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Shareholders' Equity (Details) - USD ($) $ in Thousands |  | 9 Months Ended |
--- | --- | --- | ---
May 03, 2024 | Sep. 30, 2025 | Dec. 31, 2024
Class of Stock [Line Items] |  |  |
Total capitalization |  | $ 2,874,888 | $ 2,612,233
Otter Tail Power Company |  |  |
Class of Stock [Line Items] |  |  |
Equity to total capitalization ratio |  | 55.10% |
Net assets restricted from distribution |  | $ 861,000 |
Minimum | Otter Tail Power Company | Minnesota Public Utilities Commission |  |  |
Class of Stock [Line Items] |  |  |
Public utilities, requested equity capital structure (as a percent) |  | 47.20% |
Maximum | Otter Tail Power Company |  |  |
Class of Stock [Line Items] |  |  |
Total capitalization |  | $ 2,200,000 |
Maximum | Otter Tail Power Company | Minnesota Public Utilities Commission |  |  |
Class of Stock [Line Items] |  |  |
Public utilities, requested equity capital structure (as a percent) |  | 57.70% |
Second Shelf Registration |  |  |
Class of Stock [Line Items] |  |  |
Shelf registration (in shares) | 1,500,000 |  |
Number of shares issued (in shares) |  | 75,173 |
Number of shares available for grant (in shares) |  | 1,354,358 |

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