Derivatives and Hedging (Details) gal in Millions, T in Millions, MWh in Millions, MMBTU in Millions		3 Months Ended			9 Months Ended			12 Months Ended
		Sep. 30, 2018 USD ($) MWh MMBTU T gal		Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) MWh MMBTU T gal		Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($) MWh MMBTU T gal
Cash Collateral Netting
Cash Collateral Received Netted Against Risk Management Assets		$ 15,000,000			$ 15,000,000			$ 9,400,000.0
Cash Collateral Paid Netted Against Risk Management Liabilities		1,000,000			1,000,000			9,000,000
Fair Value of Derivative Instruments
Current Risk Management Assets		191,900,000			191,900,000			126,200,000
Long-term Risk Management Assets		264,900,000			264,900,000			282,100,000
Total Assets		456,800,000			456,800,000			408,300,000
Current Risk Management Liabilities		57,300,000			57,300,000			61,600,000
Long-term Risk Management Liabilities		287,200,000			287,200,000			322,000,000
Total Liabilities		344,500,000			344,500,000			383,600,000
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		39,800,000		$ 26,600,000	268,800,000		$ 106,300,000
Carrying Amount of Hedged Asset (Liability)	[1]	(461,400,000)			(461,400,000)			(489,300,000)
Cumulative Fair Value Hedging Adjustment in the Carrying Amount of the Hedged Asset (Liability)	[1]	34,200,000			34,200,000			6,100,000
Gain (Loss) on Hedging Instruments
Gain (Loss) on Fair Value Hedging Instruments	[2]	(6,300,000)		100,000	(28,100,000)		(100,000)
Gain (Loss) on Fair Value Portion of Long Term Debt	[2]	6,300,000		(100,000)	28,100,000		100,000
Collateral Triggering Events [Abstract]
Liabilities for Contracts with Cross Default Provisions Prior to Contractual Netting Arrangements		253,100,000			253,100,000			243,600,000
Amount of Cash Collateral Posted		800,000			800,000			1,300,000
Additional Settlement Liability if Cross Default Provision is Triggered		211,200,000			$ 211,200,000			223,100,000
Derivatives and Hedging (Textuals) [Abstract]
Maximum Term for Exposure to Variability of Future Cash Flows					183 months
Appalachian Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets		68,400,000			$ 68,400,000			24,900,000
Long-term Risk Management Assets		1,400,000			1,400,000			1,100,000
Current Risk Management Liabilities		900,000			900,000			1,300,000
Long-term Risk Management Liabilities		700,000			700,000			200,000
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		24,000,000		4,500,000	133,800,000		30,500,000
Collateral Triggering Events [Abstract]
Liabilities for Contracts with Cross Default Provisions Prior to Contractual Netting Arrangements		100,000			100,000			600,000
Amount of Cash Collateral Posted		0			0			0
Additional Settlement Liability if Cross Default Provision is Triggered		100,000			100,000			500,000
AEP Texas Inc. [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets		500,000			500,000			500,000
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		200,000		400,000	600,000		0
Indiana Michigan Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets		10,900,000			10,900,000			7,600,000
Long-term Risk Management Assets		900,000			900,000			700,000
Current Risk Management Liabilities		6,400,000			6,400,000			3,500,000
Long-term Risk Management Liabilities		400,000			400,000			100,000
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		(3,400,000)		2,100,000	4,800,000		21,100,000
Collateral Triggering Events [Abstract]
Liabilities for Contracts with Cross Default Provisions Prior to Contractual Netting Arrangements		0			0			400,000
Amount of Cash Collateral Posted		0			0			0
Additional Settlement Liability if Cross Default Provision is Triggered		0			0			400,000
Ohio Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets		600,000			600,000			600,000
Long-term Risk Management Assets		100,000			100,000			0
Current Risk Management Liabilities		5,400,000			5,400,000			6,400,000
Long-term Risk Management Liabilities		89,800,000			89,800,000			126,000,000
