Derivatives and Hedging (Details) gal in Millions, T in Millions, MWh in Millions, MMBTU in Millions		3 Months Ended			6 Months Ended			12 Months Ended
		Jun. 30, 2018 USD ($) MWh MMBTU T gal		Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) MWh MMBTU T gal		Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($) MWh MMBTU T gal
Cash Collateral Netting
Cash Collateral Received Netted Against Risk Management Assets		$ 7,000,000			$ 7,000,000			$ 9,400,000.0
Cash Collateral Paid Netted Against Risk Management Liabilities		3,000,000			3,000,000			9,000,000
Fair Value of Derivative Instruments
Current Risk Management Assets		194,600,000			194,600,000			126,200,000
Long-term Risk Management Assets		264,500,000			264,500,000			282,100,000
Total Assets		459,100,000			459,100,000			408,300,000
Current Risk Management Liabilities		54,000,000			54,000,000			61,600,000
Long-term Risk Management Liabilities		279,600,000			279,600,000			322,000,000
Total Liabilities		333,600,000			333,600,000			383,600,000
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		119,700,000		$ 50,600,000	229,000,000		$ 79,700,000
Carrying Amount of Hedged Asset (Liability)	[1]	(467,500,000)			(467,500,000)			(489,300,000)
Gain (Loss) on Hedging Instruments
Gain (Loss) on Fair Value Hedging Instruments	[2]	(7,300,000)		400,000	(21,800,000)		(100,000)
Gain (Loss) on Fair Value Portion of Long Term Debt	[2]	7,300,000		(400,000)	21,800,000		100,000
Collateral Triggering Events [Abstract]
Liabilities for Contracts with Cross Default Provisions Prior to Contractual Netting Arrangements		266,400,000			266,400,000			243,600,000
Amount of Cash Collateral Posted		2,800,000			2,800,000			1,300,000
Additional Settlement Liability if Cross Default Provision is Triggered		216,200,000			$ 216,200,000			223,100,000
Derivatives and Hedging (Textuals) [Abstract]
Maximum Term for Exposure to Variability of Future Cash Flows					114 months
Cumulative Fair Value Hedging Adjustment in the Carrying Amount of the Hedged Asset (Liability)	[1]	27,900,000			$ 27,900,000			6,100,000
Appalachian Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets		60,400,000			60,400,000			24,900,000
Long-term Risk Management Assets		2,100,000			2,100,000			1,100,000
Current Risk Management Liabilities		1,400,000			1,400,000			1,300,000
Long-term Risk Management Liabilities		500,000			500,000			200,000
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		41,300,000		19,700,000	109,800,000		26,000,000
Collateral Triggering Events [Abstract]
Liabilities for Contracts with Cross Default Provisions Prior to Contractual Netting Arrangements		200,000			200,000			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		400,000			400,000			500,000
Long-term Risk Management Assets		100,000			100,000			0
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		300,000		(200,000)	400,000		(400,000)
Indiana Michigan Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets		14,400,000			14,400,000			7,600,000
Long-term Risk Management Assets		1,200,000			1,200,000			700,000
Current Risk Management Liabilities		5,400,000			5,400,000			3,500,000
Long-term Risk Management Liabilities		300,000			300,000			100,000
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		6,700,000		7,100,000	8,200,000		19,000,000
Collateral Triggering Events [Abstract]
Liabilities for Contracts with Cross Default Provisions Prior to Contractual Netting Arrangements		100,000			100,000			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		400,000			400,000			600,000
Long-term Risk Management Assets		100,000			100,000			0
Current Risk Management Liabilities		4,800,000			4,800,000			6,400,000
Long-term Risk Management Liabilities		82,000,000			82,000,000			126,000,000
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		10,500,000		(8,600,000)	42,100,000		(17,200,000)
Public Service Co Of Oklahoma [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets		24,500,000			24,500,000			6,400,000
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		19,000,000		8,700,000	31,100,000		11,100,000
