v3.26.1
TRANSACTIONS WITH AFFILIATED COMPANIES - Narrative (Details)
$ in Millions
3 Months Ended
Mar. 31, 2026
USD ($)
extension
Mar. 31, 2025
USD ($)
ATSI    
Related Party Transaction [Line Items]    
Number of additional successive periods 10  
Renewal term of lease yet to be commenced 50 years  
MAIT    
Related Party Transaction [Line Items]    
Number of additional successive periods 2  
Renewal term of lease yet to be commenced 25 years  
Number of additional renewal options 1  
Additional successive term 24 years  
Affiliates    
Related Party Transaction [Line Items]    
Defined benefit plan, plan assets, other pension and OPEB net periodic costs (credits) | $ $ 2 $ 3