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

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=77989000&loc=SL49117168-202975

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