Derivatives and Hedging (Details) gal in Millions, MWh in Millions, MMBTU in Millions		3 Months Ended			12 Months Ended
		Mar. 31, 2019 USD ($) MWh MMBTU gal		Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($) MWh MMBTU gal
Carrying Amount of Hedged Asset (Liability)	[1]	$ (489,600,000)			$ (478,300,000)
Derivative, Gain (Loss) on Derivative, Net	[2]	11,100,000		$ (14,500,000)
Gain (Loss) on Fair Value Portion of Long Term Debt	[2]	(11,100,000)		14,500,000
Cash Collateral Netting
Cash Collateral Received Netted Against Risk Management Assets		9,000,000			18,000,000
Cash Collateral Paid Netted Against Risk Management Liabilities		9,000,000			4,000,000
Fair Value of Derivative Instruments
Current Risk Management Assets		93,900,000			162,800,000
Long-term Risk Management Assets		250,400,000			254,000,000.0
Total Assets		344,300,000			416,800,000
Current Risk Management Liabilities		63,400,000			55,000,000.0
Long-term Risk Management Liabilities		267,900,000			263,400,000
Derivative Liability		331,300,000			318,400,000
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		(24,900,000)		109,300,000
Collateral Triggering Events
Liabilities for Contracts with Cross Default Provisions Prior to Contractual Netting Arrangements		219,200,000			225,500,000
Amount of Cash Collateral Posted		3,800,000			1,800,000
Additional Settlement Liability if Cross Default Provision is Triggered		$ 189,000,000.0			181,000,000.0
Derivatives and Hedging (Textuals)
Maximum Term for Exposure to Variability of Future Cash Flows		177 months
Cumulative Fair Value Hedging Adjustment in the Carrying Amount of the Hedged Asset (Liability)	[1]	$ 6,300,000			17,400,000
AEP Texas Inc. [Member]
Fair Value of Derivative Instruments
Current Risk Management Liabilities		200,000			200,000
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		400,000		100,000
Appalachian Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets		12,900,000			57,200,000
Long-term Risk Management Assets		300,000			900,000
Current Risk Management Liabilities		6,100,000			400,000
Long-term Risk Management Liabilities		200,000			200,000
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		(34,000,000.0)		68,500,000
Collateral Triggering Events
Liabilities for Contracts with Cross Default Provisions Prior to Contractual Netting Arrangements		1,400,000			900,000
Amount of Cash Collateral Posted		0			0
Additional Settlement Liability if Cross Default Provision is Triggered		100,000			0
Indiana Michigan Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets		4,400,000			8,600,000
Long-term Risk Management Assets		100,000			600,000
Current Risk Management Liabilities		300,000			300,000
Long-term Risk Management Liabilities		100,000			100,000
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		7,200,000		1,500,000
Collateral Triggering Events
Liabilities for Contracts with Cross Default Provisions Prior to Contractual Netting Arrangements		800,000			500,000
Amount of Cash Collateral Posted		0			0
Additional Settlement Liability if Cross Default Provision is Triggered		100,000			0
Ohio Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Liabilities		6,900,000			5,800,000
Long-term Risk Management Liabilities		99,400,000			93,800,000
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		(9,100,000)		31,600,000
Public Service Co Of Oklahoma [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets		5,000,000.0			10,400,000
Current Risk Management Liabilities		700,000			1,000,000.0
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		6,700,000		12,100,000
Southwestern Electric Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets		2,000,000.0			4,800,000
Current Risk Management Liabilities		200,000			400,000
Long-term Risk Management Liabilities		1,900,000			2,200,000
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		4,600,000		(1,100,000)
Collateral Triggering Events
Liabilities for Contracts with Cross Default Provisions Prior to Contractual Netting Arrangements		2,000,000.0			2,300,000
