Derivatives and Hedging (Details) gal in Millions, MWh in Millions, MMBTU in Millions		3 Months Ended			12 Months Ended
		Mar. 31, 2021 USD ($) MWh MMBTU gal		Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($) MWh MMBTU gal
Cash Collateral Netting
Cash Collateral Received Netted Against Risk Management Assets		$ 3,000,000			$ 3,000,000
Cash Collateral Paid Netted Against Risk Management Liabilities		8,000,000			7,000,000
Fair Value of Derivative Instruments
Current Risk Management Assets		72,100,000			94,700,000
Long-term Risk Management Assets		264,800,000			242,200,000
Total Assets		336,900,000			336,900,000
Current Risk Management Liabilities		39,100,000			78,800,000
Long-term Risk Management Liabilities		273,000,000.0			232,800,000
Total Liabilities		312,100,000			311,600,000
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		29,400,000		$ (32,900,000)
Carrying Amount of Hedged Asset (Liability)	[1],[2]	(959,400,000)			(995,900,000)
Cumulative Fair Value Hedging Adjustment in the Carrying Amount of the Hedged Asset (Liability)	[1],[2]	(16,600,000)			(51,700,000)
Gain (Loss) on Hedging Instruments
Gain (Loss) on Fair Value Hedging Instruments	[3]	(33,200,000)		42,500,000
Gain (Loss) on Fair Value Portion of Long Term Debt	[3]	33,200,000		(42,500,000)
Collateral Triggering Events [Abstract]
Fair Value Of Derivative Liabilities Subject To Cross Default Provisions		156,800,000			188,400,000
Amount of Cash Collateral Posted		0			0
Additional Settlement Liability if Cross Default Provision is Triggered		127,700,000			169,200,000
Derivatives and Hedging (Textuals) [Abstract]
Hedged Liability, Discontinued Fair Value Hedge, Cumulative Increase (Decrease)		(51,000,000)			(53,000,000)
Investment in Private Investee
Derivatives and Hedging (Textuals) [Abstract]
Cost Method Investments					8,000,000
Equity Method Investments, Fair Value Disclosure		35,000,000
Unrealized Gain (Loss) on Investments		27,000,000
AEP Texas Inc. [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		600,000		(1,400,000)
Appalachian Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets		6,900,000			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		4,100,000		(16,000,000.0)
Collateral Triggering Events [Abstract]
Fair Value Of Derivative Liabilities Subject To Cross Default Provisions		600,000			4,300,000
Amount of Cash Collateral Posted		0			0
Additional Settlement Liability if Cross Default Provision is Triggered		100,000			3,500,000
Indiana Michigan Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets		900,000			3,600,000
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		(4,000,000.0)		2,600,000
Collateral Triggering Events [Abstract]
Fair Value Of Derivative Liabilities Subject To Cross Default Provisions		400,000			500,000
Amount of Cash Collateral Posted		0			0
Additional Settlement Liability if Cross Default Provision is Triggered		100,000			100,000
Ohio Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Liabilities		8,100,000			8,700,000
Long-term Risk Management Liabilities		95,900,000			101,600,000
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		9,700,000		(15,000,000.0)
Public Service Co Of Oklahoma [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets		5,500,000			10,300,000
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		11,300,000		7,600,000
Southwestern Electric Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets		1,300,000			3,200,000
Current Risk Management Liabilities		0			700,000
Long-term Risk Management Liabilities		900,000			1,000,000.0
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		7,100,000		3,100,000
Collateral Triggering Events [Abstract]
Fair Value Of Derivative Liabilities Subject To Cross Default Provisions		900,000			1,800,000
Amount of Cash Collateral Posted		0			0
Additional Settlement Liability if Cross Default Provision is Triggered		900,000			1,800,000
Risk Management Contracts [Member]
Fair Value of Derivative Instruments
Total Assets	[4]	319,100,000	[5]		322,100,000	[6]
Total Liabilities	[4]	236,800,000	[5]		218,900,000	[6]
Risk Management Contracts [Member] | AEP Texas Inc. [Member]
