Investments (Cost Method Investments) (Details) $ in Millions |
Sep. 30, 2015
USD ($)
|
|---|---|
| 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 |
| Fair value of redeemable preferred shares | $ 1,700 |