Amount of Cash Collateral Posted		0			0
Additional Settlement Liability if Cross Default Provision is Triggered		1,900,000			2,300,000
Risk Management Contracts [Member]
Fair Value of Derivative Instruments
Total Assets	[3]	324,100,000	[4]		382,700,000	[5]
Derivative Liability	[3]	249,000,000.0	[4]		242,100,000	[5]
Risk Management Contracts [Member] | AEP Texas Inc. [Member]
Fair Value of Derivative Instruments
Derivative Liability	[3]	200,000			200,000
Risk Management Contracts [Member] | Appalachian Power Co [Member]
Fair Value of Derivative Instruments
Total Assets	[3],[6]	13,200,000			58,100,000
Derivative Liability	[3],[6]	6,300,000			600,000
Risk Management Contracts [Member] | Indiana Michigan Power Co [Member]
Fair Value of Derivative Instruments
Total Assets	[3],[6]	4,500,000			9,200,000
Derivative Liability	[3],[6]	400,000			400,000
Risk Management Contracts [Member] | Ohio Power Co [Member]
Fair Value of Derivative Instruments
Derivative Liability	[3],[6]	106,300,000			99,600,000
Risk Management Contracts [Member] | Public Service Co Of Oklahoma [Member]
Fair Value of Derivative Instruments
Total Assets	[3],[6]	5,000,000.0			10,400,000
Derivative Liability	[3],[6]	700,000			1,000,000.0
Risk Management Contracts [Member] | Southwestern Electric Power Co [Member]
Fair Value of Derivative Instruments
Total Assets	[3],[6]	2,000,000.0			4,800,000
Derivative Liability	[3],[6]	2,100,000			2,600,000
Commodity [Member]
Impact of Cash Flow Hedges on the Condensed Balance Sheet
AOCI Gain (Loss) Net of Tax		(52,100,000)			(23,000,000.0)
Portion Expected to be Reclassified to Net Income During the Next Twelve Months		1,600,000			10,400,000
Derivatives and Hedging (Textuals)
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	[7]	228,300,000			397,500,000
Long-term Risk Management Assets	[7]	279,000,000.0			276,400,000
Total Assets	[7]	507,300,000			673,900,000
Current Risk Management Liabilities	[7]	195,900,000			293,800,000
Long-term Risk Management Liabilities	[7]	236,600,000			225,700,000
Derivative Liability	[7]	432,500,000			519,500,000
Total MTM Derivative Contract Net Assets (Liabilities)	[7]	74,800,000			154,400,000
Commodity [Member] | Risk Management Contracts [Member] | AEP Texas Inc. [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[7]	0			0
Long-term Risk Management Assets	[7]	0			0
Total Assets	[7]	0			0
Current Risk Management Liabilities	[7]	200,000			700,000
Long-term Risk Management Liabilities	[7]	0			0
Derivative Liability	[7]	200,000			700,000
Total MTM Derivative Contract Net Assets (Liabilities)	[7]	(200,000)			(700,000)
Commodity [Member] | Risk Management Contracts [Member] | Appalachian Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[7]	40,500,000			114,400,000
Long-term Risk Management Assets	[7]	3,900,000			3,100,000
Total Assets	[7]	44,400,000			117,500,000
Current Risk Management Liabilities	[7]	33,500,000			56,700,000
Long-term Risk Management Liabilities	[7]	3,700,000			2,400,000
Derivative Liability	[7]	37,200,000			59,100,000
Total MTM Derivative Contract Net Assets (Liabilities)	[7]	7,200,000			58,400,000
Commodity [Member] | Risk Management Contracts [Member] | Indiana Michigan Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[7]	22,000,000.0			50,400,000
Long-term Risk Management Assets	[7]	2,300,000			2,000,000.0
Total Assets	[7]	24,300,000			52,400,000
Current Risk Management Liabilities	[7]	17,600,000			41,100,000
Long-term Risk Management Liabilities	[7]	2,200,000			1,600,000
Derivative Liability	[7]	19,800,000			42,700,000
Total MTM Derivative Contract Net Assets (Liabilities)	[7]	4,500,000			9,700,000
Commodity [Member] | Risk Management Contracts [Member] | Ohio Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[7]	0			0
Long-term Risk Management Assets	[7]	0			0
Total Assets	[7]	0			0
Current Risk Management Liabilities	[7]	6,900,000			6,400,000
Long-term Risk Management Liabilities	[7]	99,400,000			93,800,000
Derivative Liability	[7]	106,300,000			100,200,000