Fair Value of Derivative Instruments
Total Assets	[4]	0			0
Risk Management Contracts [Member] | Appalachian Power Co [Member]
Fair Value of Derivative Instruments
Total Assets	[4],[7]	6,900,000			20,100,000
Total Liabilities	[4],[7]	200,000			1,300,000
Risk Management Contracts [Member] | Indiana Michigan Power Co [Member]
Fair Value of Derivative Instruments
Total Assets	[4],[7]	900,000			3,700,000
Total Liabilities	[4],[7]	200,000			200,000
Risk Management Contracts [Member] | Ohio Power Co [Member]
Fair Value of Derivative Instruments
Total Assets	[4],[7]	0			0
Total Liabilities	[4],[7]	104,000,000.0			110,300,000
Risk Management Contracts [Member] | Public Service Co Of Oklahoma [Member]
Fair Value of Derivative Instruments
Total Assets	[4],[7]	5,500,000			10,300,000
Risk Management Contracts [Member] | Southwestern Electric Power Co [Member]
Fair Value of Derivative Instruments
Total Assets	[4],[7]	1,300,000			3,200,000
Total Liabilities	[4],[7]	900,000			1,700,000
Commodity [Member]
Impact of Cash Flow Hedges on the Condensed Balance Sheet
AOCI Gain (Loss) Net of Tax		(18,500,000)			(60,600,000)
Portion Expected to be Reclassified to Net Income During the Next Twelve Months		$ (300,000)			(27,100,000)
Derivatives and Hedging (Textuals) [Abstract]
Maximum Term for Exposure to Variability of Future Cash Flows		120 months
Cross Default Provisions Maximum Third Party Obligation Amount		$ 50,000,000			50,000,000
Commodity [Member] | Risk Management Contracts [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[8]	164,100,000			239,100,000
Long-term Risk Management Assets	[8]	266,900,000			275,900,000
Total Assets	[8]	431,000,000.0			515,000,000.0
Current Risk Management Liabilities	[8]	133,600,000			193,000,000.0
Long-term Risk Management Liabilities	[8]	219,800,000			222,200,000
Total Liabilities	[8]	353,400,000			415,200,000
Total MTM Derivative Contract Net Assets (Liabilities)	[8]	77,600,000			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			400,000
Long-term Risk Management Assets	[8]	0			0
Total Assets	[8]	800,000			400,000
Current Risk Management Liabilities	[8]	0			0
Long-term Risk Management Liabilities	[8]	0			0
Total Liabilities	[8]	0			0
Total MTM Derivative Contract Net Assets (Liabilities)	[8]	800,000			400,000
Commodity [Member] | Risk Management Contracts [Member] | Appalachian Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[8]	16,500,000			38,800,000
Long-term Risk Management Assets	[8]	500,000			700,000
Total Assets	[8]	17,000,000.0			39,500,000
Current Risk Management Liabilities	[8]	9,300,000			19,700,000
Long-term Risk Management Liabilities	[8]	500,000			600,000
Total Liabilities	[8]	9,800,000			20,300,000
Total MTM Derivative Contract Net Assets (Liabilities)	[8]	7,200,000			19,200,000
Commodity [Member] | Risk Management Contracts [Member] | Indiana Michigan Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[8]	6,800,000			17,200,000
Long-term Risk Management Assets	[8]	300,000			500,000
Total Assets	[8]	7,100,000			17,700,000
Current Risk Management Liabilities	[8]	6,200,000			12,100,000
Long-term Risk Management Liabilities	[8]	300,000			400,000
Total Liabilities	[8]	6,500,000			12,500,000
Total MTM Derivative Contract Net Assets (Liabilities)	[8]	600,000			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			300,000
Long-term Risk Management Assets	[8]	0			0
Total Assets	[8]	600,000			300,000
Current Risk Management Liabilities	[8]	8,100,000			8,700,000
Long-term Risk Management Liabilities	[8]	95,900,000			101,600,000
Total Liabilities	[8]	104,000,000.0			110,300,000
Total MTM Derivative Contract Net Assets (Liabilities)	[8]	(103,400,000)			(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]	5,800,000			10,500,000
Long-term Risk Management Assets	[8]	0			0
Total Assets	[8]	5,800,000			10,500,000
Current Risk Management Liabilities	[8]	0			0
Long-term Risk Management Liabilities	[8]	0			0
Total Liabilities	[8]	0			0
Total MTM Derivative Contract Net Assets (Liabilities)	[8]	5,800,000			10,500,000
