Share-based Compensation and Employee Benefits (Schedule of Components of Accumulated Other Comprehensive (Loss) Income) (Details) - USD ($) $ in Millions |
Dec. 31, 2018 |
Dec. 31, 2017 |
---|---|---|
Pension Benefits [Member] | ||
Defined Benefit Plan Disclosure [Line Items] | ||
Unrecognized net actuarial (loss) gain | $ (653) | $ (635) |
Unrecognized prior service (cost) credit | (3) | (4) |
Accumulated other comprehensive (loss) income | (656) | (639) |
OPEB [Member] | ||
Defined Benefit Plan Disclosure [Line Items] | ||
Unrecognized net actuarial (loss) gain | 117 | 88 |
Unrecognized prior service (cost) credit | 14 | 17 |
Accumulated other comprehensive (loss) income | $ 131 | $ 105 |