Income Taxes - Reconciliation of Beginning and Ending Balances of Total Amounts of Gross Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	$ 50	$ 54	$ 56
Additions to prior years' tax positions	1	0	0
Reductions to prior years' tax positions	0	0	(1)
Additions to current year tax positions	7	3	4
Reductions in tax positions due to lapse of statutory limitations	(1)	(5)	(5)
Foreign currency translation	0	(2)	0
Ending balance	$ 57	$ 50	$ 54