Income Taxes Unrecognized tax benefit (Details) - USD ($) $ in Millions |
12 Months Ended | |
|---|---|---|
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items] | ||
| Unrecognized Tax Benefits | $ 36 | $ 51 |
| Unrecognized Tax Benefits, Increases Resulting from Current Period Tax Positions | 4 | |
| Unrecognized Tax Benefits, Increases Resulting from Prior Period Tax Positions | (9) | $ 3 |
| Unrecognized Tax Benefits, Decreases Resulting from Foreign Currency Translation | $ (1) | |