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		(9,100,000)		(8,500,000)	33,000,000		(25,700,000)
Public Service Co Of Oklahoma [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets		18,500,000			18,500,000			6,400,000
Current Risk Management Liabilities		600,000			600,000			0
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		3,500,000		2,600,000	34,600,000		13,700,000
Southwestern Electric Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets		6,500,000			6,500,000			6,400,000
Current Risk Management Liabilities		200,000			200,000			200,000
Long-term Risk Management Liabilities		2,600,000			2,600,000			0
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		1,100,000		7,200,000	6,400,000		22,100,000
Collateral Triggering Events [Abstract]
Liabilities for Contracts with Cross Default Provisions Prior to Contractual Netting Arrangements		2,800,000			2,800,000			200,000
Amount of Cash Collateral Posted		0			0			0
Additional Settlement Liability if Cross Default Provision is Triggered		2,800,000			2,800,000			100,000
Risk Management Contracts [Member]
Fair Value of Derivative Instruments
Total Assets	[3]	421,100,000	[4]		421,100,000	[4]		383,800,000	[5]
Total Liabilities	[3]	251,400,000	[4]		251,400,000	[4]		309,500,000	[5]
Risk Management Contracts [Member] | Appalachian Power Co [Member]
Fair Value of Derivative Instruments
Total Assets	[3],[6]	69,800,000			69,800,000			26,000,000
Total Liabilities	[3],[6]	1,600,000			1,600,000			1,500,000
Risk Management Contracts [Member] | AEP Texas Inc. [Member]
Fair Value of Derivative Instruments
Total Assets	[3]	500,000			500,000			500,000
Risk Management Contracts [Member] | Indiana Michigan Power Co [Member]
Fair Value of Derivative Instruments
Total Assets	[3],[6]	11,800,000			11,800,000			8,300,000
Total Liabilities	[3],[6]	6,800,000			6,800,000			3,600,000
Risk Management Contracts [Member] | Ohio Power Co [Member]
Fair Value of Derivative Instruments
Total Assets	[3],[6]	700,000			700,000			600,000
Total Liabilities	[3],[6]	95,200,000			95,200,000			132,400,000
Risk Management Contracts [Member] | Public Service Co Of Oklahoma [Member]
Fair Value of Derivative Instruments
Total Assets	[3],[6]	18,500,000			18,500,000			6,400,000
Total Liabilities	[3],[6]	600,000			600,000			0
Risk Management Contracts [Member] | Southwestern Electric Power Co [Member]
Fair Value of Derivative Instruments
Total Assets	[3],[6]	6,500,000			6,500,000			6,400,000
Total Liabilities	[3],[6]	2,800,000			2,800,000			200,000
Commodity [Member]
Impact of Cash Flow Hedges on the Condensed Balance Sheet
AOCI Gain (Loss) Net of Tax		(22,800,000)			(22,800,000)			(28,400,000)
Portion Expected to be Reclassified to Net Income During the Next Twelve Months					14,400,000			5,500,000
Derivatives and Hedging (Textuals) [Abstract]
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	[7]	359,900,000			359,900,000			389,000,000
Long-term Risk Management Assets	[7]	295,300,000			295,300,000			300,900,000
Total Assets	[7]	655,200,000			655,200,000			689,900,000
Current Risk Management Liabilities	[7]	232,400,000			232,400,000			334,600,000
Long-term Risk Management Liabilities	[7]	240,000,000			240,000,000			280,600,000
Total Liabilities	[7]	472,400,000			472,400,000			615,200,000
Total MTM Derivative Contract Net Assets (Liabilities)	[7]	182,800,000			182,800,000			74,700,000
Commodity [Member] | Risk Management Contracts [Member] | Appalachian Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[7]	106,600,000			106,600,000			75,600,000
Long-term Risk Management Assets	[7]	6,000,000			6,000,000			2,400,000
Total Assets	[7]	112,600,000			112,600,000			78,000,000
Current Risk Management Liabilities	[7]	39,100,000			39,100,000			50,600,000
Long-term Risk Management Liabilities	[7]	5,500,000			5,500,000			1,400,000
Total Liabilities	[7]	44,600,000			44,600,000			52,000,000
Total MTM Derivative Contract Net Assets (Liabilities)	[7]	68,000,000			68,000,000			26,000,000
Commodity [Member] | Risk Management Contracts [Member] | AEP Texas Inc. [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[7]	500,000			500,000			500,000
