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Regulatory Matters - Narrative (Details) - North Dakota Rate Case - NDPSC - USD ($) $ in Millions | Dec. 30, 2024 | Jul. 03, 2024 | Nov. 02, 2023
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Schedule of Regulatory Assets and Liabilities [Line Items] |  |  |
Requested rate increase, amount |  |  | $ 17.4
Requested rate increase, percent (as a percent) |  |  | 8.40%
Requested return on base rate, percent (as a percent) |  |  | 7.85%
Requested return on equity, percent (as a percent) |  |  | 10.60%
Requested equity ratio, percent (as a percent) |  |  | 53.50%
Revenue, interim rate increase, amount |  |  | $ 12.4
Revenue, interim rate increase, percentage (as a percent) |  |  | 6.00%
Requested rate increase, amended, amount |  | $ 22.5 |
Requested rate increase, amended, amount (as a percent) |  | 10.90% |
Approved rate, revenue requirement | $ 225.6 |  |
Approved return on base rate, percent (as a percent) | 7.53% |  |
Approved return on equity, percent (as a percent) | 10.10% |  |
Approved equity ratio, percent (as a percent) | 53.50% |  |
Approved rate increase, amount | $ 13.1 |  |
Approved rate increase, percent (as a percent) | 6.18% |  |
Approved rate, revenue requirement reduced | $ 3.0 |  |
Earnings sharing, percentage (as a percent) | 70.00% |  |
Earnings sharing, return on equity in excess of, percentage (as a percent) | 10.20% |  |
Earnings sharing, retained, percentage (as a percent) | 30.00% |  |

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