Stockholders' Equity - Accumulated Other Comprehensive Loss (Details) - 2.5% (€650 million) senior notes due 2022 - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Foreign currency translation gains (losses), net of tax	$ (7)	$ (15)
Foreign currency translation gains (losses), before tax	$ (9)	$ (19)
Debt, interest rate (percentage)	2.50%