v3.26.1
GOODWILL AND INTANGIBLES - FINITE-LIVED INTANGIBLE ASSETS (Details) - USD ($)
$ in Millions
6 Months Ended
Jun. 30, 2026
Dec. 31, 2025
Finite-Lived Intangible Assets    
Finite-lived intangible assets, net $ 18.6 $ 17.4
Amortization to be recorded as a decrease to operating revenues    
Amortization to be recorded in the next five years    
2026 59.9  
2027 59.9  
2028 59.9  
2029 59.9  
2030 59.9  
Maple Flats    
Finite-Lived Intangible Assets    
Finite-lived intangible assets, accumulated amortization 2.0 $ 1.4
Maple Flats | Amortization to be recorded as a decrease to operating revenues    
Amortization to be recorded in the next five years    
2026 1.3  
2027 1.3  
2028 1.3  
2029 1.3  
2030 1.3  
PPAs | Maple Flats    
Finite-Lived Intangible Assets    
Gross carrying amount $ 18.8  
Weighted average remaining useful life 15 years