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Pension and Other Postretirement Benefits (Schedule Of Reconciliation Of The Plans Funded Status And Amounts Reflected) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items] |  |  |
Noncurrent liabilities | $ (261.5) | $ (303.5) |
COVID-19 related regulatory asset | 2,492.2 | 1,930.5 |
Regulatory Liabilities | 1,980.0 | 2,065.5 |
Unrecognized Pension Benefit And Other Postretirement Benefit Costs |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Regulatory Liabilities | 0.0 | 0.0 |
Unrecognized Pension Benefit And Other Postretirement Benefit Costs |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
COVID-19 related regulatory asset | 512.1 | 583.3 |
Fair Value, Inputs, Level 1, 2 and 3 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets at beginning of year | 2,404.1 |  |
Fair value of plan assets at end of year | 2,275.4 | 2,404.1 |
Pension Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Benefit obligation at beginning of year | 2,058.4 | 2,130.5 |
Service cost | 30.2 | 32.0 | $ 29.2
Interest cost | 31.4 | 51.6 | 72.3
Plan participants' contributions | 0.0 | 0.0 |
Plan amendments | 0.0 | 0.0 |
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) | (68.7) | 140.1 |
Defined Benefit Plan, Benefit Obligation, Benefits Paid | 198.9 | 174.5 |
Estimated benefits paid by incurred subsidy | 0.0 | 0.0 |
Spinoff to Eversource | 0.0 | (121.3) |
Projected benefit obligation at end of year | 1,852.4 | 2,058.4 | 2,130.5
Actual return on plan assets | 58.9 | 329.9 |
Employer contributions | 4.0 | 2.9 |
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant | 0.0 | 0.0 |
Benefits paid | (198.9) | (174.6) |
Spinoff to Eversource | 0.0 | 121.4 |
Defined Benefit Plan, Funded (Unfunded) Status of Plan | 129.3 | 59.3 |
Noncurrent assets | 159.3 | 91.4 |
Current liabilities | (2.8) | (2.9) |
Noncurrent liabilities | (27.2) | (29.2) |
Net amount recognized at end of year | 129.3 | 59.3 |
Unrecognized prior service cost | 0.3 | 0.3 |
Unrecognized actuarial loss | 438.0 | 497.2 |
Defined Benefit Plan Amounts Recognized In Other Comprehensive Income Or Regulatory Asset Or Liability | 438.3 | 497.5 |
Pension Plan | Underfunded Plan [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Benefit obligation at beginning of year | 2,026.3 |  |
Projected benefit obligation at end of year | 1,822.4 | 2,026.3 |
Fair value of plan assets at beginning of year | 2,117.7 |  |
Fair value of plan assets at end of year | 1,981.7 | 2,117.7 |
Defined Benefit Plan, Funded (Unfunded) Status of Plan | 159.3 | 91.4 |
Pension Plan | Fair Value, Inputs, Level 1, 2 and 3 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets at beginning of year | 2,117.7 | 2,080.9 |
Fair value of plan assets at end of year | 1,981.7 | 2,117.7 | 2,080.9
Other Postretirement Benefits |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Benefit obligation at beginning of year | 590.8 | 576.5 |
Service cost | 6.2 | 6.6 | 5.1
Interest cost | 9.9 | 15.4 | 19.2
Plan participants' contributions | 4.2 | 4.1 |
Plan amendments | 0.1 | 0.0 |
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) | (14.8) | 24.8 |
Defined Benefit Plan, Benefit Obligation, Benefits Paid | 40.6 | 37.0 |
Estimated benefits paid by incurred subsidy | 0.4 | 0.4 |
Spinoff to Eversource | 0.0 | 0.0 |
Projected benefit obligation at end of year | 556.2 | 590.8 | 576.5
Actual return on plan assets | 23.9 | 36.3 |
Employer contributions | 19.8 | 21.6 |
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant | 4.2 | 4.1 |
Benefits paid | (40.6) | (37.0) |
Spinoff to Eversource | 0.0 | 0.0 |
Defined Benefit Plan, Funded (Unfunded) Status of Plan | (262.5) | (304.4) |
Noncurrent assets | 0.0 | 0.0 |
Current liabilities | (1.0) | (0.9) |
Net amount recognized at end of year | (262.5) | (304.4) |
Unrecognized prior service cost | (7.8) | (10.1) |
Unrecognized actuarial loss | 88.5 | 116.4 |
Defined Benefit Plan Amounts Recognized In Other Comprehensive Income Or Regulatory Asset Or Liability | 80.7 | 106.3 |
Other Postretirement Benefits | Fair Value, Inputs, Level 1, 2 and 3 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets at beginning of year | 286.4 | 261.4 |
Fair value of plan assets at end of year | $ 293.7 | $ 286.4 | $ 261.4

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