Total MTM Derivative Contract Net Assets (Liabilities)	[7]	(106,300,000)			(100,200,000)
Commodity [Member] | Risk Management Contracts [Member] | Public Service Co Of Oklahoma [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[7]	5,400,000			10,900,000
Long-term Risk Management Assets	[7]	0			0
Total Assets	[7]	5,400,000			10,900,000
Current Risk Management Liabilities	[7]	1,100,000			1,700,000
Long-term Risk Management Liabilities	[7]	0			0
Derivative Liability	[7]	1,100,000			1,700,000
Total MTM Derivative Contract Net Assets (Liabilities)	[7]	4,300,000			9,200,000
Commodity [Member] | Risk Management Contracts [Member] | Southwestern Electric Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[7]	2,300,000			5,600,000
Long-term Risk Management Assets	[7]	0			0
Total Assets	[7]	2,300,000			5,600,000
Current Risk Management Liabilities	[7]	500,000			1,500,000
Long-term Risk Management Liabilities	[7]	1,900,000			2,200,000
Derivative Liability	[7]	2,400,000			3,700,000
Total MTM Derivative Contract Net Assets (Liabilities)	[7]	(100,000)			1,900,000
Commodity [Member] | Hedging Contracts [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[7]	20,800,000			28,500,000
Long-term Risk Management Assets	[7]	7,400,000			16,000,000.0
Total Assets	[7]	28,200,000			44,500,000
Current Risk Management Liabilities	[7]	15,400,000			13,200,000
Long-term Risk Management Liabilities	[7]	68,600,000			56,100,000
Derivative Liability	[7]	84,000,000.0			69,300,000
Total MTM Derivative Contract Net Assets (Liabilities)	[7]	(55,800,000)			(24,800,000)
Interest Rate [Member]
Commodity:
Derivative, Notional Amount		500,000,000.0			500,000,000.0
Impact of Cash Flow Hedges on the Condensed Balance Sheet
AOCI Gain (Loss) Net of Tax		(12,400,000)			(12,600,000)
Portion Expected to be Reclassified to Net Income During the Next Twelve Months		(1,500,000)			(1,100,000)
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		(4,100,000)			(4,400,000)
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
Impact of Cash Flow Hedges on the Condensed Balance Sheet
AOCI Gain (Loss) Net of Tax		1,600,000			1,800,000
Portion Expected to be Reclassified to Net Income During the Next Twelve Months		900,000			900,000
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		(11,100,000)			(11,500,000)
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
Impact of Cash Flow Hedges on the Condensed Balance Sheet
AOCI Gain (Loss) Net of Tax		700,000			1,000,000.0
Portion Expected to be Reclassified to Net Income During the Next Twelve Months		600,000			1,000,000.0
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		1,900,000			2,100,000
Portion Expected to be Reclassified to Net Income During the Next Twelve Months		1,000,000.0			1,000,000.0
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		(2,900,000)			(3,300,000)
Portion Expected to be Reclassified to Net Income During the Next Twelve Months		(1,500,000)			(1,500,000)
Interest Rate [Member] | Hedging Contracts [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[7]	0			0
Long-term Risk Management Assets	[7]	0			0
Total Assets	[7]	0			0
Current Risk Management Liabilities	[7]	1,900,000			2,000,000.0
Long-term Risk Management Liabilities	[7]	4,400,000			15,400,000
Derivative Liability	[7]	6,300,000			17,400,000
Total MTM Derivative Contract Net Assets (Liabilities)	[7]	(6,300,000)			(17,400,000)
Gross Amounts of Risk Management Assets/Liabilities Recognized [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets		249,100,000			426,000,000.0
Long-term Risk Management Assets		286,400,000			292,400,000
Total Assets		535,500,000			718,400,000
Current Risk Management Liabilities		213,200,000			309,000,000.0
Long-term Risk Management Liabilities		309,600,000			297,200,000
Derivative Liability		522,800,000			606,200,000
Total MTM Derivative Contract Net Assets (Liabilities)		12,700,000			112,200,000
Gross Amounts Offset in the Statement of Financial Position [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[8]	(155,200,000)			(263,200,000)
