ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2025 USD ($) plan state subsidiary shares	Dec. 31, 2024 USD ($) shares	Dec. 31, 2023 shares
Product Information [Line Items]
Number of states in which entity operates | state	11
Defined contribution plan, number of unfunded non-quality pension plans | plan	2
Defined benefit plan, concentration limits, in excess of all equity investments, percentage	5.00%
Defined benefit plan, concentration limits, cash equivalents of investment manager's equity portfolio, percentage	10.00%
Securities loaned, fair value | $	$ 139	$ 60
Antidilutive securities excluded from computation of earnings per share (in shares) | shares	0	0	0
Minimum
Product Information [Line Items]
Securities loaned, collateralized percentage	102.00%
AEPTCo
Product Information [Line Items]
Number of wholly-owned transmissions subsidiaries | subsidiary	7