through 2024 and other programming commitments, as well as various contracts with creative talent. As of December 31, 2017 (in millions) Programming and Talent Commitments Operating Leases 2018 $ 6,343 $ 209 2019 $ 3,893 $ 195 2020 $ 4,812 $ 182 2021 $ 3,301 $ 163 2022 $ 3,732 $ 139 Thereafter $ 17,416 $ 1,223 The table below presents our rental expense charged to operations. Year ended December 31 (in millions) 2017 2016 2015 Rental expense $ 274 $ 259 $ 213 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, 2017 , our carrying value was $1.1 billion , and the estimated value of the contractual obligation was $1.5 billion based on inputs to the contractual formula as of that date.

Financial Data by Business Segm

Financial Data by Business Segment	12 Months Ended
	Dec. 31, 2017
Segment Reporting Information [Line Items]
Financial Data by Business Segment	Note 17: Financial Data by Business Segment We present our operations in one reportable business segment for Cable Communications and four reportable business segments for NBCUniversal. The Cable Networks, Broadcast Television, Filmed Entertainment and Theme Parks segments comprise the NBCUniversal businesses and are collectively referred to as the NBCUniversal segments. We use Adjusted EBITDA to evaluate the profitability of our operating segments, and the components of net income attributable to Comcast Corporation excluded from Adjusted EBITDA are not separately evaluated. Our financial data by business 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 (f) Adjusted (g) Depreciation and Capital Cash Paid for 2017 Cable Communications (a) $ 52,519 $ 21,170 $ 8,143 $ 7,952 $ 1,382 NBCUniversal Cable Networks 10,631 4,076 755 33 19 Broadcast Television 9,546 1,253 133 180 22 Filmed Entertainment 7,658 1,277 109 58 23 Theme Parks 5,443 2,384 648 960 78 Headquarters and Other (b) 45 (741 ) 396 271 153 Eliminations (c) (326 ) (4 ) — — — NBCUniversal 32,997 8,245 2,041 1,502 295 Corporate and Other (d) 1,060 (1,394 ) 83 96 70 Eliminations (c) (2,050 ) 41 — — — Comcast Consolidated $ 84,526 $ 28,062 $ 10,267 $ 9,550 $ 1,747 (in millions) Revenue (f) Adjusted (g) Depreciation and Capital Cash Paid for 2016 Cable Communications (a) $ 50,048 $ 20,109 $ 7,670 $ 7,596 $ 1,377 NBCUniversal Cable Networks (e) 10,464 3,709 745 32 20 Broadcast Television (e) 10,147 1,320 125 153 19 Filmed Entertainment 6,360 697 47 33 16 Theme Parks 4,946 2,190 512 922 72 Headquarters and Other (b) 20 (699 ) 376 312 156 Eliminations (c) (344 ) 10 — — — NBCUniversal 31,593 7,227 1,805 1,452 283 Corporate and Other (d) 750 (874 ) 83 87 26 Eliminations (c) (1,988 ) (45 ) — — — Comcast Consolidated $ 80,403 $ 26,417 $ 9,558 $ 9,135 $ 1,686 (in millions) Revenue (f) Adjusted (g) Depreciation and Capital Cash Paid for 2015 Cable Communications (a) $ 46,928 $ 19,037 $ 7,051 $ 7,040 $ 1,151 NBCUniversal Cable Networks 9,628 3,499 784 44 22 Broadcast Television (e) 8,530 780 111 117 17 Filmed Entertainment 7,287 1,234 26 14 20 Theme Parks 3,339 1,464 292 833 54 Headquarters and Other (b) 14 (625 ) 326 378 98 Eliminations (c) (336 ) — — — — NBCUniversal 28,462 6,352 1,539 1,386 211 Corporate and Other (d) 713 (815 ) 90 73 8 Eliminations (c) (1,593 ) 104 — — — Comcast Consolidated $ 74,510 $ 24,678 $ 8,680 $ 8,499 $ 1,370 (a) For the years ended December 31, 2017 , 2016 and 2015 , Cable Communications segment revenue was derived from the following sources: 2017 2016 2015 Residential: Video 44.0 % 44.7 % 45.9 % High-speed Internet 28.1 % 27.0 % 26.6 % Voice 6.5 % 7.1 % 7.7 % Business services 11.8 % 11.0 % 10.1 % Advertising 4.3 % 4.9 % 4.7 % Other 5.3 % 5.3 % 5.0 % Total 100.0 % 100.0 % 100.0 % Subscription revenue received from residential customers who purchase bundled services at a discounted rate is allocated proportionally to each cable service based on the individual service’s price on a stand-alone basis. For 2017 , 2.7% of Cable Communications revenue was derived from franchise and other regulatory fees. For both 2016 and 2015 , 2.8% of Cable Communications revenue was derived from franchise and other regulatory fees. (b) NBCUniversal Headquarters and Other activities include costs associated with overhead, allocations, personnel costs and headquarter initiatives. (c) Included in Eliminations are transactions that our segments enter into with one another. The most common types of transactions are the following: • our Cable Networks segment generates revenue by selling programming to our Cable Communications segment, which represents a substantial majority of the revenue elimination amount • our Broadcast Television segment generates revenue from the fees received under retransmission consent agreements with our Cable Communications segment • our Cable Communications segment generates revenue by selling advertising and by selling the use of satellite feeds to our Cable Networks segment • our Filmed Entertainment and Broadcast Television segments generate revenue by licensing content to our Cable Networks segment; for segment reporting, this revenue is recognized as the programming rights asset for the licensed content is amortized based on third party revenue (d) Corporate and Other activities include costs associated with overhead and personnel, revenue and expenses associated with other business development initiatives, including our new wireless phone service, and the operations of Comcast Spectacor, which owns the Philadelphia Flyers and the Wells Fargo Center arena in Philadelphia, Pennsylvania and operates arena management-related businesses. (e) The revenue and operating costs and expenses associated with our broadcast of the 2016 Rio Olympics were reported in our Cable Networks and Broadcast Television segments. The revenue and operating costs and expenses associated with our broadcast of the 2015 Super Bowl were reported in our Broadcast Television segment. (f) Revenue from customers located outside of the United States, primarily in Europe and Asia, in 2017 , 2016 and 2015 was $7.8 billion , $6.5 billion and $5.8 billion , respectively. No single customer accounted for a significant amount of revenue in any of the periods presented. (g) We use Adjusted EBITDA as the measure of profit or loss for our operating segments. Adjusted EBITDA is defined as net income attributable to Comcast Corporation before net (income) loss attributable to noncontrolling interests and redeemable subsidiary preferred stock, income tax benefit (expense), total other income (expense), depreciation and amortization expense, and other operating gains, and excluding impairment charges related to fixed and intangible assets and gains or losses on the sale of long-lived assets, if any. From time to time we may exclude from Adjusted EBITDA the impact of events, gains, losses or other charges (such as significant legal settlements) that affect the period-to-period comparability of our operating performance. This measure eliminates the significant level of noncash depreciation and amortization expense that results from the capital-intensive nature of certain of our businesses and from intangible assets recognized in business combinations. Additionally, it is unaffected by our capital and tax structures and by our investment activities. We use this measure to evaluate the operating performance of our operating segments and to allocate resources and capital to our operating segments. It is also a significant performance measure in our annual incentive compensation programs. We believe that this measure is useful to investors because it is one of the bases for comparing our operating performance with that of other companies in our industries, although our measure may not be directly comparable to similar measures used by other companies. This measure should not be considered a substitute for operating income (loss), net income (loss), net income (loss) attributable to Comcast Corporation, net cash provided by operating activities, or other measures we have reported in accordance with GAAP. 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) 2017 2016 2015 Adjusted EBITDA $ 28,062 $ 26,417 $ 24,678 Adjustment for legal settlement (250 ) — — Depreciation (7,914 ) (7,464 ) (6,781 ) Amortization (2,353 ) (2,094 ) (1,899 ) Other operating gains 442 — — Total other income (expense) (2,665 ) (2,506 ) (2,626 ) Income before income taxes $ 15,322 $ 14,353 $ 13,372
NBCUniversal Media LLC [Member]
Segment Reporting Information [Line Items]
Financial Data by Business Segment	Note 15: Financial Data by Business Segment We present our operations in four reportable business segments: Cable Networks, Broadcast Television, Filmed Entertainment and Theme Parks. We use Adjusted EBITDA to evaluate the profitability of our operating segments, and the components of net income attributable to NBCUniversal excluded from Adjusted EBITDA are not separately evaluated. Our financial data by business 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 (d) Adjusted (e) Depreciation and Capital Cash Paid for 2017 Cable Networks $ 10,631 $ 4,076 $ 755 $ 33 $ 19 Broadcast Television 9,546 1,253 133 180 22 Filmed Entertainment 7,658 1,277 109 58 23 Theme Parks 5,443 2,384 648 960 78 Headquarters and Other (a) 45 (801 ) 396 271 153 Eliminations (b) (326 ) (4 ) — — — Total $ 32,997 $ 8,185 $ 2,041 $ 1,502 $ 295 (in millions) Revenue (d) Adjusted (e) Depreciation and Capital Cash Paid for 2016 Cable Networks (c) $ 10,464 $ 3,709 $ 745 $ 32 $ 20 Broadcast Television (c) 10,147 1,320 125 153 19 Filmed Entertainment 6,360 697 47 33 16 Theme Parks 4,946 2,190 512 922 72 Headquarters and Other (a) 20 (699 ) 376 312 156 Eliminations (b) (344 ) 10 — — — Total $ 31,593 $ 7,227 $ 1,805 $ 1,452 $ 283 (in millions) Revenue (d) Adjusted (e) Depreciation and Capital Cash Paid for 2015 Cable Networks $ 9,628 $ 3,499 $ 784 $ 44 $ 22 Broadcast Television (c) 8,530 780 111 117 17 Filmed Entertainment 7,287 1,234 26 14 20 Theme Parks 3,339 1,464 292 833 54 Headquarters and Other (a) 14 (625 ) 326 378 98 Eliminations (b) (336 ) 6 — — — Total $ 28,462 $ 6,358 $ 1,539 $ 1,386 $ 211 (a) Headquarters and Other activities include costs associated with overhead, allocations, personnel costs and headquarter initiatives. (b) Eliminations are transactions that our segments enter into with one another, which consisted primarily of the licensing of film and television content from our Filmed Entertainment and Broadcast Television segments to our Cable Networks segment; for segment reporting, revenue is recognized as the programming rights asset for the licensed content is amortized based on third party revenue. (c) The revenue and operating costs and expenses associated with our broadcast of the 2016 Rio Olympics were reported in our Cable Networks and Broadcast Television segments. The revenue and operating costs and expenses associated with our broadcast of the 2015 Super Bowl were reported in our Broadcast Television segment. (d) We operate primarily in the United States, but also in select international markets primarily in Europe and Asia. The table below summarizes revenue by geographic location. No single customer accounted for a significant amount of revenue in any of the periods presented. Year ended December 31 (in millions) 2017 2016 2015 Revenue: United States $ 25,345 $ 25,076 $ 22,663 Foreign $ 7,652 $ 6,517 $ 5,799 (e) We use Adjusted EBITDA as the measure of profit or loss for our operating segments. Adjusted EBITDA is defined as net income attributable to NBCUniversal before net (income) loss attributable to noncontrolling interests, income tax expense, total other income (expense), depreciation and amortization expense, and other operating gains, and excluding impairment charges related to fixed and intangible assets and gains or losses on the sale of long-lived assets, if any. From time to time we may exclude from Adjusted EBITDA the impact of events, gains, losses or other charges (such as significant legal settlements) that affect the period-to-period comparability of our operating performance. This measure eliminates the significant level of noncash amortization expense that results from intangible assets recognized in business combinations. Additionally, it is unaffected by our capital and tax structures and by our investment activities. We use this measure to evaluate the operating performance of our operating segments and to allocate resources and capital to our operating segments. It is also a significant performance measure in our annual incentive compensation programs. We believe that this measure is useful to investors because it is one of the bases for comparing our operating performance with that of other companies in our industries, although our measure may not be directly comparable to similar measures used by other companies. This measure should not be considered a substitute for operating income (loss), net income (loss), net income (loss) attributable to NBCUniversal, net cash provided by operating activities, or other measures we have reported in accordance with GAAP. 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) 2017 2016 2015 Adjusted EBITDA $ 8,185 $ 7,227 $ 6,358 Depreciation (994 ) (861 ) (669 ) Amortization (1,047 ) (944 ) (870 ) Other operating gains 337 — — Total other income (expense) (871 ) (571 ) (968 ) Income before income taxes $ 5,610 $ 4,851 $ 3,851

Quarterly Financial Information

Quarterly Financial Information (Unaudited)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information (Unaudited)	Note 18: Quarterly Financial Information (Unaudited) (in millions, except per share data) First Second Third Fourth Total 2017 Revenue $ 20,463 $ 21,165 $ 20,983 $ 21,915 $ 84,526 Operating income $ 4,530 $ 4,558 $ 4,792 $ 4,107 $ 17,987 Net income attributable to Comcast Corporation (a) $ 2,566 $ 2,513 $ 2,650 $ 14,985 $ 22,714 Basic earnings per common share attributable to Comcast Corporation shareholders $ 0.54 $ 0.53 $ 0.56 $ 3.22 $ 4.82 Diluted earnings per common share attributable to Comcast Corporation shareholders $ 0.53 $ 0.52 $ 0.55 $ 3.17 $ 4.75 Dividends declared per common share $ 0.1575 $ 0.1575 $ 0.1575 $ 0.1575 $ 0.63 2016 Revenue $ 18,790 $ 19,269 $ 21,319 $ 21,025 $ 80,403 Operating income $ 4,089 $ 4,066 $ 4,440 $ 4,264 $ 16,859 Net income attributable to Comcast Corporation (b) $ 2,134 $ 2,028 $ 2,237 $ 2,296 $ 8,695 Basic earnings per common share attributable to Comcast Corporation shareholders $ 0.44 $ 0.42 $ 0.47 $ 0.48 $ 1.80 Diluted earnings per common share attributable to Comcast Corporation shareholders $ 0.43 $ 0.41 $ 0.46 $ 0.48 $ 1.78 Dividends declared per common share $ 0.1375 $ 0.1375 $ 0.1375 $ 0.1375 $ 0.55 Minor differences may exist due to rounding. (a) In the fourth quarter of 2017, net income attributable to Comcast Corporation included a $12.7 billion net income tax benefit as a result of the impacts of the 2017 tax reform legislation. See Note 14 for additional information. (b) In the fourth quarter of 2016, net income attributable to Comcast Corporation included $225 million , $143 million net of tax, recognized in connection with the settlement of amounts owed to us under an agency agreement that had provided for, among other things, Verizon Wireless’ sale of our cable services.

Condensed Consolidating Financi

Condensed Consolidating Financial Information	12 Months Ended
	Dec. 31, 2017
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Condensed Consolidating Financial Information	Note 19: Condensed Consolidating Financial Information Comcast (“Comcast Parent”), Comcast Cable Communications, LLC (“CCCL Parent”) and NBCUniversal (“NBCUniversal Media Parent”) have fully and unconditionally guaranteed each other’s debt securities, including the Comcast revolving credit facility. The principal amount of debt securities within the guarantee structure totals $56.9 billion , of which $11.8 billion will mature within the next five years . Comcast Parent and CCCL Parent also fully and unconditionally guarantee NBCUniversal Enterprise’s $4.8 billion aggregate principal amount of senior notes, $1.5 billion revolving credit facility and commercial paper program. NBCUniversal Media Parent does not guarantee the NBCUniversal Enterprise senior notes, revolving credit facility or commercial paper program. Comcast Parent provides a full and unconditional guarantee of the Universal Studios Japan yen-dominated ¥435 billion term loans with a final maturity of March 2022. Comcast Parent also provides a full and unconditional subordinated guarantee of the $185 million principal amount currently outstanding of Comcast Holdings’ ZONES due October 2029 . Neither CCCL Parent nor NBCUniversal Media Parent guarantee the Comcast Holdings’ ZONES due October 2029. None of Comcast Parent, CCCL Parent nor NBCUniversal Media Parent guarantee the $62 million principal amount currently outstanding of Comcast Holdings’ ZONES due November 2029 . Condensed Consolidating Balance Sheet December 31, 2017 (in millions) Comcast Comcast CCCL NBCUniversal Non- Elimination Consolidated Assets Cash and cash equivalents $ — $ — $ — $ 496 $ 2,932 $ — $ 3,428 Receivables, net — — — — 8,546 — 8,546 Programming rights — — — — 1,613 — 1,613 Deposits — — — — 9 — 9 Other current assets 60 — 7 25 2,372 — 2,464 Total current assets 60 — 7 521 15,472 — 16,060 Film and television costs — — — — 7,076 — 7,076 Investments 146 21 108 693 5,963 — 6,931 Investments in and amounts due from subsidiaries eliminated upon consolidation 117,154 142,412 139,364 50,249 113,479 (562,658 ) — Property and equipment, net 551 — — — 37,919 — 38,470 Franchise rights — — — — 59,364 — 59,364 Goodwill — — — — 36,780 — 36,780 Other intangible assets, net 12 — — — 18,767 — 18,779 Other noncurrent assets, net 435 708 — 88 2,572 (314 ) 3,489 Total assets $ 118,358 $ 143,141 $ 139,479 $ 51,551 $ 297,392 $ (562,972 ) $ 186,949 Liabilities and Equity Accounts payable and accrued expenses related to trade creditors $ 16 $ — $ — $ — $ 6,910 $ — $ 6,926 Accrued participations and residuals — — — — 1,683 — 1,683 Deferred revenue — — — — 1,552 — 1,552 Accrued expenses and other current liabilities 1,888 92 333 326 3,627 — 6,266 Current portion of long-term debt 2,810 — — 4 2,320 — 5,134 Total current liabilities 4,714 92 333 330 16,092 — 21,561 Long-term debt, less current portion 42,428 140 2,100 7,751 7,003 — 59,422 Deferred income taxes — 285 — 67 24,247 (343 ) 24,256 Other noncurrent liabilities 2,610 — — 1,128 7,137 29 10,904 Redeemable noncontrolling interests and redeemable subsidiary preferred stock — — — — 1,357 — 1,357 Equity: Common stock 55 — — — — — 55 Other shareholders’ equity 68,551 142,624 137,046 42,275 240,713 (562,658 ) 68,551 Total Comcast Corporation shareholders’ equity 68,606 142,624 137,046 42,275 240,713 (562,658 ) 68,606 Noncontrolling interests — — — — 843 — 843 Total equity 68,606 142,624 137,046 42,275 241,556 (562,658 ) 69,449 Total liabilities and equity $ 118,358 $ 143,141 $ 139,479 $ 51,551 $ 297,392 $ (562,972 ) $ 186,949 Condensed Consolidating Balance Sheet December 31, 2016 (in millions) Comcast Comcast CCCL NBCUniversal Non- Elimination Consolidated Assets Cash and cash equivalents $ — $ — $ — $ 482 $ 2,819 $ — $ 3,301 Receivables, net — — — — 7,955 — 7,955 Programming rights — — — — 1,250 — 1,250 Deposits — — — — 1,772 — 1,772 Other current assets 151 — — 36 1,896 — 2,083 Total current assets 151 — — 518 15,692 — 16,361 Film and television costs — — — — 7,252 — 7,252 Investments 75 — — 651 4,521 — 5,247 Investments in and amounts due from subsidiaries eliminated upon consolidation 98,350 120,071 117,696 47,393 97,704 (481,214 ) — Property and equipment, net 298 — — — 35,955 — 36,253 Franchise rights — — — — 59,364 — 59,364 Goodwill — — — — 35,980 — 35,980 Other intangible assets, net 13 — — — 17,261 — 17,274 Other noncurrent assets, net 1,138 638 — 89 1,921 (1,017 ) 2,769 Total assets $ 100,025 $ 120,709 $ 117,696 $ 48,651 $ 275,650 $ (482,231 ) $ 180,500 Liabilities and Equity Accounts payable and accrued expenses related to trade creditors $ 23 $ — $ — $ — $ 6,892 $ — $ 6,915 Accrued participations and residuals — — — — 1,726 — 1,726 Deferred revenue — — — — 1,132 — 1,132 Accrued expenses and other current liabilities 1,726 — 341 302 3,913 — 6,282 Current portion of long-term debt 3,739 — 550 4 1,187 — 5,480 Total current liabilities 5,488 — 891 306 14,850 — 21,535 Long-term debt, less current portion 38,123 141 2,100 8,208 6,994 — 55,566 Deferred income taxes — 542 — 70 35,259 (1,017 ) 34,854 Other noncurrent liabilities 2,471 — — 1,166 7,288 — 10,925 Redeemable noncontrolling interests and redeemable subsidiary preferred stock — — — — 1,446 — 1,446 Equity: Common stock 56 — — — — — 56 Other shareholders’ equity 53,887 120,026 114,705 38,901 207,582 (481,214 ) 53,887 Total Comcast Corporation shareholders’ equity 53,943 120,026 114,705 38,901 207,582 (481,214 ) 53,943 Noncontrolling interests — — — — 2,231 — 2,231 Total equity 53,943 120,026 114,705 38,901 209,813 (481,214 ) 56,174 Total liabilities and equity $ 100,025 $ 120,709 $ 117,696 $ 48,651 $ 275,650 $ (482,231 ) $ 180,500 Condensed Consolidating Statement of Income For the Year Ended December 31, 2017 (in millions) Comcast Comcast CCCL NBCUniversal Non- Elimination Consolidated Revenue: Service revenue $ — $ — $ — $ — $ 84,526 $ — $ 84,526 Management fee revenue 1,128 — 1,109 — — (2,237 ) — Total revenue 1,128 — 1,109 — 84,526 (2,237 ) 84,526 Costs and Expenses: Programming and production — — — — 25,384 — 25,384 Other operating and administrative 766 — 1,109 1,044 24,331 (2,237 ) 25,013 Advertising, marketing and promotion — — — — 6,317 — 6,317 Depreciation 31 — — — 7,883 — 7,914 Amortization 6 — — — 2,347 — 2,353 Other operating gains — — — — (442 ) — (442 ) Total costs and expenses 803 — 1,109 1,044 65,820 (2,237 ) 66,539 Operating income (loss) 325 — — (1,044 ) 18,706 — 17,987 Other Income (Expense): Interest expense (2,172 ) (12 ) (207 ) (456 ) (239 ) — (3,086 ) Investment income (loss), net (1 ) 109 — (197 ) 342 — 253 Equity in net income (losses) of investees, net 24,056 21,622 19,570 6,740 5,191 (77,072 ) 107 Other income (expense), net — — — 45 16 — 61 Total other income (expense) 21,883 21,719 19,363 6,132 5,310 (77,072 ) (2,665 ) Income (loss) before income taxes 22,208 21,719 19,363 5,088 24,016 (77,072 ) 15,322 Income tax (expense) benefit 506 156 71 (4 ) 6,849 — 7,578 Net income (loss) 22,714 21,875 19,434 5,084 30,865 (77,072 ) 22,900 Net (income) loss attributable to noncontrolling interests and redeemable subsidiary preferred stock — — — — (186 ) — (186 ) Net income (loss) attributable to Comcast Corporation $ 22,714 $ 21,875 $ 19,434 $ 5,084 $ 30,679 $ (77,072 ) $ 22,714 Comprehensive income (loss) attributable to Comcast Corporation $ 22,801 $ 21,873 $ 19,437 $ 5,058 $ 30,541 $ (76,909 ) $ 22,801 Condensed Consolidating Statement of Income For the Year Ended December 31, 2016 (in millions) Comcast Comcast CCCL NBCUniversal Non- Elimination Consolidated Revenue: Service revenue $ — $ — $ — $ — $ 80,403 $ — $ 80,403 Management fee revenue 1,067 — 1,049 — — (2,116 ) — Total revenue 1,067 — 1,049 — 80,403 (2,116 ) 80,403 Costs and Expenses: Programming and production — — — — 24,463 — 24,463 Other operating and administrative 813 — 1,049 932 22,738 (2,116 ) 23,416 Advertising, marketing and promotion — — — — 6,107 — 6,107 Depreciation 28 — — — 7,436 — 7,464 Amortization 6 — — — 2,088 — 2,094 Other operating gains — — — — — — — Total costs and expenses 847 — 1,049 932 62,832 (2,116 ) 63,544 Operating income (loss) 220 — — (932 ) 17,571 — 16,859 Other Income (Expense): Interest expense (1,941 ) (12 ) (239 ) (456 ) (294 ) — (2,942 ) Investment income (loss), net 7 (5 ) — (25 ) 236 — 213 Equity in net income (losses) of investees, net 9,809 9,286 8,679 5,545 4,131 (37,554 ) (104 ) Other income (expense), net — — — 116 211 — 327 Total other income (expense) 7,875 9,269 8,440 5,180 4,284 (37,554 ) (2,506 ) Income (loss) before income taxes 8,095 9,269 8,440 4,248 21,855 (37,554 ) 14,353 Income tax (expense) benefit 600 6 84 (13 ) (5,985 ) — (5,308 ) Net income (loss) 8,695 9,275 8,524 4,235 15,870 (37,554 ) 9,045 Net (income) loss attributable to noncontrolling interests and redeemable subsidiary preferred stock — — — — (350 ) — (350 ) Net income (loss) attributable to Comcast Corporation $ 8,695 $ 9,275 $ 8,524 $ 4,235 $ 15,520 $ (37,554 ) $ 8,695 Comprehensive income (loss) attributable to Comcast Corporation $ 8,967 $ 9,317 $ 8,530 $ 4,312 $ 15,610 $ (37,769 ) $ 8,967 Condensed Consolidating Statement of Income For the Year Ended December 31, 2015 (in millions) Comcast Comcast CCCL NBCUniversal Non- Elimination Consolidated Revenue: Service revenue $ — $ — $ — $ — $ 74,510 $ — $ 74,510 Management fee revenue 1,005 — 977 — — (1,982 ) — Total revenue 1,005 — 977 — 74,510 (1,982 ) 74,510 Costs and Expenses: Programming and production — — — — 22,550 — 22,550 Other operating and administrative 760 — 977 922 20,648 (1,982 ) 21,325 Advertising, marketing and promotion — — — — 5,957 — 5,957 Depreciation 31 — — — 6,750 — 6,781 Amortization 6 — — — 1,893 — 1,899 Other operating gains — — — — — — — Total costs and expenses 797 — 977 922 57,798 (1,982 ) 58,512 Operating income (loss) 208 — — (922 ) 16,712 — 15,998 Other Income (Expense): Interest expense (1,744 ) (12 ) (270 ) (462 ) (214 ) — (2,702 ) Investment income (loss), net 6 (1 ) — (19 ) 95 — 81 Equity in net income (losses) of investees, net 9,159 8,651 8,040 4,852 3,089 (34,116 ) (325 ) Other income (expense), net (3 ) — — (31 ) 354 — 320 Total other income (expense) 7,418 8,638 7,770 4,340 3,324 (34,116 ) (2,626 ) Income (loss) before income taxes 7,626 8,638 7,770 3,418 20,036 (34,116 ) 13,372 Income tax (expense) benefit 537 4 94 (4 ) (5,590 ) — (4,959 ) Net income (loss) 8,163 8,642 7,864 3,414 14,446 (34,116 ) 8,413 Net (income) loss attributable to noncontrolling interests and redeemable subsidiary preferred stock — — — — (250 ) — (250 ) Net income (loss) attributable to Comcast Corporation $ 8,163 $ 8,642 $ 7,864 $ 3,414 $ 14,196 $ (34,116 ) $ 8,163 Comprehensive income (loss) attributable to Comcast Corporation $ 8,135 $ 8,625 $ 7,864 $ 3,361 $ 14,192 $ (34,042 ) $ 8,135 Condensed Consolidating Statement of Cash Flows For the Year Ended December 31, 2017 (in millions) Comcast Comcast CCCL NBCUniversal Non- Elimination Consolidated Net cash provided by (used in) operating activities $ 151 $ 15 $ (147 ) $ (1,439 ) $ 22,823 $ — $ 21,403 Investing Activities: Net transactions with affiliates 5,578 (5 ) 757 1,447 (7,777 ) — — Capital expenditures (12 ) — — — (9,538 ) — (9,550 ) Cash paid for intangible assets (4 ) — — — (1,743 ) — (1,747 ) Acquisitions and construction of real estate properties (267 ) — — — (151 ) — (418 ) Acquisitions, net of cash acquired — — — — (532 ) — (532 ) Proceeds from sales of businesses and investments — — — 14 136 — 150 Purchases of investments (70 ) (10 ) (60 ) (62 ) (2,090 ) — (2,292 ) Deposits — — — — — — — Other 101 — — 58 526 — 685 Net cash provided by (used in) investing activities 5,326 (15 ) 697 1,457 (21,169 ) — (13,704 ) Financing Activities: Proceeds from (repayments of) short-term borrowings, net (837 ) — — — (1,068 ) — (1,905 ) Proceeds from borrowings 5,997 — — — 5,469 — 11,466 Repurchases and repayments of debt (2,288 ) — (550 ) (4 ) (3,522 ) — (6,364 ) Repurchases of common stock under repurchase program and employee plans (5,435 ) — — — — — (5,435 ) Dividends paid (2,883 ) — — — — — (2,883 ) Purchase of Universal Studios Japan noncontrolling interests — — — — (2,299 ) — (2,299 ) Issuances of common stock — — — — — — — Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock — — — — (252 ) — (252 ) Other (31 ) — — — 131 — 100 Net cash provided by (used in) financing activities (5,477 ) — (550 ) (4 ) (1,541 ) — (7,572 ) Increase (decrease) in cash and cash equivalents — — — 14 113 — 127 Cash and cash equivalents, beginning of year — — — 482 2,819 — 3,301 Cash and cash equivalents, end of year $ — $ — $ — $ 496 $ 2,932 $ — $ 3,428 Condensed Consolidating Statement of Cash Flows For the Year Ended December 31, 2016 (in millions) Comcast Comcast CCCL NBCUniversal Non- Elimination Consolidated Net cash provided by (used in) operating activities $ (747 ) $ (189 ) $ (100 ) $ (1,453 ) $ 22,314 $ — $ 19,825 Investing Activities: Net transactions with affiliates (860 ) 189 100 2,642 (2,071 ) — — Capital expenditures (13 ) — — — (9,122 ) — (9,135 ) Cash paid for intangible assets (9 ) — — — (1,677 ) — (1,686 ) Acquisitions and construction of real estate properties (35 ) — — — (393 ) — (428 ) Acquisitions, net of cash acquired — — — — (3,929 ) — (3,929 ) Proceeds from sales of businesses and investments — — — 104 114 — 218 Purchases of investments (40 ) — — (210 ) (1,447 ) — (1,697 ) Deposits — — — — (1,749 ) — (1,749 ) Other (108 ) — — (35 ) 164 — 21 Net cash provided by (used in) investing activities (1,065 ) 189 100 2,501 (20,110 ) — (18,385 ) Financing Activities: Proceeds from (repayments of) short-term borrowings, net 1,339 — — — 451 — 1,790 Proceeds from borrowings 9,231 — — — — — 9,231 Repurchases and repayments of debt (750 ) — — (1,005 ) (1,297 ) — (3,052 ) Repurchases of common stock under repurchase program and employee plans (5,352 ) — — — — — (5,352 ) Dividends paid (2,601 ) — — — — — (2,601 ) Issuances of common stock 23 — — — — — 23 Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock — — — — (253 ) — (253 ) Other (78 ) — — 25 (167 ) — (220 ) Net cash provided by (used in) financing activities 1,812 — — (980 ) (1,266 ) — (434 ) Increase (decrease) in cash and cash equivalents — — — 68 938 — 1,006 Cash and cash equivalents, beginning of year — — — 414 1,881 — 2,295 Cash and cash equivalents, end of year $ — $ — $ — $ 482 $ 2,819 $ — $ 3,301 Condensed Consolidating Statement of Cash Flows For the Year Ended December 31, 2015 (in millions) Comcast Comcast CCCL NBCUniversal Non- Elimination Consolidated Net cash provided by (used in) operating activities $ (85 ) $ 48 $ (167 ) $ (1,398 ) $ 21,087 $ — $ 19,485 Investing Activities: Net transactions with affiliates 6,559 (48 ) 840 2,839 (10,190 ) — — Capital expenditures (27 ) — — — (8,472 ) — (8,499 ) Cash paid for intangible assets (6 ) — — — (1,364 ) — (1,370 ) Acquisitions and construction of real estate properties — — — — (178 ) — (178 ) Acquisitions, net of cash acquired — — — — (1,786 ) — (1,786 ) Proceeds from sales of businesses and investments — — — 4 429 — 433 Purchases of investments (7 ) — — (407 ) (370 ) — (784 ) Deposits — — — — (18 ) — (18 ) Other 7 — — (5 ) 236 — 238 Net cash provided by (used in) investing activities 6,526 (48 ) 840 2,431 (21,713 ) — (11,964 ) Financing Activities: Proceeds from (repayments of) short-term borrowings, net 400 — — — (265 ) — 135 Proceeds from borrowings 5,486 — — — — — 5,486 Repurchases and repayments of debt (2,650 ) — (673 ) (1,004 ) (51 ) — (4,378 ) Repurchases of common stock under repurchase program and employee plans (7,175 ) — — — — — (7,175 ) Dividends paid (2,437 ) — — — — — (2,437 ) Issuances of common stock 36 — — — — — 36 Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock — — — — (232 ) — (232 ) Other (101 ) — — — (470 ) — (571 ) Net cash provided by (used in) financing activities (6,441 ) — (673 ) (1,004 ) (1,018 ) — (9,136 ) Increase (decrease) in cash and cash equivalents — — — 29 (1,644 ) — (1,615 ) Cash and cash equivalents, beginning of year — — — 385 3,525 — 3,910 Cash and cash equivalents, end of year $ — $ — $ — $ 414 $ 1,881 $ — $ 2,295

