Basis of Presentation and Significant Accounting Policies - Foreign Currency Translation and Transactions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total foreign currency loss	$ 9	$ 3	$ 58
Unrealized foreign currency option and forward contracts losses (gains)
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total foreign currency loss	9	(20)	49
Realized foreign currency option and forward contracts losses
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total foreign currency loss	0	16	15
Foreign currency transaction and remeasurement losses (gains)
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total foreign currency loss	$ 0	$ 7	$ (6)