Property, Plant and Equipment (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2022	Dec. 31, 2021
Asset Retirement Obligations (ARO)
Beginning Balance	[1],[2],[3],[4],[5]	$ 2,741.7
Accretion Expense	[1],[2],[3],[4],[5]	25.8
Liabilities Incurred	[1],[2],[3],[4],[5]	37.2
Liabilities Settled	[1],[2],[3],[4],[5]	(4.9)
Asset Retirement Obligation, Revision of Estimate	[1],[2],[3],[4],[5]	16.6
Ending Balance	[1],[2],[3],[4],[5]	2,816.4
Indiana Michigan Power Co [Member]
Property, Plant and Equipment (Textuals)
Asset Retirement Obligations (ARO) Liability for Nuclear Decommissioning of the Cook Plant		1,940.0	$ 1,930.0
Public Service Co Of Oklahoma [Member]
Asset Retirement Obligations (ARO)
Beginning Balance	[3],[4]	57.6
Accretion Expense	[3],[4]	0.9
Liabilities Incurred	[3],[4]	12.8
Liabilities Settled	[3],[4]	0.0
Asset Retirement Obligation, Revision of Estimate	[3],[4]	0.0
Ending Balance	[3],[4]	71.3
Public Service Co Of Oklahoma [Member] | ARO Additional Liability Incurred [Member]
Asset Retirement Obligations (ARO)
Liabilities Incurred		13.0
Southwestern Electric Power Co [Member]
Asset Retirement Obligations (ARO)
Beginning Balance	[2],[3],[4]	222.7
Accretion Expense	[2],[3],[4]	2.4
Liabilities Incurred	[2],[3],[4]	15.4
Liabilities Settled	[2],[3],[4]	(4.1)
Asset Retirement Obligation, Revision of Estimate	[2],[3],[4]	13.4
Ending Balance	[2],[3],[4]	249.8
Southwestern Electric Power Co [Member] | ARO Revision Adjustment [Member]
Asset Retirement Obligations (ARO)
Asset Retirement Obligation, Revision of Estimate		13.0
Southwestern Electric Power Co [Member] | ARO Additional Liability Incurred [Member]
Asset Retirement Obligations (ARO)
Liabilities Incurred		15.0
Kentucky Power Co [Member]
Asset Retirement Obligations (ARO)
Liabilities Held for Sale		$ 19.0	$ 18.0

[1] Includes $19 million and $18 million as of March 31, 2022 and December 31, 2021, respectively, of ARO classified as Liabilities Held for Sale on the balance sheets. See “Disposition of KPCo and KTCo” section of Note 6 for additional information.

[2] Includes ARO related to Sabine and DHLC.

[3] Includes ARO related to asbestos removal.

[4] Includes ARO related to ash disposal facilities.

[5] Includes ARO related to nuclear decommissioning costs for the Cook Plant of $1.94 billion and $1.93 billion as of March 31, 2022 and December 31, 2021, respectively.