Income Taxes (Narrative) (Details) - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2016 |
Sep. 30, 2015 |
Sep. 30, 2016 |
Sep. 30, 2015 |
|
| Income Tax Disclosure [Abstract] | ||||
| Provision (benefit) for income taxes | $ 30 | $ (78) | $ 25 | $ (63) |
| Effective income tax rate | 13.00% | 73.00% | 9.00% | 94.00% |
| Increase in tax benefits | $ (108) | $ (88) | ||