Annual report pursuant to Section 13 and 15(d)

Pension And Other Postretirement Benefit Programs - Asset Allocation (Details)

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Pension And Other Postretirement Benefit Programs - Asset Allocation (Details) - Pension Plan - USD ($)
$ in Millions
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
United States      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 417.2 $ 380.7 $ 337.1
United States | Fixed income securities      
Defined Benefit Plan Disclosure [Line Items]      
Target Weight End of Period 60.00%    
Position at End of Period 54.00% 55.00%  
Fair Value of Plan Assets $ 226.5 $ 207.9  
United States | Equities      
Defined Benefit Plan Disclosure [Line Items]      
Target Weight End of Period 40.00%    
Position at End of Period 46.00% 45.00%  
United States | Other      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ (0.3) $ (0.4)  
Canadian Pension Plan      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 14.8 $ 14.2 $ 13.6
Canadian Pension Plan | Fixed income securities      
Defined Benefit Plan Disclosure [Line Items]      
Target Weight End of Period 50.00%    
Position at End of Period 50.00% 50.00%  
Fair Value of Plan Assets $ 7.5 $ 7.0  
Canadian Pension Plan | Equities      
Defined Benefit Plan Disclosure [Line Items]      
Target Weight End of Period 48.00%    
Position at End of Period 48.00% 48.00%  
Canadian Pension Plan | Other      
Defined Benefit Plan Disclosure [Line Items]      
Target Weight End of Period 2.00%    
Position at End of Period 2.00% 2.00%  
Fair Value of Plan Assets $ 0.2 $ 0.3