Long-term Risk Management Assets	[7]	0			0			0
Total Assets	[7]	500,000			500,000			500,000
Current Risk Management Liabilities	[7]	0			0			0
Long-term Risk Management Liabilities	[7]	0			0			0
Total Liabilities	[7]	0			0			0
Total MTM Derivative Contract Net Assets (Liabilities)	[7]	500,000			500,000			500,000
Commodity [Member] | Risk Management Contracts [Member] | Indiana Michigan Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[7]	39,400,000			39,400,000			47,200,000
Long-term Risk Management Assets	[7]	3,700,000			3,700,000			1,600,000
Total Assets	[7]	43,100,000			43,100,000			48,800,000
Current Risk Management Liabilities	[7]	35,200,000			35,200,000			48,500,000
Long-term Risk Management Liabilities	[7]	3,200,000			3,200,000			900,000
Total Liabilities	[7]	38,400,000			38,400,000			49,400,000
Total MTM Derivative Contract Net Assets (Liabilities)	[7]	4,700,000			4,700,000			(600,000)
Commodity [Member] | Risk Management Contracts [Member] | Ohio Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[7]	600,000			600,000			600,000
Long-term Risk Management Assets	[7]	100,000			100,000			0
Total Assets	[7]	700,000			700,000			600,000
Current Risk Management Liabilities	[7]	5,400,000			5,400,000			6,400,000
Long-term Risk Management Liabilities	[7]	89,800,000			89,800,000			126,000,000
Total Liabilities	[7]	95,200,000			95,200,000			132,400,000
Total MTM Derivative Contract Net Assets (Liabilities)	[7]	(94,500,000)			(94,500,000)			(131,800,000)
Commodity [Member] | Risk Management Contracts [Member] | Public Service Co Of Oklahoma [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[7]	18,800,000			18,800,000			6,600,000
Long-term Risk Management Assets	[7]	0			0			0
Total Assets	[7]	18,800,000			18,800,000			6,600,000
Current Risk Management Liabilities	[7]	900,000			900,000			200,000
Long-term Risk Management Liabilities	[7]	0			0			0
Total Liabilities	[7]	900,000			900,000			200,000
Total MTM Derivative Contract Net Assets (Liabilities)	[7]	17,900,000			17,900,000			6,400,000
Commodity [Member] | Risk Management Contracts [Member] | Southwestern Electric Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[7]	8,100,000			8,100,000			7,000,000
Long-term Risk Management Assets	[7]	0			0			0
Total Assets	[7]	8,100,000			8,100,000			7,000,000
Current Risk Management Liabilities	[7]	1,800,000			1,800,000			800,000
Long-term Risk Management Liabilities	[7]	2,600,000			2,600,000			0
Total Liabilities	[7]	4,400,000			4,400,000			800,000
Total MTM Derivative Contract Net Assets (Liabilities)	[7]	3,700,000			3,700,000			6,200,000
Commodity [Member] | Hedging Contracts [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[7]	29,100,000			29,100,000			17,500,000
Long-term Risk Management Assets	[7]	10,600,000			10,600,000			6,300,000
Total Assets	[7]	39,700,000			39,700,000			23,800,000
Current Risk Management Liabilities	[7]	7,500,000			7,500,000			9,000,000
Long-term Risk Management Liabilities	[7]	55,400,000			55,400,000			58,300,000
Total Liabilities	[7]	62,900,000			62,900,000			67,300,000
Total MTM Derivative Contract Net Assets (Liabilities)	[7]	(23,200,000)			(23,200,000)			(43,500,000)
Interest Rate [Member]
Commodity:
Derivative, Notional Amount		500,000,000			500,000,000			500,000,000
Impact of Cash Flow Hedges on the Condensed Balance Sheet
AOCI Gain (Loss) Net of Tax		(12,700,000)			(12,700,000)			(13,000,000)
Portion Expected to be Reclassified to Net Income During the Next Twelve Months					(800,000)			(800,000)
Interest Rate [Member] | Appalachian 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		2,000,000			2,000,000			2,200,000
Portion Expected to be Reclassified to Net Income During the Next Twelve Months					900,000			700,000
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		(4,600,000)			(4,600,000)			(4,500,000)
Portion Expected to be Reclassified to Net Income During the Next Twelve Months					(1,100,000)			(900,000)
