Basis of Presentation and Significant Accounting Policies - Foreign Currency Translation and Transactions (Details) - USD ($) $ in Millions |
12 Months Ended | ||
---|---|---|---|
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
|
Derivative Instruments and Hedging Activities Disclosures [Line Items] | |||
Total foreign currency loss (gain) | $ 3 | $ 58 | $ (40) |
Unrealized foreign currency option and forward contracts (gains) losses | |||
Derivative Instruments and Hedging Activities Disclosures [Line Items] | |||
Total foreign currency loss (gain) | (20) | 49 | (40) |
Realized foreign currency option and forward contracts losses (gains) | |||
Derivative Instruments and Hedging Activities Disclosures [Line Items] | |||
Total foreign currency loss (gain) | 16 | 15 | (3) |
Foreign currency transaction and remeasurement losses (gains) | |||
Derivative Instruments and Hedging Activities Disclosures [Line Items] | |||
Total foreign currency loss (gain) | $ 7 | $ (6) | $ 3 |