v3.25.4
Goodwill and Other Intangible Assets (Details) - USD ($)
$ in Millions
Dec. 31, 2025
Dec. 31, 2024
Goodwill And Other Intangible Assets [Line Items]    
Goodwill $ 1,485.9 $ 1,485.9
Columbia Operations    
Goodwill And Other Intangible Assets [Line Items]    
Goodwill 1,468.1  
NIPSCO Operations    
Goodwill And Other Intangible Assets [Line Items]    
Goodwill $ 17.8