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		(11,900,000)			(11,900,000)			(10,700,000)
Portion Expected to be Reclassified to Net Income During the Next Twelve Months					(1,600,000)			(1,300,000)
Interest Rate [Member] | Ohio 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		1,300,000			1,300,000			1,900,000
Portion Expected to be Reclassified to Net Income During the Next Twelve Months					1,300,000			1,100,000
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		2,400,000			2,400,000			2,600,000
Portion Expected to be Reclassified to Net Income During the Next Twelve Months					1,000,000			800,000
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		(3,700,000)			(3,700,000)			(6,000,000)
Portion Expected to be Reclassified to Net Income During the Next Twelve Months					(1,500,000)			(1,400,000)
Interest Rate [Member] | Hedging Contracts [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[7]	0			0			2,500,000
Long-term Risk Management Assets	[7]	0			0			0
Total Assets	[7]	0			0			2,500,000
Current Risk Management Liabilities	[7]	500,000			500,000			0
Long-term Risk Management Liabilities	[7]	33,700,000			33,700,000			8,600,000
Total Liabilities	[7]	34,200,000			34,200,000			8,600,000
Total MTM Derivative Contract Net Assets (Liabilities)	[7]	(34,200,000)			(34,200,000)			(6,100,000)
Gross Amounts of Risk Management Assets/Liabilities Recognized [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets		389,000,000			389,000,000			409,000,000
Long-term Risk Management Assets		305,900,000			305,900,000			307,200,000
Total Assets		694,900,000			694,900,000			716,200,000
Current Risk Management Liabilities		240,400,000			240,400,000			343,600,000
Long-term Risk Management Liabilities		329,100,000			329,100,000			347,500,000
Total Liabilities		569,500,000			569,500,000			691,100,000
Total MTM Derivative Contract Net Assets (Liabilities)		125,400,000			125,400,000			25,100,000
Gross Amounts Offset in the Statement of Financial Position [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[8]	(197,100,000)			(197,100,000)			(282,800,000)
Long-term Risk Management Assets	[8]	(41,000,000)			(41,000,000)			(25,100,000)
Total Assets	[8]	(238,100,000)			(238,100,000)			(307,900,000)
Current Risk Management Liabilities	[8]	(183,100,000)			(183,100,000)			(282,000,000)
Long-term Risk Management Liabilities	[8]	(41,900,000)			(41,900,000)			(25,500,000)
Total Liabilities	[8]	(225,000,000)			(225,000,000)			(307,500,000)
Total MTM Derivative Contract Net Assets (Liabilities)	[8]	(13,100,000)			(13,100,000)			(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	[8]	(38,200,000)			(38,200,000)			(50,700,000)
Long-term Risk Management Assets	[8]	(4,600,000)			(4,600,000)			(1,300,000)
Total Assets	[8]	(42,800,000)			(42,800,000)			(52,000,000)
Current Risk Management Liabilities	[8]	(38,200,000)			(38,200,000)			(49,300,000)
Long-term Risk Management Liabilities	[8]	(4,800,000)			(4,800,000)			(1,200,000)
Total Liabilities	[8]	(43,000,000)			(43,000,000)			(50,500,000)
Total MTM Derivative Contract Net Assets (Liabilities)	[8]	200,000			200,000			(1,500,000)
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			0
Long-term Risk Management Assets	[8]	0			0			0
Total Assets	[8]	0			0			0
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]	0			0			0
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]	(28,500,000)			(28,500,000)			(39,600,000)
Long-term Risk Management Assets	[8]	(2,800,000)			(2,800,000)			(900,000)
Total Assets	[8]	(31,300,000)			(31,300,000)			(40,500,000)
Current Risk Management Liabilities	[8]	(28,800,000)			(28,800,000)			(45,000,000)
Long-term Risk Management Liabilities	[8]	(2,800,000)			(2,800,000)			(800,000)
Total Liabilities	[8]	(31,600,000)			(31,600,000)			(45,800,000)
Total MTM Derivative Contract Net Assets (Liabilities)	[8]	300,000			300,000			5,300,000
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			0
Long-term Risk Management Assets	[8]	0			0			0
Total Assets	[8]	0			0			0
