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NDPSC (Details 2) - NDPSC [Member] - Montana-Dakota Utilities Co. [Member] - USD ($)
$ in Millions
Nov. 01, 2023
Aug. 25, 2023
Jul. 14, 2023
Electric      
Public Utilities, General Disclosures [Line Items]      
Public Utilities, Requested Rate Increase (Decrease), Amount     $ (10.7)
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount   $ 1.3  
Total Transmission Cost Adjustment Rider     2.2
Public Utilities, Requested Rate (Decrease), Net Benefit Amount     $ (7.6)
Electric | Subsequent Event [Member] | Pending Rate Case [Member]      
Public Utilities, General Disclosures [Line Items]      
Public Utilities, Requested Rate Increase (Decrease), Amount $ 5.7    
Renewable Resource Cost Adjustment Rate Tariff 21.0    
Natural gas distribution | Subsequent Event [Member] | Pending Rate Case [Member]      
Public Utilities, General Disclosures [Line Items]      
Public Utilities, Requested Rate Increase (Decrease), Amount $ 11.6    
Public Utilities, Requested Rate Increase (Decrease), Percentage 7.50%    
Public Utilities, Interim Rate Increase (Decrease), Amount $ 10.1