Annual report pursuant to Section 13 and 15(d)

Pension and Other Postretirement Benefit Programs - Benefit Obligations in Excess of Assets (Details)

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Pension and Other Postretirement Benefit Programs - Benefit Obligations in Excess of Assets (Details) - Pension Plan - USD ($)
$ in Millions
Dec. 31, 2017
Dec. 31, 2016
U.S. Pension Plan    
Defined-benefit pension plans with benefit obligations in excess of assets    
Projected benefit obligation, December 31 $ 395.8 $ 1.4
Accumulated benefit obligation, December 31 394.5 1.3
Fair value of plan assets, December 31 390.8 0.0
Canadian Pension Plan    
Defined-benefit pension plans with benefit obligations in excess of assets    
Projected benefit obligation, December 31 17.3 16.1
Accumulated benefit obligation, December 31 17.3 16.1
Fair value of plan assets, December 31 $ 16.5 $ 15.9