Commitments and Contingencies Commitments and Contingencies, Changes in Environmental Contingencies (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Loss Contingency, Range of Possible Loss, Portion Not Accrued	$ 12.5
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	17.2	$ 18.6	$ 19.3
Additional accruals	0.3	0.1	1.3
Less: expenditures	0.9	1.5	2.0
Ending balance	$ 16.6	$ 17.2	$ 18.6