Other Comprehensive Income (Component of Other Comprehensive Income) (Details) - USD ($) $ in Millions  | 
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2019  | 
Dec. 31, 2018  | 
Dec. 31, 2017  | 
|
| Other Comprehensive Income (Loss), Net of Tax [Abstract] | |||
| Foreign currency translation adjustments before tax | $ 0 | $ (49) | $ 156 | 
| Tax (expense) benefit from foreign currency translation gain (loss) | 1 | 1 | (21) | 
| Foreign currency translation adjustments, net-of-tax | $ 1 | $ (48) | $ 135 | 
| X | ||||||||||
- Definition Amount after tax, before reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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| X | ||||||||||
- Definition Amount before tax and reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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| X | ||||||||||
- Definition Amount of tax expense (benefit), before reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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| X | ||||||||||
- References No definition available. 
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