v3.26.1
Regulatory Matters - Narrative (Details) - USD ($)
$ in Millions
 3 Months Ended
Jul. 30, 2026
Mar. 10, 2026
Dec. 23, 2025
Oct. 31, 2025
Jun. 04, 2025
Jun. 30, 2026
South Dakota Rate Case | SDPUC            
Schedule of Regulatory Assets and Liabilities [Line Items]            
Requested rate increase, amount         $ 5.7  
Requested rate increase, percent (as a percent)         12.50%  
Requested return on base rate, percent (as a percent)         8.29%  
Approved rate increase, amount   $ 3.3        
Approved rate increase, percent (as a percent)   7.70%        
Approved return on base rate, percent (as a percent)   7.09%        
Amounts to be refunded to customers           $ 0.8
Minnesota Rate Case | MPUC            
Schedule of Regulatory Assets and Liabilities [Line Items]            
Requested rate increase, amount       $ 44.8    
Requested rate increase, percent (as a percent)       17.70%    
Requested return on base rate, percent (as a percent)       7.92%    
Requested return on equity, percent (as a percent)       10.65%    
Requested equity ratio, percent (as a percent)       53.50%    
Requested accelerated recovery of remaining investments       $ 4.3    
Revenue, interim rate increase, amount     $ 28.6 $ 31.8    
Revenue, interim rate increase, percentage (as a percent)     11.30% 12.60%    
Minnesota Rate Case | MPUC | Subsequent Event            
Schedule of Regulatory Assets and Liabilities [Line Items]            
Requested rate increase, amount $ 42.3