Fair Value Measurements - Gains and Losses on Derivative Financial Instruments (Details) - Fair Value, Measurements, Recurring - Foreign exchange forward contracts - Cost of sales - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Recorded into gain (loss)	$ 0	$ 0	$ 0
Recorded gains (loss) into AOCI net of tax	0	(4)	9
Less: reclassified from AOCI into gain (loss)	(1)	5	1
Gains and losses on derivative financial instruments	$ 1	$ (9)	$ 8