Commodity [Member] | Risk Management Contracts [Member] | Southwestern Electric Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[8]	1,700,000			3,400,000
Long-term Risk Management Assets	[8]	0			0
Total Assets	[8]	1,700,000			3,400,000
Current Risk Management Liabilities	[8]	0			700,000
Long-term Risk Management Liabilities	[8]	900,000			1,000,000.0
Total Liabilities	[8]	900,000			1,700,000
Total MTM Derivative Contract Net Assets (Liabilities)	[8]	800,000			1,700,000
Commodity [Member] | Hedging Contracts [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[8]	34,800,000			21,100,000
Long-term Risk Management Assets	[8]	18,800,000			18,000,000.0
Total Assets	[8]	53,600,000			39,100,000
Current Risk Management Liabilities	[8]	34,800,000			54,400,000
Long-term Risk Management Liabilities	[8]	41,600,000			60,100,000
Total Liabilities	[8]	76,400,000			114,500,000
Total MTM Derivative Contract Net Assets (Liabilities)	[8]	(22,800,000)			(75,400,000)
Interest Rate [Member]
Commodity:
Derivative, Notional Amount		950,000,000.0			1,150,000,000.0
Impact of Cash Flow Hedges on the Condensed Balance Sheet
AOCI Gain (Loss) Net of Tax		(33,300,000)			(47,500,000)
Portion Expected to be Reclassified to Net Income During the Next Twelve Months		$ (5,100,000)			(5,700,000)
Derivatives and Hedging (Textuals) [Abstract]
Maximum Term for Exposure to Variability of Future Cash Flows		117 months
Deferred (Gain) Loss on Discontinuation of Fair Value Hedge		$ 57,000,000
Notional Amount of a Discontinued Hedge		500,000,000
Interest Rate [Member] | AEP Texas Inc. [Member]
Commodity:
Derivative, Notional Amount		0			0
Impact of Cash Flow Hedges on the Condensed Balance Sheet
AOCI Gain (Loss) Net of Tax		(2,000,000.0)			(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			200,000,000.0
Impact of Cash Flow Hedges on the Condensed Balance Sheet
AOCI Gain (Loss) Net of Tax		8,200,000			(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
Impact of Cash Flow Hedges on the Condensed Balance Sheet
AOCI Gain (Loss) Net of Tax		(7,800,000)			(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
Interest Rate [Member] | Public Service Co Of Oklahoma [Member]
Commodity:
Derivative, Notional Amount		0			0
Impact of Cash Flow Hedges on the Condensed Balance Sheet
AOCI Gain (Loss) Net of Tax		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
Impact of Cash Flow Hedges on the Condensed Balance Sheet
AOCI Gain (Loss) Net of Tax		100,000			(300,000)
Portion Expected to be Reclassified to Net Income During the Next Twelve Months		(1,200,000)			(1,500,000)
Interest Rate [Member] | Hedging Contracts [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[8]	2,700,000			5,000,000.0
Long-term Risk Management Assets	[8]	0			0
Total Assets	[8]	2,700,000			5,000,000.0
Current Risk Management Liabilities	[8]	0			3,400,000
Long-term Risk Management Liabilities	[8]	37,400,000			4,100,000
Total Liabilities	[8]	37,400,000			7,500,000
Total MTM Derivative Contract Net Assets (Liabilities)	[8]	(34,700,000)			(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		201,600,000			265,200,000
Long-term Risk Management Assets		285,700,000			293,900,000
Total Assets		487,300,000			559,100,000
Current Risk Management Liabilities		168,400,000			250,800,000
Long-term Risk Management Liabilities		298,800,000			286,400,000
Total Liabilities		467,200,000			537,200,000
Total MTM Derivative Contract Net Assets (Liabilities)		20,100,000			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]	(129,500,000)			(170,500,000)
Long-term Risk Management Assets	[9]	(20,900,000)			(51,700,000)
Total Assets	[9]	(150,400,000)			(222,200,000)
Current Risk Management Liabilities	[9]	(129,300,000)			(172,000,000.0)
Long-term Risk Management Liabilities	[9]	(25,800,000)			(53,600,000)
Total Liabilities	[9]	(155,100,000)			(225,600,000)
Total MTM Derivative Contract Net Assets (Liabilities)	[9]	4,700,000			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)			(400,000)
Long-term Risk Management Assets	[9]	0			0
Total Assets	[9]	(800,000)			(400,000)
Current Risk Management Liabilities	[9]	0			0
Long-term Risk Management Liabilities	[9]	0			0
Total Liabilities	[9]	0			0
