Derivatives and Hedging (Details) gal in Millions, MWh in Millions, MMBTU in Millions		3 Months Ended			9 Months Ended			12 Months Ended
		Sep. 30, 2021 USD ($) MWh MMBTU gal		Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) MWh MMBTU gal		Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($) MWh MMBTU gal
Cash Collateral Netting
Cash Collateral Received Netted Against Risk Management Assets		$ 309,700,000			$ 309,700,000			$ 3,400,000
Cash Collateral Paid Netted Against Risk Management Liabilities		38,300,000			38,300,000			6,800,000
Fair Value of Derivative Instruments
Current Risk Management Assets		369,200,000			369,200,000			94,700,000
Long-term Risk Management Assets		278,300,000			278,300,000			242,200,000
Total Assets		647,500,000			647,500,000			336,900,000
Current Risk Management Liabilities		106,500,000			106,500,000			78,800,000
Long-term Risk Management Liabilities		199,600,000			199,600,000			232,800,000
Total Liabilities		306,100,000			306,100,000			311,600,000
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		169,400,000		$ 36,000,000.0	265,600,000		$ 81,900,000
Carrying Amount of Hedged Asset (Liability)	[1],[2]	(965,600,000)			(965,600,000)			(995,900,000)
Cumulative Fair Value Hedging Adjustment in the Carrying Amount of the Hedged Asset (Liability)	[1],[2]	(22,100,000)			(22,100,000)			(51,700,000)
Gain (Loss) on Hedging Instruments
Gain (Loss) on Fair Value Hedging Instruments	[3]	(100,000)		0	(23,800,000)		42,600,000
Gain (Loss) on Fair Value Portion of Long Term Debt	[3]	100,000		0	23,800,000		(42,600,000)
Collateral Triggering Events [Abstract]
Fair Value Of Derivative Liabilities Subject To Cross Default Provisions		128,200,000			128,200,000			188,400,000
Amount of Cash Collateral Posted		0			0			0
Additional Settlement Liability if Cross Default Provision is Triggered		95,800,000			95,800,000			169,200,000
Derivatives and Hedging (Textuals) [Abstract]
Hedged Liability, Discontinued Fair Value Hedge, Cumulative Increase (Decrease)		(47,000,000)			(47,000,000)			(53,000,000)
Credit Downgrade Trigger Exposure		25,000,000			25,000,000
Investment in Private Investee
Derivatives and Hedging (Textuals) [Abstract]
Cost Method Investments								8,000,000
Equity Method Investments, Fair Value Disclosure		30,000,000			30,000,000
Unrealized Gain (Loss) on Investments		(16,000,000)			22,000,000
AEP Texas Inc. [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		400,000		(100,000)	1,700,000		(1,300,000)
Appalachian Power Co [Member]
Cash Collateral Netting
Cash Collateral Received Netted Against Risk Management Assets		600,000			600,000			400,000
Cash Collateral Paid Netted Against Risk Management Liabilities		10,700,000			10,700,000			0
Fair Value of Derivative Instruments
Current Risk Management Assets		47,000,000.0			47,000,000.0			22,400,000
Total Assets								22,500,000
Total Liabilities								4,700,000
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		10,800,000		4,500,000	27,000,000.0		17,000,000.0
Collateral Triggering Events [Abstract]
Fair Value Of Derivative Liabilities Subject To Cross Default Provisions		1,000,000.0			1,000,000.0			4,300,000
Amount of Cash Collateral Posted		0			0			0
Additional Settlement Liability if Cross Default Provision is Triggered		0			0			3,500,000
Indiana Michigan Power Co [Member]
Cash Collateral Netting
Cash Collateral Received Netted Against Risk Management Assets		300,000			300,000			1,700,000
Cash Collateral Paid Netted Against Risk Management Liabilities		17,400,000			17,400,000			0
Fair Value of Derivative Instruments
Current Risk Management Assets		5,500,000			5,500,000			3,600,000
Current Risk Management Liabilities		2,500,000			2,500,000			100,000
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		(15,000,000.0)		2,700,000	(20,500,000)		8,400,000
Collateral Triggering Events [Abstract]
Fair Value Of Derivative Liabilities Subject To Cross Default Provisions		600,000			600,000			500,000
Amount of Cash Collateral Posted		0			0			0
Additional Settlement Liability if Cross Default Provision is Triggered		0			0			100,000
Ohio Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Liabilities		3,500,000			3,500,000			8,700,000
Long-term Risk Management Liabilities		86,900,000			86,900,000			101,600,000
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		16,000,000.0		5,800,000	26,900,000		(2,200,000)
Public Service Co Of Oklahoma [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets		18,500,000			18,500,000			10,300,000
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		14,200,000		2,600,000	40,600,000		22,900,000
Southwestern Electric Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets		17,500,000			17,500,000			3,200,000
Long-term Risk Management Assets		2,100,000			2,100,000			0
Current Risk Management Liabilities		0			0			700,000