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]	0			0			0
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]	(300,000)			(300,000)			(200,000)
Long-term Risk Management Assets	[8]	0			0			0
Total Assets	[8]	(300,000)			(300,000)			(200,000)
Current Risk Management Liabilities	[8]	(300,000)			(300,000)			(200,000)
Long-term Risk Management Liabilities	[8]	0			0			0
Total Liabilities	[8]	(300,000)			(300,000)			(200,000)
Total MTM Derivative Contract Net Assets (Liabilities)	[8]	0			0			0
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]	(1,600,000)			(1,600,000)			(600,000)
Long-term Risk Management Assets	[8]	0			0			0
Total Assets	[8]	(1,600,000)			(1,600,000)			(600,000)
Current Risk Management Liabilities	[8]	(1,600,000)			(1,600,000)			(600,000)
Long-term Risk Management Liabilities	[8]	0			0			0
Total Liabilities	[8]	(1,600,000)			(1,600,000)			(600,000)
Total MTM Derivative Contract Net Assets (Liabilities)	[8]	0			0			0
Net Amounts of Assets/Liabilities Presented in the Statement of Financial Position [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[9]	191,900,000			191,900,000			126,200,000
Long-term Risk Management Assets	[9]	264,900,000			264,900,000			282,100,000
Total Assets	[9]	456,800,000			456,800,000			408,300,000
Current Risk Management Liabilities	[9]	57,300,000			57,300,000			61,600,000
Long-term Risk Management Liabilities	[9]	287,200,000			287,200,000			322,000,000
Total Liabilities	[9]	344,500,000			344,500,000			383,600,000
Total MTM Derivative Contract Net Assets (Liabilities)	[9]	112,300,000			112,300,000			24,700,000
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]	68,400,000			68,400,000			24,900,000
Long-term Risk Management Assets	[9]	1,400,000			1,400,000			1,100,000
Total Assets	[9]	69,800,000			69,800,000			26,000,000
Current Risk Management Liabilities	[9]	900,000			900,000			1,300,000
Long-term Risk Management Liabilities	[9]	700,000			700,000			200,000
Total Liabilities	[9]	1,600,000			1,600,000			1,500,000
Total MTM Derivative Contract Net Assets (Liabilities)	[9]	68,200,000			68,200,000			24,500,000
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]	500,000			500,000			500,000
Long-term Risk Management Assets	[9]	0			0			0
Total Assets	[9]	500,000			500,000			500,000
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]	500,000			500,000			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]	10,900,000			10,900,000			7,600,000
Long-term Risk Management Assets	[9]	900,000			900,000			700,000
Total Assets	[9]	11,800,000			11,800,000			8,300,000
Current Risk Management Liabilities	[9]	6,400,000			6,400,000			3,500,000
Long-term Risk Management Liabilities	[9]	400,000			400,000			100,000
Total Liabilities	[9]	6,800,000			6,800,000			3,600,000
Total MTM Derivative Contract Net Assets (Liabilities)	[9]	5,000,000			5,000,000			4,700,000
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]	600,000			600,000			600,000
Long-term Risk Management Assets	[9]	100,000			100,000			0
Total Assets	[9]	700,000			700,000			600,000
Current Risk Management Liabilities	[9]	5,400,000			5,400,000			6,400,000
Long-term Risk Management Liabilities	[9]	89,800,000			89,800,000			126,000,000
Total Liabilities	[9]	95,200,000			95,200,000			132,400,000
Total MTM Derivative Contract Net Assets (Liabilities)	[9]	(94,500,000)			(94,500,000)			(131,800,000)
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]	18,500,000			18,500,000			6,400,000
Long-term Risk Management Assets	[9]	0			0			0
Total Assets	[9]	18,500,000			18,500,000			6,400,000
Current Risk Management Liabilities	[9]	600,000			600,000			0
Long-term Risk Management Liabilities	[9]	0			0			0
Total Liabilities	[9]	600,000			600,000			0
Total MTM Derivative Contract Net Assets (Liabilities)	[9]	17,900,000			17,900,000			6,400,000
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]	6,500,000			6,500,000			6,400,000
Long-term Risk Management Assets	[9]	0			0			0
Total Assets	[9]	6,500,000			6,500,000			6,400,000
