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Pension and Other Postretirement Benefits (Narrative) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items] |  |  |
COVID-19 related regulatory asset | $ 2,580.8 | $ 2,492.2 |
Pension Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Accumulated Benefit Obligation | 1,416.8 | 1,834.4 |
Funded status of plan | 4.6 | (129.3) |
Employer contributions | 2.7 | 4.0 |
Settlement loss | 12.4 | 11.4 | $ 10.5
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Remeasurement due to Settlement | 5.7 | $ 4.0 |
Expected contribution | $ 2.6 |  |
Expected return on plan assets | 4.80% | 5.20% | 5.70%
Other Postretirement Benefits |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Funded status of plan | $ 224.1 | $ 262.5 |
Employer contributions | 21.3 | 19.8 |
Settlement loss | 0.0 | $ 0.0 | $ 1.5
Expected contribution | $ 23.7 |  |
Expected return on plan assets | 5.72% | 5.50% | 5.67%
Unrecognized Pension Benefit And Other Postretirement Benefit Costs |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
COVID-19 related regulatory asset | $ 607.5 | $ 512.1 |

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- Definition Amount of actuarial present value of benefits attributed to employee service rendered, excluding assumptions about future compensation level. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (e) -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
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- Definition Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine net periodic benefit cost of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(3) -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 8 -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e2919-114920 + Details
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- Definition Amount of (increase) decrease to benefit obligation of defined benefit plan from remeasurement due to settlement. Excludes decrease to benefit obligation for settlement payment. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(10) -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
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