v3.26.1
Business Segments (Narrative) (Details)
$ in Millions
3 Months Ended
Mar. 31, 2026
USD ($)
mi²
segment
customer
Mar. 31, 2025
USD ($)
Dec. 31, 2025
USD ($)
Segment Reporting [Line Items]      
Number of Operating Segments | segment 1    
Approximate number of retail customers | customer 540,000    
Service area, square miles | mi² 6,000    
Assets, Total $ 3,717.3   $ 3,730.8
Revenues 338.7 $ 252.1  
Purchased power 119.0 94.8  
Operation and maintenance 80.2 63.9  
Depreciation and amortization 31.3 28.8  
Taxes other than income taxes 38.2 36.2  
Interest expense 15.4 14.7  
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest 54.4 12.4  
Income Tax Expense (Benefit) 12.2 1.7  
Net Income (Loss) Attributable to Parent 42.2 10.7  
Utility [Member]      
Segment Reporting [Line Items]      
Income Tax Expense (Benefit) 12.2    
Operating Segments [Member]      
Segment Reporting [Line Items]      
Revenues 338.7    
Purchased power 119.0    
Operation and maintenance 80.2    
Depreciation and amortization 31.3    
Taxes other than income taxes 38.2    
Interest expense 15.4    
Segment Reporting, Other Segment Item, Amount 0.2    
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest 54.4    
Operating Segments [Member] | Utility [Member]      
Segment Reporting [Line Items]      
Revenues   252.1  
Purchased power   94.8  
Operation and maintenance   63.9  
Depreciation and amortization   28.8  
Taxes other than income taxes   36.2  
Interest expense   14.7  
Segment Reporting, Other Segment Item, Amount   1.3  
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest   12.4  
Income Tax Expense (Benefit)   1.7  
Net Income (Loss) Attributable to Parent 42.2 10.7  
Segment Reporting, Long-Lived Asset, Expenditure for Addition $ 114.1 $ 85.3