Long-term Risk Management Liabilities		0			0			1,000,000.0
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		13,100,000		4,700,000	40,500,000		16,600,000
Collateral Triggering Events [Abstract]
Fair Value Of Derivative Liabilities Subject To Cross Default Provisions		0			0			1,800,000
Amount of Cash Collateral Posted		0			0			0
Additional Settlement Liability if Cross Default Provision is Triggered		0			0			1,800,000
Risk Management Contracts [Member]
Fair Value of Derivative Instruments
Total Assets	[4]	275,500,000	[5]		275,500,000	[5]		322,100,000	[6]
Total Liabilities	[4]	273,200,000	[5]		273,200,000	[5]		218,900,000	[6]
Risk Management Contracts [Member] | AEP Texas Inc. [Member]
Fair Value of Derivative Instruments
Total Assets	[4]	0			0			0
Risk Management Contracts [Member] | Appalachian Power Co [Member]
Fair Value of Derivative Instruments
Total Assets	[4],[7]	47,000,000.0			47,000,000.0			20,100,000
Total Liabilities	[4],[7]	1,300,000			1,300,000			1,300,000
Risk Management Contracts [Member] | Indiana Michigan Power Co [Member]
Fair Value of Derivative Instruments
Total Assets	[4],[7]	5,500,000			5,500,000			3,700,000
Total Liabilities	[4],[7]	2,500,000			2,500,000			200,000
Risk Management Contracts [Member] | Ohio Power Co [Member]
Fair Value of Derivative Instruments
Total Assets	[4],[7]	0			0			0
Total Liabilities	[4],[7]	90,400,000			90,400,000			110,300,000
Risk Management Contracts [Member] | Public Service Co Of Oklahoma [Member]
Fair Value of Derivative Instruments
Total Assets	[4],[7]	18,500,000			18,500,000			10,300,000
Total Liabilities	[4],[7]	0			0
Risk Management Contracts [Member] | Southwestern Electric Power Co [Member]
Fair Value of Derivative Instruments
Total Assets	[4],[7]	19,600,000			19,600,000			3,200,000
Total Liabilities	[4],[7]	0			0			1,700,000
Commodity [Member]
Impact of Cash Flow Hedges on the Condensed Balance Sheet
AOCI Gain (Loss) Net of Tax		283,900,000			283,900,000			(60,600,000)
Portion Expected to be Reclassified to Net Income During the Next Twelve Months					$ 56,500,000			(27,100,000)
Derivatives and Hedging (Textuals) [Abstract]
Maximum Term for Exposure to Variability of Future Cash Flows					114 months
Cross Default Provisions Maximum Third Party Obligation Amount		50,000,000			$ 50,000,000			50,000,000
Commodity [Member] | Risk Management Contracts [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[8]	1,005,500,000			1,005,500,000			239,100,000
Long-term Risk Management Assets	[8]	337,300,000			337,300,000			275,900,000
Total Assets	[8]	1,342,800,000			1,342,800,000			515,000,000.0
Current Risk Management Liabilities	[8]	834,500,000			834,500,000			193,000,000.0
Long-term Risk Management Liabilities	[8]	234,600,000			234,600,000			222,200,000
Total Liabilities	[8]	1,069,100,000			1,069,100,000			415,200,000
Total MTM Derivative Contract Net Assets (Liabilities)	[8]	273,700,000			273,700,000			99,800,000
Commodity [Member] | Risk Management Contracts [Member] | AEP Texas Inc. [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[8]	800,000			800,000			400,000
Long-term Risk Management Assets	[8]	100,000			100,000			0
Total Assets	[8]	900,000			900,000			400,000
Current Risk Management Liabilities	[8]	0			0			0
Long-term Risk Management Liabilities	[8]	0			0			0
Total Liabilities	[8]	0			0			0
Total MTM Derivative Contract Net Assets (Liabilities)	[8]	900,000			900,000			400,000
Commodity [Member] | Risk Management Contracts [Member] | Appalachian Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[8]	95,700,000			95,700,000			38,800,000
Long-term Risk Management Assets	[8]	200,000			200,000			700,000
Total Assets	[8]	95,900,000			95,900,000			39,500,000
Current Risk Management Liabilities	[8]	60,200,000			60,200,000			19,700,000
Long-term Risk Management Liabilities	[8]	200,000			200,000			600,000
Total Liabilities	[8]	60,400,000			60,400,000			20,300,000
Total MTM Derivative Contract Net Assets (Liabilities)	[8]	35,500,000			35,500,000			19,200,000
Commodity [Member] | Risk Management Contracts [Member] | Indiana Michigan Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[8]	37,800,000			37,800,000			17,200,000
Long-term Risk Management Assets	[8]	100,000			100,000			500,000
Total Assets	[8]	37,900,000			37,900,000			17,700,000
Current Risk Management Liabilities	[8]	51,900,000			51,900,000			12,100,000
Long-term Risk Management Liabilities	[8]	100,000			100,000			400,000
Total Liabilities	[8]	52,000,000.0			52,000,000.0			12,500,000
Total MTM Derivative Contract Net Assets (Liabilities)	[8]	(14,100,000)			(14,100,000)			5,200,000
Commodity [Member] | Risk Management Contracts [Member] | Ohio Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[8]	600,000			600,000			300,000
Long-term Risk Management Assets	[8]	100,000			100,000			0
