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Pension and Other Postretirement Benefits (Schedule Of Pension Plan And Postretirement Plan Asset Mix) (Details) - USD ($) $ in Millions | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
--- | --- | --- | ---
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 2,084.1 |  | $ 2,422.5 |  |
Pension Plan |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 1,867.7 |  | $ 2,160.0 |  | $ 1,750.9
Percentage of total asset | 100.00% |  | 100.00% |  |
Other Postretirement Benefits |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 216.3 |  | $ 262.5 |  | $ 231.4
Percentage of total asset | 100.00% |  | 100.00% |  |
Domestic Equities | Pension Plan |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 355.5 |  | $ 698.2 |  |
Percentage of total asset | 19.00% |  | 32.30% |  |
Domestic Equities | Other Postretirement Benefits |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 78.8 |  | $ 96.0 |  |
Percentage of total asset | 36.40% |  | 36.60% |  |
International Equities | Pension Plan |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 165.5 |  | $ 351.0 |  |
Percentage of total asset | 8.90% |  | 16.20% |  |
International Equities | Other Postretirement Benefits |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 17.5 |  | $ 39.8 |  |
Percentage of total asset | 8.10% |  | 15.20% |  |
Fixed Income | Pension Plan |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 1,241.9 |  | $ 977.6 |  |
Percentage of total asset | 66.50% |  | 45.30% |  |
Fixed Income | Other Postretirement Benefits |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 115.1 |  | $ 117.5 |  |
Percentage of total asset | 53.20% |  | 44.80% |  |
Real Estate | Pension Plan |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 52.7 |  | $ 49.9 |  |
Percentage of total asset | 2.80% |  | 2.30% |  |
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 | $ 52.1 |  | $ 83.3 |  |
Percentage of total asset | 2.80% |  | 3.90% |  |
Cash/Other [Member] | Other Postretirement Benefits |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 4.9 |  | $ 9.2 |  |
Percentage of total asset | 2.30% |  | 3.40% |  |
Commingled Funds | Short-Term Money Markets | Pension Plan |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 18.3 | [1] | $ 34.1 | [2] |
Commingled Funds | Short-Term Money Markets | Other Postretirement Benefits |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Defined Benefit Plan, Plan Assets, Amount | 5.2 | [1] | 9.4 | [2] |
Commingled Funds | International Equities | Pension Plan |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Defined Benefit Plan, Plan Assets, Amount | 122.3 | [1] | 265.1 | [2] |
Commingled Funds | Fixed Income | Pension Plan |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Defined Benefit Plan, Plan Assets, Amount | 365.7 | [1] | 244.9 | [2] |
Commingled Funds | United States Equities | Pension Plan |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Defined Benefit Plan, Plan Assets, Amount | 245.2 | [1] | 466.6 | [2] |
Commingled Funds | United States Equities | Other Postretirement Benefits |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 10.4 | [1] | $ 12.2 | [2] |
[1] | This class of investments is measured at fair value using the net asset value per share and has not been classified in the fair value hierarchy.
[2] | This class of investments is measured at fair value using the net asset value per share and has not been classified in the fair value hierarchy.

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