v3.26.1
RETIREMENT BENEFITS AND ASSETS HELD IN TRUST (Details) - USD ($)
$ in Millions
3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2025
Defined Benefit Plan Disclosure [Line Items]      
Defined Contribution Plan, Cost $ 1 $ 2 $ 5