SIGNIFICANT ACCOUNTING MATTERS - Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Accounting Policies [Abstract]
Earnings Attributable to AEP Common Shareholders, Basic	$ 874	$ 800
Earnings Attributable to AEP Common Shareholders, Diluted	$ 874	$ 800
Weighted-Average Number of Basic AEP Common Shares Outstanding (in shares)	542,079,269	533,391,487
Weighted-Average Number of Basic AEP Common Shares Outstanding (in dollars per share)	$ 1.61	$ 1.50
Weighted-Average Dilutive Effect (in shares)	5,000,000.0	1,300,000
Weighted-Average Dilutive Effect (in dollars per share)	$ (0.01)	$ 0
Weighted-Average Number of Diluted AEP Common Shares Outstanding (in shares)	547,054,104	534,663,493
Weighted-Average Number of Diluted AEP Common Shares Outstanding (in dollars per share)	$ 1.60	$ 1.50