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Postretirement Health Care and Life Insurance Benefits - Net Periodic Postretirement Benefit Cost (Details) - USD ($) $ in Millions | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020 | Jan. 01, 2023 | Jan. 01, 2022
Retirement Benefits [Abstract] |  |  |  |  |
Average remaining service period (in years) |  |  |  | 1 year 10 months 24 days | 2 years 10 months 24 days
Postretirement Health Care and Life Insurance Benefits |  |  |  |  |
Retirement Benefits [Abstract] |  |  |  |  |
Average remaining service period (in years) |  |  |  | 13 years | 14 years
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Service cost for benefits earned | $ 0.8 | $ 1.0 | $ 3.8 |  |
Interest cost on accumulated postretirement benefit obligation | 7.0 | 10.5 | 20.2 |  |
Expected return on plan assets | (0.8) | (1.0) | (1.5) |  |
Amortization of prior service credit | (53.8) | (46.4) | (17.3) |  |
Net actuarial (gain) loss | (51.2) | (54.5) | 16.5 |  |
Net periodic postretirement benefit (credit) cost | $ (98.0) | $ (90.4) | $ 21.7 |  |

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