Derivatives and Hedging - Offsetting of financial liabilities and derivative liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Other Current Liabilities
Derivative [Line Items]
Gross Amounts of Recognized Liabilities	$ 3	$ 6
Other Noncurrent Liabilities
Derivative [Line Items]
Gross Amounts of Recognized Liabilities	3	7
Designated as Hedging Instrument | Gross Foreign exchange contracts
Derivative [Line Items]
Gross Amounts of Recognized Liabilities	$ 3	$ 12