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Rate and Regulatory Matters (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2021 | Dec. 31, 2020
Tidewater [Member] |  |
Regulatory Liabilities [Line Items] |  |
Proceeds from net of tax refunds | $ 0.8 |
New Jersey Board Of Public Utilities [Member] | Middlesex [Member] |  |
Regulatory Liabilities [Line Items] |  |
Approved increase in annual operating revenues | 1.1 |
Pennsylvania Public Utilities Commissio [Member] | Twin Lakes [Member] |  |
Regulatory Liabilities [Line Items] |  |
Escrow account | $ 1.7 |
Delaware Public Service Commission Member | Tidewater [Member] |  |
Regulatory Liabilities [Line Items] |  |
Approved increase in annual operating revenues |  | $ 0.6

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