Schedule II Valuation and Quali

Schedule II Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2017
Valuation and Qualifying Accounts Disclosure [Line Items]
Schedule II - Valuation and Qualifying Accounts	Comcast Corporation and Subsidiaries Schedule II – Valuation and Qualifying Accounts Year ended December 31, 2017 , 2016 and 2015 Year Ended December 31 (in millions) Balance at Beginning Additions Charged to Deductions from Balance at End 2017 Allowance for doubtful accounts $ 250 $ 72 $ 34 $ 288 Allowance for returns and customer incentives 417 974 972 419 Valuation allowance on deferred tax assets 266 111 — 377 2016 Allowance for doubtful accounts $ 226 $ 86 $ 62 $ 250 Allowance for returns and customer incentives 473 1,041 1,097 417 Valuation allowance on deferred tax assets 342 23 99 266 2015 Allowance for doubtful accounts $ 205 $ 166 $ 145 $ 226 Allowance for returns and customer incentives 359 1,236 1,122 473 Valuation allowance on deferred tax assets 375 4 37 342
NBCUniversal Media LLC [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Schedule II - Valuation and Qualifying Accounts	NBCUniversal Media, LLC Schedule II – Valuation and Qualifying Accounts Year ended December 31, 2017 , 2016 and 2015 Year Ended December 31 (in millions) Balance at Beginning Additions Charged to Deductions from Balance at End 2017 Allowance for doubtful accounts $ 84 $ 23 $ 19 $ 88 Allowance for returns and customer incentives 413 955 954 414 Valuation allowance on deferred tax assets 72 15 — 87 2016 Allowance for doubtful accounts $ 69 $ 26 $ 11 $ 84 Allowance for returns and customer incentives 469 1,040 1,096 413 Valuation allowance on deferred tax assets 71 23 22 72 2015 Allowance for doubtful accounts $ 60 $ 27 $ 18 $ 69 Allowance for returns and customer incentives 356 1,233 1,120 469 Valuation allowance on deferred tax assets 87 4 20 71 (a) Additions and deductions related to allowance for returns and customer incentives include amounts for distribution on behalf of third parties.

Accounting Policies (Policies)

Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
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 in accordance with generally accepted accounting principles in the United States (“GAAP”).
Foreign Currency Translation	We translate assets and liabilities of our foreign operations where the functional currency is the local currency, primarily the Japanese yen, euro and British pound, 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.
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. We believe that the judgments and related estimates for the following items are critical in the preparation of our consolidated financial statements: • valuation and impairment testing of cable franchise rights (see Note 9) • film and television costs (see Note 6) In addition, the following accounting policies are specific to the industries in which we operate: • capitalization and amortization of film and television costs (see Note 6) • installation revenue and costs for connecting customers to our cable systems (see revenue recognition below and Note 8) 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. Below is a discussion of accounting policies and methods used in our consolidated financial statements that are not presented within other footnotes.
Revenue Recognition	Cable Communications Segment Our Cable Communications segment generates revenue primarily from residential and business customers that subscribe to our video, high-speed Internet, voice, and security and automation services (“cable services”), and from the sale of advertising. We recognize revenue from cable services as each service is provided. Customers are typically billed in advance on a monthly basis based on the services and features they receive and the type of equipment they use. Since installation revenue obtained from the connection of customers to our cable systems is less than the related direct selling costs, we recognize revenue as connections are completed. We manage credit risk by screening applicants through the use of internal customer information, identification verification tools and credit bureau data. If a customer’s account is delinquent, various measures are used to collect outstanding amounts, including termination of the customer’s cable services. As part of our distribution agreements with cable networks, we generally receive an allocation of scheduled advertising time on cable networks that we sell through our advertising business to local, regional and national advertisers. We recognize advertising revenue when the advertising is aired or viewed. In most cases, the available advertising units are sold by our sales force. 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. 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 revenue and the fees paid to representation firms and multichannel video providers in other operating and administrative expenses. Under the terms of our cable franchise agreements, we are generally required to pay to the cable franchising authority an amount based on our gross video revenue. We pass these fees through to our cable services customers and classify the fees as a component of revenue with the corresponding costs included in other operating and administrative expenses. Cable Networks and Broadcast Television Segments Our Cable Networks segment generates revenue primarily from the distribution of our cable network programming to traditional and virtual multichannel video providers; from the sale of advertising on our cable networks and digital properties; from the licensing of our owned programming, including programming from our cable television studio production operations, to cable and broadcast networks and subscription video on demand services; and from the sale of our owned programming on standard-definition digital video discs and Blu-ray discs (together, “DVDs”) and through digital distribution services such as iTunes. Our Broadcast Television segment generates revenue primarily from the sale of advertising on our broadcast networks, owned local broadcast television stations and digital properties; from the licensing of our owned programming by our broadcast television studio production operations to various distribution platforms, including to cable and broadcast networks as well as to subscription video on demand services; from the fees received under retransmission consent agreements and associated fees received from NBC-affiliated local broadcast television stations; and from the sale of our owned programming on DVDs and through digital distribution services. We recognize revenue from distributors as programming is provided, generally under multiyear distribution agreements. From time to time, the distribution agreements expire while programming continues to be provided to the distributor based on interim arrangements while the parties negotiate new contract terms. Revenue recognition is generally limited to current payments being made by the distributor, typically under the prior contract terms, until a new contract is negotiated, sometimes with effective dates that affect prior periods. Differences between actual amounts determined upon resolution of negotiations and amounts recorded during these interim arrangements are recorded in the period of resolution. Advertising revenue for our Cable Networks and Broadcast Television segments is recognized in the period in which the advertising is aired or viewed. In some instances, we guarantee audience ratings for the advertising. To the extent there is a shortfall in the ratings that were guaranteed, a portion of the revenue is deferred until the shortfall is settled, primarily by providing additional advertising units. We recognize revenue from the licensing of our owned programming, including programming produced by our studios for third parties, when the content is made available for use by the licensee and when certain other conditions are met. When license fees include advertising time, we recognize the component of revenue associated with the advertisements when they are aired or viewed. Filmed Entertainment Segment Our Filmed Entertainment segment generates revenue primarily from the worldwide distribution of our produced and acquired films for exhibition in movie theaters, from the licensing of produced and acquired films through various distribution platforms, and from the sale of produced and acquired films on DVDs and through digital distribution services. Our Filmed Entertainment segment also generates revenue from Fandango, our movie ticketing and entertainment business, the sale of consumer products, the production and licensing of live stage plays, and the distribution of filmed entertainment produced by third parties. We recognize revenue from the distribution of films to movie theaters when the films are exhibited. We recognize revenue from the licensing of a film when the film is made available for use by the licensee, and when certain other conditions are met. We recognize revenue from the sale of DVDs, net of estimated returns and customer incentives, on the date that the DVDs are delivered to and made available for sale by retailers. Theme Parks Segment Our Theme Parks segment generates revenue primarily from ticket sales and guest spending at our Universal theme parks. We recognize revenue from advance theme park ticket sales when the tickets are used. For annual passes, we recognize revenue on a straight-line basis over the period following the activation date.
Cable Communications Programming Expenses	Cable Communications programming expenses are the fees we pay to license the programming we distribute to our video customers. Programming is generally acquired under multiyear distribution agreements, with rates typically based on the number of customers that receive the programming, channel positioning and the extent of distribution. From time to time, these contracts expire and programming continues to be provided under interim arrangements while the parties negotiate new contract terms, sometimes with effective dates that affect prior periods. While payments are typically made under the prior contract’s terms, the amount of programming expenses recorded during the interim arrangement is based on our estimate of the ultimate contract terms expected to be negotiated. Differences between actual amounts determined upon resolution of negotiations and amounts recorded during these interim arrangements are recorded in the period of resolution. When our Cable Communications segment receives incentives from a cable network for the licensing of its programming, we defer a portion of these incentives, which are included in other current and noncurrent liabilities, and recognize them over the term of the contract as a reduction to programming expenses.
Advertising Expenses	Advertising costs are expensed as incurred.
Cash Equivalents	The carrying amounts of our cash equivalents approximate their fair values. Our cash equivalents consist primarily of money market funds and U.S. government obligations, as well as commercial paper and certificates of deposit with maturities of three months or less when purchased.
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. The impact of our derivative financial instruments on our consolidated financial statements was not material 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 (market approach, income approach and cost approach). 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 financial instruments and valuation models whose inputs are observable • Level 3: Values are determined using pricing 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 We use these levels of hierarchy to measure the fair value of certain financial instruments on a recurring basis, such as for investments; on a non-recurring basis, such as for acquisitions and impairment testing; for disclosure purposes, such as for long-term debt and redeemable subsidiary preferred stock; and for other applications, as discussed in their respective footnotes. Our assessment of the significance of a particular input to the fair value measurement requires judgment and may affect the valuation and classification within the fair value hierarchy.
Asset Retirement Obligations	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 any 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 retirements recorded in our consolidated financial statements.
Recent Accounting Pronouncements	Revenue Recognition In May 2014, the Financial Accounting Standards Board (“FASB”) updated the accounting guidance related to revenue recognition. The updated accounting guidance provides a single, contract-based revenue recognition model to help improve financial reporting by providing clearer guidance on when an entity should recognize revenue and by reducing the number of standards to which an entity has to refer. The updated guidance also requires additional disclosures regarding the nature, timing and uncertainty of our revenue transactions. We will adopt the updated accounting guidance in the first quarter of 2018 using the full retrospective method, which requires the adjustment of all prior periods presented to reflect the impacts of the updated guidance. The adoption of the new standard will not have a material impact to our consolidated financial position or results of operations. A summary of the changes that will be implemented in 2018 in connection with the new standard are presented below. Changes to Presentation of Revenue and Related Costs with No Impact to the Timing of Recognition • Revenue from our residential video services in our Cable Communications segment will decrease with corresponding increases to high-speed Internet and voice revenue due to a change in the allocation of revenue among our cable services included in a bundle that our residential customers purchase at a discount. • Revenue from franchise and other regulatory fees, which was previously presented in other revenue, will be presented with the corresponding cable services in our Cable Communications segment. This will result in increases to video, voice and business services revenue. • Customer late fees in our Cable Communications segment will now be presented in other and in business services revenue. These fees were previously presented as a reduction to other operating and administrative expenses. • Certain costs, including costs related to the fulfillment of contracts with customers, in our Cable Communications segment will be presented as other assets and the related costs will be recognized over time in operating costs and expenses, which are comprised of total costs and expenses, excluding depreciation and amortization expense and other operating gains. These amounts were previously presented as intangible assets, and the expenses were previously presented in amortization expense. The payments related to these assets will be presented in net cash provided by operating activities rather than in cash paid for intangible assets in our consolidated statement of cash flows. The table below presents the expected effects upon adoption these changes in presentation would have had on our Cable Communications segment revenue, operating costs and expenses and depreciation and amortization expense in 2017 and 2016. Year ended December 31 (in millions) 2017 2016 As Reported Effects of Adoption (a) Upon Adoption (a) As Reported Effects of Adoption (a) Upon Adoption (a) Cable Communications segment Revenue $ 52,519 $ 482 $ 53,001 $ 50,048 $ 471 $ 50,519 Operating costs and expenses $ 31,349 $ 619 $ 31,968 $ 29,939 $ 602 $ 30,541 Depreciation and amortization expense $ 8,143 $ (137 ) $ 8,006 $ 7,670 $ (131 ) $ 7,539 (a) Certain other immaterial changes in presentation and the impacts due to changes in timing of revenue recognition and related costs described below were excluded from the table. The final effects of the adoption will differ from the amounts presented above. Changes to the Timing of Recognition of Revenue and Related Costs • Installation revenue and commission expenses in our Cable Communications segment will be recognized as revenue and costs, respectively, over a period of time. These amounts were previously recognized immediately. • Content licensing revenue associated with renewals or extensions of existing program licensing agreements in our Cable Networks, Broadcast Television and Filmed Entertainment segments will be recognized as revenue when the licensed content becomes available under the renewal or extension. These renewals or extensions were previously recognized as revenue when the agreement was executed. Financial Assets and Financial Liabilities In January 2016, the FASB updated the accounting guidance related to the recognition and measurement of financial assets and financial liabilities. The updated accounting guidance, among other things, requires that all nonconsolidated equity investments, except those accounted for under the equity method, be measured at fair value and that the changes in fair value be recognized in net income. The updated guidance is effective for us as of January 1, 2018. With certain exceptions, the updated accounting guidance requires a cumulative effect adjustment to beginning retained earnings in the year the guidance is adopted. If we had adopted the provisions of the updated guidance as of January 1, 2017 for our equity investments classified as available-for-sale securities, primarily our investment in Snap Inc. (see Note 7), net income attributable to Comcast Corporation would have decreased by $44 million in 2017. If we had adopted the provisions of the updated guidance as of January 1, 2017 for our equity investments classified as cost method investments, the impact on our net income attributable to Comcast Corporation would not have been material. Leases In February 2016, the FASB updated the accounting guidance related to leases. The updated accounting guidance requires lessees to recognize a right-of-use asset and a lease liability on the balance sheet for all leases with the exception of short-term leases. The asset and liability are initially measured based on the present value of committed lease payments. For a lessee, the recognition, measurement and presentation of expenses and cash flows arising from a lease do not significantly change from previous guidance. For a lessor, the accounting applied is also largely unchanged from previous guidance. The updated guidance is effective for us as of January 1, 2019 and early adoption is permitted. The updated accounting guidance must be adopted using a modified retrospective approach for leases that exist or are entered into after the beginning of the earliest comparative period in the financial statements. We are currently in the process of determining the impact that the updated accounting guidance will have on our consolidated financial statements. See Note 16 for a summary of our undiscounted minimum rental commitments under operating leases as of December 31, 2017. Share-Based Compensation In March 2016, the FASB updated the accounting guidance that affects several aspects of the accounting for share-based compensation. The most significant change for us relates to the presentation of the income and withholding tax consequences of share-based compensation in our consolidated financial statements. Among the changes, the updated guidance requires that the excess income tax benefits or deficiencies that arise when the tax consequences of share-based compensation differ from amounts previously recognized in the statement of income be recognized as income tax benefit or expense in the statement of income rather than as additional paid-in capital in the balance sheet. The guidance also states that excess income tax benefits should not be presented separately from other income taxes in the statement of cash flows and, thus, should be classified as an operating activity rather than a financing activity as they were under the prior guidance. In addition, the updated guidance requires that, when an employer withholds shares upon exercise of options or the vesting of restricted stock for the purpose of meeting withholding tax requirements, the cash paid for withholding taxes be classified as a financing activity. We include these amounts in the caption “repurchases of common stock under repurchase program and employee plans” in our consolidated statement of cash flows. We previously recorded these amounts as operating activities. We adopted the updated guidance as of January 1, 2017 and as required, we prospectively adopted the provisions that relate to the recognition of the excess income tax benefits or deficiencies in our consolidated statement of income. The excess tax benefits resulted in an increase to income tax benefit in 2017 of $297 million and our diluted earnings per common share attributable to Comcast Corporation shareholders in 2017 increased by $0.04 . As required by the updated guidance, the prior year periods in our consolidated statement of income were not adjusted as a result of these provisions. In addition, we retrospectively adopted the provisions of this guidance related to changes to the statement of cash flows for all periods presented. This resulted in increases to net cash provided by operating activities and decreases to net cash provided by (used in) financing activities of $732 million , $585 million and $707 million in 2017, 2016 and 2015, respectively.
Earnings Per Share	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
Capitalization of Film and Television Costs	We capitalize film and television production costs, including direct costs, production overhead, print costs, development costs and interest. We amortize capitalized film and television production costs, including acquired libraries, and accrue costs associated with participation and residual payments to programming and production expenses. We generally record the amortization and the accrued costs using the individual film forecast computation method, which amortizes the costs in the same ratio as the associated ultimate revenue. Estimates of ultimate revenue and total costs are based on anticipated release patterns, public acceptance and historical results for similar productions. Unamortized film and television production costs, including acquired libraries, are stated at the lower of unamortized cost or fair value. 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. 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. 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 a film is less than its unamortized costs, we determine the fair value of the film and record an impairment charge for the amount by which the unamortized capitalized costs exceed the film’s fair value. The estimated fair value of a production is based on Level 3 inputs that primarily use an analysis of future expected cash flows. Adjustments to capitalized film production costs were not material in any of the periods presented. 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. 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 a third-party investor under these arrangements as a reduction to our capitalized film costs. Under these arrangements, the investor owns an undivided copyright interest in the film, and therefore in each period we record either a charge or a benefit to programming and production expenses to reflect the estimate of the third-party investor’s interest in the profit or loss of the film. The estimate of the third-party investor’s interest in the profit or loss of a film is determined using the ratio of actual revenue earned to date to the ultimate revenue expected to be recognized over the film’s useful life. We capitalize the costs of programming content that we license but do not own, including rights to multiyear, live-event sports programming, at the earlier of when payments are made for the programming or when the license period begins and the content is made available for use. We amortize capitalized programming costs as the associated programs are broadcast. We generally amortize multiyear, live-event sports programming rights using the ratio of the current period revenue to the estimated ultimate revenue or under the terms of the contract. Programming costs are recorded at the lower of unamortized cost or net realizable value on a program by program, package, channel or daypart basis. A daypart is an aggregation of programs broadcast during a particular time of day or programs of a similar type. Programming acquired by our Cable Networks segment is primarily tested on a channel basis for impairment, whereas programming acquired by our Broadcast Television segment is tested on a daypart basis. If we determine that the estimates of future cash flows are insufficient or if there is no plan to broadcast certain programming, we recognize an impairment charge to programming and production expenses.
Fair Value and 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 significant partnership or limited liability company interest. Equity method investments are recorded at cost and are adjusted to recognize (1) our proportionate share 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 (expense), 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 (expense), net. We classify publicly traded investments that are not accounted for under the equity method as available-for-sale (“AFS”) or trading securities. The estimated fair value of our publicly traded investments was primarily based on Level 1 inputs that use quoted market values. For other fair value method investments, the estimated fair value was 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 AFS securities, we record unrealized gains or losses resulting from changes in fair value between measurement dates as a component of other comprehensive income (loss), except when we consider declines in value to be other than temporary. For trading securities, we record unrealized gains or losses resulting from changes in fair value between measurement dates as a component of investment income (loss), net. We recognize realized gains and losses associated with our fair value method investments using the specific identification method. We classify the cash flows related to purchases of and proceeds from the sale of trading securities based on the nature of the securities and the purpose for which they were acquired. Snap In March 2017, we acquired an interest in Snap Inc. for $500 million as part of its initial public offering, which we have classified as an available-for-sale security. Snap is a camera company whose primary product is Snapchat, a camera app that was created to help people communicate through short videos and images.
Cost Method	We use the cost method to account for investments not accounted for under the fair value method or the equity method.
Impairment Testing of Investments	We review our investment portfolio each reporting period to determine whether there are identified events or circumstances that would indicate there is a decline in the fair value that would be considered other than temporary. 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. 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 AFS securities and our cost method investments, we record the impairment to investment income (loss), net. For our equity method investments, we record the impairment to other income (expense), 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. In accordance with the accounting guidance related to cable television companies, we capitalize 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. 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 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 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. As a result of this assessment, our reporting units are the same as our five reportable segments. 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 carrying amount of the reporting unit’s goodwill exceeds its implied fair value. Unless presented separately, the impairment charge is included as a component of amortization expense.
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. Costs we incur in negotiating and renewing cable franchise agreements are included in other intangible assets and are generally amortized on a straight-line basis over the term of the franchise agreement. 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	Finite-lived intangible assets are subject to amortization and consist primarily of customer relationships acquired in business combinations, software, cable franchise renewal costs, contractual operating rights 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. We evaluate the recoverability of our finite-lived intangible assets 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 amortization expense.
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. 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.
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, and tax planning opportunities available in the jurisdictions in which we operate. 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).
NBCUniversal Media LLC [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
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 in accordance with generally accepted accounting principles in the United States (“GAAP”). Transactions between NBCUniversal and both Comcast and Comcast’s consolidated subsidiaries are reflected in these consolidated financial statements and disclosed as related party transactions when material.
Foreign Currency Translation	We translate assets and liabilities of our foreign operations where the functional currency is the local currency, primarily the Japanese yen, euro and British pound, 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.
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. We believe that the judgments and related estimates for the following items are critical in the preparation of our consolidated financial statements: • revenue recognition (see below) • film and television costs (see Note 6) • goodwill and intangible assets (see Note 9) In addition, the following accounting policy is specific to the industries in which we operate: • capitalization and amortization of film and television costs (see Note 6) 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. Below is a discussion of accounting policies and methods used in our consolidated financial statements that are not presented within other footnotes.
Revenue Recognition	Cable Networks and Broadcast Television Segments Our Cable Networks segment generates revenue primarily from the distribution of our cable network programming to traditional and virtual multichannel video providers; from the sale of advertising on our cable networks and digital properties; from the licensing of our owned programming, including programming from our cable television studio production operations, to cable and broadcast networks and subscription video on demand services; and from the sale of our owned programming on standard-definition digital video discs and Blu-ray discs (together, “DVDs”) and through digital distribution services such as iTunes. Our Broadcast Television segment generates revenue primarily from the sale of advertising on our broadcast networks, owned local broadcast television stations and digital properties; from the licensing of our owned programming by our broadcast television studio production operations to various distribution platforms, including to cable and broadcast networks as well as to subscription video on demand services; from the fees received under retransmission consent agreements and associated fees received from NBC-affiliated local broadcast television stations; and from the sale of our owned programming on DVDs and through digital distribution services. We recognize revenue from distributors as programming is provided, generally under multiyear distribution agreements. From time to time, the distribution agreements expire while programming continues to be provided to the distributor based on interim arrangements while the parties negotiate new contract terms. Revenue recognition is generally limited to current payments being made by the distributor, typically under the prior contract terms, until a new contract is negotiated, sometimes with effective dates that affect prior periods. Differences between actual amounts determined upon resolution of negotiations and amounts recorded during these interim arrangements are recorded in the period of resolution. Advertising revenue for our Cable Networks and Broadcast Television segments is recognized in the period in which the advertising is aired or viewed. In some instances, we guarantee audience ratings for the advertising. To the extent there is a shortfall in the ratings that were guaranteed, a portion of the revenue is deferred until the shortfall is settled, primarily by providing additional advertising units. We recognize revenue from the licensing of our owned programming, including programming produced by our studios for third parties, when the content is made available for use by the licensee and when certain other conditions are met. When license fees include advertising time, we recognize the component of revenue associated with the advertisements when they are aired or viewed. Filmed Entertainment Segment Our Filmed Entertainment segment generates revenue primarily from the worldwide distribution of our produced and acquired films for exhibition in movie theaters, from the licensing of produced and acquired films through various distribution platforms, and from the sale of produced and acquired films on DVDs and through digital distribution services. Our Filmed Entertainment segment also generates revenue from Fandango, our movie ticketing and entertainment business, the sale of consumer products, the production and licensing of live stage plays, and the distribution of filmed entertainment produced by third parties. We recognize revenue from the distribution of films to movie theaters when the films are exhibited. We recognize revenue from the licensing of a film when the film is made available for use by the licensee, and when certain other conditions are met. We recognize revenue from the sale of DVDs, net of estimated returns and customer incentives, on the date that the DVDs are delivered to and made available for sale by retailers. Theme Parks Segment Our Theme Parks segment generates revenue primarily from ticket sales and guest spending at our Universal theme parks. We recognize revenue from advance theme park ticket sales when the tickets are used. For annual passes, we recognize revenue on a straight-line basis over the period following the activation date.
Advertising Expenses	Advertising costs are expensed as incurred.
Cash Equivalents	The carrying amounts of our cash equivalents approximate their fair values. Our cash equivalents consist primarily of money market funds and U.S. government obligations, as well as commercial paper and certificates of deposit with maturities of three months or less when purchased.
Derivative Financial Instruments	We use derivative financial instruments to manage our exposure to the risks associated with fluctuations in foreign exchange rates and interest rates. 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. The impact of our derivative financial instruments on our consolidated financial statements was not material 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 (market approach, income approach and cost approach). 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 financial instruments and valuation models whose inputs are observable • Level 3: Values are determined using pricing 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 We use these levels of hierarchy to measure the fair value of certain financial instruments on a recurring basis, such as for investments; on a non-recurring basis, such as for acquisitions and impairment testing; for disclosure purposes, such as long-term debt; and for other applications, as discussed in their respective footnotes. Our assessment of the significance of a particular input to the fair value measurement requires judgment and may affect the valuation and classification within the fair value hierarchy.
Recent Accounting Pronouncements	Revenue Recognition In May 2014, the Financial Accounting Standards Board (“FASB”) updated the accounting guidance related to revenue recognition. The updated accounting guidance provides a single, contract-based revenue recognition model to help improve financial reporting by providing clearer guidance on when an entity should recognize revenue and by reducing the number of standards to which an entity has to refer. The updated guidance also requires additional disclosures regarding the nature, timing and uncertainty of our revenue transactions. We will adopt the updated accounting guidance in the first quarter of 2018 using the full retrospective method, which requires the adjustment of all prior periods presented to reflect the impacts of the updated guidance. The adoption of the new standard will not have a material impact to our consolidated financial position or results of operations. However, we do expect that the new standard will impact the timing of the recognition of content licensing revenue associated with renewals or extensions of existing program licensing agreements in our Cable Networks, Broadcast Television and Filmed Entertainment segments, which will be recognized as revenue when the licensed content becomes available under the renewal or extension. These renewals or extensions were previously recognized as revenue when the agreement was executed. Financial Assets and Financial Liabilities In January 2016, the FASB updated the accounting guidance related to the recognition and measurement of financial assets and financial liabilities. The updated accounting guidance, among other things, requires that all nonconsolidated equity investments, except those accounted for under the equity method, be measured at fair value and that the changes in fair value be recognized in net income. The updated guidance is effective for us as of January 1, 2018. With certain exceptions, the updated accounting guidance requires a cumulative effect adjustment to beginning retained earnings in the year the guidance is adopted. If we had adopted the provisions of the updated guidance as of January 1, 2017 for our equity investments classified as available-for-sale securities, primarily our investment in Snap Inc. (see Note 7), net income attributable to NBCUniversal would have decreased by $233 million in 2017. If we had adopted the provisions of the updated guidance as of January 1, 2017 for our cost method investments, the impact on our net income attributable to NBCUniversal would not have been material. Leases In February 2016, the FASB updated the accounting guidance related to leases. The updated accounting guidance requires lessees to recognize a right-of-use asset and a lease liability on the balance sheet for all leases with the exception of short-term leases. The asset and liability are initially measured based on the present value of committed lease payments. For a lessee, the recognition, measurement and presentation of expenses and cash flows arising from a lease do not significantly change from previous guidance. For a lessor, the accounting applied is also largely unchanged from previous guidance. The updated guidance is effective for us as of January 1, 2019 and early adoption is permitted. The updated accounting guidance must be adopted using a modified retrospective approach for leases that exist or are entered into after the beginning of the earliest comparative period in the financial statements. We are currently in the process of determining the impact that the updated accounting guidance will have on our consolidated financial statements. See Note 14 for a summary of our undiscounted minimum rental commitments under operating leases as of December 31, 2017.
Capitalization of Film and Television Costs	We capitalize film and television production costs, including direct costs, production overhead, print costs, development costs and interest. We amortize capitalized film and television production costs, including acquired libraries, and accrue costs associated with participation and residual payments to programming and production expenses. We generally record the amortization and the accrued costs using the individual film forecast computation method, which amortizes the costs in the same ratio as the associated ultimate revenue. Estimates of ultimate revenue and total costs are based on anticipated release patterns, public acceptance and historical results for similar productions. Unamortized film and television production costs, including acquired libraries, are stated at the lower of unamortized cost or fair value. 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. 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. 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 a film is less than its unamortized costs, we determine the fair value of the film and record an impairment charge for the amount by which the unamortized capitalized costs exceed the film’s fair value. The estimated fair value of a production is based on Level 3 inputs that primarily use an analysis of future expected cash flows. Adjustments to capitalized film production costs were not material in any of the periods presented. 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. 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 a third-party investor under these arrangements as a reduction to our capitalized film costs. Under these arrangements, the investor owns an undivided copyright interest in the film, and therefore in each period we record either a charge or a benefit to programming and production expenses to reflect the estimate of the third-party investor’s interest in the profit or loss of the film. The estimate of the third-party investor’s interest in the profit or loss of a film is determined using the ratio of actual revenue earned to date to the ultimate revenue expected to be recognized over the film’s useful life. We capitalize the costs of programming content that we license but do not own, including rights to multiyear, live-event sports programming, at the earlier of when payments are made for the programming or when the license period begins and the content is made available for use. We amortize capitalized programming costs as the associated programs are broadcast. We generally amortize multiyear, live-event sports programming rights using the ratio of the current period revenue to the estimated ultimate revenue or under the terms of the contract. Programming costs are recorded at the lower of unamortized cost or net realizable value on a program by program, package, channel or daypart basis. A daypart is an aggregation of programs broadcast during a particular time of day or programs of a similar type. Programming acquired by our Cable Networks segment is primarily tested on a channel basis for impairment, whereas programming acquired by our Broadcast Television segment is tested on a daypart basis. If we determine that the estimates of future cash flows are insufficient or if there is no plan to broadcast certain programming, we recognize an impairment charge to programming and production expenses.
Fair Value and 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 significant partnership or limited liability company interest. Equity method investments are recorded at cost and are adjusted to recognize (1) our proportionate share 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 (expense), 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 (expense), net.
Cost Method	We use the cost method to account for investments not accounted for under the fair value method or the equity method.
Impairment Testing of Investments	Impairment Testing of Investments We review our investment portfolio each reporting period to determine whether there are identified events or circumstances that would indicate there is a decline in the fair value that would be considered other than temporary. 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. 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 AFS securities and our cost method investments, we record the impairment to investment income (loss), net. For our equity method investments, we record the impairment to other income (expense), 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. 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 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. As a result of this assessment, our reporting units are the same as our four reportable segments. 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 carrying amount of the reporting unit’s goodwill exceeds its implied fair value. Unless presented separately, the impairment charge is included as a component of amortization expense. We did not recognize any impairment charges in any of the periods presented.
Indefinite-Lived Intangible Assets	Indefinite-Lived Intangible Assets Indefinite-lived intangible assets consist of trade names and FCC licenses. We assess the recoverability of our indefinite-lived intangible assets annually, or more frequently whenever events or substantive changes in circumstances indicate that the assets might be impaired. We evaluate the unit of account used to test for impairment of our 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 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 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	Finite-lived intangible assets are subject to amortization and consist primarily of customer relationships acquired in business combinations, intellectual property rights and software. 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. We evaluate the recoverability of our finite-lived intangible assets 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 amortization expense.
Postretirement Benefit and Pension Plans	We sponsor various nonqualified defined benefit pension plans for domestic employees. Since the future benefits have been frozen since the beginning of 2013, we did not recognize service costs related to our pension plans in any of the periods presented. The benefits expense we recognized for our defined benefit plans was not material for any period presented. In addition to the defined benefit plans we sponsor, we are also obligated to reimburse The General Electric Company (“GE”) for future benefit payments to those participants who were vested in the supplemental pension plan sponsored by GE at the time of Comcast’s acquisition of NBCUniversal. The plan is unfunded and substantially all of our postretirement benefit obligations are recorded to noncurrent liabilities. The expense we recognize for the plan is determined using certain assumptions, including the discount rate. The benefits expense we recognized for the plan was not material in any of the periods presented.

