Investments (Schedule of Investments) (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Fair Value, Equity And Cost Method Investments [Line Items]
Fair value method	$ 685	$ 198
Equity method	3,104	2,376
Cost method	2,765	2,770
Total Investments	6,554	5,344
Less: Current investments	33	97
Noncurrent Investments	6,521	5,247
Snap [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Fair value method	522	0
Other Fair Value Method Investments [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Fair value method	163	198
Atairos [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Equity method	2,233	1,601
Hulu [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Equity method	218	225
Other Equity Method Investments [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Equity method	653	550
AirTouch [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Cost method	1,606	1,599
BuzzFeed [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Cost method	400	400
Other Cost Method Investments [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Cost method	759	771
NBCUniversal Media LLC [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Fair value method	525	6
Equity method	633	561
Cost method	751	696
Total Investments	1,909	1,263
Less: Current investments	19	0
Noncurrent Investments	1,890	1,263
NBCUniversal Media LLC [Member] | Snap [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Fair value method	522	0
NBCUniversal Media LLC [Member] | Other Fair Value Method Investments [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Fair value method	3	6
NBCUniversal Media LLC [Member] | Hulu [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Equity method	218	225
NBCUniversal Media LLC [Member] | Other Equity Method Investments [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Equity method	415	336
NBCUniversal Media LLC [Member] | BuzzFeed [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Cost method	400	400
NBCUniversal Media LLC [Member] | Other Cost Method Investments [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Cost method	$ 351	$ 296