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 ($)
$ in Millions
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Change in plan assets:      
Fair value of plan assets as of end of period $ 337.1    
Canadian Pension Plan      
Change in plan assets:      
Accumulated benefit obligation 15.6 $ 17.8  
Retiree Health and Life Insurance Plans      
Change in benefit obligation:      
Benefit obligations as of beginning of period 76.4 80.3  
Service cost 0.4 0.4 $ 0.1
Interest cost 2.6 3.2 2.6
Actuarial (gain) loss (9.0) 0.5  
Benefits paid (9.6) (9.7)  
Benefit obligation as of end of period 62.2 76.4 80.3
Change in plan assets:      
Fair value of plan assets as of beginning of period 0.0 0.0  
Employer contribution 8.0 8.0  
Plan participants' contribution 1.6 1.7  
Benefits paid (9.6) (9.7)  
Fair value of plan assets as of end of period 0.0 0.0 0.0
Funded status of the plans (62.2) (76.4)  
U.S. Pension Plan      
Change in plan assets:      
Accumulated benefit obligation 345.1 394.5  
U.S. Pension Plan      
Change in plan assets:      
Employer contribution 0.1 0.1  
U.S. Pension Plan | Pension Plan      
Change in benefit obligation:      
Benefit obligations as of beginning of period 395.8 364.4  
Liabilities transferred to AHF, LLC (11.5) 0.0  
Service cost 3.8 5.4 4.3
Interest cost 14.6 15.4 11.7
Foreign currency translation adjustment 0.0 0.0  
Actuarial (gain) loss (33.4) 28.4  
Benefits paid (22.9) (17.8)  
Benefit obligation as of end of period 346.4 395.8 364.4
Change in plan assets:      
Fair value of plan assets as of beginning of period 390.8 363.2  
Assets received from separation (8.1) 0.0  
Actual return on plan assets (22.8) 45.3  
Foreign currency translation adjustment 0.0 0.0  
Benefits paid (22.9) (17.8)  
Fair value of plan assets as of end of period 337.1 390.8 363.2
Funded status of the plans (9.3) (5.0)  
Canadian Pension Plan      
Change in plan assets:      
Employer contribution 0.1 0.0  
Canadian Pension Plan | Pension Plan      
Change in benefit obligation:      
Benefit obligations as of beginning of period 17.8 16.7  
Liabilities transferred to AHF, LLC 0.0 0.0  
Service cost 0.0 0.0  
Interest cost 0.6 0.6 0.5
Foreign currency translation adjustment (1.2) 1.2  
Actuarial (gain) loss 0.5 1.1  
Benefits paid (2.1) (1.8)  
Benefit obligation as of end of period 15.6 17.8 16.7
Change in plan assets:      
Fair value of plan assets as of beginning of period 17.1 16.5  
Assets received from separation 0.0 0.0  
Actual return on plan assets (0.4) 1.2  
Foreign currency translation adjustment (1.1) 1.2  
Benefits paid (2.1) (1.8)  
Fair value of plan assets as of end of period 13.6 17.1 $ 16.5
Funded status of the plans $ (2.0) $ (0.7)