Recent Accounting Pronounceme31

Recent Accounting Pronouncements (Tables)	12 Months Ended
	Dec. 31, 2017
Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Schedule of changes related to adoption of new accounting pronouncement	The table below presents the expected effects upon adoption these changes in presentation would have had on our Cable Communications segment revenue, operating costs and expenses and depreciation and amortization expense in 2017 and 2016. Year ended December 31 (in millions) 2017 2016 As Reported Effects of Adoption (a) Upon Adoption (a) As Reported Effects of Adoption (a) Upon Adoption (a) Cable Communications segment Revenue $ 52,519 $ 482 $ 53,001 $ 50,048 $ 471 $ 50,519 Operating costs and expenses $ 31,349 $ 619 $ 31,968 $ 29,939 $ 602 $ 30,541 Depreciation and amortization expense $ 8,143 $ (137 ) $ 8,006 $ 7,670 $ (131 ) $ 7,539 (a) Certain other immaterial changes in presentation and the impacts due to changes in timing of revenue recognition and related costs described below were excluded from the table. The final effects of the adoption will differ from the amounts presented above.

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Computation of diluted EPS	Computation of Diluted EPS 2017 2016 2015 Year ended December 31 Net Income Shares Per Share Net Income Shares Per Share Net Income Shares Per Share Basic EPS attributable to Comcast Corporation shareholders $ 22,714 4,708 $ 4.82 $ 8,695 4,819 $ 1.80 $ 8,163 4,972 $ 1.64 Effect of dilutive securities: Assumed exercise or issuance of shares relating to stock plans 78 56 63 Diluted EPS attributable to Comcast Corporation shareholders $ 22,714 4,786 $ 4.75 $ 8,695 4,875 $ 1.78 $ 8,163 5,035 $ 1.62

Significant Transactions (Table

Significant Transactions (Tables) - DreamWorks Animation [Member]	12 Months Ended
	Dec. 31, 2017
Business Acquisition [Line Items]
Schedule of Business Acquisitions, by Acquisition	The table below presents the allocation of the purchase price to the assets and liabilities of DreamWorks Animation. Allocation of Purchase Price (in millions) Film and television costs $ 838 Intangible assets 396 Working capital 156 Debt (381 ) Tax receivable agreement (146 ) Deferred income taxes 291 Other noncurrent assets (liabilities) 170 Identifiable net assets (liabilities) acquired 1,324 Noncontrolling interests (337 ) Goodwill (see Note 9) 2,786 Cash consideration transferred $ 3,773
NBCUniversal Media LLC [Member]
Business Acquisition [Line Items]
Schedule of Business Acquisitions, by Acquisition	The table below presents the allocation of the purchase price to the assets and liabilities of DreamWorks Animation. Allocation of Purchase Price (in millions) Film and television costs $ 838 Intangible assets 396 Working capital 156 Debt (381 ) Tax receivable agreement (a) (146 ) Other noncurrent assets (liabilities) and other (b) 461 Identifiable net assets (liabilities) acquired 1,324 Noncontrolling interests (337 ) Goodwill (see Note 9) 2,786 Cash consideration transferred by Comcast $ 3,773 (a) The tax receivable agreement was settled immediately following the acquisition and the payment was recorded as an operating activity in our consolidated statement of cash flows in 2016. Comcast made a separate cash capital contribution of $146 million to fund the settlement, which was recorded as a financing activity in our consolidated statement of cash flows. (b) Other included $279 million recorded to member’s capital that represented deferred income tax assets and other tax-related items recorded by Comcast but excluded from the net assets contributed to us.

Related Party Transactions (Tab

Related Party Transactions (Tables)	12 Months Ended
	Dec. 31, 2017
NBCUniversal Media LLC [Member]
Related Party Transaction [Line Items]
Related Party Transactions Condensed Financial Statements	The following tables present transactions with Comcast and its consolidated subsidiaries that are included in our consolidated financial statements. Consolidated Balance Sheet December 31 (in millions) 2017 2016 Transactions with Comcast and Consolidated Subsidiaries Receivables, net $ 326 $ 285 Accounts payable and accrued expenses related to trade creditors $ 54 $ 55 Accrued expenses and other current liabilities $ 50 $ 4 Note payable to Comcast $ 1,831 $ 2,703 Long-term debt (see Note 10) $ 610 $ — Other noncurrent liabilities $ 389 $ 389 Consolidated Statement of Income Year ended December 31 (in millions) 2017 2016 2015 Transactions with Comcast and Consolidated Subsidiaries Revenue $ 1,837 $ 1,742 $ 1,349 Total costs and expenses $ (214 ) $ (220 ) $ (246 ) Other income (expense) $ (250 ) $ (69 ) $ (37 )

Film and Television Costs (Tabl

Film and Television Costs (Tables)	12 Months Ended
	Dec. 31, 2017
Film And Television Cost [Line Items]
Film and Television Costs	December 31 (in millions) 2017 2016 Film Costs: Released, less amortization $ 1,724 $ 1,750 Completed, not released 50 50 In production and in development 1,149 1,310 2,923 3,110 Television Costs: Released, less amortization 2,259 1,953 In production and in development 818 853 3,077 2,806 Programming rights, less amortization 2,689 2,586 8,689 8,502 Less: Current portion of programming rights 1,613 1,250 Film and television costs $ 7,076 $ 7,252
NBCUniversal Media LLC [Member]
Film And Television Cost [Line Items]
Film and Television Costs	December 31 (in millions) 2017 2016 Film Costs: Released, less amortization $ 1,724 $ 1,750 Completed, not released 50 50 In production and in development 1,149 1,310 2,923 3,110 Television Costs: Released, less amortization 2,259 1,953 In production and in development 818 853 3,077 2,806 Programming rights, less amortization 2,677 2,570 8,677 8,486 Less: Current portion of programming rights 1,606 1,241 Film and television costs $ 7,071 $ 7,245

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value, Equity And Cost Method Investments [Line Items]
Investment Summary	December 31 (in millions) 2017 2016 Fair Value Method: Snap $ 430 $ — Other 167 198 597 198 Equity Method: Atairos 2,388 1,601 Hulu 249 225 Other 909 550 3,546 2,376 Cost Method: AirTouch 1,614 1,599 BuzzFeed 400 400 Other 793 771 2,807 2,770 Total investments 6,950 5,344 Less: Current investments 19 97 Noncurrent investments $ 6,931 $ 5,247
Investment Income (Loss), Net	Investment Income (Loss), Net Year ended December 31 (in millions) 2017 2016 2015 Gains (losses) on sales of investments, net $ 12 $ 46 $ 12 Investment impairment losses (29 ) (34 ) (59 ) Interest and dividend income 136 123 115 Other, net 134 78 13 Investment income (loss), net $ 253 $ 213 $ 81
NBCUniversal Media LLC [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Investment Summary	December 31 (in millions) 2017 2016 Fair Value Method: Snap $ 430 $ — Other — 6 430 6 Equity Method: Hulu 249 225 Other 441 336 690 561 Cost Method: BuzzFeed 400 400 Other 296 296 696 696 Total investments $ 1,816 $ 1,263
Summarized Financial Information	The tables below present the summarized combined financial information of our equity method investments. December 31 (in millions) 2017 2016 Current assets $ 2,612 $ 2,105 Noncurrent assets $ 3,690 $ 2,724 Current liabilities $ 2,205 $ 1,921 Noncurrent liabilities $ 3,969 $ 2,853 Year ended December 31 (in millions) 2017 2016 2015 Revenue $ 4,234 $ 4,285 $ 3,944 Operating income (loss) $ (465 ) $ (182 ) $ (1,609 ) Net income (loss) $ (656 ) $ (313 ) $ (1,820 )

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and Equipment	December 31 (in millions) Weighted-Average 2017 2016 Cable distribution system 11 years $ 36,046 $ 34,028 Customer premise equipment 6 years 26,392 28,621 Other equipment 9 years 10,518 9,471 Buildings and leasehold improvements 30 years 12,346 10,653 Construction in process N/A 1,752 1,901 Land N/A 1,332 1,273 Property and equipment, at cost 88,386 85,947 Less: Accumulated depreciation 49,916 49,694 Property and equipment, net $ 38,470 $ 36,253
NBCUniversal Media LLC [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment	December 31 (in millions) Weighted-Average 2017 2016 Buildings and leasehold improvements 31 years $ 8,124 $ 7,543 Furniture, fixtures and equipment 11 years 4,843 4,158 Construction in process N/A 1,506 1,176 Land N/A 1,039 984 Property and equipment, at cost 15,512 13,861 Less: Accumulated depreciation 4,166 3,350 Property and equipment, net $ 11,346 $ 10,511

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2017
Goodwill And Intangible Assets [Line Items]
Schedule of Goodwill	Goodwill NBCUniversal (in millions) Cable Cable Broadcast Filmed Theme Corporate Total Balance, December 31, 2015 $ 12,389 $ 12,947 $ 806 $ 267 $ 6,344 $ 192 $ 32,945 Acquisitions (a) 82 232 — 2,717 — 1 3,032 Adjustments (b) 174 — — — (250 ) (181 ) (257 ) Foreign currency translation — 4 — 9 247 — 260 Balance, December 31, 2016 12,645 13,183 806 2,993 6,341 12 35,980 Acquisitions 140 241 — 32 — 5 418 Dispositions — — — — — (11 ) (11 ) Adjustments (c) (1 ) 1 — 185 — 1 186 Foreign currency translation — 2 — 2 203 — 207 Balance, December 31, 2017 $ 12,784 $ 13,427 $ 806 $ 3,212 $ 6,544 $ 7 $ 36,780 (a) Acquisitions in 2016 in our Filmed Entertainment segment primarily included the DreamWorks Animation acquisition (see Note 5 for additional information). (b) Adjustments in 2016 primarily included the updated allocation of the purchase price for Universal Studios Japan in our Theme Parks segment and the reclassification of certain operations and businesses from Corporate and Other to our Cable Communications segment. (c) Adjustments in 2017 primarily included the updated allocation of the purchase price for DreamWorks Animation (see Note 5 for additional information).
Other Intangible Assets	Intangible Assets 2017 2016 December 31 (in millions) Weighted-Average Original Useful Life as of December 31, 2017 Gross Carrying Amount Accumulated Amortization Gross Carrying Amount Accumulated Amortization Indefinite-Lived Intangible Assets: Franchise rights N/A $ 59,364 $ 59,364 Trade names N/A 2,981 2,981 FCC licenses (a) N/A 2,238 651 Finite-Lived Intangible Assets: Customer relationships 19 years 13,612 $ (5,819 ) 13,478 $ (5,110 ) Software 4 years 8,258 (4,846 ) 7,017 (3,997 ) Cable franchise renewal costs and contractual operating rights 9 years 1,492 (834 ) 1,460 (800 ) Patents and other technology rights 7 years 259 (221 ) 257 (208 ) Other agreements and rights 16 years 2,724 (1,065 ) 2,443 (898 ) Total $ 90,928 $ (12,785 ) $ 87,651 $ (11,013 ) (a) In 2017, we acquired the rights to spectrum in the FCC Spectrum auction (see Note 5 for additional information).
Amortization of Intangible Assets	Estimated Amortization Expense of Finite-Lived Intangible Assets (in millions) 2018 $ 2,283 2019 $ 1,952 2020 $ 1,629 2021 $ 1,225 2022 $ 905
NBCUniversal Media LLC [Member]
Goodwill And Intangible Assets [Line Items]
Schedule of Goodwill	Goodwill (in millions) Cable Broadcast Filmed Theme Total Balance, December 31, 2015 $ 12,947 $ 806 $ 267 $ 6,344 $ 20,364 Acquisitions (a) 232 — 2,717 — 2,949 Adjustments (b) — — — (250 ) (250 ) Foreign currency translation 4 — 9 247 260 Balance, December 31, 2016 13,183 806 2,993 6,341 23,323 Acquisitions 241 — 32 — 273 Adjustments (c) 1 — 185 — 186 Foreign currency translation 2 — 2 203 207 Balance, December 31, 2017 $ 13,427 $ 806 $ 3,212 $ 6,544 $ 23,989 (a) Acquisitions in 2016 in our Filmed Entertainment segment primarily included the DreamWorks Animation acquisition (see Note 4 for additional information). (b) Adjustments in 2016 included the updated allocation of the purchase price for Universal Studios Japan in our Theme Parks segment. (c) Adjustments in 2017 primarily included the updated allocation of the purchase price for DreamWorks Animation (see Note 4 for additional information).
Other Intangible Assets	Intangible Assets 2017 2016 December 31 (in millions) Weighted-Average Gross Accumulated Gross Accumulated Finite-Lived Intangible Assets: Customer relationships 19 years $ 13,301 $ (5,643 ) $ 13,173 $ (4,952 ) Software 5 years 1,516 (737 ) 1,195 (563 ) Other 16 years 2,580 (1,205 ) 2,345 (1,053 ) Indefinite-Lived Intangible Assets: Trade names N/A 2,981 2,981 FCC licenses N/A 513 651 Total $ 20,891 $ (7,585 ) $ 20,345 $ (6,568 )
Amortization of Intangible Assets	Estimated Amortization Expense of Finite-Lived Intangible Assets (in millions) 2018 $ 1,018 2019 $ 1,010 2020 $ 968 2021 $ 866 2022 $ 786

Long-Term Debt (Tables)

Long-Term Debt (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Instrument [Line Items]
Schedule of Long-Term Debt	Long-Term Debt Outstanding December 31 (in millions) Weighted-Average 2017 2016 Commercial paper 1.84 % $ 903 $ 2,781 Term loans (a) 0.82 % 3,880 3,262 Senior notes with maturities of 5 years or less, at face value 4.18 % 15,680 13,850 Senior notes with maturities between 5 and 10 years, at face value 3.31 % 13,277 12,049 Senior notes with maturities greater than 10 years, at face value (b) 4.74 % 31,838 28,587 Other, including capital lease obligations — 921 842 Debt issuance costs, premiums, discounts and fair value adjustments for hedged positions, net (c) — (1,943 ) (325 ) Total debt 4.04 % (d) 64,556 61,046 Less: Current portion 5,134 5,480 Long-term debt $ 59,422 $ 55,566 (a) The December 31, 2017 and 2016 amounts primarily consist of ¥435 billion and ¥382 billion , respectively, of Universal Studios Japan term loans translated using the exchange rates as of these dates. In May 2017, Universal Studios Japan entered into ¥450 billion of new term loans with a final maturity of March 2022. We used the proceeds from these borrowings to repay in full Universal Studios Japan’s existing yen-denominated term loans and a portion of amounts outstanding under our commercial paper program. (b) The December 31, 2017 and 2016 amounts include £625 million of 5.50% notes due 2029, which translated to $845 million and $771 million , respectively, using the exchange rates as of these dates. (c) The December 31, 2017 amount includes the difference between the principal amount of the new senior notes and the carrying amount of the exchanged senior notes at the time of the senior notes exchange. See below under the heading “Senior Notes Exchange” for additional information on this transaction. (d) Includes the effects of our derivative financial instruments.
Debt Maturities	Principal Maturities of Debt (in millions) 2018 $ 5,127 2019 $ 2,367 2020 $ 3,688 2021 $ 3,884 2022 $ 5,879 Thereafter $ 45,554
Debt Borrowings	2017 Debt Borrowings Year ended December 31, 2017 (in millions) Universal Studios Japan term loans maturing 2022 $ 3,948 Comcast 3.15% senior notes due 2028 1,650 NBCUniversal Enterprise floating rate notes due 2021 1,500 Comcast 3.00% senior notes due 2024 1,250 Comcast 3.30% senior notes due 2027 1,250 Comcast 4.45% senior notes due 2047 1,005 Comcast 4.00% senior notes due 2047 850 Other 13 Total $ 11,466
Debt Repayments and Repurchases	2017 Debt Redemptions and Repayments Year ended December 31, 2017 (in millions) Universal Studios Japan term loans maturing 2020 $ 3,347 Comcast 6.30% senior notes due 2017 1,000 Comcast 6.50% senior notes due 2017 1,000 Comcast 8.875% senior notes due 2017 550 Comcast 5.00% senior notes due 2061 288 Other 179 Total $ 6,364
Schedule of senior notes exchange	We issued $5.5 billion aggregate principal amount of new senior notes in exchange for $3.9 billion aggregate principal amount of certain series of outstanding senior notes that had been issued by us and NBCUniversal, as detailed in the table below. (in millions) Principal Amount Exchanged Principal Amount Issued in Exchange Comcast 6.95% senior notes due 2037 $ 1,212 Comcast 6.45% senior notes due 2037 946 Comcast 6.40% senior notes due 2040 518 NBCUniversal 6.40% senior notes due 2040 442 Comcast 6.40% senior notes due 2038 428 Comcast 6.55% senior notes due 2039 386 Comcast 3.97% senior notes due 2047 $ 2,000 Comcast 4.00% senior notes due 2049 2,000 Comcast 4.05% senior notes due 2052 1,500 Total $ 3,932 $ 5,500
NBCUniversal Media LLC [Member]
Debt Instrument [Line Items]
Schedule of Long-Term Debt	Long-Term Debt Outstanding December 31 (in millions) Weighted-Average 2017 2016 Term loans (a) 0.79 % $ 3,860 $ 3,262 Senior notes with maturities of 5 years or less, at face value 4.76 % 4,000 4,000 Senior notes with maturities between 5 and 10 years, at face value 2.88 % 1,000 1,000 Senior notes with maturities greater than 10 years, at face value 5.50 % 2,759 3,200 Notes due 2049 to Comcast 4.00 % 610 — Other, including capital lease obligations — 276 138 Debt issuance costs, premiums, discounts and fair value adjustments for hedged positions, net — (32 ) (12 ) Total debt 3.49 % 12,473 11,588 Less: Current portion 198 127 Long-term debt $ 12,275 $ 11,461 (a) The December 31, 2017 and 2016 amounts consist of ¥435 billion and ¥382 billion , respectively, of Universal Studios Japan term loans translated using the exchange rates as of these dates. In May 2017, Universal Studios Japan entered into ¥450 billion of new term loans with a final maturity of March 2022. We used the proceeds from these borrowings to repay in full Universal Studios Japan’s existing yen-denominated term loans and a portion of amounts outstanding under our revolving credit agreement with Comcast.
Debt Maturities	Principal Maturities of Debt (in millions) 2018 $ 200 2019 $ 147 2020 $ 2,268 2021 $ 2,349 2022 $ 2,981 Thereafter $ 4,560

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Deferred Compensation Plans	Year ended December 31 (in millions) 2017 2016 2015 Benefit obligation $ 2,539 $ 2,164 $ 2,038 Interest expense $ 209 $ 178 $ 171
Postretirement and Pension Benefits	Year ended December 31 (in millions) 2017 2016 Benefit obligation $ 425 $ 538 Amounts in accumulated other comprehensive income not yet recognized in benefits expense $ (458 ) $ (372 )

Equity (Tables)

Equity (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Schedule of common stock outstanding	Shares of Common Stock Outstanding (in millions) A A Special B Balance, December 31, 2014 4,272 801 9 Stock compensation plans 25 — — Repurchases and retirements of common stock (125 ) (107 ) — Employee stock purchase plans 5 — — Reclassification of Class A Special common stock 694 (694 ) — Other 4 — — Balance, December 31, 2015 4,875 — 9 Stock compensation plans 23 — — Repurchases and retirements of common stock (161 ) — — Employee stock purchase plans 5 — — Balance, December 31, 2016 4,742 — 9 Stock compensation plans 19 — — Repurchases and retirements of common stock (131 ) — — Employee stock purchase plans 5 — — Balance, December 31, 2017 4,635 — 9
Schedule of shares repurchased	Share Repurchases Under Share Repurchase Program Authorization Year ended December 31 (in millions) 2017 2016 2015 Cash consideration $ 5,000 $ 5,000 $ 6,750 Shares repurchased 131 161 232
Schedule of accumulated other comprehensive income (loss)	Accumulated Other Comprehensive Income (Loss) December 31 (in millions) 2017 2016 Unrealized gains (losses) on marketable securities $ (43 ) $ — Deferred gains (losses) on cash flow hedges 9 (14 ) Unrecognized gains (losses) on employee benefit obligations 260 219 Cumulative translation adjustments 153 (107 ) Accumulated other comprehensive income (loss), net of deferred taxes $ 379 $ 98

Share-Based Compensation, Stock

Share-Based Compensation, Stock Options and Restricted Stock Units (Tables)	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [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) 2017 2016 2015 Restricted share units $ 349 $ 306 $ 273 Stock options 205 173 157 Employee stock purchase plans 32 28 25 Total $ 586 $ 507 $ 455
Schedule of stock option and restricted share units activity	Stock Options and Restricted Share Units As of December 31, 2017, unless otherwise stated (in millions, except per share data) Stock Options RSUs Awards granted during 2017 39 15 Weighted-average exercise price of awards granted during 2017 $ 37.47 Stock options outstanding and nonvested RSUs 191 42 Weighted-average exercise price of stock options outstanding $ 24.98 Weighted-average fair value at grant date of nonvested RSUs $ 30.93
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 2017 2016 2015 RSUs fair value $ 37.77 $ 30.02 $ 29.41 Stock options fair value $ 7.01 $ 5.78 $ 5.89 Stock Option Valuation Assumptions: Dividend yield 1.7 % 1.8 % 1.7 % Expected volatility 20.1 % 23.0 % 23.0 % Risk-free interest rate 2.2 % 1.5 % 1.6 % Expected option life (in years) 6.1 6.1 6.0

