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Pension and Savings Plans - Fair Value of Assets in the Master Trust by Asset (Details) - USD ($) $ in Millions | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020
--- | --- | --- | --- | ---
Level 3 |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined benefit plan, assets | $ 0.0 | $ 430.4 | $ 0.3 | $ 1.2
Pension Plan |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined benefit plan, assets | 116.0 | 583.3 | $ 772.4 |
Pension Plan | Fair Value, Inputs, Level 1, 2 and 3 |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined benefit plan, assets | 95.9 | 536.2 |  |
Pension Plan | Fair Value, Inputs, Level 1, 2 and 3 | Corporate bonds |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined benefit plan, assets | 66.7 | 67.2 |  |
Pension Plan | Fair Value, Inputs, Level 1, 2 and 3 | U.S. government securities |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined benefit plan, assets | 23.4 | 26.1 |  |
Pension Plan | Fair Value, Inputs, Level 1, 2 and 3 | International government securities |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined benefit plan, assets | 1.5 | 2.0 |  |
Pension Plan | Fair Value, Inputs, Level 1, 2 and 3 | Asset-backed securities |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined benefit plan, assets | 0.5 | 0.7 |  |
Pension Plan | Fair Value, Inputs, Level 1, 2 and 3 | Cash funds |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined benefit plan, assets | 3.8 | 9.8 |  |
Pension Plan | Fair Value, Inputs, Level 1, 2 and 3 | Real estate interests |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined benefit plan, assets |  | 0.3 |  |
Pension Plan | Fair Value, Inputs, Level 1, 2 and 3 | Group annuity contract |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined benefit plan, assets |  | 430.1 |  |
Pension Plan | Level 1 |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined benefit plan, assets | 23.1 | 33.1 |  |
Pension Plan | Level 1 | Corporate bonds |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined benefit plan, assets | 0.0 | 0.0 |  |
Pension Plan | Level 1 | U.S. government securities |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined benefit plan, assets | 19.3 | 23.3 |  |
Pension Plan | Level 1 | International government securities |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined benefit plan, assets | 0.0 | 0.0 |  |
Pension Plan | Level 1 | Asset-backed securities |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined benefit plan, assets | 0.0 | 0.0 |  |
Pension Plan | Level 1 | Cash funds |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined benefit plan, assets | 3.8 | 9.8 |  |
Pension Plan | Level 1 | Real estate interests |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined benefit plan, assets |  | 0.0 |  |
Pension Plan | Level 1 | Group annuity contract |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined benefit plan, assets |  | 0.0 |  |
Pension Plan | Level 2 |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined benefit plan, assets | 72.8 | 72.7 |  |
Pension Plan | Level 2 | Corporate bonds |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined benefit plan, assets | 66.7 | 67.2 |  |
Pension Plan | Level 2 | U.S. government securities |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined benefit plan, assets | 4.1 | 2.8 |  |
Pension Plan | Level 2 | International government securities |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined benefit plan, assets | 1.5 | 2.0 |  |
Pension Plan | Level 2 | Asset-backed securities |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined benefit plan, assets | 0.5 | 0.7 |  |
Pension Plan | Level 2 | Cash funds |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined benefit plan, assets | 0.0 | 0.0 |  |
Pension Plan | Level 2 | Real estate interests |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined benefit plan, assets |  | 0.0 |  |
Pension Plan | Level 2 | Group annuity contract |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined benefit plan, assets |  | 0.0 |  |
Pension Plan | Level 3 |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined benefit plan, assets | 0.0 | 430.4 |  |
Pension Plan | Level 3 | Corporate bonds |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined benefit plan, assets | 0.0 | 0.0 |  |
Pension Plan | Level 3 | U.S. government securities |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined benefit plan, assets | 0.0 | 0.0 |  |
Pension Plan | Level 3 | International government securities |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined benefit plan, assets | 0.0 | 0.0 |  |
Pension Plan | Level 3 | Asset-backed securities |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined benefit plan, assets | 0.0 | 0.0 |  |
Pension Plan | Level 3 | Cash funds |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined benefit plan, assets | 0.0 | 0.0 |  |
Pension Plan | Level 3 | Real estate interests |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined benefit plan, assets |  | 0.3 |  |
Pension Plan | Level 3 | Group annuity contract |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined benefit plan, assets |  | 430.1 |  |
Pension Plan | Fair Value Measured at Net Asset Value Per Share | Private mutual funds |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined benefit plan, assets | $ 20.1 | $ 47.1 |  |

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