VARIABLE INTEREST ENTITIES AND EQUITY METHOD INVESTMENTS - Power Purchased (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
APCo
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Amount of power purchased from OVEC	$ 120	$ 134	$ 122
I&M
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Amount of power purchased from OVEC	60	67	61
OPCo
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Amount of power purchased from OVEC	$ 153	$ 170	$ 155