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