Fair Value Measurements - Information about Assets and Liabilities Recorded at Fair Value (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Assets:
Investments	$ 10	$ 10
Foreign Exchange Contracts	35	18
Total Assets at Fair Value	45	28
Liabilities:
Foreign Exchange Contracts	3	7
Total Liabilities at Fair Value	3	7
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1)
Assets:
Investments	10	10
Foreign Exchange Contracts	0	0
Total Assets at Fair Value	10	10
Liabilities:
Foreign Exchange Contracts	0	0
Total Liabilities at Fair Value	0	0
Significant Other Observable Inputs (Level 2)
Assets:
Investments	0	0
Foreign Exchange Contracts	35	18
Total Assets at Fair Value	35	18
Liabilities:
Foreign Exchange Contracts	3	7
Total Liabilities at Fair Value	3	7
Significant Unobservable Inputs (Level 3)
Assets:
Investments	0	0
Foreign Exchange Contracts	0	0
Total Assets at Fair Value	0	0
Liabilities:
Foreign Exchange Contracts	0	0
Total Liabilities at Fair Value	$ 0	$ 0