Investments (Schedule of Investments) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Fair Value, Equity And Cost Method Investments [Line Items]
Fair value method	$ 591	$ 198
Equity method	3,351	2,376
Cost method	2,766	2,770
Total Investments	6,708	5,344
Less: Current investments	13	97
Noncurrent Investments	6,695	5,247
Snap [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Fair value method	427	0
Other Fair Value Method Investments [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Fair value method	164	198
Atairos [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Equity method	2,225	1,601
Hulu [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Equity method	255	225
Other Equity Method Investments [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Equity method	871	550
AirTouch [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Cost method	1,610	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	756	771
NBCUniversal Media LLC [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Fair value method	431	6
Equity method	687	561
Cost method	699	696
Total Investments	1,817	1,263
Noncurrent Investments	1,817	1,263
NBCUniversal Media LLC [Member] | Snap [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Fair value method	427	0
NBCUniversal Media LLC [Member] | Other Fair Value Method Investments [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Fair value method	4	6
NBCUniversal Media LLC [Member] | Hulu [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Equity method	255	225
NBCUniversal Media LLC [Member] | Other Equity Method Investments [Member]
Fair Value, Equity And Cost Method Investments [Line Items]
Equity method	432	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	$ 299	$ 296