XML 104 R74.htm IDEA: XBRL DOCUMENT v3.25.0.1
Regulatory Matters - Narrative (Details) - North Dakota Rate Case - NDPSC - USD ($)
$ in Millions
Dec. 30, 2024
Jul. 03, 2024
Nov. 02, 2023
Schedule of Regulatory Assets and Liabilities [Line Items]      
Requested rate increase, amount     $ 17.4
Requested rate increase, percent (as a percent)     8.40%
Requested return on base rate, percent (as a percent)     7.85%
Requested return on equity, percent (as a percent)     10.60%
Requested equity ratio, percent (as a percent)     53.50%
Revenue, interim rate increase, amount     $ 12.4
Revenue, interim rate increase, percentage (as a percent)     6.00%
Requested rate increase, amended, amount   $ 22.5  
Requested rate increase, amended, amount (as a percent)   10.90%  
Approved rate, revenue requirement $ 225.6    
Approved return on base rate, percent (as a percent) 7.53%    
Approved return on equity, percent (as a percent) 10.10%    
Approved equity ratio, percent (as a percent) 53.50%    
Approved rate increase, amount $ 13.1    
Approved rate increase, percent (as a percent) 6.18%    
Approved rate, revenue requirement reduced $ 3.0    
Earnings sharing, percentage (as a percent) 70.00%    
Earnings sharing, return on equity in excess of, percentage (as a percent) 10.20%    
Earnings sharing, retained, percentage (as a percent) 30.00%