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