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Postretirement Health Care and Life Insurance Benefits Details - Textual (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Accumulated Other Comprehensive Income (Loss), Net of Tax $ 189.6 $ 242.5  
Defined Benefit Plan, Equity Securities      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Asset allocation strategy for the Non-Represented trust 30.00%    
Fixed Income Securities      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Asset allocation strategy for the Non-Represented trust 70.00%    
Postretirement Health Care and Life Insurance Benefits      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Average remaining service period (in years) 12 years 13 years  
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment   $ 139.5  
Expected long-term return on plan assets 5.75% 5.75% 5.75%
Accumulated postretirement benefit obligation at end of period $ 178.0 $ 189.9 $ 258.7
Defined benefit plan, expected amortization of prior service cost (credit), next fiscal year 53.0    
Accumulated Other Comprehensive Income (Loss), Net of Tax $ 117.4    
Postretirement Health Care and Life Insurance Benefits | Retirement Plan Amendment Two      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Average remaining service period (in years) 7 years 6 months 8 years 6 months  
Accumulated Other Comprehensive Income (Loss), Net of Tax $ 7.8    
Postretirement Health Care and Life Insurance Benefits | Retirement Plan Amendment One      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Average remaining service period (in years) 1 year 10 months 24 days 2 years 10 months 24 days  
Accumulated Other Comprehensive Income (Loss), Net of Tax $ 63.5    
Postretirement Health Care and Life Insurance Benefits | Retirement Plan 2018 Amendment      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Average remaining service period (in years) 10 months 24 days 1 year 10 months 24 days  
Accumulated Other Comprehensive Income (Loss), Net of Tax $ 0.9    
Postretirement Health Care and Life Insurance Benefits | Maximum      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Expected long-term return on plan assets 5.75%