BENEFIT PLANS - Components of Net Periodic Benefit Cost (Credit) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service Cost	$ 24.0	$ 25.6
Interest Cost	52.8	51.9
Expected Return on Plan Assets	(70.3)	(80.2)
Amortization of Net Actuarial Loss	4.1	1.1
Net Periodic Benefit Cost (Credit)	10.6	(1.6)
Pension Plans | AEP Texas
Defined Benefit Plan Disclosure [Line Items]
Service Cost	2.2	2.2
Interest Cost	4.5	4.3
Expected Return on Plan Assets	(5.6)	(6.4)
Amortization of Net Actuarial Loss	0.3	0.1
Net Periodic Benefit Cost (Credit)	1.4	0.2
Pension Plans | APCo
Defined Benefit Plan Disclosure [Line Items]
Service Cost	2.4	2.4
Interest Cost	6.2	6.2
Expected Return on Plan Assets	(9.4)	(10.7)
Amortization of Net Actuarial Loss	0.4	0.1
Net Periodic Benefit Cost (Credit)	(0.4)	(2.0)
Pension Plans | I&M
Defined Benefit Plan Disclosure [Line Items]
Service Cost	3.2	3.3
Interest Cost	6.2	6.0
Expected Return on Plan Assets	(9.7)	(10.8)
Amortization of Net Actuarial Loss	0.4	0.1
Net Periodic Benefit Cost (Credit)	0.1	(1.4)
Pension Plans | OPCo
Defined Benefit Plan Disclosure [Line Items]
Service Cost	2.3	2.4
Interest Cost	4.9	4.7
Expected Return on Plan Assets	(7.3)	(8.2)
Amortization of Net Actuarial Loss	0.3	0.1
Net Periodic Benefit Cost (Credit)	0.2	(1.0)
Pension Plans | PSO
Defined Benefit Plan Disclosure [Line Items]
Service Cost	1.4	1.5
Interest Cost	2.7	2.5
Expected Return on Plan Assets	(3.9)	(4.3)
Amortization of Net Actuarial Loss	0.2	0.0
Net Periodic Benefit Cost (Credit)	0.4	(0.3)
Pension Plans | SWEPCo
Defined Benefit Plan Disclosure [Line Items]
Service Cost	1.9	1.9
Interest Cost	3.2	3.1
Expected Return on Plan Assets	(3.7)	(4.4)
Amortization of Net Actuarial Loss	0.2	0.1
Net Periodic Benefit Cost (Credit)	1.6	0.7
OPEB
Defined Benefit Plan Disclosure [Line Items]
Service Cost	0.8	1.1
Interest Cost	8.6	10.5
Expected Return on Plan Assets	(28.2)	(27.8)
Amortization of Prior Service Credit	(0.6)	(3.2)
Amortization of Net Actuarial Loss	(0.3)	0.8
Net Periodic Benefit Cost (Credit)	(19.7)	(18.6)
OPEB | AEP Texas
Defined Benefit Plan Disclosure [Line Items]
Service Cost	0.1	0.1
Interest Cost	0.6	0.8
Expected Return on Plan Assets	(2.3)	(2.3)
Amortization of Prior Service Credit	0.0	(0.3)
Amortization of Net Actuarial Loss	0.0	0.1
Net Periodic Benefit Cost (Credit)	(1.6)	(1.6)
OPEB | APCo
Defined Benefit Plan Disclosure [Line Items]
Service Cost	0.1	0.1
Interest Cost	1.4	1.7
Expected Return on Plan Assets	(4.1)	(4.0)
Amortization of Prior Service Credit	(0.1)	(0.5)
Amortization of Net Actuarial Loss	(0.1)	0.1
Net Periodic Benefit Cost (Credit)	(2.8)	(2.6)
OPEB | I&M
Defined Benefit Plan Disclosure [Line Items]
Service Cost	0.1	0.1
Interest Cost	1.0	1.2
Expected Return on Plan Assets	(3.4)	(3.4)
Amortization of Prior Service Credit	(0.1)	(0.4)
Amortization of Net Actuarial Loss	0.0	0.1
Net Periodic Benefit Cost (Credit)	(2.4)	(2.4)
OPEB | OPCo
Defined Benefit Plan Disclosure [Line Items]
Service Cost	0.1	0.1
Interest Cost	0.8	1.1
Expected Return on Plan Assets	(2.9)	(3.0)
Amortization of Prior Service Credit	(0.1)	(0.3)
Amortization of Net Actuarial Loss	0.0	0.1
Net Periodic Benefit Cost (Credit)	(2.1)	(2.0)
OPEB | PSO
Defined Benefit Plan Disclosure [Line Items]
Service Cost	0.0	0.1
Interest Cost	0.4	0.5
Expected Return on Plan Assets	(1.5)	(1.4)
Amortization of Prior Service Credit	0.0	(0.2)
Amortization of Net Actuarial Loss	0.0	0.0
Net Periodic Benefit Cost (Credit)	(1.1)	(1.0)
OPEB | SWEPCo
Defined Benefit Plan Disclosure [Line Items]
Service Cost	0.1	0.1
Interest Cost	0.5	0.7
Expected Return on Plan Assets	(1.9)	(1.9)
Amortization of Prior Service Credit	0.0	(0.3)
Amortization of Net Actuarial Loss	0.0	0.1
Net Periodic Benefit Cost (Credit)	$ (1.3)	$ (1.3)