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Employee Postretirement Benefits - Composition of Periodic Benefit Cost (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2022 | Jun. 30, 2021 | Jun. 30, 2022 | Jun. 30, 2021
Retirement Benefits [Abstract] |  |  |  |
Net Periodic Benefit Cost | $ 1,480 | $ 2,843 | $ 2,959 | $ 5,684
Net Amount Amortized (Deferred) Due to the Effect of Regulation | (204) | 123 | 324 | 7
Net Periodic Benefit Cost Recognized | $ 1,276 | $ 2,966 | $ 3,283 | $ 5,691

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