Income Taxes (Details) - USD ($) $ in Millions  | 
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2019  | 
Jun. 30, 2018  | 
Jun. 30, 2019  | 
Jun. 30, 2018  | 
|
| Income Tax Disclosure [Abstract] | ||||
| Income tax expense (benefit) | $ 0 | $ (3) | $ 3 | $ 12 | 
| U.S. corporate income tax rate | 21.00% | 21.00% | 21.00% | 21.00% | 
| X | ||||||||||
- Definition Percentage of domestic federal statutory tax rate applicable to pretax income (loss). Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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| X | ||||||||||
- References No definition available. 
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| X | ||||||||||
- Definition Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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