Investments (Cost Method Investments) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Vox Media [Member]
Cost Method Investments,Original Cost	$ 200
Vox Media [Member] | NBCUniversal Media LLC [Member]
Cost Method Investments,Original Cost	200
BuzzFeed [Member]
Cost Method Investments,Original Cost	200
BuzzFeed [Member] | NBCUniversal Media LLC [Member]
Cost Method Investments,Original Cost	200
Air Touch [Member]
Fair value of AirTouch preferred stock related to redeemable preferred shares	1,700	$ 1,700
Aggregate redemption value	1,750
Carrying amount of redeemable preferred stock	1,600	1,600
Fair value of redeemable preferred shares	1,700	1,700
Nonredeemable preferred stock	100	$ 100
Preferred Shares Redeemable in April 2020 [Member]
Aggregate redemption value	$ 1,650