Total Assets	[8]	700,000			700,000			300,000
Current Risk Management Liabilities	[8]	3,500,000			3,500,000			8,700,000
Long-term Risk Management Liabilities	[8]	86,900,000			86,900,000			101,600,000
Total Liabilities	[8]	90,400,000			90,400,000			110,300,000
Total MTM Derivative Contract Net Assets (Liabilities)	[8]	(89,700,000)			(89,700,000)			(110,000,000.0)
Commodity [Member] | Risk Management Contracts [Member] | Public Service Co Of Oklahoma [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[8]	19,000,000.0			19,000,000.0			10,500,000
Long-term Risk Management Assets	[8]	0			0			0
Total Assets	[8]	19,000,000.0			19,000,000.0			10,500,000
Current Risk Management Liabilities	[8]	200,000			200,000			0
Long-term Risk Management Liabilities	[8]	0			0			0
Total Liabilities	[8]	200,000			200,000			0
Total MTM Derivative Contract Net Assets (Liabilities)	[8]	18,800,000			18,800,000			10,500,000
Commodity [Member] | Risk Management Contracts [Member] | Southwestern Electric Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[8]	18,100,000			18,100,000			3,400,000
Long-term Risk Management Assets	[8]	2,100,000			2,100,000			0
Total Assets	[8]	20,200,000			20,200,000			3,400,000
Current Risk Management Liabilities	[8]	200,000			200,000			700,000
Long-term Risk Management Liabilities	[8]	0			0			1,000,000.0
Total Liabilities	[8]	200,000			200,000			1,700,000
Total MTM Derivative Contract Net Assets (Liabilities)	[8]	20,000,000.0			20,000,000.0			1,700,000
Commodity [Member] | Hedging Contracts [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[8]	321,100,000			321,100,000			21,100,000
Long-term Risk Management Assets	[8]	85,800,000			85,800,000			18,000,000.0
Total Assets	[8]	406,900,000			406,900,000			39,100,000
Current Risk Management Liabilities	[8]	33,100,000			33,100,000			54,400,000
Long-term Risk Management Liabilities	[8]	14,300,000			14,300,000			60,100,000
Total Liabilities	[8]	47,400,000			47,400,000			114,500,000
Total MTM Derivative Contract Net Assets (Liabilities)	[8]	359,500,000			359,500,000			(75,400,000)
Interest Rate [Member]
Commodity:
Derivative, Notional Amount		1,250,000,000			1,250,000,000			1,150,000,000
Impact of Cash Flow Hedges on the Condensed Balance Sheet
AOCI Gain (Loss) Net of Tax		(26,100,000)			(26,100,000)			(47,500,000)
Portion Expected to be Reclassified to Net Income During the Next Twelve Months					$ (2,600,000)			(5,700,000)
Derivatives and Hedging (Textuals) [Abstract]
Maximum Term for Exposure to Variability of Future Cash Flows					111 months
Deferred (Gain) Loss on Discontinuation of Fair Value Hedge		57,000,000			$ 57,000,000
Notional Amount of a Discontinued Hedge		500,000,000			500,000,000
Interest Rate [Member] | AEP Texas Inc. [Member]
Commodity:
Derivative, Notional Amount		0			0			0
Impact of Cash Flow Hedges on the Condensed Balance Sheet
AOCI Gain (Loss) Net of Tax		(1,500,000)			(1,500,000)			(2,300,000)
Portion Expected to be Reclassified to Net Income During the Next Twelve Months					(1,100,000)			(1,100,000)
Interest Rate [Member] | Appalachian Power Co [Member]
Commodity:
Derivative, Notional Amount		0			0			200,000,000.0
Impact of Cash Flow Hedges on the Condensed Balance Sheet
AOCI Gain (Loss) Net of Tax		7,700,000			7,700,000			(800,000)
Portion Expected to be Reclassified to Net Income During the Next Twelve Months					800,000			400,000
Interest Rate [Member] | Indiana Michigan Power Co [Member]
Commodity:
Derivative, Notional Amount		0			0			0
Impact of Cash Flow Hedges on the Condensed Balance Sheet
AOCI Gain (Loss) Net of Tax		(7,000,000.0)			(7,000,000.0)			(8,300,000)
Portion Expected to be Reclassified to Net Income During the Next Twelve Months					(1,600,000)			(1,600,000)
Interest Rate [Member] | Ohio Power Co [Member]
Commodity:
Derivative, Notional Amount		0			0			0
Interest Rate [Member] | Public Service Co Of Oklahoma [Member]
Commodity:
Derivative, Notional Amount		0			0			0
Impact of Cash Flow Hedges on the Condensed Balance Sheet
AOCI Gain (Loss) Net of Tax		0			0			100,000
Portion Expected to be Reclassified to Net Income During the Next Twelve Months					0			100,000
Interest Rate [Member] | Southwestern Electric Power Co [Member]
Commodity:
Derivative, Notional Amount		0			0			0
Impact of Cash Flow Hedges on the Condensed Balance Sheet
AOCI Gain (Loss) Net of Tax		800,000			800,000			(300,000)
Portion Expected to be Reclassified to Net Income During the Next Twelve Months					(400,000)			(1,500,000)
Interest Rate [Member] | Hedging Contracts [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[8]	8,300,000			8,300,000			5,000,000.0
Long-term Risk Management Assets	[8]	0			0			0
Total Assets	[8]	8,300,000			8,300,000			5,000,000.0
Current Risk Management Liabilities	[8]	0			0			3,400,000
Long-term Risk Management Liabilities	[8]	28,800,000			28,800,000			4,100,000
