Retirement Benefits (Summary Of Estimated Amortizable Amounts From Regulatory Assets and Accumulated OCI Into Net Periodic Benefit Cost) (Details) $ in Millions |
12 Months Ended |
|---|---|
|
Dec. 31, 2018
USD ($)
| |
| Pension Benefits | |
| Defined Benefit Plan Disclosure [Line Items] | |
| Prior service credit | $ (1) |
| Net actuarial (gain) loss | 24 |
| Net actuarial loss | 2 |
| Net periodic benefit cost | 25 |
| Postretirement Benefits | |
| Defined Benefit Plan Disclosure [Line Items] | |
| Prior service credit | (5) |
| Net actuarial (gain) loss | (15) |
| Net actuarial loss | 0 |
| Net periodic benefit cost | $ (20) |