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Accounting for Asset Retirement Obligations (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Asset retirement obligation [Roll Forward]    
Asset retirement liability, beginning of period $ 21.5 $ 21.4
Accretion expense 3.3 2.5
Payments (3.2) (1.6)
Foreign currency translation 0.5 (0.8)
Asset retirement liability, end of period 22.1 $ 21.5
Asset retirement obligation [Abstract]    
Asset retirement obligation current portion 1.6  
Asset retirement obligation noncurrent portion $ 20.5