Total Liabilities	[8]	28,800,000			28,800,000			7,500,000
Total MTM Derivative Contract Net Assets (Liabilities)	[8]	(20,500,000)			(20,500,000)			(2,500,000)
Interest Rate [Member] | Hedging Contracts [Member] | Appalachian Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[8]							2,400,000
Long-term Risk Management Assets	[8]							0
Total Assets	[8]							2,400,000
Current Risk Management Liabilities	[8]							3,400,000
Long-term Risk Management Liabilities	[8]							0
Total Liabilities	[8]							3,400,000
Total MTM Derivative Contract Net Assets (Liabilities)	[8]							(1,000,000.0)
Gross Amounts of Risk Management Assets/Liabilities Recognized [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets		1,334,900,000			1,334,900,000			265,200,000
Long-term Risk Management Assets		423,100,000			423,100,000			293,900,000
Total Assets		1,758,000,000			1,758,000,000			559,100,000
Current Risk Management Liabilities		867,600,000			867,600,000			250,800,000
Long-term Risk Management Liabilities		277,700,000			277,700,000			286,400,000
Total Liabilities		1,145,300,000			1,145,300,000			537,200,000
Total MTM Derivative Contract Net Assets (Liabilities)		612,700,000			612,700,000			21,900,000
Gross Amounts of Risk Management Assets/Liabilities Recognized [Member] | Appalachian Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets								41,200,000
Long-term Risk Management Assets								700,000
Total Assets								41,900,000
Current Risk Management Liabilities								23,100,000
Long-term Risk Management Liabilities								600,000
Total Liabilities								23,700,000
Total MTM Derivative Contract Net Assets (Liabilities)								18,200,000
Gross Amounts Offset in the Statement of Financial Position [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[9]	(965,700,000)			(965,700,000)			(170,500,000)
Long-term Risk Management Assets	[9]	(144,800,000)			(144,800,000)			(51,700,000)
Total Assets	[9]	(1,110,500,000)			(1,110,500,000)			(222,200,000)
Current Risk Management Liabilities	[9]	(761,100,000)			(761,100,000)			(172,000,000.0)
Long-term Risk Management Liabilities	[9]	(78,100,000)			(78,100,000)			(53,600,000)
Total Liabilities	[9]	(839,200,000)			(839,200,000)			(225,600,000)
Total MTM Derivative Contract Net Assets (Liabilities)	[9]	(271,300,000)			(271,300,000)			3,400,000
Gross Amounts Offset in the Statement of Financial Position [Member] | AEP Texas Inc. [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[9]	(800,000)			(800,000)			(400,000)
Long-term Risk Management Assets	[9]	(100,000)			(100,000)			0
Total Assets	[9]	(900,000)			(900,000)			(400,000)
Current Risk Management Liabilities	[9]	0			0			0
Long-term Risk Management Liabilities	[9]	0			0			0
Total Liabilities	[9]	0			0			0
Total MTM Derivative Contract Net Assets (Liabilities)	[9]	(900,000)			(900,000)			(400,000)
Gross Amounts Offset in the Statement of Financial Position [Member] | Appalachian Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[9]	(48,700,000)			(48,700,000)			(18,800,000)
Long-term Risk Management Assets	[9]	(200,000)			(200,000)			(600,000)
Total Assets	[9]	(48,900,000)			(48,900,000)			(19,400,000)
Current Risk Management Liabilities	[9]	(58,900,000)			(58,900,000)			(18,500,000)
Long-term Risk Management Liabilities	[9]	(200,000)			(200,000)			(500,000)
Total Liabilities	[9]	(59,100,000)			(59,100,000)			(19,000,000.0)
Total MTM Derivative Contract Net Assets (Liabilities)	[9]	10,200,000			10,200,000			(400,000)
Gross Amounts Offset in the Statement of Financial Position [Member] | Indiana Michigan Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[9]	(32,300,000)			(32,300,000)			(13,600,000)
Long-term Risk Management Assets	[9]	(100,000)			(100,000)			(400,000)
Total Assets	[9]	(32,400,000)			(32,400,000)			(14,000,000.0)
Current Risk Management Liabilities	[9]	(49,400,000)			(49,400,000)			(12,000,000.0)
Long-term Risk Management Liabilities	[9]	(100,000)			(100,000)			(300,000)
Total Liabilities	[9]	(49,500,000)			(49,500,000)			(12,300,000)
Total MTM Derivative Contract Net Assets (Liabilities)	[9]	17,100,000			17,100,000			(1,700,000)
Gross Amounts Offset in the Statement of Financial Position [Member] | Ohio Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[9]	(600,000)			(600,000)			(300,000)
Long-term Risk Management Assets	[9]	(100,000)			(100,000)			0
Total Assets	[9]	(700,000)			(700,000)			(300,000)
Current Risk Management Liabilities	[9]	0			0			0
Long-term Risk Management Liabilities	[9]	0			0			0
Total Liabilities	[9]	0			0			0
Total MTM Derivative Contract Net Assets (Liabilities)	[9]	(700,000)			(700,000)			(300,000)
Gross Amounts Offset in the Statement of Financial Position [Member] | Public Service Co Of Oklahoma [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[9]	(500,000)			(500,000)			(200,000)