Current Risk Management Liabilities	[9]	200,000			200,000			200,000
Long-term Risk Management Liabilities	[9]	2,600,000			2,600,000			0
Total Liabilities	[9]	2,800,000			2,800,000			200,000
Total MTM Derivative Contract Net Assets (Liabilities)	[9]	$ 3,700,000			$ 3,700,000			$ 6,200,000
Power [Member]
Commodity:
Derivative, Energy Notional Amount | MWh		415.7			415.7			358.7
Power [Member] | Appalachian Power Co [Member]
Commodity:
Derivative, Energy Notional Amount | MWh		88.7			88.7			57.4
Power [Member] | AEP Texas Inc. [Member]
Commodity:
Derivative, Energy Notional Amount | MWh		0.0			0.0			0.0
Power [Member] | Indiana Michigan Power Co [Member]
Commodity:
Derivative, Energy Notional Amount | MWh		52.8			52.8			38.5
Power [Member] | Ohio Power Co [Member]
Commodity:
Derivative, Energy Notional Amount | MWh		8.0			8.0			10.4
Power [Member] | Public Service Co Of Oklahoma [Member]
Commodity:
Derivative, Energy Notional Amount | MWh		19.0			19.0			10.3
Power [Member] | Southwestern Electric Power Co [Member]
Commodity:
Derivative, Energy Notional Amount | MWh		13.0			13.0			22.7
Coal [Member]
Commodity:
Derivative, Mass Notional Amount | T		0.2			0.2			2.0
Coal [Member] | Appalachian Power Co [Member]
Commodity:
Derivative, Mass Notional Amount | T		0.0			0.0			0.0
Coal [Member] | AEP Texas Inc. [Member]
Commodity:
Derivative, Mass Notional Amount | T		0.0			0.0			0.0
Coal [Member] | Indiana Michigan Power Co [Member]
Commodity:
Derivative, Mass Notional Amount | T		0.2			0.2			2.0
Coal [Member] | Ohio Power Co [Member]
Commodity:
Derivative, Mass Notional Amount | T		0.0			0.0			0.0
Coal [Member] | Public Service Co Of Oklahoma [Member]
Commodity:
Derivative, Mass Notional Amount | T		0.0			0.0			0.0
Coal [Member] | Southwestern Electric Power Co [Member]
Commodity:
Derivative, Mass Notional Amount | T		0.0			0.0			0.0
Natural Gas [Member]
Commodity:
Derivative, Energy Notional Amount | MMBTU		84.4			84.4			53.7
Natural Gas [Member] | Appalachian Power Co [Member]
Commodity:
Derivative, Energy Notional Amount | MMBTU		8.4			8.4			1.1
Natural Gas [Member] | AEP Texas Inc. [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		4.9			4.9			0.7
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		16.1			16.1			18.3
Heating Oil and Gasoline [Member]
Commodity:
Derivative, Volume Notional Amount | gal		8.3			8.3			6.9
Heating Oil and Gasoline [Member] | Appalachian Power Co [Member]
Commodity:
Derivative, Volume Notional Amount | gal		1.6			1.6			1.3
Heating Oil and Gasoline [Member] | AEP Texas Inc. [Member]
Commodity:
Derivative, Volume Notional Amount | gal		1.7			1.7			1.4
Heating Oil and Gasoline [Member] | Indiana Michigan Power Co [Member]
Commodity:
Derivative, Volume Notional Amount | gal		0.8			0.8			0.7
Heating Oil and Gasoline [Member] | Ohio Power Co [Member]
Commodity:
Derivative, Volume Notional Amount | gal		2.0			2.0			1.6
Heating Oil and Gasoline [Member] | Public Service Co Of Oklahoma [Member]
Commodity:
Derivative, Volume Notional Amount | gal		0.8			0.8			0.7
Heating Oil and Gasoline [Member] | Southwestern Electric Power Co [Member]
Commodity:
Derivative, Volume Notional Amount | gal		0.9			0.9			0.8
Interest Rate Contract [Member]
Commodity:
Derivative, Notional Amount		$ 37,700,000			$ 37,700,000			$ 50,700,000
Interest Rate Contract [Member] | Appalachian Power Co [Member]
Commodity:
Derivative, Notional Amount		0			0			0
Interest Rate Contract [Member] | AEP Texas Inc. [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
Vertically Integrated Utilities Revenues [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		(700,000)		900,000	(9,400,000)		7,000,000
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] | 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] | 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		19,300,000		17,700,000	31,700,000		38,500,000
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] | 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] | 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] | Appalachian Power Co [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		(500,000)		300,000	(1,300,000)		600,000
