Commitments and Contingencies, Environmental Contingencies (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accrual for Environmental Loss Contingencies, Gross, Fiscal Year Maturity
Environmental accrual	$ 19.3	$ 22.8	$ 21.7
Expected period related to remediation expenditures for environmental contingencies	30 years
Estimated environmental contingency loss exposure in excess of current accrual	25.1
Time period within which Company's recorded estimate of its obligation may change	12 months
Accrual for Environmental Loss Contingencies
Beginning balance	22.8	21.7	22.0
Additional accruals	0.8	4.5	1.2
Less expenditures	(4.3)	(3.4)	(1.5)
Ending balance	$ 19.3	$ 22.8	$ 21.7
Minimum
Accrual for Environmental Loss Contingencies, Gross, Fiscal Year Maturity
Period for feasibility study completion	18 months
Maximum
Accrual for Environmental Loss Contingencies, Gross, Fiscal Year Maturity
Period for feasibility study completion	24 months