Long-term Risk Management Assets	[8]	(36,000,000.0)			(38,400,000)
Total Assets	[8]	(191,200,000)			(301,600,000)
Current Risk Management Liabilities	[8]	(149,800,000)			(254,000,000.0)
Long-term Risk Management Liabilities	[8]	(41,700,000)			(33,800,000)
Derivative Liability	[8]	(191,500,000)			(287,800,000)
Total MTM Derivative Contract Net Assets (Liabilities)	[8]	300,000			(13,800,000)
Gross Amounts Offset in the Statement of Financial Position [Member] | AEP Texas Inc. [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[8]	0			0
Long-term Risk Management Assets	[8]	0			0
Total Assets	[8]	0			0
Current Risk Management Liabilities	[8]	0			(500,000)
Long-term Risk Management Liabilities	[8]	0			0
Derivative Liability	[8]	0			(500,000)
Total MTM Derivative Contract Net Assets (Liabilities)	[8]	0			500,000
Gross Amounts Offset in the Statement of Financial Position [Member] | Appalachian Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[8]	(27,600,000)			(57,200,000)
Long-term Risk Management Assets	[8]	(3,600,000)			(2,200,000)
Total Assets	[8]	(31,200,000)			(59,400,000)
Current Risk Management Liabilities	[8]	(27,400,000)			(56,300,000)
Long-term Risk Management Liabilities	[8]	(3,500,000)			(2,200,000)
Derivative Liability	[8]	(30,900,000)			(58,500,000)
Total MTM Derivative Contract Net Assets (Liabilities)	[8]	(300,000)			(900,000)
Gross Amounts Offset in the Statement of Financial Position [Member] | Indiana Michigan Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[8]	(17,600,000)			(41,800,000)
Long-term Risk Management Assets	[8]	(2,200,000)			(1,400,000)
Total Assets	[8]	(19,800,000)			(43,200,000)
Current Risk Management Liabilities	[8]	(17,300,000)			(40,800,000)
Long-term Risk Management Liabilities	[8]	(2,100,000)			(1,500,000)
Derivative Liability	[8]	(19,400,000)			(42,300,000)
Total MTM Derivative Contract Net Assets (Liabilities)	[8]	(400,000)			(900,000)
Gross Amounts Offset in the Statement of Financial Position [Member] | Ohio Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[8]	0			0
Long-term Risk Management Assets	[8]	0			0
Total Assets	[8]	0			0
Current Risk Management Liabilities	[8]	0			(600,000)
Long-term Risk Management Liabilities	[8]	0			0
Derivative Liability	[8]	0			(600,000)
Total MTM Derivative Contract Net Assets (Liabilities)	[8]	0			600,000
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	[8]	(400,000)			(500,000)
Long-term Risk Management Assets	[8]	0			0
Total Assets	[8]	(400,000)			(500,000)
Current Risk Management Liabilities	[8]	(400,000)			(700,000)
Long-term Risk Management Liabilities	[8]	0			0
Derivative Liability	[8]	(400,000)			(700,000)
Total MTM Derivative Contract Net Assets (Liabilities)	[8]	0			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	[8]	(300,000)			(800,000)
Long-term Risk Management Assets	[8]	0			0
Total Assets	[8]	(300,000)			(800,000)
Current Risk Management Liabilities	[8]	(300,000)			(1,100,000)
Long-term Risk Management Liabilities	[8]	0			0
Derivative Liability	[8]	(300,000)			(1,100,000)
Total MTM Derivative Contract Net Assets (Liabilities)	[8]	0			300,000
Net Amounts of Assets/Liabilities Presented in the Statement of Financial Position [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[9]	93,900,000			162,800,000
Long-term Risk Management Assets	[9]	250,400,000			254,000,000.0
Total Assets	[9]	344,300,000			416,800,000
Current Risk Management Liabilities	[9]	63,400,000			55,000,000.0
Long-term Risk Management Liabilities	[9]	267,900,000			263,400,000
Derivative Liability	[9]	331,300,000			318,400,000
Total MTM Derivative Contract Net Assets (Liabilities)	[9]	13,000,000.0			98,400,000
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	[9]	0			0
Long-term Risk Management Assets	[9]	0			0
Total Assets	[9]	0			0
Current Risk Management Liabilities	[9]	200,000			200,000
Long-term Risk Management Liabilities	[9]	0			0
Derivative Liability	[9]	200,000			200,000