Southwestern Electric Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets		7,400,000			7,400,000			6,400,000
Current Risk Management Liabilities		0			0			200,000
Long-term Risk Management Liabilities		2,300,000			2,300,000			0
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		6,400,000		10,400,000	5,300,000		14,900,000
Collateral Triggering Events [Abstract]
Liabilities for Contracts with Cross Default Provisions Prior to Contractual Netting Arrangements		2,300,000			2,300,000			200,000
Amount of Cash Collateral Posted		0			0			0
Additional Settlement Liability if Cross Default Provision is Triggered		2,300,000			2,300,000			100,000
Risk Management Contracts [Member]
Fair Value of Derivative Instruments
Total Assets	[3]	431,800,000	[4]		431,800,000	[4]		383,800,000	[5]
Total Liabilities	[3]	244,600,000	[4]		244,600,000	[4]		309,500,000	[5]
Risk Management Contracts [Member] | Appalachian Power Co [Member]
Fair Value of Derivative Instruments
Total Assets	[3],[6]	62,500,000			62,500,000			26,000,000
Total Liabilities	[3],[6]	1,900,000			1,900,000			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]	15,600,000			15,600,000			8,300,000
Total Liabilities	[3],[6]	5,700,000			5,700,000			3,600,000
Risk Management Contracts [Member] | Ohio Power Co [Member]
Fair Value of Derivative Instruments
Total Assets	[3],[6]	500,000			500,000			600,000
Total Liabilities	[3],[6]	86,800,000			86,800,000			132,400,000
Risk Management Contracts [Member] | Public Service Co Of Oklahoma [Member]
Fair Value of Derivative Instruments
Total Assets	[3],[6]	24,500,000			24,500,000			6,400,000
Total Liabilities	[3],[6]	0			0			0
Risk Management Contracts [Member] | Southwestern Electric Power Co [Member]
Fair Value of Derivative Instruments
Total Assets	[3],[6]	7,400,000			7,400,000			6,400,000
Total Liabilities	[3],[6]	2,300,000			2,300,000			200,000
Commodity [Member]
Impact of Cash Flow Hedges on the Condensed Balance Sheet
AOCI Gain (Loss) Net of Tax		(30,400,000)			(30,400,000)			(28,400,000)
Portion Expected to be Reclassified to Net Income During the Next Twelve Months					8,600,000			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]	343,500,000			343,500,000			389,000,000
Long-term Risk Management Assets	[7]	305,300,000			305,300,000			300,900,000
Total Assets	[7]	648,800,000			648,800,000			689,900,000
Current Risk Management Liabilities	[7]	213,300,000			213,300,000			334,600,000
Long-term Risk Management Liabilities	[7]	245,000,000			245,000,000			280,600,000
Total Liabilities	[7]	458,300,000			458,300,000			615,200,000
Total MTM Derivative Contract Net Assets (Liabilities)	[7]	190,500,000			190,500,000			74,700,000
Commodity [Member] | Risk Management Contracts [Member] | Appalachian Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[7]	95,000,000			95,000,000			75,600,000
Long-term Risk Management Assets	[7]	9,400,000			9,400,000			2,400,000
Total Assets	[7]	104,400,000			104,400,000			78,000,000
Current Risk Management Liabilities	[7]	35,300,000			35,300,000			50,600,000
Long-term Risk Management Liabilities	[7]	7,700,000			7,700,000			1,400,000
Total Liabilities	[7]	43,000,000			43,000,000			52,000,000
Total MTM Derivative Contract Net Assets (Liabilities)	[7]	61,400,000			61,400,000			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]	100,000			100,000			0
Total Assets	[7]	600,000			600,000			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]	600,000			600,000			500,000
Commodity [Member] | Risk Management Contracts [Member] | Indiana Michigan Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[7]	38,100,000			38,100,000			47,200,000
Long-term Risk Management Assets	[7]	5,600,000			5,600,000			1,600,000
Total Assets	[7]	43,700,000			43,700,000			48,800,000
Current Risk Management Liabilities	[7]	28,800,000			28,800,000			48,500,000
Long-term Risk Management Liabilities	[7]	4,500,000			4,500,000			900,000
Total Liabilities	[7]	33,300,000			33,300,000			49,400,000
