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Debt - Short-Term Debt (Details) - USD ($) $ in Thousands |  |  | 1 Months Ended | 9 Months Ended |  |
--- | --- | --- | --- | --- | --- | ---
Jan. 19, 2024 | Dec. 05, 2023 | May 31, 2023 | Apr. 30, 2023 | Mar. 31, 2023 | Sep. 30, 2024 | Sep. 30, 2023 | Dec. 31, 2023 | Jan. 20, 2023
Short-Term Debt [Line Items] |  |  |  |  |  |  |  |  |
Short-term borrowings |  |  |  |  |  | $ 0 | $ 306,400 | $ 95,000 |
Repayment of short-term borrowings |  |  |  |  |  | $ 95,000 | $ 193,500 |  |
Term Loan Agreement | Cascade Natural Gas |  |  |  |  |  |  |  |  |
Short-Term Debt [Line Items] |  |  |  |  |  |  |  |  |
Short-term borrowings |  |  |  |  |  |  |  |  | $ 150,000
Repayment of short-term borrowings | $ 50,000 | $ 100,000 |  |  |  |  |  |  |
Term Loan Agreement | Intermountain Gas Company |  |  |  |  |  |  |  |  |
Short-Term Debt [Line Items] |  |  |  |  |  |  |  |  |
Short-term borrowings |  |  |  |  |  |  |  |  | $ 125,000
Repayment of short-term borrowings | $ 45,000 |  | $ 30,000 | $ 30,000 | $ 20,000 |  |  |  |

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