Derivative Instruments - Gain (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Total net (loss) gain from derivative instruments not designated as hedges	$ (8)	$ (7)	$ 14
Derivative instruments not designated as hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Total net (loss) gain from derivative instruments not designated as hedges	(22)	5	15
Foreign exchange contracts | Foreign exchange (loss) gain | Derivative instruments not designated as hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Total net (loss) gain from derivative instruments not designated as hedges	(24)	5	11
Forward interest rate swaps | Interest expense and other, net | Derivative instruments not designated as hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Total net (loss) gain from derivative instruments not designated as hedges	$ 2	$ 0	$ 4