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Pension and Other Postretirement Benefits (Schedule of Net Asset Value Per Share) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2023 | Dec. 31, 2022
Defined Benefit Plan Disclosure [Line Items] |  |
Net Asset Value Excluded From Fair Value By Input | $ 607.8 | $ 607.5
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments | 11.6 | 11.6
Private Equity and Real Estate Limited Partnerships |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Net Asset Value Excluded From Fair Value By Input | 10.1 | 13.7
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments | 11.6 | 11.6
Commingled Funds | Short-Term Money Markets |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Net Asset Value Excluded From Fair Value By Input | 70.5 | 63.6
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments | $ 0.0 | $ 0.0
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Frequency | Daily | Daily
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Notice Period | 1 day | 1 day
Commingled Funds | United States Equities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Net Asset Value Excluded From Fair Value By Input | $ 159.9 | $ 144.4
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments | $ 0.0 | $ 0.0
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Frequency | Daily | Daily
Commingled Funds | United States Equities | Maximum |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Notice Period | 5 days | 5 days
Commingled Funds | United States Equities | Minimum |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Notice Period | 1 day | 1 day
Commingled Funds | International Equities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Net Asset Value Excluded From Fair Value By Input | $ 125.1 | $ 109.9
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments | $ 0.0 | $ 0.0
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Frequency | Monthly | Monthly
Commingled Funds | International Equities | Maximum |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Notice Period | 30 days | 30 days
Commingled Funds | International Equities | Minimum |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Notice Period | 10 days | 10 days
Commingled Funds | Fixed Income Funds |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Net Asset Value Excluded From Fair Value By Input | $ 242.2 | $ 275.9
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments | $ 0.0 | $ 0.0
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Frequency | Daily | Daily
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Notice Period | 3 days | 3 days

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- Definition States the frequency (for example, annually, semi-annually, quarterly) with which the entity can redeem its investment, or portion thereof, for each of those certain investments for which net asset value per share is calculated (including by unit, membership interest, or other equity (ownership interest) unit measure) (alternative investments), by major category. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 6A -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482106/820-10-50-6A + Details
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