Total MTM Derivative Contract Net Assets (Liabilities)	[9]	(800,000)			(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]	(9,600,000)			(18,800,000)
Long-term Risk Management Assets	[9]	(500,000)			(600,000)
Total Assets	[9]	(10,100,000)			(19,400,000)
Current Risk Management Liabilities	[9]	(9,100,000)			(18,500,000)
Long-term Risk Management Liabilities	[9]	(500,000)			(500,000)
Total Liabilities	[9]	(9,600,000)			(19,000,000.0)
Total MTM Derivative Contract Net Assets (Liabilities)	[9]	(500,000)			(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]	(5,900,000)			(13,600,000)
Long-term Risk Management Assets	[9]	(300,000)			(400,000)
Total Assets	[9]	(6,200,000)			(14,000,000.0)
Current Risk Management Liabilities	[9]	(6,000,000.0)			(12,000,000.0)
Long-term Risk Management Liabilities	[9]	(300,000)			(300,000)
Total Liabilities	[9]	(6,300,000)			(12,300,000)
Total MTM Derivative Contract Net Assets (Liabilities)	[9]	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)			(300,000)
Long-term Risk Management Assets	[9]	0			0
Total Assets	[9]	(600,000)			(300,000)
Current Risk Management Liabilities	[9]	0			0
Long-term Risk Management Liabilities	[9]	0			0
Total Liabilities	[9]	0			0
Total MTM Derivative Contract Net Assets (Liabilities)	[9]	(600,000)			(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]	(300,000)			(200,000)
Long-term Risk Management Assets	[9]	0			0
Total Assets	[9]	(300,000)			(200,000)
Current Risk Management Liabilities	[9]	0			0
Long-term Risk Management Liabilities	[9]	0			0
Total Liabilities	[9]	0			0
Total MTM Derivative Contract Net Assets (Liabilities)	[9]	(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]	(400,000)			(200,000)
Long-term Risk Management Assets	[9]	0			0
Total Assets	[9]	(400,000)			(200,000)
Current Risk Management Liabilities	[9]	0			0
Long-term Risk Management Liabilities	[9]	0			0
Total Liabilities	[9]	0			0
Total MTM Derivative Contract Net Assets (Liabilities)	[9]	(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]	72,100,000			94,700,000
Long-term Risk Management Assets	[10]	264,800,000			242,200,000
Total Assets	[10]	336,900,000			336,900,000
Current Risk Management Liabilities	[10]	39,100,000			78,800,000
Long-term Risk Management Liabilities	[10]	273,000,000.0			232,800,000
Total Liabilities	[10]	312,100,000			311,600,000
Total MTM Derivative Contract Net Assets (Liabilities)	[10]	24,800,000			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
Long-term Risk Management Assets	[10]	0			0
Total Assets	[10]	0			0
Current Risk Management Liabilities	[10]	0			0
Long-term Risk Management Liabilities	[10]	0			0
Total Liabilities	[10]	0			0
Total MTM Derivative Contract Net Assets (Liabilities)	[10]	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]	6,900,000			22,400,000
Long-term Risk Management Assets	[10]	0			100,000
Total Assets	[10]	6,900,000			22,500,000
Current Risk Management Liabilities	[10]	200,000			4,600,000
Long-term Risk Management Liabilities	[10]	0			100,000
Total Liabilities	[10]	200,000			4,700,000
Total MTM Derivative Contract Net Assets (Liabilities)	[10]	6,700,000			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]	900,000			3,600,000
Long-term Risk Management Assets	[10]	0			100,000
Total Assets	[10]	900,000			3,700,000
Current Risk Management Liabilities	[10]	200,000			100,000
Long-term Risk Management Liabilities	[10]	0			100,000
Total Liabilities	[10]	200,000			200,000
Total MTM Derivative Contract Net Assets (Liabilities)	[10]	700,000			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
Long-term Risk Management Assets	[10]	0			0
Total Assets	[10]	0			0
Current Risk Management Liabilities	[10]	8,100,000			8,700,000
Long-term Risk Management Liabilities	[10]	95,900,000			101,600,000
Total Liabilities	[10]	104,000,000.0			110,300,000
Total MTM Derivative Contract Net Assets (Liabilities)	[10]	(104,000,000.0)			(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]	5,500,000			10,300,000
Long-term Risk Management Assets	[10]	0			0
Total Assets	[10]	5,500,000			10,300,000
Current Risk Management Liabilities	[10]	0			0
