Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Revenue	$ 26,858	$ 21,735	$ 53,717	$ 44,526
Cable Communications [Member]
Disaggregation of Revenue [Line Items]
Revenue	14,450	13,912	28,730	27,615
Cable Communications [Member] | Residential, High-Speed Internet [Member]
Disaggregation of Revenue [Line Items]
Revenue	4,663	4,262	9,240	8,419
Cable Communications [Member] | Residential, Video [Member]
Disaggregation of Revenue [Line Items]
Revenue	5,594	5,628	11,222	11,287
Cable Communications [Member] | Residential, Voice [Member]
Disaggregation of Revenue [Line Items]
Revenue	982	994	1,972	2,000
Cable Communications [Member] | Residential, Wireless [Member]
Disaggregation of Revenue [Line Items]
Revenue	244	202	469	387
Cable Communications [Member] | Business Services [Member]
Disaggregation of Revenue [Line Items]
Revenue	1,933	1,761	3,824	3,487
Cable Communications [Member] | Advertising [Member]
Disaggregation of Revenue [Line Items]
Revenue	607	666	1,163	1,248
Cable Communications [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ 427	$ 399	$ 840	$ 787
Cable Communications [Member] | Franchise And Other Regulatory Fees [Member]
Disaggregation of Revenue [Line Items]
Cable segment revenue types as percentage of total cable revenue	2.50%	2.70%	2.50%	2.70%
Cable Networks [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ 2,947	$ 2,874	$ 5,815	$ 6,031
Cable Networks [Member] | Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenue	1,707	1,650	3,442	3,511
Cable Networks [Member] | Advertising [Member]
Disaggregation of Revenue [Line Items]
Revenue	931	929	1,783	1,906
Cable Networks [Member] | Content Licensing And Other [Member]
Disaggregation of Revenue [Line Items]
Revenue	309	295	590	614
Broadcast Television [Member]
Disaggregation of Revenue [Line Items]
Revenue	2,402	2,391	4,869	5,888
Broadcast Television [Member] | Advertising [Member]
Disaggregation of Revenue [Line Items]
Revenue	1,329	1,387	2,646	3,752
Broadcast Television [Member] | Content Licensing [Member]
Disaggregation of Revenue [Line Items]
Revenue	472	481	1,032	1,003
Broadcast Television [Member] | Distribution And Other [Member]
Disaggregation of Revenue [Line Items]
Revenue	601	523	1,191	1,133
Filmed Entertainment [Member]
Disaggregation of Revenue [Line Items]
Revenue	1,457	1,710	3,225	3,357
Filmed Entertainment [Member] | Content Licensing [Member]
Disaggregation of Revenue [Line Items]
Revenue	712	648	1,529	1,381
Filmed Entertainment [Member] | Theatrical [Member]
Disaggregation of Revenue [Line Items]
Revenue	252	540	697	963
Filmed Entertainment [Member] | Home Entertainment [Member]
Disaggregation of Revenue [Line Items]
Revenue	229	225	496	473
Filmed Entertainment [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue	264	297	503	540
Theme Parks [Member]
Disaggregation of Revenue [Line Items]
Revenue	1,464	1,361	2,740	2,642
NBCUniversal Segments [Member]
Disaggregation of Revenue [Line Items]
Revenue	8,206	8,273	16,519	17,770
Sky Limited [Member]
Disaggregation of Revenue [Line Items]
Revenue	4,828	0	9,625	0
Sky Limited [Member] | Advertising [Member]
Disaggregation of Revenue [Line Items]
Revenue	563	0	1,156	0
Sky Limited [Member] | Direct To Consumer [Member]
Disaggregation of Revenue [Line Items]
Revenue	3,889	0	7,723	0
Sky Limited [Member] | Content [Member]
Disaggregation of Revenue [Line Items]
Revenue	376	0	746	0
Corporate, Non-Segment [Member]
Disaggregation of Revenue [Line Items]
Revenue	56	96	164	339
Corporate, Non-Segment [Member] | NBCUniversal Segments [Member]
Disaggregation of Revenue [Line Items]
Revenue	22	15	39	29
Eliminations [Member]
Disaggregation of Revenue [Line Items]
Revenue	(682)	(546)	(1,321)	(1,198)
Eliminations [Member] | NBCUniversal Segments [Member]
Disaggregation of Revenue [Line Items]
Revenue	(86)	(78)	(169)	(177)
NBCUniversal Media LLC [Member]
Disaggregation of Revenue [Line Items]
Revenue	8,227	8,313	16,572	17,843
NBCUniversal Media LLC [Member] | Cable Networks [Member]
Disaggregation of Revenue [Line Items]
Revenue	2,947	2,874	5,815	6,031
NBCUniversal Media LLC [Member] | Cable Networks [Member] | Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenue	1,707	1,650	3,442	3,511
NBCUniversal Media LLC [Member] | Cable Networks [Member] | Advertising [Member]
Disaggregation of Revenue [Line Items]
Revenue	931	929	1,783	1,906
NBCUniversal Media LLC [Member] | Cable Networks [Member] | Content Licensing And Other [Member]
Disaggregation of Revenue [Line Items]
Revenue	309	295	590	614
NBCUniversal Media LLC [Member] | Broadcast Television [Member]
Disaggregation of Revenue [Line Items]
Revenue	2,402	2,391	4,869	5,888
NBCUniversal Media LLC [Member] | Broadcast Television [Member] | Advertising [Member]
Disaggregation of Revenue [Line Items]
Revenue	1,329	1,387	2,646	3,752
NBCUniversal Media LLC [Member] | Broadcast Television [Member] | Content Licensing [Member]
Disaggregation of Revenue [Line Items]
Revenue	472	481	1,032	1,003
NBCUniversal Media LLC [Member] | Broadcast Television [Member] | Distribution And Other [Member]
Disaggregation of Revenue [Line Items]
Revenue	601	523	1,191	1,133
NBCUniversal Media LLC [Member] | Filmed Entertainment [Member]
Disaggregation of Revenue [Line Items]
Revenue	1,457	1,710	3,225	3,357
NBCUniversal Media LLC [Member] | Filmed Entertainment [Member] | Content Licensing [Member]
Disaggregation of Revenue [Line Items]
Revenue	712	648	1,529	1,381
NBCUniversal Media LLC [Member] | Filmed Entertainment [Member] | Theatrical [Member]
Disaggregation of Revenue [Line Items]
Revenue	252	540	697	963
NBCUniversal Media LLC [Member] | Filmed Entertainment [Member] | Home Entertainment [Member]
Disaggregation of Revenue [Line Items]
Revenue	229	225	496	473
NBCUniversal Media LLC [Member] | Filmed Entertainment [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue	264	297	503	540
NBCUniversal Media LLC [Member] | Theme Parks [Member]
Disaggregation of Revenue [Line Items]
Revenue	1,464	1,361	2,740	2,642
NBCUniversal Media LLC [Member] | Corporate, Non-Segment [Member]
Disaggregation of Revenue [Line Items]
Revenue	45	57	96	108
NBCUniversal Media LLC [Member] | Eliminations [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ (88)	$ (80)	$ (173)	$ (183)