Commitments and Contingencies, Environmental (Details) $ in Millions	3 Months Ended
	Mar. 31, 2017 USD ($)
Environmental Contingency
Environmental accrual	$ 17.1
Expected period related to remediation expenditures for environmental contingencies period	30 years
Potential increase in environmental costs	$ 12.3
Time period within which Companys recorded estimate of its obligation may change	12 months
Minimum
Environmental Contingency
Period for final feasibility study	12 months
Maximum
Environmental Contingency
Period for final feasibility study	15 months