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Retirement Plans and Other Postretirement Benefits - Contributions and Plan Assets (Details) - Pension Plan - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Contributions to employees' accounts | $ 0.0 | $ 0.0 | $ 0.0 |
Total assets at the end of the year | 13.6 | 19.8 | 22.0 | $ 23.2
Qualified Plan | 401(k) plan |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Contributions to employees' accounts | 9.4 | 8.2 | 8.2 |
Total assets at the end of the year | 207.1 | 246.9 | 228.4 |
Nonqualified Plan |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Total assets at the end of the year | 0.0 | 0.0 | 0.0 |
Contributions to employees' accounts | $ 0.1 | $ 0.1 | $ 0.1 |

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