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Goodwill and Other Intangible Assets (Gross and Net Intangible Assets) (Details) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2020 | Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items] |  |
Gross Carrying Amount | $ 40.0 | $ 46.1
Accumulated Amortization | 6.2 | 11.4
Total | 33.8 | 34.7
Customer contracts |  |
Finite-Lived Intangible Assets [Line Items] |  |
Gross Carrying Amount | 0.0 | 7.7
Accumulated Amortization | 0.0 | 7.2
Total | $ 0.0 | 0.5
Customer relationships |  |
Finite-Lived Intangible Assets [Line Items] |  |
Weighted - Average Remaining Amortization Years | 4 years |
Gross Carrying Amount | $ 6.7 | 6.7
Accumulated Amortization | 4.5 | 3.9
Total | $ 2.2 | 2.8
Permits |  |
Finite-Lived Intangible Assets [Line Items] |  |
Weighted - Average Remaining Amortization Years | 22 years |
Gross Carrying Amount | $ 31.7 | 31.7
Accumulated Amortization | 1.7 | 0.3
Total | $ 30.0 | 31.4
Other |  |
Finite-Lived Intangible Assets [Line Items] |  |
Weighted - Average Remaining Amortization Years | 30 years |
Gross Carrying Amount | $ 1.6 | 0.0
Accumulated Amortization | 0.0 | 0.0
Total | $ 1.6 | $ 0.0

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