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Summary of Significant Accounting Policies - Other Expense (Income) - Net (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Accounting Policies [Abstract] |  |  |
Interest income | $ 5,949 | $ 1,957 | $ 1,943
Interest on regulatory deferrals | 8,713 | 1,914 | 1,206
Equity-related AFUDC | 6,886 | 6,704 | 7,004
Non-service portion of pension and other postretirement benefit expenses | 630 | 3,037 | (1,386)
Earnings (losses) on investments | (3,227) | 48,492 | 21,402
Other income | 575 | 613 | 3,129
Total | $ 19,526 | $ 62,717 | $ 33,298

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