v3.26.1
RELATED PARTY TRANSACTIONS Schedule of Related Party Transactions (Details) - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Dec. 31, 2025
Accounts receivable $ 167   $ 164
Accrued taxes 71   81
General and administrative 49 $ 40  
Fortis and Fortis affiliates [Member] | Affiliated Entity      
Accounts receivable 0   1
General and administrative 4 4  
Other operating expenses (income), net 2 $ 1  
ITC Investment Holdings | Affiliated Entity | Balance Sheet Location [Axis]: us-gaap:PrepaidExpenseAndOtherAssetsCurrent      
Income Taxes Receivable, Current $ 4   $ 2