Supplemental Financial Information (Net Cash Provided by Operating Activities)(Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Supplemental Financial Information [Line Items]
Net income	$ 2,683	$ 2,324	$ 7,865	$ 6,628
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and other operating gains			7,181	7,062
Share-based compensation			594	495
Noncash interest expense (income), net			187	172
Equity in net (income) losses of investees, net	39	34	(12)	64
Cash received from investees			72	58
Net (gain) loss on investment activity and other			(193)	(159)
Deferred income taxes			678	985
Changes in operating assets and liabilities, net of effects of acquisitions and divestitures:
Current and noncurrent receivables, net			28	(315)
Film and television costs, net			(71)	(593)
Accounts payable and accrued expenses related to trade creditors			(17)	46
Other operating assets and liabilities			(351)	(454)
Net cash provided by operating activities			15,961	13,989
NBCUniversal Media LLC [Member]
Supplemental Financial Information [Line Items]
Net income	1,842	1,367	4,403	3,424
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and other operating gains			1,197	1,324
Equity in net (income) losses of investees, net	$ 52	$ 34	107	55
Cash received from investees			63	45
Net (gain) loss on investment activity and other			(45)	(72)
Deferred income taxes			(6)	139
Changes in operating assets and liabilities, net of effects of acquisitions and divestitures:
Current and noncurrent receivables, net			152	(338)
Film and television costs, net			(75)	(600)
Accounts payable and accrued expenses related to trade creditors			(270)	(114)
Other operating assets and liabilities			46	(524)
Net cash provided by operating activities			$ 5,572	$ 3,339