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Employee Benefits - Fair Value of Plan Assets (Details) - USD ($) $ in Millions | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
--- | --- | --- | ---
Salaried VEBA |  |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 43.1 | $ 42.4 | $ 59.2
Pension Plans |  |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Amount | 20.5 | 14.9 | $ 9.8
Level 1 | Fair Value, Measurements, Recurring |  |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Amount | 73.6 | 67.1 |
Deferred Compensation Plan Assets | 11.1 | 9.8 |
Level 1 | Postretirement Health Coverage | Salaried VEBA | Equity Funds | Fair Value, Measurements, Recurring |  |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Amount | 25.5 | 27.4 |
Level 1 | Postretirement Health Coverage | Salaried VEBA | Fixed Income Funds | Fair Value, Measurements, Recurring |  |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Amount | 16.5 | 15.0 |
Level 1 | Pension Plans | Equity Funds | Fair Value, Measurements, Recurring |  |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Amount | 7.1 | 4.1 |
Level 1 | Pension Plans | Fixed Income Funds | Fair Value, Measurements, Recurring |  |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Amount | 4.1 | 2.6 |
Level 1 | Pension Plans | Diversified Investment Funds In Registered Investment Companies | Fair Value, Measurements, Recurring |  |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 9.3 | $ 8.2 |

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