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Taxes [Line Items]
Schedule for the components of income tax expense	Components of Income Tax Expense (Benefit) Year ended December 31 (in millions) 2017 2016 2015 Current Expense (Benefit): Federal $ 2,411 $ 3,190 $ 3,210 State 277 480 570 Foreign 389 194 221 3,077 3,864 4,001 Deferred Expense (Benefit): Federal (10,659 ) 1,192 890 State 10 154 66 Foreign (6 ) 98 2 (10,655 ) 1,444 958 Income tax expense (benefit) $ (7,578 ) $ 5,308 $ 4,959
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) 2017 2016 2015 Federal tax at statutory rate $ 5,363 $ 5,024 $ 4,680 State income taxes, net of federal benefit 298 373 326 Foreign income taxes, net of federal credit 70 65 13 Nontaxable income attributable to noncontrolling interests (45 ) (128 ) (69 ) Adjustments to uncertain and effectively settled tax positions, net (62 ) 24 15 Accrued interest on uncertain and effectively settled tax positions, net 3 17 73 Excess tax benefits recognized on share-based compensation (297 ) — — 2017 federal tax reform enactment (12,679 ) — — Other (229 ) (67 ) (79 ) Income tax expense (benefit) $ (7,578 ) $ 5,308 $ 4,959
Schedule of the components of net deferred tax liability	Components of Net Deferred Tax Liability December 31 (in millions) 2017 2016 (a) Deferred Tax Assets: Net operating loss carryforwards $ 481 $ 544 Nondeductible accruals and other 2,026 3,797 Less: Valuation allowance 377 266 2,130 4,075 Deferred Tax Liabilities: Differences between book and tax basis of property and equipment and intangible assets 25,154 36,957 Differences between book and tax basis of investments 466 498 Differences between book and tax basis of long-term debt 673 571 Differences between book and tax basis of foreign subsidiaries and undistributed foreign earnings 39 862 26,332 38,888 Net deferred tax liability $ 24,202 $ 34,813
Reconciliation of unrecognized tax benefits	Reconciliation of Unrecognized Tax Benefits (in millions) 2017 2016 (a) 2015 (a) Gross unrecognized tax benefits, January 1 $ 1,443 $ 1,441 $ 1,455 Additions based on tax positions related to the current year 121 74 67 Additions based on tax positions related to prior years 319 72 98 Additions from acquired subsidiaries — 13 — Reductions for tax positions of prior years (251 ) (66 ) (101 ) Reductions due to expiration of statutes of limitations (70 ) (44 ) (41 ) Settlements with tax authorities (65 ) (47 ) (37 ) Gross unrecognized tax benefits, December 31 1,497 1,443 1,441 Positions paid (688 ) (340 ) (305 ) Liability for uncertain tax positions $ 809 $ 1,103 $ 1,136 (a) We have updated the presentation of the table above to include amounts related to positions previously paid and have updated prior year amounts to conform.
NBCUniversal Media LLC [Member]
Income Taxes [Line Items]
Schedule for the components of income tax expense	Components of Income Tax Expense Year ended December 31 (in millions) 2017 2016 2015 Foreign Current income tax expense $ 201 $ 38 $ 81 Deferred income tax expense (7 ) 96 2 Withholding tax expense 187 158 139 U.S. domestic tax expense 11 13 5 Income tax expense $ 392 $ 305 $ 227

Supplemental Financial Inform44

Supplemental Financial Information (Tables)	12 Months Ended
	Dec. 31, 2017
Supplemental Financial Information [Line Items]
Schedule of receivables, net	Receivables December 31 (in millions) 2017 2016 Receivables, gross $ 9,253 $ 8,622 Less: Allowance for returns and customer incentives 419 417 Less: Allowance for doubtful accounts 288 250 Receivables, net $ 8,546 $ 7,955
Schedule of accumulated other comprehensive income (loss)	Accumulated Other Comprehensive Income (Loss) December 31 (in millions) 2017 2016 Unrealized gains (losses) on marketable securities $ (43 ) $ — Deferred gains (losses) on cash flow hedges 9 (14 ) Unrecognized gains (losses) on employee benefit obligations 260 219 Cumulative translation adjustments 153 (107 ) Accumulated other comprehensive income (loss), net of deferred taxes $ 379 $ 98
Schedule of cash payments for interest and income taxes	Cash Payments for Interest and Income Taxes Year ended December 31 (in millions) 2017 2016 2015 Interest $ 2,820 $ 2,565 $ 2,443 Income taxes $ 4,057 $ 3,693 $ 3,726
NBCUniversal Media LLC [Member]
Supplemental Financial Information [Line Items]
Schedule of receivables, net	Receivables December 31 (in millions) 2017 2016 Receivables, gross $ 7,184 $ 6,799 Less: Allowance for returns and customer incentives 414 413 Less: Allowance for doubtful accounts 88 84 Receivables, net $ 6,682 $ 6,302
Schedule of accumulated other comprehensive income (loss)	Accumulated Other Comprehensive Income (Loss) December 31 (in millions) 2017 2016 Unrealized gains (losses) on marketable securities $ (233 ) $ — Deferred gains (losses) on cash flow hedges 10 23 Unrecognized gains (losses) on employee benefit obligations 126 14 Cumulative translation adjustments 77 (172 ) Accumulated other comprehensive income (loss) $ (20 ) $ (135 )
Schedule of cash payments for interest and income taxes	Cash Payments for Interest and Income Taxes Year ended December 31 (in millions) 2017 2016 2015 Interest $ 517 $ 548 $ 456 Income taxes $ 282 $ 208 $ 182

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2017
Commitment And Contingencies [Line Items]
Schedule of minimum annual programming and talent commitments	The table below summarizes our minimum annual programming and talent commitments and our minimum annual rental commitments under operating leases for office space, equipment and transponder service agreements. Programming and talent commitments include acquired film and television programming, including U.S. broadcast rights to the Olympic Games through 2032, Sunday Night Football through the 2022-23 season , certain NASCAR events through 2024 and other programming commitments, as well as various contracts with creative talent. As of December 31, 2017 (in millions) Programming and Talent Commitments Operating Leases 2018 $ 6,350 $ 559 2019 $ 3,895 $ 512 2020 $ 4,812 $ 457 2021 $ 3,301 $ 391 2022 $ 3,732 $ 326 Thereafter $ 17,416 $ 1,829
Schedule of rental expenses charged to operations	The table below presents our rental expense charged to operations. Year ended December 31 (in millions) 2017 2016 2015 Rental expense $ 839 $ 744 $ 608
NBCUniversal Media LLC [Member]
Commitment And Contingencies [Line Items]
Schedule of minimum annual programming and talent commitments	The table below summarizes our minimum annual programming and talent commitments and our minimum annual rental commitments under operating leases for office space and equipment. Programming and talent commitments include acquired film and television programming, including U.S. broadcast rights to the Olympic Games through 2032, Sunday Night Football through the 2022-23 season , certain NASCAR events through 2024 and other programming commitments, as well as various contracts with creative talent. As of December 31, 2017 (in millions) Programming and Talent Commitments Operating Leases 2018 $ 6,343 $ 209 2019 $ 3,893 $ 195 2020 $ 4,812 $ 182 2021 $ 3,301 $ 163 2022 $ 3,732 $ 139 Thereafter $ 17,416 $ 1,223
Schedule of rental expenses charged to operations	The table below presents our rental expense charged to operations. Year ended December 31 (in millions) 2017 2016 2015 Rental expense $ 274 $ 259 $ 213

Financial Data by Business Se46

Financial Data by Business Segment (Tables)	12 Months Ended
	Dec. 31, 2017
Segment Reporting Information [Line Items]
Financial Data by Business Segment	Our financial data by business 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 (f) Adjusted (g) Depreciation and Capital Cash Paid for 2017 Cable Communications (a) $ 52,519 $ 21,170 $ 8,143 $ 7,952 $ 1,382 NBCUniversal Cable Networks 10,631 4,076 755 33 19 Broadcast Television 9,546 1,253 133 180 22 Filmed Entertainment 7,658 1,277 109 58 23 Theme Parks 5,443 2,384 648 960 78 Headquarters and Other (b) 45 (741 ) 396 271 153 Eliminations (c) (326 ) (4 ) — — — NBCUniversal 32,997 8,245 2,041 1,502 295 Corporate and Other (d) 1,060 (1,394 ) 83 96 70 Eliminations (c) (2,050 ) 41 — — — Comcast Consolidated $ 84,526 $ 28,062 $ 10,267 $ 9,550 $ 1,747 (in millions) Revenue (f) Adjusted (g) Depreciation and Capital Cash Paid for 2016 Cable Communications (a) $ 50,048 $ 20,109 $ 7,670 $ 7,596 $ 1,377 NBCUniversal Cable Networks (e) 10,464 3,709 745 32 20 Broadcast Television (e) 10,147 1,320 125 153 19 Filmed Entertainment 6,360 697 47 33 16 Theme Parks 4,946 2,190 512 922 72 Headquarters and Other (b) 20 (699 ) 376 312 156 Eliminations (c) (344 ) 10 — — — NBCUniversal 31,593 7,227 1,805 1,452 283 Corporate and Other (d) 750 (874 ) 83 87 26 Eliminations (c) (1,988 ) (45 ) — — — Comcast Consolidated $ 80,403 $ 26,417 $ 9,558 $ 9,135 $ 1,686 (in millions) Revenue (f) Adjusted (g) Depreciation and Capital Cash Paid for 2015 Cable Communications (a) $ 46,928 $ 19,037 $ 7,051 $ 7,040 $ 1,151 NBCUniversal Cable Networks 9,628 3,499 784 44 22 Broadcast Television (e) 8,530 780 111 117 17 Filmed Entertainment 7,287 1,234 26 14 20 Theme Parks 3,339 1,464 292 833 54 Headquarters and Other (b) 14 (625 ) 326 378 98 Eliminations (c) (336 ) — — — — NBCUniversal 28,462 6,352 1,539 1,386 211 Corporate and Other (d) 713 (815 ) 90 73 8 Eliminations (c) (1,593 ) 104 — — — Comcast Consolidated $ 74,510 $ 24,678 $ 8,680 $ 8,499 $ 1,370 (a) For the years ended December 31, 2017 , 2016 and 2015 , Cable Communications segment revenue was derived from the following sources: 2017 2016 2015 Residential: Video 44.0 % 44.7 % 45.9 % High-speed Internet 28.1 % 27.0 % 26.6 % Voice 6.5 % 7.1 % 7.7 % Business services 11.8 % 11.0 % 10.1 % Advertising 4.3 % 4.9 % 4.7 % Other 5.3 % 5.3 % 5.0 % Total 100.0 % 100.0 % 100.0 % Subscription revenue received from residential customers who purchase bundled services at a discounted rate is allocated proportionally to each cable service based on the individual service’s price on a stand-alone basis. For 2017 , 2.7% of Cable Communications revenue was derived from franchise and other regulatory fees. For both 2016 and 2015 , 2.8% of Cable Communications revenue was derived from franchise and other regulatory fees. (b) NBCUniversal Headquarters and Other activities include costs associated with overhead, allocations, personnel costs and headquarter initiatives. (c) Included in Eliminations are transactions that our segments enter into with one another. The most common types of transactions are the following: • our Cable Networks segment generates revenue by selling programming to our Cable Communications segment, which represents a substantial majority of the revenue elimination amount • our Broadcast Television segment generates revenue from the fees received under retransmission consent agreements with our Cable Communications segment • our Cable Communications segment generates revenue by selling advertising and by selling the use of satellite feeds to our Cable Networks segment • our Filmed Entertainment and Broadcast Television segments generate revenue by licensing content to our Cable Networks segment; for segment reporting, this revenue is recognized as the programming rights asset for the licensed content is amortized based on third party revenue (d) Corporate and Other activities include costs associated with overhead and personnel, revenue and expenses associated with other business development initiatives, including our new wireless phone service, and the operations of Comcast Spectacor, which owns the Philadelphia Flyers and the Wells Fargo Center arena in Philadelphia, Pennsylvania and operates arena management-related businesses. (e) The revenue and operating costs and expenses associated with our broadcast of the 2016 Rio Olympics were reported in our Cable Networks and Broadcast Television segments. The revenue and operating costs and expenses associated with our broadcast of the 2015 Super Bowl were reported in our Broadcast Television segment. (f) Revenue from customers located outside of the United States, primarily in Europe and Asia, in 2017 , 2016 and 2015 was $7.8 billion , $6.5 billion and $5.8 billion , respectively. No single customer accounted for a significant amount of revenue in any of the periods presented. (g) We use Adjusted EBITDA as the measure of profit or loss for our operating segments. Adjusted EBITDA is defined as net income attributable to Comcast Corporation before net (income) loss attributable to noncontrolling interests and redeemable subsidiary preferred stock, income tax benefit (expense), total other income (expense), depreciation and amortization expense, and other operating gains, and excluding impairment charges related to fixed and intangible assets and gains or losses on the sale of long-lived assets, if any. From time to time we may exclude from Adjusted EBITDA the impact of events, gains, losses or other charges (such as significant legal settlements) that affect the period-to-period comparability of our operating performance. This measure eliminates the significant level of noncash depreciation and amortization expense that results from the capital-intensive nature of certain of our businesses and from intangible assets recognized in business combinations. Additionally, it is unaffected by our capital and tax structures and by our investment activities. We use this measure to evaluate the operating performance of our operating segments and to allocate resources and capital to our operating segments. It is also a significant performance measure in our annual incentive compensation programs. We believe that this measure is useful to investors because it is one of the bases for comparing our operating performance with that of other companies in our industries, although our measure may not be directly comparable to similar measures used by other companies. This measure should not be considered a substitute for operating income (loss), net income (loss), net income (loss) attributable to Comcast Corporation, net cash provided by operating activities, or other measures we have reported in accordance with GAAP. 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) 2017 2016 2015 Adjusted EBITDA $ 28,062 $ 26,417 $ 24,678 Adjustment for legal settlement (250 ) — — Depreciation (7,914 ) (7,464 ) (6,781 ) Amortization (2,353 ) (2,094 ) (1,899 ) Other operating gains 442 — — Total other income (expense) (2,665 ) (2,506 ) (2,626 ) Income before income taxes $ 15,322 $ 14,353 $ 13,372
Cable Communications Segment Revenue Sources	For the years ended December 31, 2017 , 2016 and 2015 , Cable Communications segment revenue was derived from the following sources: 2017 2016 2015 Residential: Video 44.0 % 44.7 % 45.9 % High-speed Internet 28.1 % 27.0 % 26.6 % Voice 6.5 % 7.1 % 7.7 % Business services 11.8 % 11.0 % 10.1 % Advertising 4.3 % 4.9 % 4.7 % Other 5.3 % 5.3 % 5.0 % Total 100.0 % 100.0 % 100.0 %
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) 2017 2016 2015 Adjusted EBITDA $ 28,062 $ 26,417 $ 24,678 Adjustment for legal settlement (250 ) — — Depreciation (7,914 ) (7,464 ) (6,781 ) Amortization (2,353 ) (2,094 ) (1,899 ) Other operating gains 442 — — Total other income (expense) (2,665 ) (2,506 ) (2,626 ) Income before income taxes $ 15,322 $ 14,353 $ 13,372
NBCUniversal Media LLC [Member]
Segment Reporting Information [Line Items]
Financial Data by Business Segment	We use Adjusted EBITDA to evaluate the profitability of our operating segments, and the components of net income attributable to NBCUniversal excluded from Adjusted EBITDA are not separately evaluated. Our financial data by business 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 (d) Adjusted (e) Depreciation and Capital Cash Paid for 2017 Cable Networks $ 10,631 $ 4,076 $ 755 $ 33 $ 19 Broadcast Television 9,546 1,253 133 180 22 Filmed Entertainment 7,658 1,277 109 58 23 Theme Parks 5,443 2,384 648 960 78 Headquarters and Other (a) 45 (801 ) 396 271 153 Eliminations (b) (326 ) (4 ) — — — Total $ 32,997 $ 8,185 $ 2,041 $ 1,502 $ 295 (in millions) Revenue (d) Adjusted (e) Depreciation and Capital Cash Paid for 2016 Cable Networks (c) $ 10,464 $ 3,709 $ 745 $ 32 $ 20 Broadcast Television (c) 10,147 1,320 125 153 19 Filmed Entertainment 6,360 697 47 33 16 Theme Parks 4,946 2,190 512 922 72 Headquarters and Other (a) 20 (699 ) 376 312 156 Eliminations (b) (344 ) 10 — — — Total $ 31,593 $ 7,227 $ 1,805 $ 1,452 $ 283 (in millions) Revenue (d) Adjusted (e) Depreciation and Capital Cash Paid for 2015 Cable Networks $ 9,628 $ 3,499 $ 784 $ 44 $ 22 Broadcast Television (c) 8,530 780 111 117 17 Filmed Entertainment 7,287 1,234 26 14 20 Theme Parks 3,339 1,464 292 833 54 Headquarters and Other (a) 14 (625 ) 326 378 98 Eliminations (b) (336 ) 6 — — — Total $ 28,462 $ 6,358 $ 1,539 $ 1,386 $ 211 (a) Headquarters and Other activities include costs associated with overhead, allocations, personnel costs and headquarter initiatives. (b) Eliminations are transactions that our segments enter into with one another, which consisted primarily of the licensing of film and television content from our Filmed Entertainment and Broadcast Television segments to our Cable Networks segment; for segment reporting, revenue is recognized as the programming rights asset for the licensed content is amortized based on third party revenue. (c) The revenue and operating costs and expenses associated with our broadcast of the 2016 Rio Olympics were reported in our Cable Networks and Broadcast Television segments. The revenue and operating costs and expenses associated with our broadcast of the 2015 Super Bowl were reported in our Broadcast Television segment. (d) We operate primarily in the United States, but also in select international markets primarily in Europe and Asia. The table below summarizes revenue by geographic location. No single customer accounted for a significant amount of revenue in any of the periods presented. Year ended December 31 (in millions) 2017 2016 2015 Revenue: United States $ 25,345 $ 25,076 $ 22,663 Foreign $ 7,652 $ 6,517 $ 5,799 (e) We use Adjusted EBITDA as the measure of profit or loss for our operating segments. Adjusted EBITDA is defined as net income attributable to NBCUniversal before net (income) loss attributable to noncontrolling interests, income tax expense, total other income (expense), depreciation and amortization expense, and other operating gains, and excluding impairment charges related to fixed and intangible assets and gains or losses on the sale of long-lived assets, if any. From time to time we may exclude from Adjusted EBITDA the impact of events, gains, losses or other charges (such as significant legal settlements) that affect the period-to-period comparability of our operating performance. This measure eliminates the significant level of noncash amortization expense that results from intangible assets recognized in business combinations. Additionally, it is unaffected by our capital and tax structures and by our investment activities. We use this measure to evaluate the operating performance of our operating segments and to allocate resources and capital to our operating segments. It is also a significant performance measure in our annual incentive compensation programs. We believe that this measure is useful to investors because it is one of the bases for comparing our operating performance with that of other companies in our industries, although our measure may not be directly comparable to similar measures used by other companies. This measure should not be considered a substitute for operating income (loss), net income (loss), net income (loss) attributable to NBCUniversal, net cash provided by operating activities, or other measures we have reported in accordance with GAAP. 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) 2017 2016 2015 Adjusted EBITDA $ 8,185 $ 7,227 $ 6,358 Depreciation (994 ) (861 ) (669 ) Amortization (1,047 ) (944 ) (870 ) Other operating gains 337 — — Total other income (expense) (871 ) (571 ) (968 ) Income before income taxes $ 5,610 $ 4,851 $ 3,851
Revenue from External Customers by Geographic Areas	The table below summarizes revenue by geographic location. No single customer accounted for a significant amount of revenue in any of the periods presented. Year ended December 31 (in millions) 2017 2016 2015 Revenue: United States $ 25,345 $ 25,076 $ 22,663 Foreign $ 7,652 $ 6,517 $ 5,799

Quarterly Financial Informati47

Quarterly Financial Information (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Schedule of quarterly financial information	(in millions, except per share data) First Second Third Fourth Total 2017 Revenue $ 20,463 $ 21,165 $ 20,983 $ 21,915 $ 84,526 Operating income $ 4,530 $ 4,558 $ 4,792 $ 4,107 $ 17,987 Net income attributable to Comcast Corporation (a) $ 2,566 $ 2,513 $ 2,650 $ 14,985 $ 22,714 Basic earnings per common share attributable to Comcast Corporation shareholders $ 0.54 $ 0.53 $ 0.56 $ 3.22 $ 4.82 Diluted earnings per common share attributable to Comcast Corporation shareholders $ 0.53 $ 0.52 $ 0.55 $ 3.17 $ 4.75 Dividends declared per common share $ 0.1575 $ 0.1575 $ 0.1575 $ 0.1575 $ 0.63 2016 Revenue $ 18,790 $ 19,269 $ 21,319 $ 21,025 $ 80,403 Operating income $ 4,089 $ 4,066 $ 4,440 $ 4,264 $ 16,859 Net income attributable to Comcast Corporation (b) $ 2,134 $ 2,028 $ 2,237 $ 2,296 $ 8,695 Basic earnings per common share attributable to Comcast Corporation shareholders $ 0.44 $ 0.42 $ 0.47 $ 0.48 $ 1.80 Diluted earnings per common share attributable to Comcast Corporation shareholders $ 0.43 $ 0.41 $ 0.46 $ 0.48 $ 1.78 Dividends declared per common share $ 0.1375 $ 0.1375 $ 0.1375 $ 0.1375 $ 0.55 Minor differences may exist due to rounding. (a) In the fourth quarter of 2017, net income attributable to Comcast Corporation included a $12.7 billion net income tax benefit as a result of the impacts of the 2017 tax reform legislation. See Note 14 for additional information. (b) In the fourth quarter of 2016, net income attributable to Comcast Corporation included $225 million , $143 million net of tax, recognized in connection with the settlement of amounts owed to us under an agency agreement that had provided for, among other things, Verizon Wireless’ sale of our cable services.

