Financial Data by Business Segment (Reconciliation of Adjusted EBITDA from Segment to Consolidated Statements) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Adjusted EBITDA	$ 7,099	$ 6,455	$ 14,131	$ 12,822
Depreciation	(1,970)	(1,868)	(3,885)	(3,653)
Amortization	(571)	(521)	(1,158)	(1,014)
Other income (expense) items, net	(659)	(708)	(1,284)	(1,262)
Income before income taxes	3,899	3,358	7,804	6,893
NBCUniversal Media LLC [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Adjusted EBITDA	2,071	1,689	4,088	3,311
Depreciation	(265)	(223)	(496)	(415)
Amortization	(255)	(242)	(532)	(464)
Other income (expense) items, net	(164)	(175)	(308)	(203)
Income before income taxes	$ 1,387	$ 1,049	$ 2,752	$ 2,229