Long-term Risk Management Assets	[9]	0			0			0
Total Assets	[9]	(500,000)			(500,000)			(200,000)
Current Risk Management Liabilities	[9]	(200,000)			(200,000)			0
Long-term Risk Management Liabilities	[9]	0			0			0
Total Liabilities	[9]	(200,000)			(200,000)			0
Total MTM Derivative Contract Net Assets (Liabilities)	[9]	(300,000)			(300,000)			(200,000)
Gross Amounts Offset in the Statement of Financial Position [Member] | Southwestern Electric Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[9]	(600,000)			(600,000)			(200,000)
Long-term Risk Management Assets	[9]	0			0			0
Total Assets	[9]	(600,000)			(600,000)			(200,000)
Current Risk Management Liabilities	[9]	(200,000)			(200,000)			0
Long-term Risk Management Liabilities	[9]	0			0			0
Total Liabilities	[9]	(200,000)			(200,000)			0
Total MTM Derivative Contract Net Assets (Liabilities)	[9]	(400,000)			(400,000)			(200,000)
Net Amounts of Assets/Liabilities Presented in the Statement of Financial Position [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[10]	369,200,000			369,200,000			94,700,000
Long-term Risk Management Assets	[10]	278,300,000			278,300,000			242,200,000
Total Assets	[10]	647,500,000			647,500,000			336,900,000
Current Risk Management Liabilities	[10]	106,500,000			106,500,000			78,800,000
Long-term Risk Management Liabilities	[10]	199,600,000			199,600,000			232,800,000
Total Liabilities	[10]	306,100,000			306,100,000			311,600,000
Total MTM Derivative Contract Net Assets (Liabilities)	[10]	341,400,000			341,400,000			25,300,000
Net Amounts of Assets/Liabilities Presented in the Statement of Financial Position [Member] | AEP Texas Inc. [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[10]	0			0			0
Long-term Risk Management Assets	[10]	0			0			0
Total Assets	[10]	0			0			0
Current Risk Management Liabilities	[10]	0			0			0
Long-term Risk Management Liabilities	[10]	0			0			0
Total Liabilities	[10]	0			0			0
Total MTM Derivative Contract Net Assets (Liabilities)	[10]	0			0			0
Net Amounts of Assets/Liabilities Presented in the Statement of Financial Position [Member] | Appalachian Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[10]	47,000,000.0			47,000,000.0			22,400,000
Long-term Risk Management Assets	[10]	0			0			100,000
Total Assets	[10]	47,000,000.0			47,000,000.0			22,500,000
Current Risk Management Liabilities	[10]	1,300,000			1,300,000			4,600,000
Long-term Risk Management Liabilities	[10]	0			0			100,000
Total Liabilities	[10]	1,300,000			1,300,000			4,700,000
Total MTM Derivative Contract Net Assets (Liabilities)	[10]	45,700,000			45,700,000			17,800,000
Net Amounts of Assets/Liabilities Presented in the Statement of Financial Position [Member] | Indiana Michigan Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[10]	5,500,000			5,500,000			3,600,000
Long-term Risk Management Assets	[10]	0			0			100,000
Total Assets	[10]	5,500,000			5,500,000			3,700,000
Current Risk Management Liabilities	[10]	2,500,000			2,500,000			100,000
Long-term Risk Management Liabilities	[10]	0			0			100,000
Total Liabilities	[10]	2,500,000			2,500,000			200,000
Total MTM Derivative Contract Net Assets (Liabilities)	[10]	3,000,000.0			3,000,000.0			3,500,000
Net Amounts of Assets/Liabilities Presented in the Statement of Financial Position [Member] | Ohio Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[10]	0			0			0
Long-term Risk Management Assets	[10]	0			0			0
Total Assets	[10]	0			0			0
Current Risk Management Liabilities	[10]	3,500,000			3,500,000			8,700,000
Long-term Risk Management Liabilities	[10]	86,900,000			86,900,000			101,600,000
Total Liabilities	[10]	90,400,000			90,400,000			110,300,000
Total MTM Derivative Contract Net Assets (Liabilities)	[10]	(90,400,000)			(90,400,000)			(110,300,000)
Net Amounts of Assets/Liabilities Presented in the Statement of Financial Position [Member] | Public Service Co Of Oklahoma [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[10]	18,500,000			18,500,000			10,300,000
Long-term Risk Management Assets	[10]	0			0			0
Total Assets	[10]	18,500,000			18,500,000			10,300,000
Current Risk Management Liabilities	[10]	0			0			0
Long-term Risk Management Liabilities	[10]	0			0			0
Total Liabilities	[10]	0			0			0
Total MTM Derivative Contract Net Assets (Liabilities)	[10]	18,500,000			18,500,000			10,300,000
Net Amounts of Assets/Liabilities Presented in the Statement of Financial Position [Member] | Southwestern Electric Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[10]	17,500,000			17,500,000			3,200,000
Long-term Risk Management Assets	[10]	2,100,000			2,100,000			0
Total Assets	[10]	19,600,000			19,600,000			3,200,000
Current Risk Management Liabilities	[10]	0			0			700,000
Long-term Risk Management Liabilities	[10]	0			0			1,000,000.0
Total Liabilities	[10]	0			0			1,700,000
