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Regulatory matters - SDPUC (Details) - Pending Rate Case - SDPUC - Montana-Dakota Utilities Co.
$ in Millions
Jan. 26, 2024
USD ($)
Aug. 15, 2023
USD ($)
Jul. 26, 2024
USD ($)
Public Utilities, General Disclosures [Line Items]      
Public utilities, interim rate increase (decrease), amount $ 2.7    
Public utilities, interim rate increase (decrease), percentage 15.40%    
Subsequent Event      
Public Utilities, General Disclosures [Line Items]      
Public utilities, annual revenue increase (decrease)     $ 1.4
Public utilities, annual revenue increase (decrease), percentage     0.086
Electric      
Public Utilities, General Disclosures [Line Items]      
Public utilities, requested rate increase (decrease), amount   $ 3.0  
Public utilities, requested rate increase (decrease), percentage   17.30%  
Natural gas distribution      
Public Utilities, General Disclosures [Line Items]      
Public utilities, requested rate increase (decrease), amount   $ 7.4  
Public utilities, requested rate increase (decrease), percentage   11.20%  
Natural gas distribution | Subsequent Event      
Public Utilities, General Disclosures [Line Items]      
Public utilities, annual revenue increase (decrease)     $ 5.4
Public utilities, annual revenue increase (decrease), percentage     0.081