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] | 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)		600,000	(7,800,000)		6,300,000
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		(100,000)	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		300,000		1,000,000	8,300,000		4,900,000
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		300,000		300,000	7,300,000		1,600,000
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] | 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	800,000		500,000
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		500,000		100,000	1,300,000		500,000
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	200,000		0
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	300,000		100,000
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		0	200,000		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	300,000		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		100,000		0	200,000		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		100,000		0	200,000		0
Maintenance Expense [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		600,000		100,000	1,500,000		400,000
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	300,000		100,000
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	300,000		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	200,000		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		100,000	300,000		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		100,000		0	200,000		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	200,000		0
Regulatory Assets [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts	[10]	(14,000,000)		(8,800,000)	29,200,000		(26,800,000)
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	[10]	0		100,000	0		0
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]	0		100,000	0		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]	(3,500,000)		(800,000)	(300,000)		(1,000,000)
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]	(9,300,000)		(8,700,000)	31,800,000		(25,900,000)
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	[10]	(600,000)		0	(600,000)		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]	(600,000)		300,000	(1,700,000)		100,000
Regulatory Liabilities [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts	[10]	33,800,000		15,600,000	206,200,000		81,800,000
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]	24,000,000		3,700,000	127,300,000		28,200,000
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	[10]	0		100,000	0		(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	[10]	0		2,100,000	11,700,000		15,300,000
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	600,000		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]	3,900,000		2,600,000	34,800,000		13,700,000
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]	$ 1,500,000		$ 7,000,000	$ 7,600,000		$ 22,000,000

[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 September 30, 2018 maturity of the net fair value of risk management contracts prior to cash collateral, assets/(liabilities), is as follows: Level 2 matures $(2) million in 2018 and $(2) million in periods 2019-2021 and $3 million in periods 2022-2023; Level 3 matures $40 million in 2018, $122 million in periods 2019-2021, $21 million in periods 2022-2023 and $1 million in periods 2024-2032. Risk management commodity contracts are substantially comprised of power contracts.

[5] The December 31, 2017 maturity of the net fair value of risk management contracts prior to cash collateral, assets/(liabilities), is as follows: Level 1 matures $(1) million in 2018; Level 2 matures $(3) million in 2018 and $2 million in periods 2022-2023; Level 3 matures $59 million in 2018, $33 million in periods 2019-2021, $14 million in periods 2022-2023 and $(29) million in periods 2024-2032. 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.