Total MTM Derivative Contract Net Assets (Liabilities)	[10]	$ 19,600,000			$ 19,600,000			$ 1,500,000
Power [Member]
Commodity:
Derivative, Energy Notional Amount | MWh		341.9			341.9			331.3
Power [Member] | AEP Texas Inc. [Member]
Commodity:
Derivative, Energy Notional Amount | MWh		0.0			0.0			0.0
Power [Member] | Appalachian Power Co [Member]
Commodity:
Derivative, Energy Notional Amount | MWh		55.4			55.4			46.9
Power [Member] | Indiana Michigan Power Co [Member]
Commodity:
Derivative, Energy Notional Amount | MWh		23.1			23.1			19.7
Power [Member] | Ohio Power Co [Member]
Commodity:
Derivative, Energy Notional Amount | MWh		2.8			2.8			3.0
Power [Member] | Public Service Co Of Oklahoma [Member]
Commodity:
Derivative, Energy Notional Amount | MWh		18.7			18.7			11.9
Power [Member] | Southwestern Electric Power Co [Member]
Commodity:
Derivative, Energy Notional Amount | MWh		5.4			5.4			4.0
Natural Gas [Member]
Commodity:
Derivative, Energy Notional Amount | MMBTU		28.1			28.1			26.9
Natural Gas [Member] | AEP Texas Inc. [Member]
Commodity:
Derivative, Energy Notional Amount | MMBTU		0.0			0.0			0.0
Natural Gas [Member] | Appalachian Power Co [Member]
Commodity:
Derivative, Energy Notional Amount | MMBTU		0.0			0.0			0.0
Natural Gas [Member] | Indiana Michigan Power Co [Member]
Commodity:
Derivative, Energy Notional Amount | MMBTU		0.0			0.0			0.0
Natural Gas [Member] | Ohio Power Co [Member]
Commodity:
Derivative, Energy Notional Amount | MMBTU		0.0			0.0			0.0
Natural Gas [Member] | Public Service Co Of Oklahoma [Member]
Commodity:
Derivative, Energy Notional Amount | MMBTU		0.0			0.0			0.0
Natural Gas [Member] | Southwestern Electric Power Co [Member]
Commodity:
Derivative, Energy Notional Amount | MMBTU		5.2			5.2			7.9
Heating Oil and Gasoline [Member]
Commodity:
Derivative, Volume Notional Amount | gal		7.8			7.8			6.9
Heating Oil and Gasoline [Member] | AEP Texas Inc. [Member]
Commodity:
Derivative, Volume Notional Amount | gal		2.0			2.0			1.8
Heating Oil and Gasoline [Member] | Appalachian Power Co [Member]
Commodity:
Derivative, Volume Notional Amount | gal		1.2			1.2			1.1
Heating Oil and Gasoline [Member] | Indiana Michigan Power Co [Member]
Commodity:
Derivative, Volume Notional Amount | gal		0.7			0.7			0.6
Heating Oil and Gasoline [Member] | Ohio Power Co [Member]
Commodity:
Derivative, Volume Notional Amount | gal		1.5			1.5			1.4
Heating Oil and Gasoline [Member] | Public Service Co Of Oklahoma [Member]
Commodity:
Derivative, Volume Notional Amount | gal		0.9			0.9			0.7
Heating Oil and Gasoline [Member] | Southwestern Electric Power Co [Member]
Commodity:
Derivative, Volume Notional Amount | gal		1.1			1.1			0.9
Interest Rate Contract [Member]
Commodity:
Derivative, Notional Amount		$ 116,500,000			$ 116,500,000			$ 129,800,000
Interest Rate Contract [Member] | AEP Texas Inc. [Member]
Commodity:
Derivative, Notional Amount		0			0			0
Interest Rate Contract [Member] | Appalachian Power Co [Member]
Commodity:
Derivative, Notional Amount		0			0			0
Interest Rate Contract [Member] | Indiana Michigan Power Co [Member]
Commodity:
Derivative, Notional Amount		0			0			0
Interest Rate Contract [Member] | Ohio Power Co [Member]
Commodity:
Derivative, Notional Amount		0			0			0
Interest Rate Contract [Member] | Public Service Co Of Oklahoma [Member]
Commodity:
Derivative, Notional Amount		0			0			0
Interest Rate Contract [Member] | Southwestern Electric Power Co [Member]
Commodity:
Derivative, Notional Amount		0			0			0
Warrants Held in Investee
Fair Value of Derivative Instruments
Total Assets		16,000,000			16,000,000			$ 32,000,000
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		(10,000,000)			(16,000,000)
Vertically Integrated Utilities Revenues [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		(900,000)		500,000	(600,000)		800,000
Vertically Integrated Utilities Revenues [Member] | AEP Texas Inc. [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		0		0	0		0
Vertically Integrated Utilities Revenues [Member] | Appalachian Power Co [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		0		0	0		0
Vertically Integrated Utilities Revenues [Member] | Indiana Michigan Power Co [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		0		0	0		0
Vertically Integrated Utilities Revenues [Member] | Ohio Power Co [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		0		0	0		0
Vertically Integrated Utilities Revenues [Member] | Public Service Co Of Oklahoma [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		0		0	0		0
Vertically Integrated Utilities Revenues [Member] | Southwestern Electric Power Co [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		0		0	0		0
Generation and Marketing Revenues [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		128,800,000		11,500,000	144,900,000		11,100,000
