Annual report pursuant to Section 13 and 15(d)

Pension And Other Postretirement Benefit Programs - Schedule of Change in Benefit Obligation and Change in Plan Assets (Details)

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Pension And Other Postretirement Benefit Programs - Schedule of Change in Benefit Obligation and Change in Plan Assets (Details) - USD ($)
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Retiree Health and Life Insurance Plans      
Change in benefit obligation:      
Benefit obligations as of beginning of period $ 65,300,000 $ 62,200,000  
Service cost 0 200,000 $ 400,000
Interest cost 1,900,000 2,500,000 2,600,000
Actuarial (gain) loss 4,500,000 10,000,000.0  
Benefits paid (6,900,000) (9,200,000)  
Benefit obligation as of end of period 59,600,000 65,300,000 62,200,000
Change in plan assets:      
Fair value of plan assets as of beginning of period 0 0  
Employer contribution 5,700,000 7,000,000.0  
Plan participants' contribution 1,200,000 2,200,000  
Benefits paid (6,900,000) (9,200,000)  
Fair value of plan assets as of end of period 0 0 0
Funded status of the plans (59,600,000) (65,300,000)  
United States | Pension Plan      
Change in benefit obligation:      
Benefit obligations as of beginning of period 394,600,000 346,400,000  
Service cost 2,600,000 2,700,000 3,800,000
Interest cost 12,500,000 15,000,000.0 14,600,000
Effect of plan curtailment (900,000) 0  
Actuarial (gain) loss 30,400,000 49,200,000  
Benefits paid (20,800,000) (18,700,000)  
Benefit obligation as of end of period 418,400,000 394,600,000 346,400,000
Change in plan assets:      
Fair value of plan assets as of beginning of period 380,700,000 337,100,000  
Actual return on plan assets 57,200,000 62,200,000  
Employer contribution 100,000 100,000  
Benefits paid (20,800,000) (18,700,000)  
Fair value of plan assets as of end of period 417,200,000 380,700,000 337,100,000
Funded status of the plans (1,200,000) (13,900,000)  
Accumulated benefit obligation 418,400,000 393,200,000  
Canadian Pension Plan | Pension Plan      
Change in benefit obligation:      
Benefit obligations as of beginning of period 16,300,000 15,600,000  
Service cost 0 0 0
Interest cost 500,000 600,000 600,000
Foreign currency translation adjustment 400,000 600,000  
Actuarial (gain) loss 1,200,000 1,300,000  
Benefits paid (1,300,000) (1,800,000)  
Benefit obligation as of end of period 17,100,000 16,300,000 15,600,000
Change in plan assets:      
Fair value of plan assets as of beginning of period 14,200,000 13,600,000  
Actual return on plan assets 1,400,000 1,700,000  
Employer contribution 100,000 100,000  
Foreign currency translation adjustment 400,000 600,000  
Benefits paid (1,300,000) (1,800,000)  
Fair value of plan assets as of end of period 14,800,000 14,200,000 $ 13,600,000
Funded status of the plans (2,300,000) (2,100,000)  
Accumulated benefit obligation $ 17,100,000 $ 16,300,000