Income Taxes (Operating and Capital Loss Carryforwards) (Details) - USD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
|
| Operating Loss Carryforwards [Line Items] | |||
| Alternative minimum tax credits | $ 0 | $ 66 | |
| Effective tax rate | (22.20%) | 23.40% | 26.70% |
| Federal | |||
| Operating Loss Carryforwards [Line Items] | |||
| Operating loss carryforwards | $ 0 | $ 0 | |
| State and local | |||
| Operating Loss Carryforwards [Line Items] | |||
| Operating loss carryforwards | 5,806 | 4,201 | |
| Foreign operations | |||
| Operating Loss Carryforwards [Line Items] | |||
| Operating loss carryforwards | 58 | $ 45 | |
| Foreign operations | Operating loss expiring between 2018 and 2035 | |||
| Operating Loss Carryforwards [Line Items] | |||
| Operating loss carryforwards | 16 | ||
| Foreign operations | Operating loss unlimited carryforward | |||
| Operating Loss Carryforwards [Line Items] | |||
| Operating loss carryforwards | $ 42 | ||