Generation and Marketing Revenues [Member] | AEP Texas Inc. [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		0		0	0		0
Generation and Marketing Revenues [Member] | Appalachian Power Co [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		0		0	0		0
Generation and Marketing Revenues [Member] | Indiana Michigan Power Co [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		0		0	0		0
Generation and Marketing Revenues [Member] | Ohio Power Co [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		0		0	0		0
Generation and Marketing Revenues [Member] | Public Service Co Of Oklahoma [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		0		0	0		0
Generation and Marketing Revenues [Member] | Southwestern Electric Power Co [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		0		0	0		0
Electric Generation, Transmission and Distribution Revenues [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		0		0	0		0
Electric Generation, Transmission and Distribution Revenues [Member] | AEP Texas Inc. [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		0		0	0		0
Electric Generation, Transmission and Distribution Revenues [Member] | Appalachian Power Co [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		(900,000)		300,000	(600,000)		400,000
Electric Generation, Transmission and Distribution Revenues [Member] | Indiana Michigan Power Co [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		0		0	0		100,000
Electric Generation, Transmission and Distribution Revenues [Member] | Ohio Power Co [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		0		0	0		0
Electric Generation, Transmission and Distribution Revenues [Member] | Public Service Co Of Oklahoma [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		0		0	0		0
Electric Generation, Transmission and Distribution Revenues [Member] | Southwestern Electric Power Co [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		0		0	0		100,000
Purchased Electricity for Resale [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		200,000		300,000	1,200,000		1,200,000
Purchased Electricity for Resale [Member] | AEP Texas Inc. [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		0		0	0		0
Purchased Electricity for Resale [Member] | Appalachian Power Co [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		100,000		200,000	1,000,000.0		1,000,000.0
Purchased Electricity for Resale [Member] | Indiana Michigan Power Co [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		0		100,000	100,000		100,000
Purchased Electricity for Resale [Member] | Ohio Power Co [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		0		0	0		0
Purchased Electricity for Resale [Member] | Public Service Co Of Oklahoma [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		0		0	0		0
Purchased Electricity for Resale [Member] | Southwestern Electric Power Co [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		0		0	0		0
Other Operation Expense [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		900,000		(400,000)	1,900,000		(1,400,000)
Other Operation Expense [Member] | AEP Texas Inc. [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		300,000		(100,000)	600,000		(400,000)
Other Operation Expense [Member] | Appalachian Power Co [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		100,000		(100,000)	200,000		(200,000)
Other Operation Expense [Member] | Indiana Michigan Power Co [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		100,000		(100,000)	200,000		(200,000)
Other Operation Expense [Member] | Ohio Power Co [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		100,000		(100,000)	300,000		(300,000)
Other Operation Expense [Member] | Public Service Co Of Oklahoma [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		100,000		(100,000)	200,000		(200,000)
Other Operation Expense [Member] | Southwestern Electric Power Co [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		200,000		(100,000)	300,000		(200,000)
Maintenance Expense [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		1,100,000		(800,000)	2,400,000		(2,200,000)
Maintenance Expense [Member] | AEP Texas Inc. [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		200,000		(200,000)	600,000		(600,000)
Maintenance Expense [Member] | Appalachian Power Co [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		200,000		(100,000)	400,000		(300,000)
Maintenance Expense [Member] | Indiana Michigan Power Co [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		100,000		(100,000)	200,000		(200,000)
Maintenance Expense [Member] | Ohio Power Co [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		200,000		(200,000)	400,000		(400,000)
Maintenance Expense [Member] | Public Service Co Of Oklahoma [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		100,000		0	200,000		(200,000)
