Income Taxes (Details) - USD ($) $ in Millions |
1 Months Ended | 3 Months Ended | 9 Months Ended | |||
|---|---|---|---|---|---|---|
Mar. 31, 2016 |
Sep. 30, 2016 |
Jun. 30, 2016 |
Sep. 30, 2015 |
Sep. 30, 2016 |
Sep. 30, 2015 |
|
| Income Taxes (Textuals) [Abstract] | ||||||
| Effective tax rate (percent) | 39.80% | 36.40% | ||||
| Impairment | $ 800 | $ 800 | ||||
| Non-deductible expense from impairment of goodwill | 433 | |||||
| Unrecognized tax benefits from lapse of statute of limitations | 54 | |||||
| Unrecognized tax benefits that would impact effective tax rate | $ 15 | $ 15 | ||||
| FES | ||||||
| Income Taxes (Textuals) [Abstract] | ||||||
| Effective tax rate (percent) | 58.30% | 36.80% | 1.80% | 40.00% | ||
| Impairment | 23 | |||||
| Non-deductible expense from impairment of goodwill | $ 23 | |||||
| State and Local Jurisdiction | ||||||
| Income Taxes (Textuals) [Abstract] | ||||||
| Valuation allowance | $ 159 | |||||
| Increase resulting from settlements with taxing authorities | $ 69 | |||||
| State and Local Jurisdiction | FES | ||||||
| Income Taxes (Textuals) [Abstract] | ||||||
| Valuation allowance | $ 65 | $ 65 | ||||