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NDPSC (Details 3) - Electric - NDPSC [Member] - Montana-Dakota Utilities Co. [Member] - USD ($) $ in Millions | Jul. 14, 2023 | Apr. 26, 2023 | Jul. 14, 2022 | May 16, 2022
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Public Utilities, General Disclosures [Line Items] |  |  |  |
Public Utilities, Interim Rate Increase (Decrease), Amount |  |  | $ 10.9 |
Public Utilities, Interim Rate Increase (Decrease), Percentage |  |  | 5.30% |
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount |  | $ 15.3 |  |
Public Utilities, Requested Rate Increase (Decrease), Amended, Percentage |  | 7.40% |  |
Public Utilities, Requested Return on Equity, Percentage |  | 9.75% |  |
Pending Rate Case [Member] |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |
Public Utilities, Requested Rate Increase (Decrease), Amount |  |  |  | $ 25.4
Public Utilities, Requested Rate Increase (Decrease), Percentage |  |  |  | 12.30%
Pending Rate Case [Member] | Subsequent Event [Member] |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |
Public Utilities, Requested Rate Increase (Decrease), Amount | $ (10.7) |  |  |
Total Transmission Cost Adjustment Rider | 2.2 |  |  |
Public Utilities, Requested Rate (Decrease), Net Benefit Amount | $ (7.6) |  |  |

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