Maintenance Expense [Member] | Southwestern Electric Power Co [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		100,000		(100,000)	300,000		(300,000)
Regulatory Assets [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts	[11]	(7,200,000)		7,900,000	(7,800,000)		(8,500,000)
Regulatory Assets [Member] | AEP Texas Inc. [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts	[11]	0		200,000	0		(300,000)
Regulatory Assets [Member] | Appalachian Power Co [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts	[11]	(2,900,000)		400,000	(2,900,000)		(100,000)
Regulatory Assets [Member] | Indiana Michigan Power Co [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts	[11]	(16,900,000)		200,000	(22,900,000)		(200,000)
Regulatory Assets [Member] | Ohio Power Co [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts	[11]	14,900,000		4,400,000	20,300,000		(9,900,000)
Regulatory Assets [Member] | Public Service Co Of Oklahoma [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts	[11]	0		(400,000)	0		(600,000)
Regulatory Assets [Member] | Southwestern Electric Power Co [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts	[11]	100,000		2,900,000	1,400,000		2,200,000
Regulatory Liabilities [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts	[11]	46,500,000		17,000,000.0	123,600,000		80,900,000
Regulatory Liabilities [Member] | AEP Texas Inc. [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts	[11]	(100,000)		0	500,000		0
Regulatory Liabilities [Member] | Appalachian Power Co [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts	[11]	14,200,000		3,800,000	28,900,000		16,200,000
Regulatory Liabilities [Member] | Indiana Michigan Power Co [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts	[11]	1,700,000		2,600,000	1,900,000		8,800,000
Regulatory Liabilities [Member] | Ohio Power Co [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts	[11]	800,000		1,700,000	5,900,000		8,400,000
Regulatory Liabilities [Member] | Public Service Co Of Oklahoma [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts	[11]	14,000,000.0		3,100,000	40,200,000		23,900,000
Regulatory Liabilities [Member] | Southwestern Electric Power Co [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts	[11]	$ 12,700,000		$ 2,000,000.0	$ 38,500,000		$ 14,800,000

[1] Amounts include $(47) million and $(53) million as of September 30, 2021 and December 31, 2020, respectively, for the fair value hedge adjustment of hedged debt obligations for which hedge accounting has been discontinued.

[2] Amounts included on the balance sheets within Long-term Debt Due within One Year and Long-term Debt, respectively.

[3] Gain (Loss) is included in Interest Expense on the statements of income.

[4] Amounts in “Other’’ column primarily represent counterparty netting of risk management and hedging contracts and associated cash collateral under the accounting guidance for “Derivatives and Hedging.’’

[5] The September 30, 2021 maturity of the net fair value of risk management contracts prior to cash collateral, assets/(liabilities), were as follows: Level 1 matures $2 million in 2021 and $7 million in periods 2022-2024; Level 2 matures $20 million in 2021, $112 million in periods 2022-2024, $22 million in periods 2025-2026 and $13 million in periods 2027-2033; Level 3 matures $96 million in 2021, $18 million in periods 2022-2024, $5 million in periods 2025-2026 and $(21) million in periods 2027-2033.  Risk management commodity contracts are substantially comprised of power contracts.

[6] The December 31, 2020 maturity of the net fair value of risk management contracts prior to cash collateral, assets/(liabilities), were as follows: Level 2 matures $3 million in periods 2022-2024, $11 million in periods 2025-2026 and $1 million in periods 2027-2033; Level 3 matures $47 million in 2021, $37 million in periods 2022-2024, $14 million in periods 2025-2026 and $(13) million in periods 2027-2033.  Risk management commodity contracts are substantially comprised of power contracts.

[7] Substantially comprised of power contracts for the Registrant Subsidiaries.

[8] Derivative instruments within these categories are disclosed as gross.  These instruments are subject to master netting agreements and are presented on the balance sheets on a net basis in accordance with the accounting guidance for “Derivatives and Hedging.”

[9] Amounts include counterparty netting of risk management and hedging contracts and associated cash collateral in accordance with the accounting guidance for “Derivatives and Hedging.”

[10] All derivative contracts subject to a master netting arrangement or similar agreement are offset in the statement of financial position.

[11] Represents realized and unrealized gains and losses subject to regulatory accounting treatment recorded as either current or noncurrent on the balance sheets.