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Pension and Other Postretirement Benefits (Schedule Of Pension Plan And Postretirement Plan Asset Mix) (Details) - USD ($) $ in Millions | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
--- | --- | --- | ---
Fair Value, Inputs, Level 1, 2 and 3 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 2,404.1 | $ 2,342.3 |
Pension Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Percentage of total asset | 100.00% | 100.00% |
Pension Plan | Fair Value, Inputs, Level 1, 2 and 3 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 2,117.7 | $ 2,080.9 | $ 1,867.7
Other Postretirement Benefits |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Percentage of total asset | 100.00% | 100.00% |
Other Postretirement Benefits | Fair Value, Inputs, Level 1, 2 and 3 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 286.4 | $ 261.4 | $ 216.3
Domestic Equities | Pension Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 446.3 | $ 446.4 |
Percentage of total asset | 21.00% | 21.50% |
Domestic Equities | Other Postretirement Benefits |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 108.8 | $ 93.8 |
Percentage of total asset | 38.00% | 35.90% |
International Equities | Pension Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 230.1 | $ 205.0 |
Percentage of total asset | 10.90% | 9.90% |
International Equities | Other Postretirement Benefits |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 48.2 | $ 40.7 |
Percentage of total asset | 16.80% | 15.60% |
Fixed Income | Pension Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 1,291.2 | $ 1,337.2 |
Percentage of total asset | 61.00% | 64.20% |
Fixed Income | Other Postretirement Benefits |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 122.0 | $ 119.5 |
Percentage of total asset | 42.60% | 45.70% |
Real Estate | Pension Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 52.9 | $ 53.9 |
Percentage of total asset | 2.50% | 2.60% |
Real Estate | Other Postretirement Benefits |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 0.0 | $ 0.0 |
Percentage of total asset | 0.00% | 0.00% |
Cash/Other [Member] | Pension Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 97.2 | $ 38.4 |
Percentage of total asset | 4.60% | 1.80% |
Cash/Other [Member] | Other Postretirement Benefits |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 7.4 | $ 7.4 |
Percentage of total asset | 2.60% | 2.80% |
Commingled Funds | Short-Term Money Markets | Pension Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 78.8 | $ 14.8 |
Commingled Funds | Short-Term Money Markets | Other Postretirement Benefits |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Amount | 7.6 | 7.7 |
Commingled Funds | International Equities | Pension Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Amount | 176.8 | 148.1 |
Commingled Funds | International Equities | Other Postretirement Benefits |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Amount | 24.1 | 20.1 |
Commingled Funds | Fixed Income | Pension Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Amount | 337.6 | 351.8 |
Commingled Funds | United States Equities | Pension Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Amount | 279.7 | 305.9 |
Commingled Funds | United States Equities | Other Postretirement Benefits |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 14.0 | $ 12.1 |

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