COMMITMENTS, GUARANTEES AND CONTINGENCIES - ARO CCR Rule (Details) $ in Millions	3 Months Ended
	Jun. 30, 2024 USD ($)
CCR Rule Revision
Other Commitments [Line Items]
Increase in ARO	$ 674
Increase in Generation Property
Other Commitments [Line Items]
Increase in ARO	177
Increase in Regulatory Assets
Other Commitments [Line Items]
Increase in ARO	355
Charged to Operating Expenses
Other Commitments [Line Items]
Increase in ARO	142
APPALACHIAN POWER COMPANY | CCR Rule Revision
Other Commitments [Line Items]
Increase in ARO	312
APPALACHIAN POWER COMPANY | Increase in Generation Property
Other Commitments [Line Items]
Increase in ARO	75
APPALACHIAN POWER COMPANY | Increase in Regulatory Assets
Other Commitments [Line Items]
Increase in ARO	237
APPALACHIAN POWER COMPANY | Charged to Operating Expenses
Other Commitments [Line Items]
Increase in ARO	0
INDIANA MICHIGAN POWER COMPANY | CCR Rule Revision
Other Commitments [Line Items]
Increase in ARO	85
INDIANA MICHIGAN POWER COMPANY | Increase in Generation Property
Other Commitments [Line Items]
Increase in ARO	0
INDIANA MICHIGAN POWER COMPANY | Increase in Regulatory Assets
Other Commitments [Line Items]
Increase in ARO	72
INDIANA MICHIGAN POWER COMPANY | Charged to Operating Expenses
Other Commitments [Line Items]
Increase in ARO	13
OHIO POWER COMPANY | CCR Rule Revision
Other Commitments [Line Items]
Increase in ARO	53
OHIO POWER COMPANY | Increase in Generation Property
Other Commitments [Line Items]
Increase in ARO	0
OHIO POWER COMPANY | Increase in Regulatory Assets
Other Commitments [Line Items]
Increase in ARO	0
OHIO POWER COMPANY | Charged to Operating Expenses
Other Commitments [Line Items]
Increase in ARO	53
PUBLIC SERVICE COMPANY OF OKLAHOMA | CCR Rule Revision
Other Commitments [Line Items]
Increase in ARO	34
PUBLIC SERVICE COMPANY OF OKLAHOMA | Increase in Generation Property
Other Commitments [Line Items]
Increase in ARO	34
PUBLIC SERVICE COMPANY OF OKLAHOMA | Increase in Regulatory Assets
Other Commitments [Line Items]
Increase in ARO	0
PUBLIC SERVICE COMPANY OF OKLAHOMA | Charged to Operating Expenses
Other Commitments [Line Items]
Increase in ARO	0
SOUTHWESTERN ELECTRIC POWER COMPANY | CCR Rule Revision
Other Commitments [Line Items]
Increase in ARO	24
SOUTHWESTERN ELECTRIC POWER COMPANY | Increase in Generation Property
Other Commitments [Line Items]
Increase in ARO	24
SOUTHWESTERN ELECTRIC POWER COMPANY | Increase in Regulatory Assets
Other Commitments [Line Items]
Increase in ARO	0
SOUTHWESTERN ELECTRIC POWER COMPANY | Charged to Operating Expenses
Other Commitments [Line Items]
Increase in ARO	0
Non-Registrants | CCR Rule Revision
Other Commitments [Line Items]
Increase in ARO	166
Non-Registrants | Increase in Generation Property
Other Commitments [Line Items]
Increase in ARO	44
Non-Registrants | Increase in Regulatory Assets
Other Commitments [Line Items]
Increase in ARO	46
Non-Registrants | Charged to Operating Expenses
Other Commitments [Line Items]
Increase in ARO	$ 76