Total MTM Derivative Contract Net Assets (Liabilities)	[7]	10,400,000			10,400,000			(600,000)
Commodity [Member] | Risk Management Contracts [Member] | Ohio Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[7]	500,000			500,000			600,000
Long-term Risk Management Assets	[7]	100,000			100,000			0
Total Assets	[7]	600,000			600,000			600,000
Current Risk Management Liabilities	[7]	4,800,000			4,800,000			6,400,000
Long-term Risk Management Liabilities	[7]	82,000,000			82,000,000			126,000,000
Total Liabilities	[7]	86,800,000			86,800,000			132,400,000
Total MTM Derivative Contract Net Assets (Liabilities)	[7]	(86,200,000)			(86,200,000)			(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]	24,900,000			24,900,000			6,600,000
Long-term Risk Management Assets	[7]	0			0			0
Total Assets	[7]	24,900,000			24,900,000			6,600,000
Current Risk Management Liabilities	[7]	300,000			300,000			200,000
Long-term Risk Management Liabilities	[7]	0			0			0
Total Liabilities	[7]	300,000			300,000			200,000
Total MTM Derivative Contract Net Assets (Liabilities)	[7]	24,600,000			24,600,000			6,400,000
Commodity [Member] | Risk Management Contracts [Member] | Southwestern Electric Power Co [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[7]	9,800,000			9,800,000			7,000,000
Long-term Risk Management Assets	[7]	0			0			0
Total Assets	[7]	9,800,000			9,800,000			7,000,000
Current Risk Management Liabilities	[7]	2,300,000			2,300,000			800,000
Long-term Risk Management Liabilities	[7]	2,300,000			2,300,000			0
Total Liabilities	[7]	4,600,000			4,600,000			800,000
Total MTM Derivative Contract Net Assets (Liabilities)	[7]	5,200,000			5,200,000			6,200,000
Commodity [Member] | Hedging Contracts [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[7]	23,100,000			23,100,000			17,500,000
Long-term Risk Management Assets	[7]	6,400,000			6,400,000			6,300,000
Total Assets	[7]	29,500,000			29,500,000			23,800,000
Current Risk Management Liabilities	[7]	7,500,000			7,500,000			9,000,000
Long-term Risk Management Liabilities	[7]	55,800,000			55,800,000			58,300,000
Total Liabilities	[7]	63,300,000			63,300,000			67,300,000
Total MTM Derivative Contract Net Assets (Liabilities)	[7]	(33,800,000)			(33,800,000)			(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		(15,300,000)			(15,300,000)			(13,000,000)
Portion Expected to be Reclassified to Net Income During the Next Twelve Months					(1,000,000)			(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		2,300,000			2,300,000			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		(4,900,000)			(4,900,000)			(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		(12,200,000)			(12,200,000)			(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		1,700,000			1,700,000			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		2,600,000			2,600,000			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		(6,400,000)			(6,400,000)			(6,000,000)
Portion Expected to be Reclassified to Net Income During the Next Twelve Months					(1,700,000)			(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]	700,000			700,000			0
Long-term Risk Management Liabilities	[7]	27,200,000			27,200,000			8,600,000
Total Liabilities	[7]	27,900,000			27,900,000			8,600,000
Total MTM Derivative Contract Net Assets (Liabilities)	[7]	(27,900,000)			(27,900,000)			(6,100,000)
Gross Amounts of Risk Management Assets/Liabilities Recognized [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets		366,600,000			366,600,000			409,000,000
Long-term Risk Management Assets		311,700,000			311,700,000			307,200,000
Total Assets		678,300,000			678,300,000			716,200,000
Current Risk Management Liabilities		221,500,000			221,500,000			343,600,000
Long-term Risk Management Liabilities		328,000,000			328,000,000			347,500,000
Total Liabilities		549,500,000			549,500,000			691,100,000
Total MTM Derivative Contract Net Assets (Liabilities)		128,800,000			128,800,000			25,100,000
Gross Amounts Offset in the Statement of Financial Position [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[8]	(172,000,000)			(172,000,000)			(282,800,000)
