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Commitments and Contingencies, Environmental (Details) $ in Millions | 3 Months Ended
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Mar. 31, 2018 USD ($)
Environmental Contingency |
Environmental accrual | $ 16.6
Expected period related to remediation expenditures for environmental contingencies period | 30 years
Potential increase in environmental costs | $ 12.2
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 | 18 months

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