Condensed Consolidating Finan48

Condensed Consolidating Financial Information (Tables)	12 Months Ended
	Dec. 31, 2017
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Condensed Consolidating Balance Sheet	Condensed Consolidating Balance Sheet December 31, 2017 (in millions) Comcast Comcast CCCL NBCUniversal Non- Elimination Consolidated Assets Cash and cash equivalents $ — $ — $ — $ 496 $ 2,932 $ — $ 3,428 Receivables, net — — — — 8,546 — 8,546 Programming rights — — — — 1,613 — 1,613 Deposits — — — — 9 — 9 Other current assets 60 — 7 25 2,372 — 2,464 Total current assets 60 — 7 521 15,472 — 16,060 Film and television costs — — — — 7,076 — 7,076 Investments 146 21 108 693 5,963 — 6,931 Investments in and amounts due from subsidiaries eliminated upon consolidation 117,154 142,412 139,364 50,249 113,479 (562,658 ) — Property and equipment, net 551 — — — 37,919 — 38,470 Franchise rights — — — — 59,364 — 59,364 Goodwill — — — — 36,780 — 36,780 Other intangible assets, net 12 — — — 18,767 — 18,779 Other noncurrent assets, net 435 708 — 88 2,572 (314 ) 3,489 Total assets $ 118,358 $ 143,141 $ 139,479 $ 51,551 $ 297,392 $ (562,972 ) $ 186,949 Liabilities and Equity Accounts payable and accrued expenses related to trade creditors $ 16 $ — $ — $ — $ 6,910 $ — $ 6,926 Accrued participations and residuals — — — — 1,683 — 1,683 Deferred revenue — — — — 1,552 — 1,552 Accrued expenses and other current liabilities 1,888 92 333 326 3,627 — 6,266 Current portion of long-term debt 2,810 — — 4 2,320 — 5,134 Total current liabilities 4,714 92 333 330 16,092 — 21,561 Long-term debt, less current portion 42,428 140 2,100 7,751 7,003 — 59,422 Deferred income taxes — 285 — 67 24,247 (343 ) 24,256 Other noncurrent liabilities 2,610 — — 1,128 7,137 29 10,904 Redeemable noncontrolling interests and redeemable subsidiary preferred stock — — — — 1,357 — 1,357 Equity: Common stock 55 — — — — — 55 Other shareholders’ equity 68,551 142,624 137,046 42,275 240,713 (562,658 ) 68,551 Total Comcast Corporation shareholders’ equity 68,606 142,624 137,046 42,275 240,713 (562,658 ) 68,606 Noncontrolling interests — — — — 843 — 843 Total equity 68,606 142,624 137,046 42,275 241,556 (562,658 ) 69,449 Total liabilities and equity $ 118,358 $ 143,141 $ 139,479 $ 51,551 $ 297,392 $ (562,972 ) $ 186,949 Condensed Consolidating Balance Sheet December 31, 2016 (in millions) Comcast Comcast CCCL NBCUniversal Non- Elimination Consolidated Assets Cash and cash equivalents $ — $ — $ — $ 482 $ 2,819 $ — $ 3,301 Receivables, net — — — — 7,955 — 7,955 Programming rights — — — — 1,250 — 1,250 Deposits — — — — 1,772 — 1,772 Other current assets 151 — — 36 1,896 — 2,083 Total current assets 151 — — 518 15,692 — 16,361 Film and television costs — — — — 7,252 — 7,252 Investments 75 — — 651 4,521 — 5,247 Investments in and amounts due from subsidiaries eliminated upon consolidation 98,350 120,071 117,696 47,393 97,704 (481,214 ) — Property and equipment, net 298 — — — 35,955 — 36,253 Franchise rights — — — — 59,364 — 59,364 Goodwill — — — — 35,980 — 35,980 Other intangible assets, net 13 — — — 17,261 — 17,274 Other noncurrent assets, net 1,138 638 — 89 1,921 (1,017 ) 2,769 Total assets $ 100,025 $ 120,709 $ 117,696 $ 48,651 $ 275,650 $ (482,231 ) $ 180,500 Liabilities and Equity Accounts payable and accrued expenses related to trade creditors $ 23 $ — $ — $ — $ 6,892 $ — $ 6,915 Accrued participations and residuals — — — — 1,726 — 1,726 Deferred revenue — — — — 1,132 — 1,132 Accrued expenses and other current liabilities 1,726 — 341 302 3,913 — 6,282 Current portion of long-term debt 3,739 — 550 4 1,187 — 5,480 Total current liabilities 5,488 — 891 306 14,850 — 21,535 Long-term debt, less current portion 38,123 141 2,100 8,208 6,994 — 55,566 Deferred income taxes — 542 — 70 35,259 (1,017 ) 34,854 Other noncurrent liabilities 2,471 — — 1,166 7,288 — 10,925 Redeemable noncontrolling interests and redeemable subsidiary preferred stock — — — — 1,446 — 1,446 Equity: Common stock 56 — — — — — 56 Other shareholders’ equity 53,887 120,026 114,705 38,901 207,582 (481,214 ) 53,887 Total Comcast Corporation shareholders’ equity 53,943 120,026 114,705 38,901 207,582 (481,214 ) 53,943 Noncontrolling interests — — — — 2,231 — 2,231 Total equity 53,943 120,026 114,705 38,901 209,813 (481,214 ) 56,174 Total liabilities and equity $ 100,025 $ 120,709 $ 117,696 $ 48,651 $ 275,650 $ (482,231 ) $ 180,500
Condensed Consolidating Statement of Income	Condensed Consolidating Statement of Income For the Year Ended December 31, 2017 (in millions) Comcast Comcast CCCL NBCUniversal Non- Elimination Consolidated Revenue: Service revenue $ — $ — $ — $ — $ 84,526 $ — $ 84,526 Management fee revenue 1,128 — 1,109 — — (2,237 ) — Total revenue 1,128 — 1,109 — 84,526 (2,237 ) 84,526 Costs and Expenses: Programming and production — — — — 25,384 — 25,384 Other operating and administrative 766 — 1,109 1,044 24,331 (2,237 ) 25,013 Advertising, marketing and promotion — — — — 6,317 — 6,317 Depreciation 31 — — — 7,883 — 7,914 Amortization 6 — — — 2,347 — 2,353 Other operating gains — — — — (442 ) — (442 ) Total costs and expenses 803 — 1,109 1,044 65,820 (2,237 ) 66,539 Operating income (loss) 325 — — (1,044 ) 18,706 — 17,987 Other Income (Expense): Interest expense (2,172 ) (12 ) (207 ) (456 ) (239 ) — (3,086 ) Investment income (loss), net (1 ) 109 — (197 ) 342 — 253 Equity in net income (losses) of investees, net 24,056 21,622 19,570 6,740 5,191 (77,072 ) 107 Other income (expense), net — — — 45 16 — 61 Total other income (expense) 21,883 21,719 19,363 6,132 5,310 (77,072 ) (2,665 ) Income (loss) before income taxes 22,208 21,719 19,363 5,088 24,016 (77,072 ) 15,322 Income tax (expense) benefit 506 156 71 (4 ) 6,849 — 7,578 Net income (loss) 22,714 21,875 19,434 5,084 30,865 (77,072 ) 22,900 Net (income) loss attributable to noncontrolling interests and redeemable subsidiary preferred stock — — — — (186 ) — (186 ) Net income (loss) attributable to Comcast Corporation $ 22,714 $ 21,875 $ 19,434 $ 5,084 $ 30,679 $ (77,072 ) $ 22,714 Comprehensive income (loss) attributable to Comcast Corporation $ 22,801 $ 21,873 $ 19,437 $ 5,058 $ 30,541 $ (76,909 ) $ 22,801 Condensed Consolidating Statement of Income For the Year Ended December 31, 2016 (in millions) Comcast Comcast CCCL NBCUniversal Non- Elimination Consolidated Revenue: Service revenue $ — $ — $ — $ — $ 80,403 $ — $ 80,403 Management fee revenue 1,067 — 1,049 — — (2,116 ) — Total revenue 1,067 — 1,049 — 80,403 (2,116 ) 80,403 Costs and Expenses: Programming and production — — — — 24,463 — 24,463 Other operating and administrative 813 — 1,049 932 22,738 (2,116 ) 23,416 Advertising, marketing and promotion — — — — 6,107 — 6,107 Depreciation 28 — — — 7,436 — 7,464 Amortization 6 — — — 2,088 — 2,094 Other operating gains — — — — — — — Total costs and expenses 847 — 1,049 932 62,832 (2,116 ) 63,544 Operating income (loss) 220 — — (932 ) 17,571 — 16,859 Other Income (Expense): Interest expense (1,941 ) (12 ) (239 ) (456 ) (294 ) — (2,942 ) Investment income (loss), net 7 (5 ) — (25 ) 236 — 213 Equity in net income (losses) of investees, net 9,809 9,286 8,679 5,545 4,131 (37,554 ) (104 ) Other income (expense), net — — — 116 211 — 327 Total other income (expense) 7,875 9,269 8,440 5,180 4,284 (37,554 ) (2,506 ) Income (loss) before income taxes 8,095 9,269 8,440 4,248 21,855 (37,554 ) 14,353 Income tax (expense) benefit 600 6 84 (13 ) (5,985 ) — (5,308 ) Net income (loss) 8,695 9,275 8,524 4,235 15,870 (37,554 ) 9,045 Net (income) loss attributable to noncontrolling interests and redeemable subsidiary preferred stock — — — — (350 ) — (350 ) Net income (loss) attributable to Comcast Corporation $ 8,695 $ 9,275 $ 8,524 $ 4,235 $ 15,520 $ (37,554 ) $ 8,695 Comprehensive income (loss) attributable to Comcast Corporation $ 8,967 $ 9,317 $ 8,530 $ 4,312 $ 15,610 $ (37,769 ) $ 8,967 Condensed Consolidating Statement of Income For the Year Ended December 31, 2015 (in millions) Comcast Comcast CCCL NBCUniversal Non- Elimination Consolidated Revenue: Service revenue $ — $ — $ — $ — $ 74,510 $ — $ 74,510 Management fee revenue 1,005 — 977 — — (1,982 ) — Total revenue 1,005 — 977 — 74,510 (1,982 ) 74,510 Costs and Expenses: Programming and production — — — — 22,550 — 22,550 Other operating and administrative 760 — 977 922 20,648 (1,982 ) 21,325 Advertising, marketing and promotion — — — — 5,957 — 5,957 Depreciation 31 — — — 6,750 — 6,781 Amortization 6 — — — 1,893 — 1,899 Other operating gains — — — — — — — Total costs and expenses 797 — 977 922 57,798 (1,982 ) 58,512 Operating income (loss) 208 — — (922 ) 16,712 — 15,998 Other Income (Expense): Interest expense (1,744 ) (12 ) (270 ) (462 ) (214 ) — (2,702 ) Investment income (loss), net 6 (1 ) — (19 ) 95 — 81 Equity in net income (losses) of investees, net 9,159 8,651 8,040 4,852 3,089 (34,116 ) (325 ) Other income (expense), net (3 ) — — (31 ) 354 — 320 Total other income (expense) 7,418 8,638 7,770 4,340 3,324 (34,116 ) (2,626 ) Income (loss) before income taxes 7,626 8,638 7,770 3,418 20,036 (34,116 ) 13,372 Income tax (expense) benefit 537 4 94 (4 ) (5,590 ) — (4,959 ) Net income (loss) 8,163 8,642 7,864 3,414 14,446 (34,116 ) 8,413 Net (income) loss attributable to noncontrolling interests and redeemable subsidiary preferred stock — — — — (250 ) — (250 ) Net income (loss) attributable to Comcast Corporation $ 8,163 $ 8,642 $ 7,864 $ 3,414 $ 14,196 $ (34,116 ) $ 8,163 Comprehensive income (loss) attributable to Comcast Corporation $ 8,135 $ 8,625 $ 7,864 $ 3,361 $ 14,192 $ (34,042 ) $ 8,135
Condensed Consolidating Statement of Cash Flows	Condensed Consolidating Statement of Cash Flows For the Year Ended December 31, 2017 (in millions) Comcast Comcast CCCL NBCUniversal Non- Elimination Consolidated Net cash provided by (used in) operating activities $ 151 $ 15 $ (147 ) $ (1,439 ) $ 22,823 $ — $ 21,403 Investing Activities: Net transactions with affiliates 5,578 (5 ) 757 1,447 (7,777 ) — — Capital expenditures (12 ) — — — (9,538 ) — (9,550 ) Cash paid for intangible assets (4 ) — — — (1,743 ) — (1,747 ) Acquisitions and construction of real estate properties (267 ) — — — (151 ) — (418 ) Acquisitions, net of cash acquired — — — — (532 ) — (532 ) Proceeds from sales of businesses and investments — — — 14 136 — 150 Purchases of investments (70 ) (10 ) (60 ) (62 ) (2,090 ) — (2,292 ) Deposits — — — — — — — Other 101 — — 58 526 — 685 Net cash provided by (used in) investing activities 5,326 (15 ) 697 1,457 (21,169 ) — (13,704 ) Financing Activities: Proceeds from (repayments of) short-term borrowings, net (837 ) — — — (1,068 ) — (1,905 ) Proceeds from borrowings 5,997 — — — 5,469 — 11,466 Repurchases and repayments of debt (2,288 ) — (550 ) (4 ) (3,522 ) — (6,364 ) Repurchases of common stock under repurchase program and employee plans (5,435 ) — — — — — (5,435 ) Dividends paid (2,883 ) — — — — — (2,883 ) Purchase of Universal Studios Japan noncontrolling interests — — — — (2,299 ) — (2,299 ) Issuances of common stock — — — — — — — Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock — — — — (252 ) — (252 ) Other (31 ) — — — 131 — 100 Net cash provided by (used in) financing activities (5,477 ) — (550 ) (4 ) (1,541 ) — (7,572 ) Increase (decrease) in cash and cash equivalents — — — 14 113 — 127 Cash and cash equivalents, beginning of year — — — 482 2,819 — 3,301 Cash and cash equivalents, end of year $ — $ — $ — $ 496 $ 2,932 $ — $ 3,428 Condensed Consolidating Statement of Cash Flows For the Year Ended December 31, 2016 (in millions) Comcast Comcast CCCL NBCUniversal Non- Elimination Consolidated Net cash provided by (used in) operating activities $ (747 ) $ (189 ) $ (100 ) $ (1,453 ) $ 22,314 $ — $ 19,825 Investing Activities: Net transactions with affiliates (860 ) 189 100 2,642 (2,071 ) — — Capital expenditures (13 ) — — — (9,122 ) — (9,135 ) Cash paid for intangible assets (9 ) — — — (1,677 ) — (1,686 ) Acquisitions and construction of real estate properties (35 ) — — — (393 ) — (428 ) Acquisitions, net of cash acquired — — — — (3,929 ) — (3,929 ) Proceeds from sales of businesses and investments — — — 104 114 — 218 Purchases of investments (40 ) — — (210 ) (1,447 ) — (1,697 ) Deposits — — — — (1,749 ) — (1,749 ) Other (108 ) — — (35 ) 164 — 21 Net cash provided by (used in) investing activities (1,065 ) 189 100 2,501 (20,110 ) — (18,385 ) Financing Activities: Proceeds from (repayments of) short-term borrowings, net 1,339 — — — 451 — 1,790 Proceeds from borrowings 9,231 — — — — — 9,231 Repurchases and repayments of debt (750 ) — — (1,005 ) (1,297 ) — (3,052 ) Repurchases of common stock under repurchase program and employee plans (5,352 ) — — — — — (5,352 ) Dividends paid (2,601 ) — — — — — (2,601 ) Issuances of common stock 23 — — — — — 23 Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock — — — — (253 ) — (253 ) Other (78 ) — — 25 (167 ) — (220 ) Net cash provided by (used in) financing activities 1,812 — — (980 ) (1,266 ) — (434 ) Increase (decrease) in cash and cash equivalents — — — 68 938 — 1,006 Cash and cash equivalents, beginning of year — — — 414 1,881 — 2,295 Cash and cash equivalents, end of year $ — $ — $ — $ 482 $ 2,819 $ — $ 3,301 Condensed Consolidating Statement of Cash Flows For the Year Ended December 31, 2015 (in millions) Comcast Comcast CCCL NBCUniversal Non- Elimination Consolidated Net cash provided by (used in) operating activities $ (85 ) $ 48 $ (167 ) $ (1,398 ) $ 21,087 $ — $ 19,485 Investing Activities: Net transactions with affiliates 6,559 (48 ) 840 2,839 (10,190 ) — — Capital expenditures (27 ) — — — (8,472 ) — (8,499 ) Cash paid for intangible assets (6 ) — — — (1,364 ) — (1,370 ) Acquisitions and construction of real estate properties — — — — (178 ) — (178 ) Acquisitions, net of cash acquired — — — — (1,786 ) — (1,786 ) Proceeds from sales of businesses and investments — — — 4 429 — 433 Purchases of investments (7 ) — — (407 ) (370 ) — (784 ) Deposits — — — — (18 ) — (18 ) Other 7 — — (5 ) 236 — 238 Net cash provided by (used in) investing activities 6,526 (48 ) 840 2,431 (21,713 ) — (11,964 ) Financing Activities: Proceeds from (repayments of) short-term borrowings, net 400 — — — (265 ) — 135 Proceeds from borrowings 5,486 — — — — — 5,486 Repurchases and repayments of debt (2,650 ) — (673 ) (1,004 ) (51 ) — (4,378 ) Repurchases of common stock under repurchase program and employee plans (7,175 ) — — — — — (7,175 ) Dividends paid (2,437 ) — — — — — (2,437 ) Issuances of common stock 36 — — — — — 36 Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock — — — — (232 ) — (232 ) Other (101 ) — — — (470 ) — (571 ) Net cash provided by (used in) financing activities (6,441 ) — (673 ) (1,004 ) (1,018 ) — (9,136 ) Increase (decrease) in cash and cash equivalents — — — 29 (1,644 ) — (1,615 ) Cash and cash equivalents, beginning of year — — — 385 3,525 — 3,910 Cash and cash equivalents, end of year $ — $ — $ — $ 414 $ 1,881 $ — $ 2,295

Business and Basis of Present49

Business and Basis of Presentation (Details) customer in Millions	Jan. 24, 2017	Dec. 31, 2017segmentcustomerbusiness
Business And Basis Of Presentation [Line Items]
Number of primary businesses | business		2
Number of reportable segments | segment		5
Stock split, conversion ratio	2
NBCUniversal Media LLC [Member]
Business And Basis Of Presentation [Line Items]
Number of reportable segments | segment		4
Cable Communications [Member]
Business And Basis Of Presentation [Line Items]
Number of reportable segments | segment		1
Total customer relationships		29.3
Cable Communications [Member] | Video Customers [Member]
Business And Basis Of Presentation [Line Items]
Number of customers		22.4
Cable Communications [Member] | High-speed Internet Customers [Member]
Business And Basis Of Presentation [Line Items]
Number of customers		25.9
Cable Communications [Member] | Voice Customers [Member]
Business And Basis Of Presentation [Line Items]
Number of customers		11.6
Cable Communications [Member] | Residential Customers [Member]
Business And Basis Of Presentation [Line Items]
Total customer relationships		27.2
Cable Communications [Member] | Business Customers [Member]
Business And Basis Of Presentation [Line Items]
Total customer relationships		2.2
NBCUniversal Segments [Member]
Business And Basis Of Presentation [Line Items]
Number of reportable segments | segment		4

Recent Accounting Pronounceme50

Recent Accounting Pronouncements (Effects of Changes in Revenue Recognition) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue	$ 21,915	$ 20,983	$ 21,165	$ 20,463	$ 21,025	$ 21,319	$ 19,269	$ 18,790	$ 84,526	$ 80,403	$ 74,510
Depreciation and amortization expense									10,267	9,558	$ 8,680
Cable Communications [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue									52,519	50,048
Operating Expenses Excluding Depreciation And Amortization									31,349	29,939
Depreciation and amortization expense									8,143	7,670
Cable Communications [Member] | Accounting Standards Update 2014-09 [Member] | Upon Adoption [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue									53,001	50,519
Operating Expenses Excluding Depreciation And Amortization									31,968	30,541
Depreciation and amortization expense									8,006	7,539
Cable Communications [Member] | Accounting Standards Update 2014-09 [Member] | Effect of Adoption [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue									482	471
Operating Expenses Excluding Depreciation And Amortization									619	602
Depreciation and amortization expense									$ (137)	$ (131)

Recent Accounting Pronounceme51

Recent Accounting Pronouncements (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in income tax benefit	$ 297	$ 0	$ 0
Net cash provided by operating activities	21,403	19,825	19,485
Net cash provided by (used in) financing activities	(7,572)	(434)	(9,136)
NBCUniversal Media LLC [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash provided by operating activities	7,076	4,897	5,304
Net cash provided by (used in) financing activities	(4,819)	(2,097)	(1,742)
Accounting Standards Update 2016-01 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New accounting pronouncement impact on net income if adopted	(44)
Accounting Standards Update 2016-01 [Member] | NBCUniversal Media LLC [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New accounting pronouncement impact on net income if adopted	(233)
Accounting Standards Update 2016-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in income tax benefit	$ 297
Increase in diluted earnings per share (in dollars per share)	$ 0.04
Net cash provided by operating activities	$ 732	585	707
Net cash provided by (used in) financing activities	$ (732)	$ (585)	$ (707)

Earnings Per Share (Details)

Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Net Income Attributable to Comcast Corporation	$ 14,985	$ 2,650	$ 2,513	$ 2,566	$ 2,296	$ 2,237	$ 2,028	$ 2,134	$ 22,714	$ 8,695	$ 8,163
Basic EPS attributable to Comcast Corporation shareholders (in shares)									4,708	4,819	4,972
Basic earnings per common share attributable to Comcast Corporation shareholders (in dollars per share)	$ 3.22	$ 0.56	$ 0.53	$ 0.54	$ 0.48	$ 0.47	$ 0.42	$ 0.44	$ 4.82	$ 1.80	$ 1.64
Effect of dilutive securities:
Net Income Attributable to Comcast Corporation	$ 14,985	$ 2,650	$ 2,513	$ 2,566	$ 2,296	$ 2,237	$ 2,028	$ 2,134	$ 22,714	$ 8,695	$ 8,163
Assumed exercise or issuance of shares relating to stock plans (in shares)									78	56	63
Diluted EPS attributable to Comcast Corporation shareholders (in shares)									4,786	4,875	5,035
Diluted earnings per common share attributable to Comcast Corporation shareholders (in dollars per share)	$ 3.17	$ 0.55	$ 0.52	$ 0.53	$ 0.48	$ 0.46	$ 0.41	$ 0.43	$ 4.75	$ 1.78	$ 1.62

Significant Transactions (FCC S

Significant Transactions (FCC Spectrum Auction) (Details) - FCC Spectrum [Member] - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jul. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Jun. 30, 2017
FCC Spectrum Auction [Line Items]
Proceeds from FCC spectrum auction	$ 482
Gain on sale of spectrum rights		$ 337
Amount of spectrum acquired		2,238	$ 651	$ 1,700
Deposit to acquire intangible asset			1,800
NBCUniversal Media LLC [Member]
FCC Spectrum Auction [Line Items]
Proceeds from FCC spectrum auction	$ 482
Gain on sale of spectrum rights		337
Amount of spectrum acquired		$ 513	$ 651

Significant Transactions (Unive

Significant Transactions (Universal Studios Japan) (Details) - USD ($) $ in Millions	Apr. 06, 2017	Nov. 13, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Payments to acquire additional interest in noncontrolling interest			$ 2,299	$ 0	$ 0
Goodwill			36,780	35,980	32,945
NBCUniversal Media LLC [Member]
Business Acquisition [Line Items]
Payments to acquire additional interest in noncontrolling interest			2,299	0	0
Goodwill			$ 23,989	$ 23,323	$ 20,364
Universal Studios Japan [Member]
Business Acquisition [Line Items]
Payments to acquire additional interest in noncontrolling interest	$ 2,300
Ownership percentage		51.00%
Cash consideration transferred		$ 1,500
Goodwill		5,100
Long-term debt		3,300
Noncontrolling interest		$ 1,400
Universal Studios Japan [Member] | NBCUniversal Media LLC [Member]
Business Acquisition [Line Items]
Payments to acquire additional interest in noncontrolling interest	$ 2,300
Ownership percentage		51.00%
Cash consideration transferred		$ 1,500
Goodwill		5,100
Long-term debt		3,300
Noncontrolling interest		$ 1,400

Significant Transactions (Dream

Significant Transactions (DreamWorks Animation) (Details) - DreamWorks Animation [Member] $ / shares in Units, $ in Millions	Aug. 22, 2016USD ($)$ / shares
Business Acquisition [Line Items]
Cash consideration transferred	$ 3,773
Business acquisition, price paid per share (in dollars per share) | $ / shares	$ 41
NBCUniversal Media LLC [Member]
Business Acquisition [Line Items]
Cash consideration transferred	$ 3,773
Consideration Transferred By Comcast [Member] | NBCUniversal Media LLC [Member]
Business Acquisition [Line Items]
Cash consideration transferred	$ 3,800
Business acquisition, price paid per share (in dollars per share) | $ / shares	$ 41

Significant Transactions (Alloc

Significant Transactions (Allocation of Purchase Price) (Details) - USD ($) $ in Millions	Aug. 22, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Goodwill (see Note 9)		$ 36,780	$ 35,980	$ 32,945
NBCUniversal Media LLC [Member]
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Goodwill (see Note 9)		23,989	23,323	20,364
Contribution from member		$ 662	$ 3,655	$ 252
DreamWorks Animation [Member]
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Film and television costs	$ 838
Intangible assets	396
Working capital	156
Debt	(381)
Tax receivable agreement	(146)
Deferred income taxes	291
Other noncurrent assets (liabilities)	170
Identifiable net assets (liabilities) acquired	1,324
Noncontrolling interests	(337)
Goodwill (see Note 9)	2,786
Cash consideration transferred by Comcast	3,773
DreamWorks Animation [Member] | NBCUniversal Media LLC [Member]
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Film and television costs	838
Intangible assets	396
Working capital	156
Debt	(381)
Tax receivable agreement	(146)
Other noncurrent assets (liabilities)	461
Identifiable net assets (liabilities) acquired	1,324
Noncontrolling interests	(337)
Goodwill (see Note 9)	2,786
Cash consideration transferred by Comcast	3,773
DreamWorks Animation [Member] | Member's contribution that represented Deferred Income Tax Assets and Other Tax-related Items recorded by Parent but excluded from net assets contributed [Member] | NBCUniversal Media LLC [Member]
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Contribution from member	279
DreamWorks Animation [Member] | Tax Receivable Agreement [Member] | NBCUniversal Media LLC [Member]
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Contribution from member	$ 146

Significant Transactions (Time

Significant Transactions (Time Warner Cable Merger) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)
Time Warner Cable Merger and Related Divestiture Transactions [Member]
Business Acquisition [Line Items]
Transaction costs and transaction-related costs	$ 198

Related Party Transactions (Nar

Related Party Transactions (Narrative) (Details) - USD ($) $ in Millions	Mar. 01, 2018	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2016
Related Party Transaction [Line Items]
Other noncurrent liabilities		$ 10,904	$ 10,925
NBCUniversal Media LLC [Member]
Related Party Transaction [Line Items]
Other noncurrent liabilities		4,109	4,130
NBCUniversal Media LLC [Member] | Carrying Value Of Related Party Contractual Obligation [Member]
Related Party Transaction [Line Items]
Other noncurrent liabilities		$ 383	$ 383
NBCUniversal Media LLC [Member] | NBCUniversal Holdings Preferred Stock [Member]
Related Party Transaction [Line Items]
Preferred stock, dividend rate		8.25%
Preferred stock liquidation preference value		$ 9,400
Preferred stock dividend rate, spread on variable rate	7.44%
NBCUniversal Media LLC [Member] | Former Comcast And NBCUniversal Revolving Credit Agreements [Member]
Related Party Transaction [Line Items]
Revolving credit agreement capacity				$ 3,000
NBCUniversal Media LLC [Member] | Comcast and NBCUniversal Revolving Credit Agreements [Member]
Related Party Transaction [Line Items]
Revolving credit agreement capacity				$ 5,000
Borrowing margin for LIBOR based borrowings		1.00%

Related Party Transactions (Con

Related Party Transactions (Condensed Consolidated Balance Sheet) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Receivables, net	$ 8,546	$ 7,955
Accounts payable and accrued expenses related to trade creditors	6,926	6,915
Accrued expenses and other current liabilities	6,266	6,282
Long-term debt, less current portion	59,422	55,566
Other noncurrent liabilities	10,904	10,925
NBCUniversal Media LLC [Member]
Related Party Transaction [Line Items]
Receivables, net	6,682	6,302
Accounts payable and accrued expenses related to trade creditors	1,663	1,647
Accrued expenses and other current liabilities	2,044	1,888
Note payable to Comcast	1,831	2,703
Long-term debt, less current portion	12,275	11,461
Other noncurrent liabilities	4,109	4,130
Comcast And Consolidated Subsidiaries [Member] | NBCUniversal Media LLC [Member]
Related Party Transaction [Line Items]
Receivables, net	326	285
Accounts payable and accrued expenses related to trade creditors	54	55
Accrued expenses and other current liabilities	50	4
Note payable to Comcast	1,831	2,703
Long-term debt, less current portion	610	0
Other noncurrent liabilities	$ 389	$ 389

Related Party Transactions (C60

Related Party Transactions (Condensed Consolidated Statement of Income) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Revenue	$ 21,915	$ 20,983	$ 21,165	$ 20,463	$ 21,025	$ 21,319	$ 19,269	$ 18,790	$ 84,526	$ 80,403	$ 74,510
Operating costs and expenses									(66,539)	(63,544)	(58,512)
NBCUniversal Media LLC [Member]
Related Party Transaction [Line Items]
Revenue									32,997	31,593	28,462
Operating costs and expenses									(26,516)	(26,171)	(23,643)
Comcast And Consolidated Subsidiaries [Member] | NBCUniversal Media LLC [Member]
Related Party Transaction [Line Items]
Revenue									1,837	1,742	1,349
Operating costs and expenses									(214)	(220)	(246)
Other income (expense)									$ (250)	$ (69)	$ (37)

Related Party Transactions (Sha

Related Party Transactions (Share-Based Compensation) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized share-based compensation expense	$ 586	$ 507	$ 455
NBCUniversal Media LLC [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized share-based compensation expense	133	99	94
Restricted share units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized share-based compensation expense	349	306	273
Unrecognized pretax compensation expense on nonvested awards	$ 806
Unrecognized pretax compensation expense on nonvested awards, weighted average period of recognition (in years)	1 year 8 months
Restricted share units [Member] | NBCUniversal Media LLC [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized pretax compensation expense on nonvested awards	$ 245
Unrecognized pretax compensation expense on nonvested awards, weighted average period of recognition (in years)	1 year 9 months
Stock options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized share-based compensation expense	$ 205	$ 173	$ 157
Unrecognized pretax compensation expense on nonvested awards	$ 404
Unrecognized pretax compensation expense on nonvested awards, weighted average period of recognition (in years)	1 year 8 months
Stock options [Member] | NBCUniversal Media LLC [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized pretax compensation expense on nonvested awards	$ 32
Unrecognized pretax compensation expense on nonvested awards, weighted average period of recognition (in years)	1 year 5 months

Film and Television Costs (Sche

Film and Television Costs (Schedule) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Film Costs:
Released, less amortization	$ 1,724	$ 1,750
Completed, not released	50	50
In production and in development	1,149	1,310
Total film costs	2,923	3,110
Television Costs:
Released, less amortization	2,259	1,953
In production and in development	818	853
Total television costs	3,077	2,806
Programming rights, less amortization	2,689	2,586
Total film costs, television costs and programming rights	8,689	8,502
Less: Current portion of programming rights	1,613	1,250
Film and television costs	7,076	7,252
NBCUniversal Media LLC [Member]
Film Costs:
Released, less amortization	1,724	1,750
Completed, not released	50	50
In production and in development	1,149	1,310
Total film costs	2,923	3,110
Television Costs:
Released, less amortization	2,259	1,953
In production and in development	818	853
Total television costs	3,077	2,806
Programming rights, less amortization	2,677	2,570
Total film costs, television costs and programming rights	8,677	8,486
Less: Current portion of programming rights	1,606	1,241
Film and television costs	$ 7,071	$ 7,245

Film and Television Costs (Narr

Film and Television Costs (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)
Film And Television Cost [Line Items]
Amortization of completed film and television production expected to be amortized during the next fiscal year	$ 1,700
Expected amortization percentage of released and unamortized film and television costs during the next three fiscal years	86.00%
Remaining unamortized costs of acquired film and television libraries	$ 475
Expected amortization percentage of unamortized acquired film and television library costs during the next three fiscal years	44.00%
NBCUniversal Media LLC [Member]
Film And Television Cost [Line Items]
Amortization of completed film and television production expected to be amortized during the next fiscal year	$ 1,700
Expected amortization percentage of released and unamortized film and television costs during the next three fiscal years	86.00%
Remaining unamortized costs of acquired film and television libraries	$ 475
Expected amortization percentage of unamortized acquired film and television library costs during the next three fiscal years	44.00%
Maximum [Member]
Film And Television Cost [Line Items]
Amortization period of acquired film and television library costs	20 years
Maximum [Member] | NBCUniversal Media LLC [Member]
Film And Television Cost [Line Items]
Amortization period of acquired film and television library costs	20 years

Investments (Schedule of Invest

Investments (Schedule of Investments) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Equity And Cost Method Investments [Line Items]
Fair Value Method	$ 597	$ 198
Equity Method	3,546	2,376
Cost Method	2,807	2,770
Total Investments	6,950	5,344
Less: Current investments	19	97
Noncurrent investments	6,931	5,247
Snap [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Fair Value Method	430	0
Other Fair Value Method Investments [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Fair Value Method	167	198
Atairos [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Equity Method	2,388	1,601
Hulu [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Equity Method	249	225
Other Equity Method Investments [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Equity Method	909	550
Air Touch [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Cost Method	1,614	1,599
BuzzFeed [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Cost Method	400	400
Other Cost Method Investments [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Cost Method	793	771
NBCUniversal Media LLC [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Fair Value Method	430	6
Equity Method	690	561
Cost Method	696	696
Noncurrent investments	1,816	1,263
NBCUniversal Media LLC [Member] | Snap [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Fair Value Method	430	0
NBCUniversal Media LLC [Member] | Other Fair Value Method Investments [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Fair Value Method	0	6
NBCUniversal Media LLC [Member] | Hulu [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Equity Method	249	225
NBCUniversal Media LLC [Member] | Other Equity Method Investments [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Equity Method	441	336
NBCUniversal Media LLC [Member] | BuzzFeed [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Cost Method	400	400
NBCUniversal Media LLC [Member] | Other Cost Method Investments [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Cost Method	$ 296	$ 296

Investments (Investment Income

Investments (Investment Income (Loss), Net) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Gains (losses) on sales of investments, net	$ 12	$ 46	$ 12
Investment impairment losses	(29)	(34)	(59)
Interest and dividend income	136	123	115
Other, net	134	78	13
Investment income (loss), net	$ 253	$ 213	$ 81

