COMMITMENTS, GUARANTEES AND CONTINGENCIES - ARO CCR Rule (Details) - USD ($) $ in Millions	Dec. 31, 2024	Jun. 30, 2024	Dec. 31, 2023	Dec. 31, 2022
Other Commitments [Line Items]
Increase in ARO	$ 3,611.7		$ 3,031.2	$ 2,943.6
CCR Rule Revision
Other Commitments [Line Items]
Increase in ARO		$ 674.4
Increase in Generation Property | CCR Rule Revision
Other Commitments [Line Items]
Increase in ARO		176.9
Increase in Regulatory Assets | CCR Rule Revision
Other Commitments [Line Items]
Increase in ARO		355.0
Charged to Operating Expenses | CCR Rule Revision
Other Commitments [Line Items]
Increase in ARO		142.5
APPALACHIAN POWER COMPANY
Other Commitments [Line Items]
Increase in ARO	801.7		464.0	427.7
APPALACHIAN POWER COMPANY | CCR Rule Revision
Other Commitments [Line Items]
Increase in ARO		312.2
APPALACHIAN POWER COMPANY | Increase in Generation Property | CCR Rule Revision
Other Commitments [Line Items]
Increase in ARO		75.6
APPALACHIAN POWER COMPANY | Increase in Regulatory Assets | CCR Rule Revision
Other Commitments [Line Items]
Increase in ARO		236.6
APPALACHIAN POWER COMPANY | Charged to Operating Expenses | CCR Rule Revision
Other Commitments [Line Items]
Increase in ARO		0.0
INDIANA MICHIGAN POWER COMPANY
Other Commitments [Line Items]
Increase in ARO	2,093.8		2,106.0	2,028.1
INDIANA MICHIGAN POWER COMPANY | CCR Rule Revision
Other Commitments [Line Items]
Increase in ARO		85.7
INDIANA MICHIGAN POWER COMPANY | Increase in Generation Property | CCR Rule Revision
Other Commitments [Line Items]
Increase in ARO		0.0
INDIANA MICHIGAN POWER COMPANY | Increase in Regulatory Assets | CCR Rule Revision
Other Commitments [Line Items]
Increase in ARO		72.3
INDIANA MICHIGAN POWER COMPANY | Charged to Operating Expenses | CCR Rule Revision
Other Commitments [Line Items]
Increase in ARO		13.4
OHIO POWER COMPANY
Other Commitments [Line Items]
Increase in ARO	56.3		2.1	5.0
OHIO POWER COMPANY | CCR Rule Revision
Other Commitments [Line Items]
Increase in ARO		52.9
OHIO POWER COMPANY | Increase in Generation Property | CCR Rule Revision
Other Commitments [Line Items]
Increase in ARO		0.0
OHIO POWER COMPANY | Increase in Regulatory Assets | CCR Rule Revision
Other Commitments [Line Items]
Increase in ARO		0.0
OHIO POWER COMPANY | Charged to Operating Expenses | CCR Rule Revision
Other Commitments [Line Items]
Increase in ARO		52.9
PUBLIC SERVICE COMPANY OF OKLAHOMA
Other Commitments [Line Items]
Increase in ARO	121.8		84.2	75.7
PUBLIC SERVICE COMPANY OF OKLAHOMA | CCR Rule Revision
Other Commitments [Line Items]
Increase in ARO		33.7
PUBLIC SERVICE COMPANY OF OKLAHOMA | Increase in Generation Property | CCR Rule Revision
Other Commitments [Line Items]
Increase in ARO		33.7
PUBLIC SERVICE COMPANY OF OKLAHOMA | Increase in Regulatory Assets | CCR Rule Revision
Other Commitments [Line Items]
Increase in ARO		0.0
PUBLIC SERVICE COMPANY OF OKLAHOMA | Charged to Operating Expenses | CCR Rule Revision
Other Commitments [Line Items]
Increase in ARO		0.0
SOUTHWESTERN ELECTRIC POWER COMPANY
Other Commitments [Line Items]
Increase in ARO	$ 278.7		$ 281.6	$ 280.9
SOUTHWESTERN ELECTRIC POWER COMPANY | CCR Rule Revision
Other Commitments [Line Items]
Increase in ARO		23.8
SOUTHWESTERN ELECTRIC POWER COMPANY | Increase in Generation Property | CCR Rule Revision
Other Commitments [Line Items]
Increase in ARO		23.8
SOUTHWESTERN ELECTRIC POWER COMPANY | Increase in Regulatory Assets | CCR Rule Revision
Other Commitments [Line Items]
Increase in ARO		0.0
SOUTHWESTERN ELECTRIC POWER COMPANY | Charged to Operating Expenses | CCR Rule Revision
Other Commitments [Line Items]
Increase in ARO		0.0
Non Registrant | CCR Rule Revision
Other Commitments [Line Items]
Increase in ARO		166.1
Non Registrant | Increase in Generation Property | CCR Rule Revision
Other Commitments [Line Items]
Increase in ARO		43.8
Non Registrant | Increase in Regulatory Assets | CCR Rule Revision
Other Commitments [Line Items]
Increase in ARO		46.1
Non Registrant | Charged to Operating Expenses | CCR Rule Revision
Other Commitments [Line Items]
Increase in ARO		$ 76.2