Segment Information (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) segment	Jun. 30, 2017 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment			5
Financial Data by Business Segment
Revenue	$ 21,735	$ 21,286	$ 44,526	$ 41,873
Adjusted EBITDA	7,417	7,075	14,661	14,085
Depreciation and Amortization	2,603	2,507	5,202	4,975
Capital Expenditures	2,250	2,327	4,223	4,405
Cash Paid for Intangible Assets	511	386	$ 930	771
NBCUniversal Media LLC [Member]
Segment Reporting Information [Line Items]
Number of reportable segments | segment			4
Financial Data by Business Segment
Revenue	8,313	8,318	$ 17,843	16,171
Adjusted EBITDA	2,160	2,074	4,445	4,093
Depreciation and Amortization	553	520	1,063	1,028
Capital Expenditures	461	338	730	623
Cash Paid for Intangible Assets	166	73	296	128
Cable Communications [Member]
Financial Data by Business Segment
Revenue	13,710	13,257	27,228	26,307
Depreciation and Amortization		1,967		3,913
Cable Networks [Member]
Financial Data by Business Segment
Revenue	2,916	2,696	6,110	5,336
Cable Networks [Member] | NBCUniversal Media LLC [Member]
Financial Data by Business Segment
Revenue	2,916	2,696	6,110	5,336
Broadcast Television [Member]
Financial Data by Business Segment
Revenue	2,391	2,241	5,888	4,449
Broadcast Television [Member] | NBCUniversal Media LLC [Member]
Financial Data by Business Segment
Revenue	2,391	2,241	5,888	4,449
Filmed Entertainment [Member]
Financial Data by Business Segment
Revenue	1,710	2,142	3,357	4,109
Filmed Entertainment [Member] | NBCUniversal Media LLC [Member]
Financial Data by Business Segment
Revenue	1,710	2,142	3,357	4,109
Theme Parks [Member]
Financial Data by Business Segment
Revenue	1,361	1,314	2,642	2,432
Theme Parks [Member] | NBCUniversal Media LLC [Member]
Financial Data by Business Segment
Revenue	1,361	1,314	2,642	2,432
NBCUniversal Segments [Member]
Financial Data by Business Segment
Revenue	8,313	8,318	17,843	16,171
Adjusted EBITDA	2,160	2,074	4,445	4,093
Depreciation and Amortization	553	520	1,063	1,028
Capital Expenditures	461	338	730	623
Cash Paid for Intangible Assets	166	73	296	128
Operating Segments [Member] | Cable Communications [Member]
Financial Data by Business Segment
Revenue	13,710	13,257	27,228	26,307
Adjusted EBITDA	5,638	5,293	11,053	10,467
Depreciation and Amortization	2,047	1,967	4,100	3,913
Capital Expenditures	1,766	1,956	3,454	3,737
Cash Paid for Intangible Assets	328	291	597	613
Operating Segments [Member] | Cable Networks [Member]
Financial Data by Business Segment
Revenue	2,916	2,696	6,110	5,336
Adjusted EBITDA	1,186	1,055	2,454	2,170
Depreciation and Amortization	179	181	368	395
Capital Expenditures	8	8	11	10
Cash Paid for Intangible Assets	5	4	9	7
Operating Segments [Member] | Cable Networks [Member] | NBCUniversal Media LLC [Member]
Financial Data by Business Segment
Revenue	2,916	2,696	6,110	5,336
Adjusted EBITDA	1,186	1,055	2,454	2,170
Depreciation and Amortization	179	181	368	395
Capital Expenditures	8	8	11	10
Cash Paid for Intangible Assets	5	4	9	7
Operating Segments [Member] | Broadcast Television [Member]
Financial Data by Business Segment
Revenue	2,391	2,241	5,888	4,449
Adjusted EBITDA	417	416	924	738