Investments (Fair Value Method

Investments (Fair Value Method Investments) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Snap [Member]
Schedule of Fair Value Method Investments [Line Items]
Payments to acquire available-for-sale securities		$ 500
NBCUniversal Media LLC [Member]
Schedule of Fair Value Method Investments [Line Items]
Contributed investment from Comcast			$ 662	$ 3,655	$ 252
NBCUniversal Media LLC [Member] | Snap [Member]
Schedule of Fair Value Method Investments [Line Items]
Contributed investment from Comcast	$ 662

Investments (Equity Method Inve

Investments (Equity Method Investments) (Details) - USD ($) $ in Millions	Jan. 01, 2016	Jul. 31, 2017	Aug. 31, 2016	Jan. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jul. 31, 2016
Schedule of Equity Method Investments [Line Items]
Equity in net income (losses) of investees					$ 107	$ (104)	$ (325)
NBCUniversal Media LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity in net income (losses) of investees					(201)	(99)	(376)
Atairos [Member]
Schedule of Equity Method Investments [Line Items]
Term of agreement	12 years
Funding commitment	$ 4,000
Management fee funding commitment	$ 40
Percent of losses	99.00%
Percentage of residual returns	86.50%
Purchases of investments					994	1,200
Equity in net income (losses) of investees					281	(38)
Pretax gain, sale of business		$ 105
Atairos [Member] | Maximum [Member]
Schedule of Equity Method Investments [Line Items]
Funding commitment by management company investors	$ 100
Atairos [Member] | Minimum [Member] | Former CFO [Member]
Schedule of Equity Method Investments [Line Items]
Funding commitment by management company investors	$ 40
Hulu [Member]
Schedule of Equity Method Investments [Line Items]
Equity in net income (losses) of investees					(276)	(168)	(106)
Cash capital contribution, equity method investment					300	50	123
Ownership percentage			30.00%					33.00%
Put/call period			3 years
Deferred gain			$ 159
Hulu [Member] | NBCUniversal Media LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity in net income (losses) of investees					(276)	(168)	(106)
Cash capital contribution, equity method investment					$ 300	$ 50	123
Ownership percentage			30.00%					33.00%
Put/call period			3 years
Deferred gain			$ 159
Hulu [Member] | Time Warner, Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Ownership percentage			10.00%
Hulu [Member] | Time Warner, Inc. [Member] | NBCUniversal Media LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership percentage			10.00%
The Weather Channel [Member]
Schedule of Equity Method Investments [Line Items]
Pretax gain on sale of investment				$ 108
Goodwill impairment loss from equity method investments							333
The Weather Channel [Member] | NBCUniversal Media LLC [Member]
Schedule of Equity Method Investments [Line Items]
Pretax gain on sale of investment				$ 108
Goodwill impairment loss from equity method investments							$ 333

Investments (Equity Method In68

Investments (Equity Method Investments Summarized Financial Information) (Details) - NBCUniversal Media LLC [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Equity Method Investments [Line Items]
Current assets	$ 2,612	$ 2,105
Noncurrent assets	3,690	2,724
Current liabilities	2,205	1,921
Noncurrent liabilities	3,969	2,853
Revenue	4,234	4,285	$ 3,944
Operating income (loss)	(465)	(182)	(1,609)
Net income (loss)	$ (656)	$ (313)	$ (1,820)

Investments (Cost Method Invest

Investments (Cost Method Investments) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)preferred_stock_series	Dec. 31, 2016USD ($)	Nov. 30, 2016USD ($)	Sep. 30, 2015USD ($)
Air Touch [Member]
Schedule of Cost-method Investments [Line Items]
Number of series of preferred stock | preferred_stock_series	3
Preferred stock aggregate redemption value	$ 1,750
Redeemable subsidiary preferred shares	1,600	$ 1,600
Nonredeemable subsidiary preferred shares	100	100
Level 2 [Member] | Air Touch [Member]
Schedule of Cost-method Investments [Line Items]
Fair value of redeemable preferred shares	$ 1,700	1,700
Air Touch [Member]
Schedule of Cost-method Investments [Line Items]
Number of series of preferred stock | preferred_stock_series	2
Preferred stock aggregate redemption value	$ 1,650
Air Touch [Member] | Level 2 [Member]
Schedule of Cost-method Investments [Line Items]
Fair value of cost method Investment redeemable preferred shares	$ 1,700	$ 1,700
Vox Media [Member]
Schedule of Cost-method Investments [Line Items]
Purchases of investments				$ 200
Vox Media [Member] | NBCUniversal Media LLC [Member]
Schedule of Cost-method Investments [Line Items]
Purchases of investments				200
BuzzFeed [Member]
Schedule of Cost-method Investments [Line Items]
Purchases of investments			$ 200	200
BuzzFeed [Member] | NBCUniversal Media LLC [Member]
Schedule of Cost-method Investments [Line Items]
Purchases of investments			$ 200	$ 200

Property and Equipment (Details

Property and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	$ 88,386	$ 85,947
Less: Accumulated depreciation	49,916	49,694
Property and equipment, net	38,470	36,253
NBCUniversal Media LLC [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	15,512	13,861
Less: Accumulated depreciation	4,166	3,350
Property and equipment, net	$ 11,346	10,511
Cable Distribution System [Member]
Property, Plant and Equipment [Line Items]
Weighted-Average Original Useful Life	11 years
Property and equipment, at cost	$ 36,046	34,028
Customer Premise Equipment [Member]
Property, Plant and Equipment [Line Items]
Weighted-Average Original Useful Life	6 years
Property and equipment, at cost	$ 26,392	28,621
Other Equipment [Member]
Property, Plant and Equipment [Line Items]
Weighted-Average Original Useful Life	9 years
Property and equipment, at cost	$ 10,518	9,471
Building and Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Weighted-Average Original Useful Life	30 years
Property and equipment, at cost	$ 12,346	10,653
Building and Leasehold Improvements [Member] | NBCUniversal Media LLC [Member]
Property, Plant and Equipment [Line Items]
Weighted-Average Original Useful Life	31 years
Property and equipment, at cost	$ 8,124	7,543
Furniture, Fixtures and Equipment [Member] | NBCUniversal Media LLC [Member]
Property, Plant and Equipment [Line Items]
Weighted-Average Original Useful Life	11 years
Property and equipment, at cost	$ 4,843	4,158
Construction in Process [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	1,752	1,901
Construction in Process [Member] | NBCUniversal Media LLC [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	1,506	1,176
Land [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	1,332	1,273
Land [Member] | NBCUniversal Media LLC [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	$ 1,039	$ 984

Goodwill and Intangible Asset71

Goodwill and Intangible Assets (Schedule of Change in Goodwill) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Roll Forward]
Balance, beginning of period	$ 35,980	$ 32,945
Acquisitions	418	3,032
Dispositions	(11)
Adjustments	186	(257)
Foreign currency translation	207	260
Balance, end of period	36,780	35,980
NBCUniversal Media LLC [Member]
Goodwill [Roll Forward]
Balance, beginning of period	23,323	20,364
Acquisitions	273	2,949
Adjustments	186	(250)
Foreign currency translation	(207)	(260)
Balance, end of period	23,989	23,323
Operating Segments [Member] | Cable Communications [Member]
Goodwill [Roll Forward]
Balance, beginning of period	12,645	12,389
Acquisitions	140	82
Dispositions	0
Adjustments	(1)	174
Foreign currency translation	0	0
Balance, end of period	12,784	12,645
Operating Segments [Member] | Cable Networks [Member]
Goodwill [Roll Forward]
Balance, beginning of period	13,183	12,947
Acquisitions	241	232
Dispositions	0
Adjustments	1	0
Foreign currency translation	2	4
Balance, end of period	13,427	13,183
Operating Segments [Member] | Cable Networks [Member] | NBCUniversal Media LLC [Member]
Goodwill [Roll Forward]
Balance, beginning of period	13,183	12,947
Acquisitions	241	232
Adjustments	1	0
Foreign currency translation	(2)	(4)
Balance, end of period	13,427	13,183
Operating Segments [Member] | Broadcast Television [Member]
Goodwill [Roll Forward]
Balance, beginning of period	806	806
Acquisitions	0	0
Dispositions	0
Adjustments	0	0
Foreign currency translation	0	0
Balance, end of period	806	806
Operating Segments [Member] | Broadcast Television [Member] | NBCUniversal Media LLC [Member]
Goodwill [Roll Forward]
Balance, beginning of period	806	806
Acquisitions	0	0
Adjustments	0	0
Foreign currency translation	0	0
Balance, end of period	806	806
Operating Segments [Member] | Filmed Entertainment [Member]
Goodwill [Roll Forward]
Balance, beginning of period	2,993	267
Acquisitions	32	2,717
Dispositions	0
Adjustments	185	0
Foreign currency translation	2	9
Balance, end of period	3,212	2,993
Operating Segments [Member] | Filmed Entertainment [Member] | NBCUniversal Media LLC [Member]
Goodwill [Roll Forward]
Balance, beginning of period	2,993	267
Acquisitions	32	2,717
Adjustments	185	0
Foreign currency translation	(2)	(9)
Balance, end of period	3,212	2,993
Operating Segments [Member] | Theme Parks [Member]
Goodwill [Roll Forward]
Balance, beginning of period	6,341	6,344
Acquisitions	0	0
Dispositions	0
Adjustments	0	(250)
Foreign currency translation	203	247
Balance, end of period	6,544	6,341
Operating Segments [Member] | Theme Parks [Member] | NBCUniversal Media LLC [Member]
Goodwill [Roll Forward]
Balance, beginning of period	6,341	6,344
Acquisitions	0	0
Adjustments	0	(250)
Foreign currency translation	(203)	(247)
Balance, end of period	6,544	6,341
Corporate, Non-Segment [Member]
Goodwill [Roll Forward]
Balance, beginning of period	12	192
Acquisitions	5	1
Dispositions	(11)
Adjustments	1	(181)
Foreign currency translation	0	0
Balance, end of period	$ 7	$ 12

Goodwill and Intangible Asset72

Goodwill and Intangible Assets (Narrative) (Details)	12 Months Ended
	Dec. 31, 2017segmentdivision
Segment Reporting Information [Line Items]
Number of reportable segments	5
NBCUniversal Media LLC [Member]
Segment Reporting Information [Line Items]
Number of reportable segments	4
Software [Member]
Segment Reporting Information [Line Items]
Finite-lived intangible asset amortization period	4 years
Software [Member] | NBCUniversal Media LLC [Member]
Segment Reporting Information [Line Items]
Finite-lived intangible asset amortization period	5 years
Maximum [Member] | Software [Member]
Segment Reporting Information [Line Items]
Finite-lived intangible asset amortization period	5 years
Maximum [Member] | Software [Member] | NBCUniversal Media LLC [Member]
Segment Reporting Information [Line Items]
Finite-lived intangible asset amortization period	5 years
Cable Communications [Member]
Segment Reporting Information [Line Items]
Number of reportable segments	1
Cable Communications [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Number of divisions | division	3

Goodwill and Intangible Asset73

Goodwill and Intangible Assets (Intangible Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Schedule of Indefinite and Finite-Lived Intangible Assets [Line Items]
Total	$ 90,928		$ 87,651
Finite-Lived Intangible Assets [Line Items]
Accumulated Amortization	(12,785)		(11,013)
Franchise Rights [Member]
Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	59,364		59,364
Trade Names [Member]
Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	2,981		2,981
FCC Licenses [Member]
Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 2,238	$ 1,700	651
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted-Average Original Useful Life	19 years
Gross Carrying Amount	$ 13,612		13,478
Accumulated Amortization	$ (5,819)		(5,110)
Software [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted-Average Original Useful Life	4 years
Gross Carrying Amount	$ 8,258		7,017
Accumulated Amortization	$ (4,846)		(3,997)
Cable franchise renewal costs and contractual operating rights [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted-Average Original Useful Life	9 years
Gross Carrying Amount	$ 1,492		1,460
Accumulated Amortization	$ (834)		(800)
Patents and other technology rights [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted-Average Original Useful Life	7 years
Gross Carrying Amount	$ 259		257
Accumulated Amortization	$ (221)		(208)
Other agreements and rights [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted-Average Original Useful Life	16 years
Gross Carrying Amount	$ 2,724		2,443
Accumulated Amortization	(1,065)		(898)
NBCUniversal Media LLC [Member]
Schedule of Indefinite and Finite-Lived Intangible Assets [Line Items]
Total	20,891		20,345
Finite-Lived Intangible Assets [Line Items]
Accumulated Amortization	(7,585)		(6,568)
NBCUniversal Media LLC [Member] | Trade Names [Member]
Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	2,981		2,981
NBCUniversal Media LLC [Member] | FCC Licenses [Member]
Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 513		651
NBCUniversal Media LLC [Member] | Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted-Average Original Useful Life	19 years
Gross Carrying Amount	$ 13,301		13,173
Accumulated Amortization	$ (5,643)		(4,952)
NBCUniversal Media LLC [Member] | Software [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted-Average Original Useful Life	5 years
Gross Carrying Amount	$ 1,516		1,195
Accumulated Amortization	$ (737)		(563)
NBCUniversal Media LLC [Member] | Other agreements and rights [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted-Average Original Useful Life	16 years
Gross Carrying Amount	$ 2,580		2,345
Accumulated Amortization	$ (1,205)		$ (1,053)

Goodwill and Intangible Asset74

Goodwill and Intangible Assets (Amortization of Intangible Assets) (Details) $ in Millions	Dec. 31, 2017USD ($)
Estimated Amortization Expense of Finite-Lived Intangible Assets
2,018	$ 2,283
2,019	1,952
2,020	1,629
2,021	1,225
2,022	905
NBCUniversal Media LLC [Member]
Estimated Amortization Expense of Finite-Lived Intangible Assets
2,018	1,018
2,019	1,010
2,020	968
2,021	866
2,022	$ 786

Long-Term Debt (Schedule of Deb

Long-Term Debt (Schedule of Debt Outstanding) (Details) £ in Millions, $ in Millions, ¥ in Billions	Dec. 31, 2017USD ($)	Dec. 31, 2017JPY (¥)	Dec. 31, 2017GBP (£)	May 31, 2017JPY (¥)	Dec. 31, 2016USD ($)	Dec. 31, 2016JPY (¥)	Dec. 31, 2016GBP (£)
Debt Instrument [Line Items]
Weighted-Average Interest Rate	4.04%	4.04%	4.04%
Debt issuance costs, premiums, discounts and fair value adjustments for hedged positions, net	$ (1,943)				$ (325)
Total debt	64,556				61,046
Less: Current portion	5,134				5,480
Long-term debt	$ 59,422				55,566
Commercial Paper [Member]
Debt Instrument [Line Items]
Weighted-Average Interest Rate	1.84%	1.84%	1.84%
Commercial paper	$ 903				2,781
Term Loans [Member]
Debt Instrument [Line Items]
Weighted-Average Interest Rate	0.82%	0.82%	0.82%
Term loans	$ 3,880				3,262
Senior notes with maturities of 5 years or less, at face value [Member]
Debt Instrument [Line Items]
Weighted-Average Interest Rate	4.18%	4.18%	4.18%
Senior notes	$ 15,680				13,850
Senior notes with maturities between 5 and 10 years, at face value [Member]
Debt Instrument [Line Items]
Weighted-Average Interest Rate	3.31%	3.31%	3.31%
Senior notes	$ 13,277				12,049
Senior notes with maturities greater than 10 years, at face value [Member]
Debt Instrument [Line Items]
Weighted-Average Interest Rate	4.74%	4.74%	4.74%
Senior notes	$ 31,838				28,587
Other Including Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Other, including capital lease obligations	921				842
Universal Studios Japan Term Loan Maturing March 2022 [Member]
Debt Instrument [Line Items]
Debt face amount | ¥				¥ 450
Notes 5.50% Due 2029 [Member]
Debt Instrument [Line Items]
Senior notes	$ 845		£ 625		$ 771		£ 625
Interest rate	5.50%	5.50%	5.50%		5.50%	5.50%	5.50%
Universal Studios Japan Term Loans [Member]
Debt Instrument [Line Items]
Term loans | ¥		¥ 435				¥ 382
Debt face amount	$ 3,948
NBCUniversal Media LLC [Member]
Debt Instrument [Line Items]
Weighted-Average Interest Rate	3.49%	3.49%	3.49%
Debt issuance costs, premiums, discounts and fair value adjustments for hedged positions, net	$ (32)				$ (12)
Total debt	12,473				11,588
Less: Current portion	198				127
Long-term debt	$ 12,275				11,461
NBCUniversal Media LLC [Member] | Term Loans [Member]
Debt Instrument [Line Items]
Weighted-Average Interest Rate	0.79%	0.79%	0.79%
Term loans	$ 3,860				3,262
NBCUniversal Media LLC [Member] | Senior notes with maturities of 5 years or less, at face value [Member]
Debt Instrument [Line Items]
Weighted-Average Interest Rate	4.76%	4.76%	4.76%
Senior notes	$ 4,000				4,000
NBCUniversal Media LLC [Member] | Senior notes with maturities between 5 and 10 years, at face value [Member]
Debt Instrument [Line Items]
Weighted-Average Interest Rate	2.88%	2.88%	2.88%
Senior notes	$ 1,000				1,000
NBCUniversal Media LLC [Member] | Senior notes with maturities greater than 10 years, at face value [Member]
Debt Instrument [Line Items]
Weighted-Average Interest Rate	5.50%	5.50%	5.50%
Senior notes	$ 2,759				3,200
NBCUniversal Media LLC [Member] | 4.00% Notes Due 2049 To Comcast [Member]
Debt Instrument [Line Items]
Weighted-Average Interest Rate	4.00%	4.00%	4.00%
Notes due 2049 to Comcast	$ 610				0
NBCUniversal Media LLC [Member] | Other Including Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Other, including capital lease obligations	$ 276				$ 138
NBCUniversal Media LLC [Member] | Universal Studios Japan Term Loan Maturing March 2022 [Member]
Debt Instrument [Line Items]
Debt face amount | ¥				¥ 450
NBCUniversal Media LLC [Member] | Universal Studios Japan Term Loans [Member]
Debt Instrument [Line Items]
Term loans | ¥		¥ 435				¥ 382

Long-Term Debt (Debt Maturities

Long-Term Debt (Debt Maturities) (Details) $ in Millions	Dec. 31, 2017USD ($)
Long-term Debt, Fiscal Year Maturity [Abstract]
2,018	$ 5,127
2,019	2,367
2,020	3,688
2,021	3,884
2,022	5,879
Thereafter	45,554
NBCUniversal Media LLC [Member]
Long-term Debt, Fiscal Year Maturity [Abstract]
2,018	200
2,019	147
2,020	2,268
2,021	2,349
2,022	2,981
Thereafter	$ 4,560

Long-Term Debt (Debt Borrowings

Long-Term Debt (Debt Borrowings) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Proceeds from borrowings	$ 11,466	$ 9,231	$ 5,486
Universal Studios Japan Term Loans [Member]
Debt Instrument [Line Items]
Debt face amount	3,948
Other Borrowings [Member]
Debt Instrument [Line Items]
Other borrowings	13
Senior Notes [Member] | Senior 3.15% Notes Due 2026 [Member]
Debt Instrument [Line Items]
Debt face amount	$ 1,650
Interest rate	3.15%
Senior Notes [Member] | Floating Rate Notes Due 2021 [Member]
Debt Instrument [Line Items]
Debt face amount	$ 1,500
Senior Notes [Member] | Senior 3.00% Notes Due 2024 [Member]
Debt Instrument [Line Items]
Debt face amount	$ 1,250
Interest rate	3.00%
Senior Notes [Member] | Senior 3.30% Notes Due 2027 [Member]
Debt Instrument [Line Items]
Debt face amount	$ 1,250
Interest rate	3.30%
Senior Notes [Member] | Senior 4.45% Notes Due 2047 [Member]
Debt Instrument [Line Items]
Debt face amount	$ 1,005
Interest rate	4.45%
Senior Notes [Member] | Senior 4.00% Notes Due 2047 [Member]
Debt Instrument [Line Items]
Debt face amount	$ 850
Interest rate	4.00%

Long-Term Debt (Debt Repayments

Long-Term Debt (Debt Repayments) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Repurchases and repayments of debt	$ 6,364	$ 3,052	$ 4,378
NBCUniversal Media LLC [Member]
Debt Instrument [Line Items]
Repurchases and repayments of debt	3,498	$ 1,565	$ 1,022
Universal Studios Japan Term Loans [Member]
Debt Instrument [Line Items]
Repurchases and repayments of debt	3,347
Other Long-Term Debt [Member]
Debt Instrument [Line Items]
Repurchases and repayments of debt	179
Senior Notes [Member] | Senior 6.30% Notes Due 2017 [Member]
Debt Instrument [Line Items]
Repurchases and repayments of debt	$ 1,000
Interest rate	6.30%
Senior Notes [Member] | Senior 6.50% Notes Due 2017 [Member]
Debt Instrument [Line Items]
Repurchases and repayments of debt	$ 1,000
Interest rate	6.50%
Senior Notes [Member] | Senior 8.875% Notes Due 2017 [Member]
Debt Instrument [Line Items]
Repurchases and repayments of debt	$ 550
Interest rate	8.875%
Senior Notes [Member] | Senior 5.00% Notes Due 2061 [Member]
Debt Instrument [Line Items]
Repurchases and repayments of debt	$ 288
Interest rate	5.00%

Long-Term Debt (Narrative) (Det

Long-Term Debt (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Fair value of debt	$ 71,700,000,000		$ 66,300,000,000
Amounts available under revolving credit facilities	7,400,000,000
Unused irrevocable standby letters of credit	439,000,000
NBCUniversal Media LLC [Member]
Debt Instrument [Line Items]
Fair value of debt	$ 13,500,000,000		12,600,000,000
Ownership in cable holding company subsidiaries	100.00%
NBCUniversal Enterprise [Member]
Debt Instrument [Line Items]
Related party liquidation preference preferred stock not subject to guarantee	$ 725,000,000
NBCUniversal Enterprise [Member] | NBCUniversal Media LLC [Member]
Debt Instrument [Line Items]
Related party aggregate principal amount senior notes not subject to guarantee	4,800,000,000
Related party credit facility not subject to guarantee	1,500,000,000
Related party liquidation preference preferred stock not subject to guarantee	$ 725,000,000
London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Borrowing margin for LIBOR based borrowings	1.00%
Comcast Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 7,000,000,000		7,000,000,000
Revolving credit facility amount outstanding	0		0
Potential increase of maximum borrowing capacity	10,000,000,000
Comcast Revolving Credit Facility [Member] | NBCUniversal Media LLC [Member]
Debt Instrument [Line Items]
Principal amount of debt securities subject to guarantee	7,000,000,000
NBCUniversal Enterprise Credit Facility [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity	1,500,000,000		1,500,000,000
Revolving credit facility amount outstanding	0		$ 0
Potential increase of maximum borrowing capacity	2,000,000,000
Amounts available under revolving credit facilities	1,500,000,000
Commercial Paper [Member]
Debt Instrument [Line Items]
Commercial paper capacity		$ 7,000,000,000
NBCUniversal Enterprise Commercial Paper [Member]
Debt Instrument [Line Items]
Commercial paper capacity		$ 1,500,000,000
Comcast And Comcast Cable Debt Securities [Member] | NBCUniversal Media LLC [Member]
Debt Instrument [Line Items]
Principal amount of debt securities subject to guarantee	$ 49,100,000,000

Long-Term Debt (Senior Notes Ex

Long-Term Debt (Senior Notes Exchange) (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Oct. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Interest expense		$ 3,086	$ 2,942	$ 2,702
Senior Notes Exchange [Member] | Senior Notes [Member] | Comcast and NBCUniversal Senior Notes [Member]
Debt Instrument [Line Items]
Aggregate principal amount issued	$ 5,500
Aggregate principal amount of certain series of outstanding notes	3,932
Senior Notes Exchange [Member] | Senior Notes [Member] | Senior 6.95% Notes Due 2037 [Member]
Debt Instrument [Line Items]
Aggregate principal amount of certain series of outstanding notes	$ 1,212
Interest rate	6.95%
Senior Notes Exchange [Member] | Senior Notes [Member] | Senior 6.45% Notes Due 2037 [Member]
Debt Instrument [Line Items]
Aggregate principal amount of certain series of outstanding notes	$ 946
Interest rate	6.45%
Senior Notes Exchange [Member] | Senior Notes [Member] | Senior 6.40% Notes Due 2040 [Member]
Debt Instrument [Line Items]
Aggregate principal amount of certain series of outstanding notes	$ 518
Interest rate	6.40%
Senior Notes Exchange [Member] | Senior Notes [Member] | NBCUniversal Senior 6.40% Notes Due 2040 [Member]
Debt Instrument [Line Items]
Aggregate principal amount of certain series of outstanding notes	$ 442
Interest rate	6.40%
Senior Notes Exchange [Member] | Senior Notes [Member] | Senior 6.40% Notes Due 2038 [Member]
Debt Instrument [Line Items]
Aggregate principal amount of certain series of outstanding notes	$ 428
Interest rate	6.40%
Senior Notes Exchange [Member] | Senior Notes [Member] | Senior 6.55% Notes Due 2039 [Member]
Debt Instrument [Line Items]
Aggregate principal amount of certain series of outstanding notes	$ 386
Interest rate	6.55%
Senior Notes Exchange [Member] | Senior Notes [Member] | Senior 3.97% Notes Due 2047 [Member]
Debt Instrument [Line Items]
Aggregate principal amount issued	$ 2,000
Interest rate	3.97%
Senior Notes Exchange [Member] | Senior Notes [Member] | Senior 4.00% Notes Due 2049 [Member]
Debt Instrument [Line Items]
Aggregate principal amount issued	$ 2,000
Interest rate	4.00%
Senior Notes Exchange [Member] | Senior Notes [Member] | Senior 4.05% Notes Dues 2052 [Member]
Debt Instrument [Line Items]
Aggregate principal amount issued	$ 1,500
Interest rate	4.05%
NBCUniversal Media LLC [Member]
Debt Instrument [Line Items]
Interest expense		$ 727	$ 595	$ 495
NBCUniversal Media LLC [Member] | Senior Notes Exchange [Member] | Comcast and NBCUniversal Senior Notes [Member]
Debt Instrument [Line Items]
Interest expense	$ 157
NBCUniversal Media LLC [Member] | Senior Notes Exchange [Member] | 4.00% Notes Due 2049 To Comcast [Member]
Debt Instrument [Line Items]
Aggregate principal amount issued	$ 610
Interest rate	4.00%
NBCUniversal Media LLC [Member] | Senior Notes Exchange [Member] | Senior Notes [Member] | Comcast and NBCUniversal Senior Notes [Member]
Debt Instrument [Line Items]
Aggregate principal amount of certain series of outstanding notes	$ 3,900
NBCUniversal Media LLC [Member] | Senior Notes Exchange [Member] | Senior Notes [Member] | Senior 6.40% Notes Due 2040 [Member]
Debt Instrument [Line Items]
Aggregate principal amount of certain series of outstanding notes	$ 442
Interest rate	6.40%
NBCUniversal Media LLC [Member] | Senior Notes Exchange [Member] | Senior Notes [Member] | Senior 3.97% Notes Due 2047 [Member]
Debt Instrument [Line Items]
Aggregate principal amount issued	$ 2,000
Interest rate	3.97%
NBCUniversal Media LLC [Member] | Senior Notes Exchange [Member] | Senior Notes [Member] | Senior 4.00% Notes Due 2049 [Member]
Debt Instrument [Line Items]
Aggregate principal amount issued	$ 2,000
Interest rate	4.00%
NBCUniversal Media LLC [Member] | Senior Notes Exchange [Member] | Senior Notes [Member] | Senior 4.05% Notes Due 2052 [Member]
Debt Instrument [Line Items]
Aggregate principal amount issued	$ 1,500
Interest rate	4.05%

Employee Benefit Plans (Deferre

Employee Benefit Plans (Deferred Compensation Plans) (Details) - Deferred Compensation Plans [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefit obligation	$ 2,539	$ 2,164	$ 2,038
Interest expense	209	178	171
NBCUniversal Media LLC [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefit obligation	621	494	417
Interest expense	$ 64	$ 48	$ 28

