v3.26.1
Business Segments (Narrative) (Details)
$ in Millions
3 Months Ended
Mar. 31, 2026
USD ($)
mi²
customer
segment
Mar. 31, 2025
USD ($)
Dec. 31, 2025
USD ($)
Segment Reporting [Line Items]      
Assets, Total $ 3,773.5   $ 3,781.0
Revenues $ 341.1 $ 254.3  
Number of reportable segments | segment 1    
Revenue from external customers      
Segment Reporting [Line Items]      
Revenues $ 341.1 254.3  
Intersegment revenue      
Segment Reporting [Line Items]      
Revenues $ 0.0 0.0  
Subsidiaries [Member]      
Segment Reporting [Line Items]      
Approximate number of retail customers | customer 540,000    
Service area, square miles | mi² 6,000    
Assets, Total $ 3,717.3   3,730.8
Utility [Member]      
Segment Reporting [Line Items]      
Revenues 338.7 252.1  
Operating Segments [Member] | Utility [Member]      
Segment Reporting [Line Items]      
Revenues 338.7 252.1  
Operating Segments [Member] | Utility [Member] | Revenue from external customers      
Segment Reporting [Line Items]      
Revenues 338.7 251.8  
Operating Segments [Member] | Utility [Member] | Intersegment revenue      
Segment Reporting [Line Items]      
Revenues 0.0 0.3  
Corporate, Non-Segment [Member]      
Segment Reporting [Line Items]      
Assets, Total 56.2   $ 50.2
Revenues 3.8 3.7  
Corporate, Non-Segment [Member] | Revenue from external customers      
Segment Reporting [Line Items]      
Revenues 2.7 2.5  
Corporate, Non-Segment [Member] | Intersegment revenue      
Segment Reporting [Line Items]      
Revenues 1.1 1.2  
Intersegment Eliminations      
Segment Reporting [Line Items]      
Revenues (1.4) (1.5)  
Intersegment Eliminations | Revenue from external customers      
Segment Reporting [Line Items]      
Revenues (0.3) 0.0  
Intersegment Eliminations | Intersegment revenue      
Segment Reporting [Line Items]      
Revenues $ (1.1) $ (1.5)