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Retirement Benefits (Details 7) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020
Accumulated Other Comprehensive Income (Loss), before Tax [Roll Forward] |  |  |
Amortization of net actuarial loss | $ 76.7 | $ 89.5 | $ 85.3
Amortization to net income (loss) of net prior service credits | (0.5) | (1.8) | (3.1)
Settlement loss (gain) included in net income (loss) | 29.5 | (21.9) | 0.0
Net gain (loss) arising during the period | 155.0 | 155.9 | (128.4)
Pension Benefits [Member] |  |  |
Accumulated Other Comprehensive Income (Loss), before Tax [Roll Forward] |  |  |
Beginning of year accumulated other comprehensive loss | (1,376.5) | (1,600.3) |
Amortization of net actuarial loss | 63.5 | 75.6 |
Amortization to net income (loss) of net prior service credits | 0.4 | 0.6 |
Settlement loss (gain) included in net income (loss) | 29.5 | 0.0 |
Net gain (loss) arising during the period | 101.9 | 147.6 |
End of year accumulated other comprehensive loss | (1,181.2) | (1,376.5) | (1,600.3)
Net change in accumulated other comprehensive loss | 195.3 | 223.8 |
Other Postretirement Benefits |  |  |
Accumulated Other Comprehensive Income (Loss), before Tax [Roll Forward] |  |  |
Beginning of year accumulated other comprehensive loss | (121.2) | (119.1) |
Amortization of net actuarial loss | 13.2 | 13.9 |
Amortization to net income (loss) of net prior service credits | (0.9) | (2.4) |
Settlement loss (gain) included in net income (loss) | 0.0 | (21.9) |
Net gain (loss) arising during the period | 53.1 | 8.3 |
End of year accumulated other comprehensive loss | (55.8) | (121.2) | $ (119.1)
Net change in accumulated other comprehensive loss | $ 65.4 | $ (2.1) |

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