Income Taxes (Components of Income Tax Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current (Expense) Benefit:
Federal	$ (2,085)	$ (2,026)	$ (2,411)
State	(425)	(639)	(277)
Foreign	(600)	(425)	(389)
Current income tax (expense) benefit	(3,110)	(3,090)	(3,077)
Deferred (Expense) Benefit:
Federal	(902)	(546)	10,651
State	15	167	(11)
Foreign	324	89	6
Deferred income tax (expense) benefit	(563)	(290)	10,646
Income tax (expense) benefit	(3,673)	(3,380)	7,569
NBCUniversal Media LLC [Member]
Current (Expense) Benefit:
Foreign	(184)	(230)	(201)
Deferred (Expense) Benefit:
Foreign	44	31	7
Deferred income tax (expense) benefit	42	39	(2)
Withholding tax expense	(145)	(163)	(187)
U.S. domestic tax expense	(35)	11	(11)
Income tax (expense) benefit	$ (320)	$ (351)	$ (392)