Annual report pursuant to Section 13 and 15(d)

Pension and Other Postretirement Benefit Programs - Amounts Recognized in AOCI (Details)

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Pension and Other Postretirement Benefit Programs - Amounts Recognized in AOCI (Details) - USD ($)
$ in Millions
Dec. 31, 2016
Dec. 31, 2015
U.S. Defined Benefit Pension Plans    
Defined Benefit Plan Disclosure [Line Items]    
Net actuarial gain (loss) $ (132.2)  
Prior service (cost) (0.5)  
Accumulated other comprehensive (loss) (132.7)  
Canadian Defined Benefit Pension Plans    
Defined Benefit Plan Disclosure [Line Items]    
Net actuarial gain (loss) (2.9)  
Prior service (cost) 0.0  
Accumulated other comprehensive (loss) (2.9)  
Retiree Health and Life Insurance Plans    
Defined Benefit Plan Disclosure [Line Items]    
Net actuarial gain (loss) $ 37.0 $ (0.6)