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Pension And Other Postretirement Benefits (Narrative) (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2021 | Mar. 31, 2021 | Jun. 30, 2020 | Jun. 30, 2021 | Jun. 30, 2020
Pension Plan |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Employer contributions |  |  |  | $ 2.0 |
Defined Benefit Plan, Pension Asset, (Increase)Decrease For Remeasurement Due To Settlement |  | $ (5.8) |  |  |
Change in Regulatory Assets Due to Interim Measurement |  | 2.1 |  |  |
Change in Accumulated Other Comprehensive Income Due to Interim Measurement |  | 0.4 |  |  |
Change to Defined Benefit Plan Net Periodic Costs Due to Interim Measurement |  | 4.0 |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement and Curtailment | $ 3.3 | $ 3.3 | $ 0.0 | 6.6 | $ 0.0
Other Postretirement Benefit Plan |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Employer contributions |  |  |  | 10.2 |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement and Curtailment | $ 0.0 |  | $ 0.0 | $ 0.0 | $ 0.0

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