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Commitments and Contingencies, Narrative (Details) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract] |  |  |  |
Timing of final feasibility study | 12 months |  |  |
Accrual for Environmental Loss Contingencies, Gross, Fiscal Year Maturity |  |  |  |
Operating Leases, Rent Expense |  | $ 8.2 | $ 7.9 |
Environmental accrual | $ 17.0 | $ 16.9 | $ 16.6 | $ 17.2
Expected period related to remediation expenditures for environmental contingencies | 30 years |  |  |
Estimated environmental contingency loss exposure in excess of current accrual | $ 11.6 |  |  |
Time period within which Company's recorded estimate of its obligation may change | 12 months |  |  |

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