| Income Taxes (Details) - USD ($) $ in Millions | 12 Months Ended | ||
|---|---|---|---|
| Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015 | |
| Income Tax Expense (Benefit) [Abstract] | |||
| Federal | $ 38 | $ (39) | $ (17) | 
| State and local | (30) | (29) | (17) | 
| Foreign | (9) | (1) | |
| Current Income Tax Expense (Benefit) | (1) | (68) | (35) | 
| Federal | 578 | (388) | (145) | 
| State and local | (21) | (39) | (30) | 
| Foreign | 507 | ||
| Deferred Income Tax Expense (Benefit), Total | 1,064 | (427) | (175) | 
| Income tax benefit (expense) | $ 1,063 | $ (495) | $ (210) | 
| X | ||||||||||
| 
- References No definition available. 
 | 
| X | ||||||||||
| 
- Definition Amount of current federal tax expense (benefit) pertaining to income (loss) from continuing operations. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
 | 
| X | ||||||||||
| 
- Definition Amount of current foreign income tax expense (benefit) pertaining to income (loss) from continuing operations. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
 | 
| X | ||||||||||
| 
- Definition Amount of current income tax expense (benefit) pertaining to taxable income (loss) from continuing operations. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
 | 
| X | ||||||||||
| 
- Definition Amount of current state and local tax expense (benefit) pertaining to income (loss) from continuing operations. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
 | 
| X | ||||||||||
| 
- Definition Amount of deferred federal income tax expense (benefit) pertaining to income (loss) from continuing operations. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
 | 
| X | ||||||||||
| 
- Definition Amount of deferred foreign income tax expense (benefit) pertaining to income (loss) from continuing operations. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
 | 
| X | ||||||||||
| 
- Definition Amount of deferred income tax expense (benefit) pertaining to income (loss) from continuing operations. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
 | 
| X | ||||||||||
| 
- Definition Amount of deferred state and local tax expense (benefit) pertaining to income (loss) from continuing operations. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
 | 
| 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/presentationRef 
 |