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Litigation (Details) - USD ($) $ in Millions | Jun. 30, 2021 | Dec. 31, 2020 | Jun. 30, 2020
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Loss Contingencies [Line Items] |  |  |
Potential liabilities related to litigation and environmental matters | $ 30.8 | $ 41.5 | $ 34.5
Insurance Receivable | 6.9 | 17.5 | 21.1
Regulatory Assets | $ 21.2 | $ 21.3 | $ 10.4

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