Long-term Risk Management Assets	[8]	(47,200,000)			(47,200,000)			(25,100,000)
Total Assets	[8]	(219,200,000)			(219,200,000)			(307,900,000)
Current Risk Management Liabilities	[8]	(167,500,000)			(167,500,000)			(282,000,000)
Long-term Risk Management Liabilities	[8]	(48,400,000)			(48,400,000)			(25,500,000)
Total Liabilities	[8]	(215,900,000)			(215,900,000)			(307,500,000)
Total MTM Derivative Contract Net Assets (Liabilities)	[8]	(3,300,000)			(3,300,000)			(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]	(34,600,000)			(34,600,000)			(50,700,000)
Long-term Risk Management Assets	[8]	(7,300,000)			(7,300,000)			(1,300,000)
Total Assets	[8]	(41,900,000)			(41,900,000)			(52,000,000)
Current Risk Management Liabilities	[8]	(33,900,000)			(33,900,000)			(49,300,000)
Long-term Risk Management Liabilities	[8]	(7,200,000)			(7,200,000)			(1,200,000)
Total Liabilities	[8]	(41,100,000)			(41,100,000)			(50,500,000)
Total MTM Derivative Contract Net Assets (Liabilities)	[8]	(800,000)			(800,000)			(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]	(100,000)			(100,000)			0
Long-term Risk Management Assets	[8]	0			0			0
Total Assets	[8]	(100,000)			(100,000)			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]	(100,000)			(100,000)			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]	(23,700,000)			(23,700,000)			(39,600,000)
Long-term Risk Management Assets	[8]	(4,400,000)			(4,400,000)			(900,000)
Total Assets	[8]	(28,100,000)			(28,100,000)			(40,500,000)
Current Risk Management Liabilities	[8]	(23,400,000)			(23,400,000)			(45,000,000)
Long-term Risk Management Liabilities	[8]	(4,200,000)			(4,200,000)			(800,000)
Total Liabilities	[8]	(27,600,000)			(27,600,000)			(45,800,000)
Total MTM Derivative Contract Net Assets (Liabilities)	[8]	(500,000)			(500,000)			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]	(100,000)			(100,000)			0
Long-term Risk Management Assets	[8]	0			0			0
Total Assets	[8]	(100,000)			(100,000)			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]	(100,000)			(100,000)			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]	(400,000)			(400,000)			(200,000)
Long-term Risk Management Assets	[8]	0			0			0
Total Assets	[8]	(400,000)			(400,000)			(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]	(100,000)			(100,000)			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]	(2,400,000)			(2,400,000)			(600,000)
Long-term Risk Management Assets	[8]	0			0			0
Total Assets	[8]	(2,400,000)			(2,400,000)			(600,000)
Current Risk Management Liabilities	[8]	(2,300,000)			(2,300,000)			(600,000)
Long-term Risk Management Liabilities	[8]	0			0			0
Total Liabilities	[8]	(2,300,000)			(2,300,000)			(600,000)
Total MTM Derivative Contract Net Assets (Liabilities)	[8]	(100,000)			(100,000)			0
Net Amounts of Assets/Liabilities Presented in the Statement of Financial Position [Member]
Fair Value of Derivative Instruments
Current Risk Management Assets	[9]	194,600,000			194,600,000			126,200,000
Long-term Risk Management Assets	[9]	264,500,000			264,500,000			282,100,000
Total Assets	[9]	459,100,000			459,100,000			408,300,000
Current Risk Management Liabilities	[9]	54,000,000			54,000,000			61,600,000
Long-term Risk Management Liabilities	[9]	279,600,000			279,600,000			322,000,000
Total Liabilities	[9]	333,600,000			333,600,000			383,600,000
Total MTM Derivative Contract Net Assets (Liabilities)	[9]	125,500,000			125,500,000			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]	60,400,000			60,400,000			24,900,000
Long-term Risk Management Assets	[9]	2,100,000			2,100,000			1,100,000
Total Assets	[9]	62,500,000			62,500,000			26,000,000
Current Risk Management Liabilities	[9]	1,400,000			1,400,000			1,300,000
Long-term Risk Management Liabilities	[9]	500,000			500,000			200,000
Total Liabilities	[9]	1,900,000			1,900,000			1,500,000