Long-term Risk Management Liabilities	[10]	0			0
Total Liabilities	[10]	0			0
Total MTM Derivative Contract Net Assets (Liabilities)	[10]	5,500,000			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]	1,300,000			3,200,000
Long-term Risk Management Assets	[10]	0			0
Total Assets	[10]	1,300,000			3,200,000
Current Risk Management Liabilities	[10]	0			700,000
Long-term Risk Management Liabilities	[10]	900,000			1,000,000.0
Total Liabilities	[10]	900,000			1,700,000
Total MTM Derivative Contract Net Assets (Liabilities)	[10]	$ 400,000			$ 1,500,000
Power [Member]
Commodity:
Derivative, Energy Notional Amount | MWh		271.2			331.3
Power [Member] | AEP Texas Inc. [Member]
Commodity:
Derivative, Energy Notional Amount | MWh		0.0			0.0
Power [Member] | Appalachian Power Co [Member]
Commodity:
Derivative, Energy Notional Amount | MWh		23.3			46.9
Power [Member] | Indiana Michigan Power Co [Member]
Commodity:
Derivative, Energy Notional Amount | MWh		10.8			19.7
Power [Member] | Ohio Power Co [Member]
Commodity:
Derivative, Energy Notional Amount | MWh		2.9			3.0
Power [Member] | Public Service Co Of Oklahoma [Member]
Commodity:
Derivative, Energy Notional Amount | MWh		3.8			11.9
Power [Member] | Southwestern Electric Power Co [Member]
Commodity:
Derivative, Energy Notional Amount | MWh		1.6			4.0
Natural Gas [Member]
Commodity:
Derivative, Energy Notional Amount | MMBTU		22.7			26.9
Natural Gas [Member] | AEP Texas Inc. [Member]
Commodity:
Derivative, Energy Notional Amount | MMBTU		0.0			0.0
Natural Gas [Member] | Appalachian Power Co [Member]
Commodity:
Derivative, Energy Notional Amount | MMBTU		0.0			0.0
Natural Gas [Member] | Indiana Michigan Power Co [Member]
Commodity:
Derivative, Energy Notional Amount | MMBTU		0.0			0.0
Natural Gas [Member] | Ohio Power Co [Member]
Commodity:
Derivative, Energy Notional Amount | MMBTU		0.0			0.0
Natural Gas [Member] | Public Service Co Of Oklahoma [Member]
Commodity:
Derivative, Energy Notional Amount | MMBTU		0.0			0.0
Natural Gas [Member] | Southwestern Electric Power Co [Member]
Commodity:
Derivative, Energy Notional Amount | MMBTU		7.0			7.9
Heating Oil and Gasoline [Member]
Commodity:
Derivative, Volume Notional Amount | gal		5.0			6.9
Heating Oil and Gasoline [Member] | AEP Texas Inc. [Member]
Commodity:
Derivative, Volume Notional Amount | gal		1.3			1.8
Heating Oil and Gasoline [Member] | Appalachian Power Co [Member]
Commodity:
Derivative, Volume Notional Amount | gal		0.8			1.1
Heating Oil and Gasoline [Member] | Indiana Michigan Power Co [Member]
Commodity:
Derivative, Volume Notional Amount | gal		0.5			0.6
Heating Oil and Gasoline [Member] | Ohio Power Co [Member]
Commodity:
Derivative, Volume Notional Amount | gal		1.0			1.4
Heating Oil and Gasoline [Member] | Public Service Co Of Oklahoma [Member]
Commodity:
Derivative, Volume Notional Amount | gal		0.5			0.7
Heating Oil and Gasoline [Member] | Southwestern Electric Power Co [Member]
Commodity:
Derivative, Volume Notional Amount | gal		0.7			0.9
Interest Rate Contract [Member]
Commodity:
Derivative, Notional Amount		$ 123,600,000			$ 129,800,000
Interest Rate Contract [Member] | AEP Texas Inc. [Member]
Commodity:
Derivative, Notional Amount		0			0
Interest Rate Contract [Member] | Appalachian Power Co [Member]
Commodity:
Derivative, Notional Amount		0			0
Interest Rate Contract [Member] | Indiana Michigan Power Co [Member]
Commodity:
Derivative, Notional Amount		0			0
Interest Rate Contract [Member] | Ohio Power Co [Member]
Commodity:
Derivative, Notional Amount		0			0
Interest Rate Contract [Member] | Public Service Co Of Oklahoma [Member]
Commodity:
Derivative, Notional Amount		0			0
Interest Rate Contract [Member] | Southwestern Electric Power Co [Member]
Commodity:
Derivative, Notional Amount		0			0
Warrants Held in Investee
Fair Value of Derivative Instruments
Total Assets		22,000,000			$ 32,000,000
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		10,000,000
Vertically Integrated Utilities Revenues [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		200,000		400,000
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