Total MTM Derivative Contract Net Assets (Liabilities)	[9]	(200,000)			(200,000)
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	[9]	12,900,000			57,200,000
Long-term Risk Management Assets	[9]	300,000			900,000
Total Assets	[9]	13,200,000			58,100,000
Current Risk Management Liabilities	[9]	6,100,000			400,000
Long-term Risk Management Liabilities	[9]	200,000			200,000
Derivative Liability	[9]	6,300,000			600,000
Total MTM Derivative Contract Net Assets (Liabilities)	[9]	6,900,000			57,500,000
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	[9]	4,400,000			8,600,000
Long-term Risk Management Assets	[9]	100,000			600,000
Total Assets	[9]	4,500,000			9,200,000
Current Risk Management Liabilities	[9]	300,000			300,000
Long-term Risk Management Liabilities	[9]	100,000			100,000
Derivative Liability	[9]	400,000			400,000
Total MTM Derivative Contract Net Assets (Liabilities)	[9]	4,100,000			8,800,000
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	[9]	0			0
Long-term Risk Management Assets	[9]	0			0
Total Assets	[9]	0			0
Current Risk Management Liabilities	[9]	6,900,000			5,800,000
Long-term Risk Management Liabilities	[9]	99,400,000			93,800,000
Derivative Liability	[9]	106,300,000			99,600,000
Total MTM Derivative Contract Net Assets (Liabilities)	[9]	(106,300,000)			(99,600,000)
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	[9]	5,000,000.0			10,400,000
Long-term Risk Management Assets	[9]	0			0
Total Assets	[9]	5,000,000.0			10,400,000
Current Risk Management Liabilities	[9]	700,000			1,000,000.0
Long-term Risk Management Liabilities	[9]	0			0
Derivative Liability	[9]	700,000			1,000,000.0
Total MTM Derivative Contract Net Assets (Liabilities)	[9]	4,300,000			9,400,000
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	[9]	2,000,000.0			4,800,000
Long-term Risk Management Assets	[9]	0			0
Total Assets	[9]	2,000,000.0			4,800,000
Current Risk Management Liabilities	[9]	200,000			400,000
Long-term Risk Management Liabilities	[9]	1,900,000			2,200,000
Derivative Liability	[9]	2,100,000			2,600,000
Total MTM Derivative Contract Net Assets (Liabilities)	[9]	$ (100,000)			$ 2,200,000
Power [Member]
Commodity:
Derivative, Energy Notional Amount | MWh		310.4			371.1
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		43.9			66.4
Power [Member] | Indiana Michigan Power Co [Member]
Commodity:
Derivative, Energy Notional Amount | MWh		25.9			40.9
Power [Member] | Ohio Power Co [Member]
Commodity:
Derivative, Energy Notional Amount | MWh		7.6			7.8
Power [Member] | Public Service Co Of Oklahoma [Member]
Commodity:
Derivative, Energy Notional Amount | MWh		7.8			15.2
Power [Member] | Southwestern Electric Power Co [Member]
Commodity:
Derivative, Energy Notional Amount | MWh		2.0			4.5
Natural Gas [Member]
Commodity:
Derivative, Energy Notional Amount | MMBTU		80.6			87.9
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		4.0			4.0
Natural Gas [Member] | Indiana Michigan Power Co [Member]
Commodity:
Derivative, Energy Notional Amount | MMBTU		2.3			2.3
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		14.3			15.2
Heating Oil and Gasoline [Member]
Commodity:
Derivative, Volume Notional Amount | gal		5.4			7.4
Heating Oil and Gasoline [Member] | AEP Texas Inc. [Member]
Commodity:
Derivative, Volume Notional Amount | gal		1.1			1.5
Heating Oil and Gasoline [Member] | Appalachian Power Co [Member]
Commodity:
Derivative, Volume Notional Amount | gal		1.0			1.4
Heating Oil and Gasoline [Member] | Indiana Michigan Power Co [Member]
Commodity:
Derivative, Volume Notional Amount | gal		0.5			0.7
Heating Oil and Gasoline [Member] | Ohio Power Co [Member]
Commodity:
Derivative, Volume Notional Amount | gal		1.3			1.8
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		0.6			0.8
Interest Rate Contract [Member]
Commodity:
Derivative, Notional Amount		$ 33,800,000			$ 37,700,000
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
Vertically Integrated Utilities Revenues [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		300,000		(5,500,000)
