Contingencies, Environmental and Legal Matters - ARO Liability and Related Changes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Loss Contingency Accrual [Roll Forward]
AROs, beginning of period	$ 17.5	$ 18.5	$ 4.8
Acquisitions	2.7	0.4	13.2
Additional obligations incurred	0.0	0.0	0.5
Accretion expense	1.2	1.0	0.7
Remeasurements	0.0	(0.2)	0.0
Payments	(1.3)	(0.4)	(0.2)
Foreign currency translation	(0.3)	(1.8)	(0.5)
AROs, end of period	$ 19.8	$ 17.5	$ 18.5