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Commitments and Contingent Liabilities (Black Lung Benefit Liabilities) (Details)
$ in Millions
 12 Months Ended
Feb. 21, 2020
USD ($)
Dec. 31, 2022
USD ($)
claim
Dec. 31, 2021
USD ($)
claim
Dec. 31, 2020
USD ($)
Dec. 31, 2013
USD ($)
Defined Benefit Plan Disclosure [Line Items]          
Accrual for black lung   $ 5.9 $ 5.4    
Black Lung Benefit          
Defined Benefit Plan Disclosure [Line Items]          
Discount rate   4.90% 2.40%    
Active claims | claim   332 332    
Total black lung liability (dollars in millions)   $ 58.1 $ 63.3    
Increase in black lung expense   1.1      
Payments   5.0 4.4 $ 6.0  
(Benefit) expense   (0.2) $ 3.1 $ 15.4  
Uninsured Risk          
Defined Benefit Plan Disclosure [Line Items]          
Payments $ 40.4 $ 8.4     $ 8.4