Stock-based Compensation - Options Vested and Expected to Vest (Parenthetical) (Details) - Long-term incentive and director compensation plans - Employee Stock Option shares in Millions, $ in Millions |
Dec. 31, 2015
USD ($)
shares
|
|---|---|
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |
| Expected forfeitures, effects of which are included (in shares) | shares | 1 |
| Aggregate intrinsic value of stock options outstanding, excluding the effects of expected forfeitures | $ | $ 986 |