Employee Benefit Plans (Narrati

Employee Benefit Plans (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Cash surrender value of life insurance policies	$ 820	$ 709
Expenses related to retirement investment plans	458	446	$ 416
Severance Costs	203	315	181
NBCUniversal Media LLC [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expenses related to retirement investment plans	201	185	174
Severance Costs	108	165	113
DreamWorks Animation [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Severance Costs		61
DreamWorks Animation [Member] | NBCUniversal Media LLC [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Severance Costs		61
Multiemployer Plans, Pension [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Multiemployer plan contributions	97	84	77
Multiemployer Plans, Pension [Member] | NBCUniversal Media LLC [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Multiemployer plan contributions	97	84	77
Multiemployer Plans, Postretirement Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Multiemployer plan contributions	152	136	119
Multiemployer Plans, Postretirement Benefit [Member] | NBCUniversal Media LLC [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Multiemployer plan contributions	152	136	$ 119
Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Reduction of benefit obligations due to plan amendments	146	361
Benefit obligation	425	538
Postretirement Benefit Plan [Member] | NBCUniversal Media LLC [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Reduction of benefit obligations due to plan amendments	146
Benefit obligation	51	192
Pension Plans [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefit obligation	338	314
Pension Plans [Member] | NBCUniversal Media LLC [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefit obligation	$ 338	$ 314

Employee Benefit Plans (Informa

Employee Benefit Plans (Information On Our Pension Benefit Plans) (Details) - Postretirement Benefit Plan [Member] - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefit obligation	$ 425	$ 538
Amounts in accumulated other comprehensive income not yet recognized in benefits expense	(458)	(372)
NBCUniversal Media LLC [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefit obligation	51	192
Amounts in accumulated other comprehensive income not yet recognized in benefits expense	$ (177)	$ (42)

Equity (Narrative) (Details)

Equity (Narrative) (Details) $ in Billions	Dec. 11, 2015shares	Dec. 31, 2017USD ($)vote
Equity [Line Items]
Number of votes entitled of each class B common stock | vote		15
Shares awarded per exchanged share (in shares) | shares	1
New Authorization [Member]
Equity [Line Items]
Stock repurchase program, authorized amount		$ 12
Remaining authorized repurchase amount		$ 7
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, 2017	Dec. 31, 2016	Dec. 31, 2015
Class A Common Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock, shares outstanding at beginning of period (in shares)	4,742,159,011	4,875,000,000	4,272,000,000
Stock compensation plans (in shares)	19,000,000	23,000,000	25,000,000
Repurchases and retirements of common stock (in shares)	(131,000,000)	(161,000,000)	(125,000,000)
Employee stock purchase plan (in shares)	5,000,000	5,000,000	5,000,000
Reclassification of Class A Special common stock (in shares)			694,000,000
Other (in shares)			4,000,000
Common stock, shares outstanding at end of period (in shares)	4,635,063,642	4,742,159,011	4,875,000,000
Class A Special Common Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock, shares outstanding at beginning of period (in shares)	0	0	801,000,000
Stock compensation plans (in shares)	0	0	0
Repurchases and retirements of common stock (in shares)	0	0	(107,000,000)
Employee stock purchase plan (in shares)	0	0	0
Reclassification of Class A Special common stock (in shares)			(694,000,000)
Other (in shares)			0
Common stock, shares outstanding at end of period (in shares)	0	0	0
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	0	0
Employee stock purchase plan (in shares)	0	0	0
Reclassification of Class A Special common stock (in shares)			0
Other (in shares)			0
Common stock, shares outstanding at end of period (in shares)	9,444,375	9,444,375	9,000,000

Equity (Aggregate Share Repurch

Equity (Aggregate Share Repurchases) (Details) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Equity, Class of Treasury Stock [Line Items]
Cash consideration	$ 5,435	$ 5,352	$ 7,175
New Authorization [Member]
Equity, Class of Treasury Stock [Line Items]
Cash consideration	$ 5,000	$ 5,000	$ 6,750
Shares repurchased (in shares)	131	161	232

Equity (Components of Accumulat

Equity (Components of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Equity [Abstract]
Unrealized gains (losses) on marketable securities	$ (43)	$ 0
Deferred gains (losses) on cash flow hedges	9	(14)
Unrecognized gains (losses) on employee benefit obligations	260	219
Cumulative translation adjustments	153	(107)
Accumulated other comprehensive income (loss)	$ 379	$ 98

Share-Based Compensation (Recog

Share-Based Compensation (Recognized Share-Based Compensation Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized share-based compensation expense	$ 586	$ 507	$ 455
Restricted share units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized share-based compensation expense	349	306	273
Stock options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized share-based compensation expense	205	173	157
Employee stock purchase plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized share-based compensation expense	$ 32	$ 28	$ 25

Share-Based Compensation (Narra

Share-Based Compensation (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
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		$ 233	$ 311
Restricted share units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized pretax compensation expense on nonvested awards	$ 806
Unrecognized pretax compensation expense on nonvested awards, weighted average period of recognition (in years)	1 year 8 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	$ 404
Unrecognized pretax compensation expense on nonvested awards, weighted average period of recognition (in years)	1 year 8 months

Share-Based Compensation (Stock

Share-Based Compensation (Stock Options and Restricted Share Units) (Details) shares in Millions	12 Months Ended
	Dec. 31, 2017$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted (in shares)	39
Weighted-average exercise price of awards granted during the year (in dollars per share) | $ / shares	$ 37.47
Stock options outstanding (in shares)	191
Weighted-average exercise price of shares outstanding (in dollars per share) | $ / shares	$ 24.98
Restricted share units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted (in shares)	15
Awards nonvested (in shares)	42
Weighted-average fair value at grant date of nonvested awards (in dollars per share) | $ / shares	$ 30.93

Share-Based Compensation (Restr

Share-Based Compensation (Restricted Share Units and Stock Option Fair Value) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option fair value (in dollars per share)	$ 7.01	$ 5.78	$ 5.89
Stock Option Valuation Assumptions:
Dividend yield	1.70%	1.80%	1.70%
Expected volatility	20.10%	23.00%	23.00%
Risk-free interest rate	2.20%	1.50%	1.60%
Expected option life (in years)	6 years 1 month	6 years 1 month	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)	$ 37.77	$ 30.02	$ 29.41

Income Taxes (Components of Inc

Income Taxes (Components of Income Tax Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current Expense (Benefit):
Federal	$ 2,411	$ 3,190	$ 3,210
State	277	480	570
Foreign	389	194	221
Current income tax expense (benefit)	3,077	3,864	4,001
Deferred Expense (Benefit):
Federal	(10,659)	1,192	890
State	10	154	66
Foreign	(6)	98	2
Deferred income tax expense (benefit)	(10,655)	1,444	958
Income tax expense (benefit)	(7,578)	5,308	4,959
NBCUniversal Media LLC [Member]
Current Expense (Benefit):
Foreign	201	38	81
Deferred Expense (Benefit):
Foreign	(7)	96	2
Deferred income tax expense (benefit)	2	89	(11)
Withholding tax expense	187	158	139
U.S. domestic tax expense	11	13	5
Income tax expense (benefit)	$ 392	$ 305	$ 227

Income Taxes (Federal Statutory

Income Taxes (Federal Statutory) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Taxes [Line Items]
Federal tax at statutory rate		$ 5,363	$ 5,024	$ 4,680
State income taxes, net of federal benefit		298	373	326
Foreign income taxes, net of federal credit		70	65	13
Nontaxable income attributable to noncontrolling interests		(45)	(128)	(69)
Other adjustments		(229)	(67)	(79)
Excess tax benefits recognized on share-based compensation		(297)	0	0
2017 federal tax reform enactment	$ (12,700)	(12,679)	0	0
Income tax expense (benefit)		(7,578)	5,308	4,959
Adjustments to uncertain and effectively settled tax positions, net [Member]
Income Taxes [Line Items]
Other adjustments		(62)	24	15
Accrued interest on uncertain and effectively settled tax positions, net [Member]
Income Taxes [Line Items]
Other adjustments		$ 3	$ 17	$ 73

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Taxes [Line Items]
Foreign income before taxes		$ 1,000	$ 871	$ 704
Federal corporate income tax rate	21.00%	35.00%	35.00%	35.00%
Reduction of net deferred tax liabilities		$ 12,400
Net tax benefit related to cumulative undistributed foreign earnings and foreign tax credits		382
One-time repatriation tax on cumulative undistributed foreign earnings and profits		101
Deferred tax liability attributable to temporary differences in other comprehensive income		108
Increase in deferred income tax liabilities related to acquisitions		51
Deferred tax related to purchase of noncontrolling interest		112
Net deferred tax liability, franchise rights		15,000
Liability for Uncertainty in Income Taxes, Noncurrent		809	$ 1,103	$ 1,136
Unrecognized tax benefits that would impact effective tax rate		1,200
Unrecognized tax benefits, interest on income taxes accrued		173	483
Uncertain Tax Positions Indemnified by GE [Member]
Income Taxes [Line Items]
Liability for Uncertainty in Income Taxes, Noncurrent		162
Unrecognized tax benefits, interest on income taxes accrued		43	$ 39
Federal Tax Authority [Member]
Income Taxes [Line Items]
Operating loss carryforwards		348
Foreign Tax Authority [Member]
Income Taxes [Line Items]
Operating loss carryforwards		$ 387

Income Taxes (Components of Net

Income Taxes (Components of Net Deferred Tax Liability) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Deferred Tax Assets:
Net operating loss carryforwards	$ 481	$ 544
Nondeductible accruals and other	2,026	3,797
Less: Valuation allowance	377	266
Total deferred tax assets, net of valuation allowance	2,130	4,075
Deferred Tax Liabilities:
Differences between book and tax basis of property and equipment and intangible assets	25,154	36,957
Differences between book and tax basis of investments	466	498
Differences between book and tax basis of long-term debt	673	571
Differences between book and tax basis of foreign subsidiaries and undistributed foreign earnings	39	862
Total deferred tax liabilities	26,332	38,888
Net deferred tax liability	$ 24,202	$ 34,813

Income Taxes (Reconciliation of

Income Taxes (Reconciliation of Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Gross unrecognized tax benefits, January 1	$ 1,443	$ 1,441	$ 1,455
Additions based on tax positions related to the current year	121	74	67
Additions based on tax positions related to prior years	319	72	98
Additions from acquired subsidiaries	0	13	0
Reductions for tax positions of prior years	(251)	(66)	(101)
Reductions due to expiration of statutes of limitations	(70)	(44)	(41)
Settlements with tax authorities	(65)	(47)	(37)
Gross unrecognized tax benefits, December 31	1,497	1,443	1,441
Unrecognized tax benefits positions paid	(688)	(340)	(305)
Liability for uncertain tax positions	$ 809	$ 1,103	$ 1,136

Supplemental Financial Inform97

Supplemental Financial Information (Receivables)(Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Supplemental Financial Information [Line Items]
Receivables, gross	$ 9,253	$ 8,622
Less: Allowance for returns and customer incentives	419	417
Less: Allowance for doubtful accounts	288	250
Receivables, net	8,546	7,955
Noncurrent receivables, net	1,300	939
NBCUniversal Media LLC [Member]
Supplemental Financial Information [Line Items]
Receivables, gross	7,184	6,799
Less: Allowance for returns and customer incentives	414	413
Less: Allowance for doubtful accounts	88	84
Receivables, net	6,682	6,302
Noncurrent receivables, net	$ 1,200	$ 939

Supplemental Financial Inform98

Supplemental Financial Information (Components of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Unrealized gains (losses) on marketable securities	$ (43)	$ 0
Deferred gains (losses) on cash flow hedges	9	(14)
Unrecognized gains (losses) on employee benefit obligations	260	219
Cumulative translation adjustments	153	(107)
Accumulated other comprehensive income (loss)	379	98
NBCUniversal Media LLC [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Unrealized gains (losses) on marketable securities	(233)	0
Deferred gains (losses) on cash flow hedges	10	23
Unrecognized gains (losses) on employee benefit obligations	126	14
Cumulative translation adjustments	77	(172)
Accumulated other comprehensive income (loss)	$ (20)	$ (135)

Supplemental Financial Inform99

Supplemental Financial Information (Cash Payments for Interest and Income Taxes)(Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash Payments for Interest and Income Taxes
Interest	$ 2,820	$ 2,565	$ 2,443
Income taxes	4,057	3,693	3,726
NBCUniversal Media LLC [Member]
Cash Payments for Interest and Income Taxes
Interest	517	548	456
Income taxes	$ 282	$ 208	$ 182

Supplemental Financial Infor100

Supplemental Financial Information (Noncash Investing and Financing Activities)(Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Supplemental Financial Information [Line Items]
Capital expenditures incurred but not yet paid	$ 1,200	$ 1,300	$ 1,100
Dividends payable	$ 732	$ 653	$ 612
Dividends payable (in dollars per share)	$ 0.1575	$ 0.1375	$ 0.125
Capital Contribution to VIE accrued but not yet paid		$ 447
Fair value equity securities settlement			$ 517
NBCUniversal Media LLC [Member]
Supplemental Financial Information [Line Items]
Capital expenditures incurred but not yet paid	$ 325	189	287
Contribution from member	$ 662	$ 3,655	$ 252

Commitments and Contingencie101

Commitments and Contingencies (Narrative) (Details) $ in Millions	1 Months Ended	12 Months Ended
	Jun. 30, 2015USD ($)	Dec. 31, 2017USD ($)employee	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Commitment And Contingencies [Line Items]
Carrying value of contractual obligation		$ 1,100
Contractual value of a potential obligation		1,500
Payment for contingent consideration	$ 450
Gain on settlement of contingent consideration	$ 240
Charge related to legal settlement		250	$ 0	$ 0
Sprint Communications Company L.P. Lawsuit [Member] | Settled Litigation [Member]
Commitment And Contingencies [Line Items]
Charge related to legal settlement		250
NBCUniversal Enterprise [Member]
Commitment And Contingencies [Line Items]
Related party liquidation preference preferred stock not subject to guarantee		$ 725
NBCUniversal Enterprise [Member] | Redeemable Subsidiary Preferred Stock [Member]
Commitment 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
NBCUniversal Enterprise [Member] | Redeemable Subsidiary Preferred Stock [Member] | Level 2 [Member]
Commitment And Contingencies [Line Items]
Temporary equity, fair value of redeemable subsidiary preferred stock		$ 748	$ 741
NBCUniversal Media LLC [Member]
Commitment And Contingencies [Line Items]
Carrying value of contractual obligation		1,100
Contractual value of a potential obligation		1,500
NBCUniversal Media LLC [Member] | NBCUniversal Enterprise [Member]
Commitment And Contingencies [Line Items]
Related party liquidation preference preferred stock not subject to guarantee		$ 725
Workforce Subject to Collective Bargaining Arrangements [Member]
Commitment And Contingencies [Line Items]
Number of employees covered under collective bargaining agreements | employee		9,500
Workforce Subject to Collective Bargaining Arrangements [Member] | NBCUniversal Media LLC [Member]
Commitment And Contingencies [Line Items]
Number of employees covered under collective bargaining agreements | employee		9,500
Workforce Subject to Collective Bargaining Arrangements Expiring within One Year [Member]
Commitment And Contingencies [Line Items]
Percentage of full-time equivalent employees covered by collective bargaining agreements that have expired or are schedule to expire during the next year		63.00%
Workforce Subject to Collective Bargaining Arrangements Expiring within One Year [Member] | NBCUniversal Media LLC [Member]
Commitment And Contingencies [Line Items]
Percentage of full-time equivalent employees covered by collective bargaining agreements that have expired or are schedule to expire during the next year		63.00%

Commitments and Contingencie102

Commitments and Contingencies (Minimum Annual Commitments under the Programming License Agreements and Operating Leases) (Details) $ in Millions	Dec. 31, 2017USD ($)
Programming and Talent Commitments
2,018	$ 6,350
2,019	3,895
2,020	4,812
2,021	3,301
2,022	3,732
Thereafter	17,416
Operating Leases
2,018	559
2,019	512
2,020	457
2,021	391
2,022	326
Thereafter	1,829
NBCUniversal Media LLC [Member]
Programming and Talent Commitments
2,018	6,343
2,019	3,893
2,020	4,812
2,021	3,301
2,022	3,732
Thereafter	17,416
Operating Leases
2,018	209
2,019	195
2,020	182
2,021	163
2,022	139
Thereafter	$ 1,223

Commitments and Contingencie103

Commitments and Contingencies (Rental expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Commitment And Contingencies [Line Items]
Rent expense	$ 839	$ 744	$ 608
NBCUniversal Media LLC [Member]
Commitment And Contingencies [Line Items]
Rent expense	$ 274	$ 259	$ 213

Financial Data by Business S104

Financial Data by Business Segment (Details) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017USD ($)	Sep. 30, 2017USD ($)	Jun. 30, 2017USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Sep. 30, 2016USD ($)	Jun. 30, 2016USD ($)	Mar. 31, 2016USD ($)	Dec. 31, 2017USD ($)segment	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment									5
Revenue	$ 21,915	$ 20,983	$ 21,165	$ 20,463	$ 21,025	$ 21,319	$ 19,269	$ 18,790	$ 84,526	$ 80,403	$ 74,510
Adjusted EBITDA									28,062	26,417	24,678
Depreciation and Amortization									10,267	9,558	8,680
Capital Expenditures									9,550	9,135	8,499
Cash Paid for Intangible Assets									$ 1,747	1,686	1,370
NBCUniversal Media LLC [Member]
Segment Reporting Information [Line Items]
Number of reportable segments | segment									4
Revenue									$ 32,997	31,593	28,462
Adjusted EBITDA									8,185	7,227	6,358
Depreciation and Amortization									2,041	1,805	1,539
Capital Expenditures									1,502	1,452	1,386
Cash Paid for Intangible Assets									$ 295	283	$ 211
Cable Communications [Member]
Segment Reporting Information [Line Items]
Number of reportable segments | segment									1
Revenue									$ 52,519	50,048
Depreciation and Amortization									$ 8,143	$ 7,670
Cable Communications [Member] | Residential Video Products And Services [Member]
Segment Reporting Information [Line Items]
Cable segment revenue types as percentage of total cable revenue									44.00%	44.70%	45.90%
Cable Communications [Member] | Residential High-speed Internet Products And Services [Member]
Segment Reporting Information [Line Items]
Cable segment revenue types as percentage of total cable revenue									28.10%	27.00%	26.60%
Cable Communications [Member] | Residential Voice Products And Services [Member]
Segment Reporting Information [Line Items]
Cable segment revenue types as percentage of total cable revenue									6.50%	7.10%	7.70%
Cable Communications [Member] | Business Products And Services [Member]
Segment Reporting Information [Line Items]
Cable segment revenue types as percentage of total cable revenue									11.80%	11.00%	10.10%
Cable Communications [Member] | Advertising Products And Services [Member]
Segment Reporting Information [Line Items]
Cable segment revenue types as percentage of total cable revenue									4.30%	4.90%	4.70%
Cable Communications [Member] | Other Products And Services [Member]
Segment Reporting Information [Line Items]
Cable segment revenue types as percentage of total cable revenue									5.30%	5.30%	5.00%
NBCUniversal Segments [Member]
Segment Reporting Information [Line Items]
Number of reportable segments | segment									4
Revenue									$ 32,997	$ 31,593	$ 28,462
Adjusted EBITDA									8,245	7,227	6,352
Depreciation and Amortization									2,041	1,805	1,539
Capital Expenditures									1,502	1,452	1,386
Cash Paid for Intangible Assets									295	283	211
Operating Segments [Member] | Cable Communications [Member]
Segment Reporting Information [Line Items]
Revenue									52,519	50,048	46,928
Adjusted EBITDA									21,170	20,109	19,037
Depreciation and Amortization									8,143	7,670	7,051
Capital Expenditures									7,952	7,596	7,040
Cash Paid for Intangible Assets									$ 1,382	$ 1,377	$ 1,151
Cable segment revenue types as percentage of total cable revenue									100.00%	100.00%	100.00%
Operating Segments [Member] | Cable Communications [Member] | Franchise And Other Regulatory Fees [Member]
Segment Reporting Information [Line Items]
Cable segment revenue types as percentage of total cable revenue									2.70%	2.80%	2.80%
Operating Segments [Member] | Cable Networks [Member]
Segment Reporting Information [Line Items]
Revenue									$ 10,631	$ 10,464	$ 9,628
Adjusted EBITDA									4,076	3,709	3,499
Depreciation and Amortization									755	745	784
Capital Expenditures									33	32	44
Cash Paid for Intangible Assets									19	20	22
Operating Segments [Member] | Cable Networks [Member] | NBCUniversal Media LLC [Member]
Segment Reporting Information [Line Items]
Revenue									10,631	10,464	9,628
Adjusted EBITDA									4,076	3,709	3,499
Depreciation and Amortization									755	745	784
Capital Expenditures									33	32	44
Cash Paid for Intangible Assets									19	20	22
Operating Segments [Member] | Broadcast Television [Member]
Segment Reporting Information [Line Items]
Revenue									9,546	10,147	8,530
Adjusted EBITDA									1,253	1,320	780
Depreciation and Amortization									133	125	111
Capital Expenditures									180	153	117
Cash Paid for Intangible Assets									22	19	17
Operating Segments [Member] | Broadcast Television [Member] | NBCUniversal Media LLC [Member]
Segment Reporting Information [Line Items]
Revenue									9,546	10,147	8,530
Adjusted EBITDA									1,253	1,320	780
Depreciation and Amortization									133	125	111
Capital Expenditures									180	153	117
Cash Paid for Intangible Assets									22	19	17
Operating Segments [Member] | Filmed Entertainment [Member]
Segment Reporting Information [Line Items]
Revenue									7,658	6,360	7,287
Adjusted EBITDA									1,277	697	1,234
Depreciation and Amortization									109	47	26
Capital Expenditures									58	33	14
Cash Paid for Intangible Assets									23	16	20
Operating Segments [Member] | Filmed Entertainment [Member] | NBCUniversal Media LLC [Member]
Segment Reporting Information [Line Items]
Revenue									7,658	6,360	7,287
Adjusted EBITDA									1,277	697	1,234
Depreciation and Amortization									109	47	26
Capital Expenditures									58	33	14
Cash Paid for Intangible Assets									23	16	20
Operating Segments [Member] | Theme Parks [Member]
Segment Reporting Information [Line Items]
Revenue									5,443	4,946	3,339
Adjusted EBITDA									2,384	2,190	1,464
Depreciation and Amortization									648	512	292
Capital Expenditures									960	922	833
Cash Paid for Intangible Assets									78	72	54
Operating Segments [Member] | Theme Parks [Member] | NBCUniversal Media LLC [Member]
Segment Reporting Information [Line Items]
Revenue									5,443	4,946	3,339
Adjusted EBITDA									2,384	2,190	1,464
Depreciation and Amortization									648	512	292
Capital Expenditures									960	922	833
Cash Paid for Intangible Assets									78	72	54
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Revenue									1,060	750	713
Adjusted EBITDA									(1,394)	(874)	(815)
Depreciation and Amortization									83	83	90
Capital Expenditures									96	87	73
Cash Paid for Intangible Assets									70	26	8
Corporate, Non-Segment [Member] | NBCUniversal Media LLC [Member]
Segment Reporting Information [Line Items]
Revenue									45	20	14
Adjusted EBITDA									(801)	(699)	(625)
Depreciation and Amortization									396	376	326
Capital Expenditures									271	312	378
Cash Paid for Intangible Assets									153	156	98
Corporate, Non-Segment [Member] | NBCUniversal Segments [Member]
Segment Reporting Information [Line Items]
Revenue									45	20	14
Adjusted EBITDA									(741)	(699)	(625)
Depreciation and Amortization									396	376	326
Capital Expenditures									271	312	378
Cash Paid for Intangible Assets									153	156	98
Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue									(2,050)	(1,988)	(1,593)
Adjusted EBITDA									41	(45)	104
Depreciation and Amortization									0	0	0
Capital Expenditures									0	0	0
Cash Paid for Intangible Assets									0	0	0
Eliminations [Member] | NBCUniversal Media LLC [Member]
Segment Reporting Information [Line Items]
Revenue									(326)	(344)	(336)
Adjusted EBITDA									(4)	10	6
Depreciation and Amortization									0	0	0
Capital Expenditures									0	0	0
Cash Paid for Intangible Assets									0	0	0
Eliminations [Member] | NBCUniversal Segments [Member]
Segment Reporting Information [Line Items]
Revenue									(326)	(344)	(336)
Adjusted EBITDA									(4)	10	0
Depreciation and Amortization									0	0	0
Capital Expenditures									0	0	0
Cash Paid for Intangible Assets									$ 0	$ 0	$ 0

Financial Data by Business S105

Financial Data by Business Segment (Revenue by Geographic Location) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues from External Customers [Line Items]
Revenue	$ 21,915	$ 20,983	$ 21,165	$ 20,463	$ 21,025	$ 21,319	$ 19,269	$ 18,790	$ 84,526	$ 80,403	$ 74,510
NBCUniversal Media LLC [Member]
Revenues from External Customers [Line Items]
Revenue									32,997	31,593	28,462
United States [Member] | NBCUniversal Media LLC [Member]
Revenues from External Customers [Line Items]
Revenue									25,345	25,076	22,663
Foreign [Member]
Revenues from External Customers [Line Items]
Revenue									7,800	6,500	5,800
Foreign [Member] | NBCUniversal Media LLC [Member]
Revenues from External Customers [Line Items]
Revenue									$ 7,652	$ 6,517	$ 5,799

Financial Data by Business S106

Financial Data by Business Segment (Reconciliation of Adjusted EBITDA from Segment to Consolidated Statements) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Adjusted EBITDA	$ 28,062	$ 26,417	$ 24,678
Adjustment for legal settlement	(250)	0	0
Depreciation	(7,914)	(7,464)	(6,781)
Amortization	(2,353)	(2,094)	(1,899)
Other operating gains	442	0	0
Total other income (expense)	(2,665)	(2,506)	(2,626)
Income before income taxes	15,322	14,353	13,372
NBCUniversal Media LLC [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Adjusted EBITDA	8,185	7,227	6,358
Depreciation	(994)	(861)	(669)
Amortization	(1,047)	(944)	(870)
Other operating gains	337	0	0
Total other income (expense)	(871)	(571)	(968)
Income before income taxes	$ 5,610	$ 4,851	$ 3,851

Quarterly Financial Informat107

Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information [Line Items]
Revenue	$ 21,915	$ 20,983	$ 21,165	$ 20,463	$ 21,025	$ 21,319	$ 19,269	$ 18,790	$ 84,526	$ 80,403	$ 74,510
Operating income	4,107	4,792	4,558	4,530	4,264	4,440	4,066	4,089	17,987	16,859	15,998
Net income attributable to Comcast Corporation	$ 14,985	$ 2,650	$ 2,513	$ 2,566	$ 2,296	$ 2,237	$ 2,028	$ 2,134	$ 22,714	$ 8,695	$ 8,163
Basic earnings per common share attributable to Comcast Corporation shareholders (in dollars per share)	$ 3.22	$ 0.56	$ 0.53	$ 0.54	$ 0.48	$ 0.47	$ 0.42	$ 0.44	$ 4.82	$ 1.80	$ 1.64
Diluted earnings per common share attributable to Comcast Corporation shareholders (in dollars per share)	3.17	0.55	0.52	0.53	0.48	0.46	0.41	0.43	4.75	1.78	1.62
Dividends declared per common share (in dollars per share)	$ 0.1575	$ 0.1575	$ 0.1575	$ 0.1575	$ 0.1375	$ 0.1375	$ 0.1375	$ 0.1375	$ 0.63	$ 0.55	$ 0.50
Income tax benefit as a result of the impact of the 2017 tax reform	$ 12,700								$ 12,679	$ 0	$ 0
Verizon Wireless [Member]
Quarterly Financial Information [Line Items]
Income resulting from an agency agreement					$ 225
Income resulting from an agency agreement, net of tax					$ 143

Condensed Consolidating Fina108

Condensed Consolidating Financial Information (Narrative) (Details) - Dec. 31, 2017 $ in Millions	USD ($)	JPY (¥)
Guarantor Subsidiaries [Member]
Debt Instrument [Line Items]
Principal amount of debt securities subject to guarantee	$ 56,900
Maturing In Next Five Years [Member]
Debt Instrument [Line Items]
Principal amount of debt securities subject to guarantee	11,800
NBCUniversal Enterprise Senior Debt Securities [Member]
Debt Instrument [Line Items]
Principal amount of debt securities subject to guarantee	4,800
NBCUniversal Enterprise Credit Facility [Member]
Debt Instrument [Line Items]
Guarantee Obligations, Line Of Credit Facility	1,500
Universal Studios Japan Term Loan Maturing March 2022 [Member]
Debt Instrument [Line Items]
Term loans subject to guarantee | ¥		¥ 435,000,000,000
Comcast Holdings' ZONES due October 2029 [Member]
Debt Instrument [Line Items]
Principal amount of debt securities subject to guarantee	185
Comcast Holdings' ZONES due November 2029 [Member]
Debt Instrument [Line Items]
Principal amount of debt securities not subject to guarantee	$ 62

