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Benefit Plans - Narrative (Details) | 3 Months Ended | 6 Months Ended
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Jun. 30, 2021 USD ($) | Jun. 30, 2021 USD ($)
Defined Benefit Plan Disclosure [Line Items] |  |
Estimated employer contributions for the current fiscal year | $ 9,043,000 | $ 9,043,000
Employer plan contributions | $ 1,480,000 | $ 1,480,000
CTWS Employees |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Rate of compensation increase |  | 1.50%

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