Depreciation and Amortization	40	31	74	63
Capital Expenditures	32	30	62	59
Cash Paid for Intangible Assets	3	4	75	7
Operating Segments [Member] | Broadcast Television [Member] | NBCUniversal Media LLC [Member]
Financial Data by Business Segment
Revenue	2,391	2,241	5,888	4,449
Adjusted EBITDA	417	416	924	738
Depreciation and Amortization	40	31	74	63
Capital Expenditures	32	30	62	59
Cash Paid for Intangible Assets	3	4	75	7
Operating Segments [Member] | Filmed Entertainment [Member]
Financial Data by Business Segment
Revenue	1,710	2,142	3,357	4,109
Adjusted EBITDA	138	287	341	658
Depreciation and Amortization	63	25	91	47
Capital Expenditures	8	19	15	29
Cash Paid for Intangible Assets	8	6	14	11
Operating Segments [Member] | Filmed Entertainment [Member] | NBCUniversal Media LLC [Member]
Financial Data by Business Segment
Revenue	1,710	2,142	3,357	4,109
Adjusted EBITDA	138	287	341	658
Depreciation and Amortization	63	25	91	47
Capital Expenditures	8	19	15	29
Cash Paid for Intangible Assets	8	6	14	11
Operating Segments [Member] | Theme Parks [Member]
Financial Data by Business Segment
Revenue	1,361	1,314	2,642	2,432
Adjusted EBITDA	569	551	1,064	948
Depreciation and Amortization	167	186	322	328
Capital Expenditures	360	243	542	472
Cash Paid for Intangible Assets	119	26	135	39
Operating Segments [Member] | Theme Parks [Member] | NBCUniversal Media LLC [Member]
Financial Data by Business Segment
Revenue	1,361	1,314	2,642	2,432
Adjusted EBITDA	569	551	1,064	948
Depreciation and Amortization	167	186	322	328
Capital Expenditures	360	243	542	472
Cash Paid for Intangible Assets	119	26	135	39
Corporate, Non-Segment [Member]
Financial Data by Business Segment
Revenue	255	205	646	413
Adjusted EBITDA	(392)	(302)	(789)	(496)
Depreciation and Amortization	3	20	39	34
Capital Expenditures	23	33	39	45
Cash Paid for Intangible Assets	17	22	37	30
Corporate, Non-Segment [Member] | NBCUniversal Media LLC [Member]
Financial Data by Business Segment
Revenue	15	9	29	17
Adjusted EBITDA	(148)	(235)	(336)	(420)
Depreciation and Amortization	104	97	208	195
Capital Expenditures	53	38	100	53
Cash Paid for Intangible Assets	31	33	63	64
Corporate, Non-Segment [Member] | NBCUniversal Segments [Member]
Financial Data by Business Segment
Revenue	15	9	29	17
Adjusted EBITDA	(148)	(235)	(336)	(420)
Depreciation and Amortization	104	97	208	195
Capital Expenditures	53	38	100	53
Cash Paid for Intangible Assets	31	33	63	64
Eliminations [Member]
Financial Data by Business Segment
Revenue	(543)	(494)	(1,191)	(1,018)
Adjusted EBITDA	11	10	(48)	21
Depreciation and Amortization	0	0	0	0
Capital Expenditures	0	0	0	0
Cash Paid for Intangible Assets	0	0	0	0
Eliminations [Member] | NBCUniversal Media LLC [Member]
Financial Data by Business Segment
Revenue	(80)	(84)	(183)	(172)
Adjusted EBITDA	(2)	0	(2)	(1)
Depreciation and Amortization	0	0	0	0
Capital Expenditures	0	0	0	0
Cash Paid for Intangible Assets	0	0	0	0
Eliminations [Member] | NBCUniversal Segments [Member]
Financial Data by Business Segment
Revenue	(80)	(84)	(183)	(172)
Adjusted EBITDA	(2)	0	(2)	(1)
Depreciation and Amortization	0	0	0	0
Capital Expenditures	0	0	0	0
Cash Paid for Intangible Assets	$ 0	$ 0	$ 0	$ 0