Total MTM Derivative Contract Net Assets (Liabilities)	[9]	60,600,000			60,600,000			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]	400,000			400,000			500,000
Long-term Risk Management Assets	[9]	100,000			100,000			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]	14,400,000			14,400,000			7,600,000
Long-term Risk Management Assets	[9]	1,200,000			1,200,000			700,000
Total Assets	[9]	15,600,000			15,600,000			8,300,000
Current Risk Management Liabilities	[9]	5,400,000			5,400,000			3,500,000
Long-term Risk Management Liabilities	[9]	300,000			300,000			100,000
Total Liabilities	[9]	5,700,000			5,700,000			3,600,000
Total MTM Derivative Contract Net Assets (Liabilities)	[9]	9,900,000			9,900,000			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]	400,000			400,000			600,000
Long-term Risk Management Assets	[9]	100,000			100,000			0
Total Assets	[9]	500,000			500,000			600,000
Current Risk Management Liabilities	[9]	4,800,000			4,800,000			6,400,000
Long-term Risk Management Liabilities	[9]	82,000,000			82,000,000			126,000,000
Total Liabilities	[9]	86,800,000			86,800,000			132,400,000
Total MTM Derivative Contract Net Assets (Liabilities)	[9]	(86,300,000)			(86,300,000)			(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]	24,500,000			24,500,000			6,400,000
Long-term Risk Management Assets	[9]	0			0			0
Total Assets	[9]	24,500,000			24,500,000			6,400,000
Current Risk Management Liabilities	[9]	0			0			0
Long-term Risk Management Liabilities	[9]	0			0			0
Total Liabilities	[9]	0			0			0
Total MTM Derivative Contract Net Assets (Liabilities)	[9]	24,500,000			24,500,000			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]	7,400,000			7,400,000			6,400,000
Long-term Risk Management Assets	[9]	0			0			0
Total Assets	[9]	7,400,000			7,400,000			6,400,000
Current Risk Management Liabilities	[9]	0			0			200,000
Long-term Risk Management Liabilities	[9]	2,300,000			2,300,000			0
Total Liabilities	[9]	2,300,000			2,300,000			200,000
Total MTM Derivative Contract Net Assets (Liabilities)	[9]	$ 5,100,000			$ 5,100,000			$ 6,200,000
Power [Member]
Commodity:
Derivative, Energy Notional Amount | MWh		480.2			480.2			358.7
Power [Member] | Appalachian Power Co [Member]
Commodity:
Derivative, Energy Notional Amount | MWh		113.2			113.2			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		62.3			62.3			38.5
Power [Member] | Ohio Power Co [Member]
Commodity:
Derivative, Energy Notional Amount | MWh		8.1			8.1			10.4
Power [Member] | Public Service Co Of Oklahoma [Member]
Commodity:
Derivative, Energy Notional Amount | MWh		28.6			28.6			10.3
Power [Member] | Southwestern Electric Power Co [Member]
Commodity:
Derivative, Energy Notional Amount | MWh		20.0			20.0			22.7
Coal [Member]
Commodity:
Derivative, Mass Notional Amount | T		0.4			0.4			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		0.4			0.4			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		69.1			69.1			53.7
Natural Gas [Member] | Appalachian Power Co [Member]
Commodity:
Derivative, Energy Notional Amount | MMBTU		3.7			3.7			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		2.1			2.1			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		17.0			17.0			18.3
Heating Oil and Gasoline [Member]
Commodity:
Derivative, Volume Notional Amount | gal		7.2			7.2			6.9
Heating Oil and Gasoline [Member] | Appalachian Power Co [Member]
Commodity:
Derivative, Volume Notional Amount | gal		1.4			1.4			1.3
Heating Oil and Gasoline [Member] | AEP Texas Inc. [Member]
Commodity:
Derivative, Volume Notional Amount | gal		1.5			1.5			1.4
Heating Oil and Gasoline [Member] | Indiana Michigan Power Co [Member]
Commodity:
Derivative, Volume Notional Amount | gal		0.7			0.7			0.7
Heating Oil and Gasoline [Member] | Ohio Power Co [Member]
Commodity:
Derivative, Volume Notional Amount | gal		1.7			1.7			1.6
Heating Oil and Gasoline [Member] | Public Service Co Of Oklahoma [Member]
Commodity:
Derivative, Volume Notional Amount | gal		0.7			0.7			0.7
Heating Oil and Gasoline [Member] | Southwestern Electric Power Co [Member]
Commodity:
Derivative, Volume Notional Amount | gal		0.8			0.8			0.8
Interest Rate Contract [Member]
Commodity:
Derivative, Notional Amount		$ 43,000,000			$ 43,000,000			$ 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		(3,200,000)		600,000	(8,700,000)		6,100,000
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		27,500,000		10,300,000	12,400,000		20,800,000
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)		(100,000)	(800,000)		300,000
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		(2,600,000)		500,000	(7,700,000)		5,700,000
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		100,000		0	100,000		100,000
Purchased Electricity for Resale [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		3,100,000		1,500,000	8,000,000		3,900,000
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		2,400,000		500,000	7,000,000		1,300,000
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		600,000		200,000	800,000		300,000
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		200,000	800,000		400,000
Other Operation Expense [Member] | Appalachian Power Co [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		100,000		0	100,000		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		0	200,000		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		100,000		0	100,000		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		0	200,000		0
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	100,000		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	100,000		0
Maintenance Expense [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts		500,000		100,000	900,000		300,000
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		0	200,000		0
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		0	200,000		0
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	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	200,000		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	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	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]	5,900,000		(3,100,000)	43,200,000		(18,000,000)
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		5,700,000	0		(100,000)
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]	0		(100,000)	0		(100,000)
Regulatory Assets [Member] | Indiana Michigan Power Co [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts	[10]	(3,000,000)		0	3,200,000		(200,000)
Regulatory Assets [Member] | Ohio Power Co [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts	[10]	9,700,000		(8,600,000)	41,100,000		(17,200,000)
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]	0		0	0		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]	(800,000)		0	(1,100,000)		(200,000)
Regulatory Liabilities [Member]
Amount of Gain (Loss) Recognized on Risk Management Contracts
Amount of Gain (Loss) Recognized on Risk Management Contracts	[10]	85,400,000		41,000,000	172,400,000		66,200,000
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]	39,200,000		13,600,000	103,300,000		24,500,000
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]	100,000		(100,000)	0		(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	[10]	11,500,000		6,400,000	11,700,000		13,200,000
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]	600,000		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]	18,800,000		8,700,000	30,900,000		11,100,000
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]	$ 6,900,000		$ 10,400,000	$ 6,100,000		$ 15,000,000

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

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

[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 June 30, 2018 maturity of the net fair value of risk management contracts prior to cash collateral, assets/(liabilities), is as follows: Level 2 matures $(5) million in 2018 and $(7) million in periods 2019-2021 and $3 million in periods 2022-2023; Level 3 matures $77 million in 2018, $97 million in periods 2019-2021, $22 million in periods 2022-2023 and $3 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.