Annual report pursuant to Section 13 and 15(d)

Postretirement Benefits Pretax Activity in Accumulated Other Comprehensive Income (Loss) (Details)

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Postretirement Benefits Pretax Activity in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
Prior Service Costs (Credits) [Abstract]      
Amount Recognized as Component of Net Benefit Costs [1] $ (0.2) $ (0.7) $ (0.7)
Net Actuarial Losses [Abstract]      
Amount Recognized as Component of Net Benefit Costs [1] $ 1.1 1.1 6.2
Percentage of Benefit Obligation or Market Value of Assets, Over Which Actuarial Gains and Losses are Subject to Amortization (in Hundredths) 10.00%    
Pension Plans [Member]      
Prior Service Costs (Credits) [Abstract]      
Beginning Balance $ 0.0 0.0  
Amount Recognized as Component of Net Benefit Costs 0.0 0.0  
Ending Balance 0.0 0.0 0.0
Net Actuarial Losses [Abstract]      
Beginning Balance 13.5 12.0  
Actuarial (Gains) Losses Arising During the Period 0.0 2.1  
Amount Recognized as Component of Net Benefit Costs (0.8) (0.6)  
Ending Balance 12.7 13.5 12.0
Total 12.7 13.5  
Other Postretirement Benefit Plans [Member]      
Prior Service Costs (Credits) [Abstract]      
Beginning Balance (7.4) (8.1)  
Amount Recognized as Component of Net Benefit Costs 0.0 0.7  
Ending Balance (7.4) (7.4) (8.1)
Net Actuarial Losses [Abstract]      
Beginning Balance 0.4 (1.4)  
Actuarial (Gains) Losses Arising During the Period (2.3) 1.8  
Amount Recognized as Component of Net Benefit Costs 0.0 0.0  
Ending Balance (1.9) 0.4 $ (1.4)
Total $ (9.3) $ (7.0)  
[1] (A)    These Accumulated other comprehensive loss components are included in the computation of net pension and other benefit costs. See Note 17 – Postretirement Benefits for additional details.