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 & Marketing Revenues [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		2,700,000		(15,100,000)
Generation & 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 & 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 & 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 & 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 & 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 & 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		(100,000)		(300,000)
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		300,000		(5,100,000)
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		100,000		0
Purchased Electricity for Resale [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		1,400,000		4,900,000
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		0		4,600,000
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		200,000
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
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		(400,000)		300,000
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		(100,000)		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)		400,000
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		0		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		0		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)		100,000
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		0		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	[10]	(6,400,000)		37,300,000
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	[10]	600,000		0
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	[10]	(2,100,000)		0
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	[10]	300,000		6,200,000
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	[10]	(8,900,000)		31,400,000
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	[10]	500,000		0
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	[10]	(100,000)		(300,000)
Regulatory Liabilities [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts	[10]	(22,000,000.0)		87,000,000.0
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	[10]	0		(100,000)
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	[10]	(31,700,000)		64,100,000
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	[10]	6,600,000		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	[10]	0		0
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	[10]	6,200,000		12,100,000
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	[10]	$ 4,700,000		$ (800,000)

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

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

[3] 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.”

[4] The March 31, 2019 maturity of the net fair value of risk management contracts prior to cash collateral, assets/(liabilities), is as follows: Level 2 matures $(7) million in 2019, $2 million in periods 2023-2024 and $1 million in periods 2025-2032; Level 3 matures $27 million in 2019, $42 million in periods 2020-2022, $23 million in periods 2023-2024 and $(13) million in periods 2025-2032.  Risk management commodity contracts are substantially comprised of power contracts.

[5] The December 31, 2018 maturity of the net fair value of risk management contracts prior to cash collateral, assets/(liabilities), is as follows: Level 2 matures $(4) million in 2019, $1 million in periods 2020-2022, $1 million in periods 2023-2024 and $1 million in periods 2025-2032; Level 3 matures $108 million in 2019, $37 million in periods 2020-2022, $23 million in periods 2023-2024 and $(12) million in periods 2025-2032.  Risk management commodity contracts are substantially comprised of power contracts.

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

[7] 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.”

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

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

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