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
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
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
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
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
Generation and Marketing Revenues [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		(400,000)		(10,300,000)
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
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
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
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
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
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
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
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
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		200,000		200,000
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		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
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
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
Purchased Electricity for Resale [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		400,000		100,000
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
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		400,000		100,000
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		0
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
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
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
Other Operation Expense [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		300,000		(200,000)
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		100,000		(100,000)
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		0		0
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		0		0
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)
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		0		0
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		0		0
Maintenance Expense [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		500,000		(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		100,000		(100,000)
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		100,000		(100,000)
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		0
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		100,000		0
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
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		0
Regulatory Assets [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts	[11]	6,400,000		(33,900,000)
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		(1,200,000)
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]	0		(8,900,000)
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]	(900,000)		(700,000)
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]	6,600,000		(18,400,000)
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		(500,000)
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]	800,000		(200,000)
Regulatory Liabilities [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts	[11]	22,000,000.0		11,200,000
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]	400,000		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]	3,400,000		(7,300,000)
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]	(3,200,000)		3,200,000
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]	2,900,000		3,500,000
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]	11,200,000		8,100,000
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]	$ 6,200,000		$ 3,300,000

[1] Amounts include $(51) million and $(53) million as of March 31, 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 March 31, 2021 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 2021, $11 million in periods 2022-2024, $17 million in periods 2025-2026 and $10 million in periods 2027-2033; Level 3 matures $23 million in 2021, $32 million in periods 2022-2024, $8 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 reported 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.