Financial Instruments - Derivatives and hedging (Details) - USD ($) $ in Millions |
Sep. 30, 2017 |
Dec. 31, 2016 |
---|---|---|
Derivatives, Fair Value [Line Items] | ||
Assets, fair value | $ 212 | $ 318 |
Liabilities, fair value | (196) | (375) |
Currency exchange contracts | Designated as hedging instrument | ||
Derivatives, Fair Value [Line Items] | ||
Assets, fair value | 10 | 2 |
Liabilities, fair value | 0 | (9) |
Currency exchange contracts | Not designated as hedging instrument | ||
Derivatives, Fair Value [Line Items] | ||
Assets, fair value | 202 | 316 |
Liabilities, fair value | $ (196) | $ (366) |