Condensed Consolidating Fina109

Condensed Consolidating Financial Information (Condensed Consolidating Balance Sheet) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Assets
Cash and cash equivalents	$ 3,428	$ 3,301	$ 2,295	$ 3,910
Receivables, net	8,546	7,955
Programming rights	1,613	1,250
Deposits	9	1,772
Other current assets	2,464	2,083
Total current assets	16,060	16,361
Film and television costs	7,076	7,252
Investments	6,931	5,247
Investments in and amounts due from subsidiaries eliminated upon consolidation	0	0
Property and equipment, net	38,470	36,253
Franchise rights	59,364	59,364
Goodwill	36,780	35,980	32,945
Other intangible assets, net	18,779	17,274
Other noncurrent assets, net	3,489	2,769
Total assets	186,949	180,500
Liabilities and Equity
Accounts payable and accrued expenses related to trade creditors	6,926	6,915
Accrued participations and residuals	1,683	1,726
Deferred revenue	1,552	1,132
Accrued expenses and other current liabilities	6,266	6,282
Current portion of long-term debt	5,134	5,480
Total current liabilities	21,561	21,535
Long-term debt, less current portion	59,422	55,566
Deferred income taxes	24,256	34,854
Other noncurrent liabilities	10,904	10,925
Redeemable noncontrolling interests	1,357	1,446
Equity:
Common stock	55	56
Other shareholders’ equity	68,551	53,887
Total Comcast Corporation shareholders’ equity	68,606	53,943
Noncontrolling interests	843	2,231
Total equity	69,449	56,174	53,978	53,068
Total liabilities and equity	186,949	180,500
Elimination and Consolidation Adjustments [Member]
Assets
Cash and cash equivalents	0	0	0	0
Receivables, net	0	0
Programming rights	0	0
Deposits	0	0
Other current assets	0	0
Total current assets	0	0
Film and television costs	0	0
Investments	0	0
Investments in and amounts due from subsidiaries eliminated upon consolidation	(562,658)	(481,214)
Property and equipment, net	0	0
Franchise rights	0	0
Goodwill	0	0
Other intangible assets, net	0	0
Other noncurrent assets, net	(314)	(1,017)
Total assets	(562,972)	(482,231)
Liabilities and Equity
Accounts payable and accrued expenses related to trade creditors	0	0
Accrued participations and residuals	0	0
Deferred revenue	0	0
Accrued expenses and other current liabilities	0	0
Current portion of long-term debt	0	0
Total current liabilities	0	0
Long-term debt, less current portion	0	0
Deferred income taxes	(343)	(1,017)
Other noncurrent liabilities	29	0
Redeemable noncontrolling interests	0	0
Equity:
Common stock	0	0
Other shareholders’ equity	(562,658)	(481,214)
Total Comcast Corporation shareholders’ equity	(562,658)	(481,214)
Noncontrolling interests	0	0
Total equity	(562,658)	(481,214)
Total liabilities and equity	(562,972)	(482,231)
Comcast Parent [Member] | Reportable Legal Entities [Member]
Assets
Cash and cash equivalents	0	0	0	0
Receivables, net	0	0
Programming rights	0	0
Deposits	0	0
Other current assets	60	151
Total current assets	60	151
Film and television costs	0	0
Investments	146	75
Investments in and amounts due from subsidiaries eliminated upon consolidation	117,154	98,350
Property and equipment, net	551	298
Franchise rights	0	0
Goodwill	0	0
Other intangible assets, net	12	13
Other noncurrent assets, net	435	1,138
Total assets	118,358	100,025
Liabilities and Equity
Accounts payable and accrued expenses related to trade creditors	16	23
Accrued participations and residuals	0	0
Deferred revenue	0	0
Accrued expenses and other current liabilities	1,888	1,726
Current portion of long-term debt	2,810	3,739
Total current liabilities	4,714	5,488
Long-term debt, less current portion	42,428	38,123
Deferred income taxes	0	0
Other noncurrent liabilities	2,610	2,471
Redeemable noncontrolling interests	0	0
Equity:
Common stock	55	56
Other shareholders’ equity	68,551	53,887
Total Comcast Corporation shareholders’ equity	68,606	53,943
Noncontrolling interests	0	0
Total equity	68,606	53,943
Total liabilities and equity	118,358	100,025
Subsidiary Issuer [Member] | Reportable Legal Entities [Member] | Comcast Holdings [Member]
Assets
Cash and cash equivalents	0	0	0	0
Receivables, net	0	0
Programming rights	0	0
Deposits	0	0
Other current assets	0	0
Total current assets	0	0
Film and television costs	0	0
Investments	21	0
Investments in and amounts due from subsidiaries eliminated upon consolidation	142,412	120,071
Property and equipment, net	0	0
Franchise rights	0	0
Goodwill	0	0
Other intangible assets, net	0	0
Other noncurrent assets, net	708	638
Total assets	143,141	120,709
Liabilities and Equity
Accounts payable and accrued expenses related to trade creditors	0	0
Accrued participations and residuals	0	0
Deferred revenue	0	0
Accrued expenses and other current liabilities	92	0
Current portion of long-term debt	0	0
Total current liabilities	92	0
Long-term debt, less current portion	140	141
Deferred income taxes	285	542
Other noncurrent liabilities	0	0
Redeemable noncontrolling interests	0	0
Equity:
Common stock	0	0
Other shareholders’ equity	142,624	120,026
Total Comcast Corporation shareholders’ equity	142,624	120,026
Noncontrolling interests	0	0
Total equity	142,624	120,026
Total liabilities and equity	143,141	120,709
Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member] | CCCL Parent [Member]
Assets
Cash and cash equivalents	0	0	0	0
Receivables, net	0	0
Programming rights	0	0
Deposits	0	0
Other current assets	7	0
Total current assets	7	0
Film and television costs	0	0
Investments	108	0
Investments in and amounts due from subsidiaries eliminated upon consolidation	139,364	117,696
Property and equipment, net	0	0
Franchise rights	0	0
Goodwill	0	0
Other intangible assets, net	0	0
Other noncurrent assets, net	0	0
Total assets	139,479	117,696
Liabilities and Equity
Accounts payable and accrued expenses related to trade creditors	0	0
Accrued participations and residuals	0	0
Deferred revenue	0	0
Accrued expenses and other current liabilities	333	341
Current portion of long-term debt	0	550
Total current liabilities	333	891
Long-term debt, less current portion	2,100	2,100
Deferred income taxes	0	0
Other noncurrent liabilities	0	0
Redeemable noncontrolling interests	0	0
Equity:
Common stock	0	0
Other shareholders’ equity	137,046	114,705
Total Comcast Corporation shareholders’ equity	137,046	114,705
Noncontrolling interests	0	0
Total equity	137,046	114,705
Total liabilities and equity	139,479	117,696
Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member] | NBCUniversal Media Parent [Member]
Assets
Cash and cash equivalents	496	482	414	385
Receivables, net	0	0
Programming rights	0	0
Deposits	0	0
Other current assets	25	36
Total current assets	521	518
Film and television costs	0	0
Investments	693	651
Investments in and amounts due from subsidiaries eliminated upon consolidation	50,249	47,393
Property and equipment, net	0	0
Franchise rights	0	0
Goodwill	0	0
Other intangible assets, net	0	0
Other noncurrent assets, net	88	89
Total assets	51,551	48,651
Liabilities and Equity
Accounts payable and accrued expenses related to trade creditors	0	0
Accrued participations and residuals	0	0
Deferred revenue	0	0
Accrued expenses and other current liabilities	326	302
Current portion of long-term debt	4	4
Total current liabilities	330	306
Long-term debt, less current portion	7,751	8,208
Deferred income taxes	67	70
Other noncurrent liabilities	1,128	1,166
Redeemable noncontrolling interests	0	0
Equity:
Common stock	0	0
Other shareholders’ equity	42,275	38,901
Total Comcast Corporation shareholders’ equity	42,275	38,901
Noncontrolling interests	0	0
Total equity	42,275	38,901
Total liabilities and equity	51,551	48,651
Non-Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
Assets
Cash and cash equivalents	2,932	2,819	$ 1,881	$ 3,525
Receivables, net	8,546	7,955
Programming rights	1,613	1,250
Deposits	9	1,772
Other current assets	2,372	1,896
Total current assets	15,472	15,692
Film and television costs	7,076	7,252
Investments	5,963	4,521
Investments in and amounts due from subsidiaries eliminated upon consolidation	113,479	97,704
Property and equipment, net	37,919	35,955
Franchise rights	59,364	59,364
Goodwill	36,780	35,980
Other intangible assets, net	18,767	17,261
Other noncurrent assets, net	2,572	1,921
Total assets	297,392	275,650
Liabilities and Equity
Accounts payable and accrued expenses related to trade creditors	6,910	6,892
Accrued participations and residuals	1,683	1,726
Deferred revenue	1,552	1,132
Accrued expenses and other current liabilities	3,627	3,913
Current portion of long-term debt	2,320	1,187
Total current liabilities	16,092	14,850
Long-term debt, less current portion	7,003	6,994
Deferred income taxes	24,247	35,259
Other noncurrent liabilities	7,137	7,288
Redeemable noncontrolling interests	1,357	1,446
Equity:
Common stock	0	0
Other shareholders’ equity	240,713	207,582
Total Comcast Corporation shareholders’ equity	240,713	207,582
Noncontrolling interests	843	2,231
Total equity	241,556	209,813
Total liabilities and equity	$ 297,392	$ 275,650

Condensed Consolidating Fina110

Condensed Consolidating Financial Information (Condensed Consolidating Statement of Income) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue:
Service revenue									$ 84,526	$ 80,403	$ 74,510
Management fee revenue									0	0	0
Total revenue	$ 21,915	$ 20,983	$ 21,165	$ 20,463	$ 21,025	$ 21,319	$ 19,269	$ 18,790	84,526	80,403	74,510
Costs and Expenses:
Programming and production									25,384	24,463	22,550
Other operating and administrative									25,013	23,416	21,325
Advertising, marketing and promotion									6,317	6,107	5,957
Depreciation									7,914	7,464	6,781
Amortization									2,353	2,094	1,899
Other operating gains									(442)	0	0
Total costs and expenses									66,539	63,544	58,512
Operating income	4,107	4,792	4,558	4,530	4,264	4,440	4,066	4,089	17,987	16,859	15,998
Other Income (Expense):
Interest expense									(3,086)	(2,942)	(2,702)
Investment income (loss), net									253	213	81
Equity in net income (losses) of investees, net									107	(104)	(325)
Other income (expense), net									61	327	320
Total other income (expense)									(2,665)	(2,506)	(2,626)
Income before income taxes									15,322	14,353	13,372
Income tax (expense) benefit									7,578	(5,308)	(4,959)
Net income									22,900	9,045	8,413
Net (income) loss attributable to noncontrolling interests and redeemable subsidiary preferred stock									(186)	(350)	(250)
Net Income Attributable to Comcast Corporation	$ 14,985	$ 2,650	$ 2,513	$ 2,566	$ 2,296	$ 2,237	$ 2,028	$ 2,134	22,714	8,695	8,163
Comprehensive income attributable to Parent									22,801	8,967	8,135
Elimination and Consolidation Adjustments [Member]
Revenue:
Service revenue									0	0	0
Management fee revenue									(2,237)	(2,116)	(1,982)
Total revenue									(2,237)	(2,116)	(1,982)
Costs and Expenses:
Programming and production									0	0	0
Other operating and administrative									(2,237)	(2,116)	(1,982)
Advertising, marketing and promotion									0	0	0
Depreciation									0	0	0
Amortization									0	0	0
Other operating gains									0	0	0
Total costs and expenses									(2,237)	(2,116)	(1,982)
Operating income									0	0	0
Other Income (Expense):
Interest expense									0	0	0
Investment income (loss), net									0	0	0
Equity in net income (losses) of investees, net									(77,072)	(37,554)	(34,116)
Other income (expense), net									0	0	0
Total other income (expense)									(77,072)	(37,554)	(34,116)
Income before income taxes									(77,072)	(37,554)	(34,116)
Income tax (expense) benefit									0	0	0
Net income									(77,072)	(37,554)	(34,116)
Net (income) loss attributable to noncontrolling interests and redeemable subsidiary preferred stock									0	0	0
Net Income Attributable to Comcast Corporation									(77,072)	(37,554)	(34,116)
Comprehensive income attributable to Parent									(76,909)	(37,769)	(34,042)
Comcast Parent [Member] | Reportable Legal Entities [Member]
Revenue:
Service revenue									0	0	0
Management fee revenue									1,128	1,067	1,005
Total revenue									1,128	1,067	1,005
Costs and Expenses:
Programming and production									0	0	0
Other operating and administrative									766	813	760
Advertising, marketing and promotion									0	0	0
Depreciation									31	28	31
Amortization									6	6	6
Other operating gains									0	0	0
Total costs and expenses									803	847	797
Operating income									325	220	208
Other Income (Expense):
Interest expense									(2,172)	(1,941)	(1,744)
Investment income (loss), net									(1)	7	6
Equity in net income (losses) of investees, net									24,056	9,809	9,159
Other income (expense), net									0	0	(3)
Total other income (expense)									21,883	7,875	7,418
Income before income taxes									22,208	8,095	7,626
Income tax (expense) benefit									506	600	537
Net income									22,714	8,695	8,163
Net (income) loss attributable to noncontrolling interests and redeemable subsidiary preferred stock									0	0	0
Net Income Attributable to Comcast Corporation									22,714	8,695	8,163
Comprehensive income attributable to Parent									22,801	8,967	8,135
Subsidiary Issuer [Member] | Reportable Legal Entities [Member] | Comcast Holdings [Member]
Revenue:
Service revenue									0	0	0
Management fee revenue									0	0	0
Total revenue									0	0	0
Costs and Expenses:
Programming and production									0	0	0
Other operating and administrative									0	0	0
Advertising, marketing and promotion									0	0	0
Depreciation									0	0	0
Amortization									0	0	0
Other operating gains									0	0	0
Total costs and expenses									0	0	0
Operating income									0	0	0
Other Income (Expense):
Interest expense									(12)	(12)	(12)
Investment income (loss), net									109	(5)	(1)
Equity in net income (losses) of investees, net									21,622	9,286	8,651
Other income (expense), net									0	0	0
Total other income (expense)									21,719	9,269	8,638
Income before income taxes									21,719	9,269	8,638
Income tax (expense) benefit									156	6	4
Net income									21,875	9,275	8,642
Net (income) loss attributable to noncontrolling interests and redeemable subsidiary preferred stock									0	0	0
Net Income Attributable to Comcast Corporation									21,875	9,275	8,642
Comprehensive income attributable to Parent									21,873	9,317	8,625
Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member] | CCCL Parent [Member]
Revenue:
Service revenue									0	0	0
Management fee revenue									1,109	1,049	977
Total revenue									1,109	1,049	977
Costs and Expenses:
Programming and production									0	0	0
Other operating and administrative									1,109	1,049	977
Advertising, marketing and promotion									0	0	0
Depreciation									0	0	0
Amortization									0	0	0
Other operating gains									0	0	0
Total costs and expenses									1,109	1,049	977
Operating income									0	0	0
Other Income (Expense):
Interest expense									(207)	(239)	(270)
Investment income (loss), net									0	0	0
Equity in net income (losses) of investees, net									19,570	8,679	8,040
Other income (expense), net									0	0	0
Total other income (expense)									19,363	8,440	7,770
Income before income taxes									19,363	8,440	7,770
Income tax (expense) benefit									71	84	94
Net income									19,434	8,524	7,864
Net (income) loss attributable to noncontrolling interests and redeemable subsidiary preferred stock									0	0	0
Net Income Attributable to Comcast Corporation									19,434	8,524	7,864
Comprehensive income attributable to Parent									19,437	8,530	7,864
Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member] | NBCUniversal Media Parent [Member]
Revenue:
Service revenue									0	0	0
Management fee revenue									0	0	0
Total revenue									0	0	0
Costs and Expenses:
Programming and production									0	0	0
Other operating and administrative									1,044	932	922
Advertising, marketing and promotion									0	0	0
Depreciation									0	0	0
Amortization									0	0	0
Other operating gains									0	0	0
Total costs and expenses									1,044	932	922
Operating income									(1,044)	(932)	(922)
Other Income (Expense):
Interest expense									(456)	(456)	(462)
Investment income (loss), net									(197)	(25)	(19)
Equity in net income (losses) of investees, net									6,740	5,545	4,852
Other income (expense), net									45	116	(31)
Total other income (expense)									6,132	5,180	4,340
Income before income taxes									5,088	4,248	3,418
Income tax (expense) benefit									(4)	(13)	(4)
Net income									5,084	4,235	3,414
Net (income) loss attributable to noncontrolling interests and redeemable subsidiary preferred stock									0	0	0
Net Income Attributable to Comcast Corporation									5,084	4,235	3,414
Comprehensive income attributable to Parent									5,058	4,312	3,361
Non-Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
Revenue:
Service revenue									84,526	80,403	74,510
Management fee revenue									0	0	0
Total revenue									84,526	80,403	74,510
Costs and Expenses:
Programming and production									25,384	24,463	22,550
Other operating and administrative									24,331	22,738	20,648
Advertising, marketing and promotion									6,317	6,107	5,957
Depreciation									7,883	7,436	6,750
Amortization									2,347	2,088	1,893
Other operating gains									(442)	0	0
Total costs and expenses									65,820	62,832	57,798
Operating income									18,706	17,571	16,712
Other Income (Expense):
Interest expense									(239)	(294)	(214)
Investment income (loss), net									342	236	95
Equity in net income (losses) of investees, net									5,191	4,131	3,089
Other income (expense), net									16	211	354
Total other income (expense)									5,310	4,284	3,324
Income before income taxes									24,016	21,855	20,036
Income tax (expense) benefit									6,849	(5,985)	(5,590)
Net income									30,865	15,870	14,446
Net (income) loss attributable to noncontrolling interests and redeemable subsidiary preferred stock									(186)	(350)	(250)
Net Income Attributable to Comcast Corporation									30,679	15,520	14,196
Comprehensive income attributable to Parent									$ 30,541	$ 15,610	$ 14,192

Condensed Consolidating Fina111

Condensed Consolidating Financial Information (Condensed Consolidating Statement of Cash Flows) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Activities
Net cash provided by operating activities	$ 21,403	$ 19,825	$ 19,485
Investing Activities
Net transactions with affiliates	0	0	0
Capital expenditures	(9,550)	(9,135)	(8,499)
Cash paid for intangible assets	(1,747)	(1,686)	(1,370)
Acquisitions and construction of real estate properties	(418)	(428)	(178)
Acquisitions, net of cash acquired	(532)	(3,929)	(1,786)
Proceeds from sales of businesses and investments	150	218	433
Purchases of investments	(2,292)	(1,697)	(784)
Deposits	0	(1,749)	(18)
Other	685	21	238
Net cash provided by (used in) investing activities	(13,704)	(18,385)	(11,964)
Financing Activities
Proceeds from (repayments of) short-term borrowings, net	(1,905)	1,790	135
Proceeds from borrowings	11,466	9,231	5,486
Repurchases and repayments of debt	(6,364)	(3,052)	(4,378)
Repurchases of common stock under repurchase program and employee plans	(5,435)	(5,352)	(7,175)
Dividends paid	(2,883)	(2,601)	(2,437)
Purchase of Universal Studios Japan noncontrolling interests	(2,299)	0	0
Issuances of common stock	0	23	36
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock	(252)	(253)	(232)
Other	100	(220)	(571)
Net cash provided by (used in) financing activities	(7,572)	(434)	(9,136)
Increase (decrease) in cash and cash equivalents	127	1,006	(1,615)
Cash and cash equivalents, beginning of year	3,301	2,295	3,910
Cash and cash equivalents, end of year	3,428	3,301	2,295
Elimination and Consolidation Adjustments [Member]
Operating Activities
Net cash provided by operating activities	0	0	0
Investing Activities
Net transactions with affiliates	0	0	0
Capital expenditures	0	0	0
Cash paid for intangible assets	0	0	0
Acquisitions and construction of real estate properties	0	0	0
Acquisitions, net of cash acquired	0	0	0
Proceeds from sales of businesses and investments	0	0	0
Purchases of investments	0	0	0
Deposits	0	0	0
Other	0	0	0
Net cash provided by (used in) investing activities	0	0	0
Financing Activities
Proceeds from (repayments of) short-term borrowings, net	0	0	0
Proceeds from borrowings	0	0	0
Repurchases and repayments of debt	0	0	0
Repurchases of common stock under repurchase program and employee plans	0	0	0
Dividends paid	0	0	0
Purchase of Universal Studios Japan noncontrolling interests	0
Issuances of common stock	0	0	0
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock	0	0	0
Other	0	0	0
Net cash provided by (used in) financing activities	0	0	0
Increase (decrease) in cash and cash equivalents	0	0	0
Cash and cash equivalents, beginning of year	0	0	0
Cash and cash equivalents, end of year	0	0	0
Comcast Parent [Member] | Reportable Legal Entities [Member]
Operating Activities
Net cash provided by operating activities	151	(747)	(85)
Investing Activities
Net transactions with affiliates	5,578	(860)	6,559
Capital expenditures	(12)	(13)	(27)
Cash paid for intangible assets	(4)	(9)	(6)
Acquisitions and construction of real estate properties	(267)	(35)	0
Acquisitions, net of cash acquired	0	0	0
Proceeds from sales of businesses and investments	0	0	0
Purchases of investments	(70)	(40)	(7)
Deposits	0	0	0
Other	101	(108)	7
Net cash provided by (used in) investing activities	5,326	(1,065)	6,526
Financing Activities
Proceeds from (repayments of) short-term borrowings, net	(837)	1,339	400
Proceeds from borrowings	5,997	9,231	5,486
Repurchases and repayments of debt	(2,288)	(750)	(2,650)
Repurchases of common stock under repurchase program and employee plans	(5,435)	(5,352)	(7,175)
Dividends paid	(2,883)	(2,601)	(2,437)
Purchase of Universal Studios Japan noncontrolling interests	0
Issuances of common stock	0	23	36
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock	0	0	0
Other	(31)	(78)	(101)
Net cash provided by (used in) financing activities	(5,477)	1,812	(6,441)
Increase (decrease) in cash and cash equivalents	0	0	0
Cash and cash equivalents, beginning of year	0	0	0
Cash and cash equivalents, end of year	0	0	0
Subsidiary Issuer [Member] | Reportable Legal Entities [Member] | Comcast Holdings [Member]
Operating Activities
Net cash provided by operating activities	15	(189)	48
Investing Activities
Net transactions with affiliates	(5)	189	(48)
Capital expenditures	0	0	0
Cash paid for intangible assets	0	0	0
Acquisitions and construction of real estate properties	0	0	0
Acquisitions, net of cash acquired	0	0	0
Proceeds from sales of businesses and investments	0	0	0
Purchases of investments	(10)	0	0
Deposits	0	0	0
Other	0	0	0
Net cash provided by (used in) investing activities	(15)	189	(48)
Financing Activities
Proceeds from (repayments of) short-term borrowings, net	0	0	0
Proceeds from borrowings	0	0	0
Repurchases and repayments of debt	0	0	0
Repurchases of common stock under repurchase program and employee plans	0	0	0
Dividends paid	0	0	0
Purchase of Universal Studios Japan noncontrolling interests	0
Issuances of common stock	0	0	0
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock	0	0	0
Other	0	0	0
Net cash provided by (used in) financing activities	0	0	0
Increase (decrease) in cash and cash equivalents	0	0	0
Cash and cash equivalents, beginning of year	0	0	0
Cash and cash equivalents, end of year	0	0	0
Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member] | CCCL Parent [Member]
Operating Activities
Net cash provided by operating activities	(147)	(100)	(167)
Investing Activities
Net transactions with affiliates	757	100	840
Capital expenditures	0	0	0
Cash paid for intangible assets	0	0	0
Acquisitions and construction of real estate properties	0	0	0
Acquisitions, net of cash acquired	0	0	0
Proceeds from sales of businesses and investments	0	0	0
Purchases of investments	(60)	0	0
Deposits	0	0	0
Other	0	0	0
Net cash provided by (used in) investing activities	697	100	840
Financing Activities
Proceeds from (repayments of) short-term borrowings, net	0	0	0
Proceeds from borrowings	0	0	0
Repurchases and repayments of debt	(550)	0	(673)
Repurchases of common stock under repurchase program and employee plans	0	0	0
Dividends paid	0	0	0
Purchase of Universal Studios Japan noncontrolling interests	0
Issuances of common stock	0	0	0
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock	0	0	0
Other	0	0	0
Net cash provided by (used in) financing activities	(550)	0	(673)
Increase (decrease) in cash and cash equivalents	0	0	0
Cash and cash equivalents, beginning of year	0	0	0
Cash and cash equivalents, end of year	0	0	0
Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member] | NBCUniversal Media Parent [Member]
Operating Activities
Net cash provided by operating activities	(1,439)	(1,453)	(1,398)
Investing Activities
Net transactions with affiliates	1,447	2,642	2,839
Capital expenditures	0	0	0
Cash paid for intangible assets	0	0	0
Acquisitions and construction of real estate properties	0	0	0
Acquisitions, net of cash acquired	0	0	0
Proceeds from sales of businesses and investments	14	104	4
Purchases of investments	(62)	(210)	(407)
Deposits	0	0	0
Other	58	(35)	(5)
Net cash provided by (used in) investing activities	1,457	2,501	2,431
Financing Activities
Proceeds from (repayments of) short-term borrowings, net	0	0	0
Proceeds from borrowings	0	0	0
Repurchases and repayments of debt	(4)	(1,005)	(1,004)
Repurchases of common stock under repurchase program and employee plans	0	0	0
Dividends paid	0	0	0
Purchase of Universal Studios Japan noncontrolling interests	0
Issuances of common stock	0	0	0
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock	0	0	0
Other	0	25	0
Net cash provided by (used in) financing activities	(4)	(980)	(1,004)
Increase (decrease) in cash and cash equivalents	14	68	29
Cash and cash equivalents, beginning of year	482	414	385
Cash and cash equivalents, end of year	496	482	414
Non-Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
Operating Activities
Net cash provided by operating activities	22,823	22,314	21,087
Investing Activities
Net transactions with affiliates	(7,777)	(2,071)	(10,190)
Capital expenditures	(9,538)	(9,122)	(8,472)
Cash paid for intangible assets	(1,743)	(1,677)	(1,364)
Acquisitions and construction of real estate properties	(151)	(393)	(178)
Acquisitions, net of cash acquired	(532)	(3,929)	(1,786)
Proceeds from sales of businesses and investments	136	114	429
Purchases of investments	(2,090)	(1,447)	(370)
Deposits	0	(1,749)	(18)
Other	526	164	236
Net cash provided by (used in) investing activities	(21,169)	(20,110)	(21,713)
Financing Activities
Proceeds from (repayments of) short-term borrowings, net	(1,068)	451	(265)
Proceeds from borrowings	5,469	0	0
Repurchases and repayments of debt	(3,522)	(1,297)	(51)
Repurchases of common stock under repurchase program and employee plans	0	0	0
Dividends paid	0	0	0
Purchase of Universal Studios Japan noncontrolling interests	(2,299)
Issuances of common stock	0	0	0
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock	(252)	(253)	(232)
Other	131	(167)	(470)
Net cash provided by (used in) financing activities	(1,541)	(1,266)	(1,018)
Increase (decrease) in cash and cash equivalents	113	938	(1,644)
Cash and cash equivalents, beginning of year	2,819	1,881	3,525
Cash and cash equivalents, end of year	$ 2,932	$ 2,819	$ 1,881

Schedule II Valuation and Qu112

Schedule II Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for doubtful accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	$ 250	$ 226	$ 205
Additions Charged to Costs and Expenses	72	86	166
Deductions from Reserves	34	62	145
Balance at End of Year	288	250	226
Allowance for doubtful accounts [Member] | NBCUniversal Media LLC [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	84	69	60
Additions Charged to Costs and Expenses	23	26	27
Deductions from Reserves	19	11	18
Balance at End of Year	88	84	69
Allowance for returns and customer incentives [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	417	473	359
Additions Charged to Costs and Expenses	974	1,041	1,236
Deductions from Reserves	972	1,097	1,122
Balance at End of Year	419	417	473
Allowance for returns and customer incentives [Member] | NBCUniversal Media LLC [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	413	469	356
Additions Charged to Costs and Expenses	955	1,040	1,233
Deductions from Reserves	954	1,096	1,120
Balance at End of Year	414	413	469
Valuation allowance on deferred tax assets [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	266	342	375
Additions Charged to Costs and Expenses	111	23	4
Deductions from Reserves	0	99	37
Balance at End of Year	377	266	342
Valuation allowance on deferred tax assets [Member] | NBCUniversal Media LLC [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	72	71	87
Additions Charged to Costs and Expenses	15	23	4
Deductions from Reserves	0	22	20
Balance at End of Year	$ 87	$ 72	$ 71