Fair Value Assets and Liabilities (Details) $ in Millions		3 Months Ended			6 Months Ended			12 Months Ended
		Jun. 30, 2018 USD ($) $ / MWh $ / MMBTU		Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) $ / MWh $ / MMBTU		Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($) $ / MWh $ / MMBTU
Assets, Fair Value Disclosure
Other Short-term Investments		$ 339.2			$ 339.2			$ 359.7
Risk Management Assets
Risk Management Assets		459.1			459.1			408.3
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		2,554.9			2,554.9			2,527.6
Total Assets		3,353.2			3,353.2			3,295.6
Liabilities, Fair Value Disclosure
Risk Management Liabilities		333.6			333.6			383.6
Changes in the Fair Value of Net Trading Derivatives and other investments
Beginning Balance		62.0		$ (18.5)	40.3		$ 2.5	2.5
Realized Gain (Loss) Included in Net Income (or Changes in Net Assets)	[1],[2]	55.0		17.1	152.6		32.0
Unrealized Gain (Loss) Included in Net Income (or Changes in Net Assets) Relating to Assets Still Held at the Reporting Date	[1]	5.9		8.7	8.0		25.2
Realized and Unrealized Gains (Losses) Included in Other Comprehensive Income		(10.3)		12.1	7.6		(5.1)
Settlements		(75.8)		(16.1)	(204.6)		(44.3)
Transfers into Level 3	[3],[4]	12.6		6.2	14.7		10.7
Transfers out of Level 3	[4]	0.4		(1.1)	(1.5)		(9.4)
Changes in Fair Value Allocated to Regulated Jurisdiction	[5]	122.5		78.9	155.2		75.7
Ending Balance		172.3		87.3	$ 172.3		87.3	$ 40.3
Low [Member]
Level 3 Quantitative Information
Counterparty Credit Risk	[6]				0.13%			0.08%
High [Member]
Level 3 Quantitative Information
Counterparty Credit Risk	[6]				4.42%			4.56%
Weighted Average [Member]
Level 3 Quantitative Information
Counterparty Credit Risk	[6]				1.73%			1.80%
Other [Member]
Assets, Fair Value Disclosure
Other Short-term Investments		11.0			$ 11.0			$ 36.9
Risk Management Assets
Risk Management Assets		(188.4)			(188.4)			(285.4)
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		7.7			7.7			9.7
Total Assets		(169.7)			(169.7)			(238.8)
Liabilities, Fair Value Disclosure
Risk Management Liabilities		(185.1)			(185.1)			(285.0)
Level 1 [Member]
Assets, Fair Value Disclosure
Other Short-term Investments		301.7			301.7			322.8
Risk Management Assets
Risk Management Assets		1.4			1.4			3.9
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		1,508.4			1,508.4			1,469.2
Total Assets		1,811.5			1,811.5			1,795.9
Liabilities, Fair Value Disclosure
Risk Management Liabilities		1.1			1.1			5.1
Level 2 [Member]
Assets, Fair Value Disclosure
Other Short-term Investments		26.5			26.5			0.0
Risk Management Assets
Risk Management Assets		277.6			277.6			411.0
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		1,038.8			1,038.8			1,048.7
Total Assets		1,342.9			1,342.9			1,459.7
Liabilities, Fair Value Disclosure
Risk Management Liabilities		321.4			321.4			425.0
Level 3 [Member]
Assets, Fair Value Disclosure
Other Short-term Investments		0.0			0.0			0.0
Risk Management Assets
Risk Management Assets		368.5			368.5			278.8
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		0.0			0.0			0.0
Total Assets		368.5			368.5			278.8
Liabilities, Fair Value Disclosure
Risk Management Liabilities		196.2			196.2			238.5
2018 [Member] | Level 1 [Member]
Fair Value Measurements 1 (Textuals)
Maturity of Net Fair Value of Risk Management Contracts Prior to Cash Collateral, Assets/Liabilities								(1.0)
2018 [Member] | Level 2 [Member]
Fair Value Measurements 1 (Textuals)
Maturity of Net Fair Value of Risk Management Contracts Prior to Cash Collateral, Assets/Liabilities		(5.0)			(5.0)			(3.0)
2018 [Member] | Level 3 [Member]
Fair Value Measurements 1 (Textuals)
Maturity of Net Fair Value of Risk Management Contracts Prior to Cash Collateral, Assets/Liabilities		77.0			77.0			59.0
2019 - 2021 [Member] | Level 2 [Member]
Fair Value Measurements 1 (Textuals)
Maturity of Net Fair Value of Risk Management Contracts Prior to Cash Collateral, Assets/Liabilities		(7.0)			(7.0)
2019 - 2021 [Member] | Level 3 [Member]
Fair Value Measurements 1 (Textuals)
Maturity of Net Fair Value of Risk Management Contracts Prior to Cash Collateral, Assets/Liabilities		97.0			97.0			33.0
2022 - 2023 [Member] | Level 2 [Member]
Fair Value Measurements 1 (Textuals)
Maturity of Net Fair Value of Risk Management Contracts Prior to Cash Collateral, Assets/Liabilities		3.0			3.0			2.0
2022 - 2023 [Member] | Level 3 [Member]
Fair Value Measurements 1 (Textuals)
Maturity of Net Fair Value of Risk Management Contracts Prior to Cash Collateral, Assets/Liabilities		22.0			22.0			14.0
2024 - 2032 [Member] | Level 3 [Member]
Fair Value Measurements 1 (Textuals)
Maturity of Net Fair Value of Risk Management Contracts Prior to Cash Collateral, Assets/Liabilities		3.0			3.0			(29.0)
Risk Management Commodity Contracts [Member]
Risk Management Assets
Risk Management Assets	[7]	431.8	[8]		431.8	[8]		383.8	[9]
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7]	244.6	[8]		244.6	[8]		309.5	[9]
Risk Management Commodity Contracts [Member] | Other [Member]
Risk Management Assets
Risk Management Assets	[7]	(191.2)	[8]		(191.2)	[8]		(285.4)	[9]
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7]	(187.9)	[8]		(187.9)	[8]		(285.0)	[9]
Risk Management Commodity Contracts [Member] | Level 1 [Member]
Risk Management Assets
Risk Management Assets	[7]	1.4	[8]		1.4	[8]		3.9	[9]
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7]	1.1	[8]		1.1	[8]		5.1	[9]
Risk Management Commodity Contracts [Member] | Level 2 [Member]
Risk Management Assets
Risk Management Assets	[7]	259.4	[8]		259.4	[8]		391.2	[9]
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7]	269.0	[8]		269.0	[8]		392.5	[9]
Risk Management Commodity Contracts [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets	[7]	362.2	[8]		362.2	[8]		274.1	[9]
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7]	162.4	[8]		162.4	[8]		196.9	[9]
Energy Contracts [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets		240.8			240.8			225.1
Liabilities, Fair Value Disclosure
Risk Management Liabilities		$ 187.1			$ 187.1			$ 233.7
Energy Contracts [Member] | Level 3 [Member] | Low [Member]
Level 3 Quantitative Information
Fair Value Significant Unobservable Input Price Per Unit | $ / MWh	[10]	5.28			5.28			(0.05)
Energy Contracts [Member] | Level 3 [Member] | High [Member]
Level 3 Quantitative Information
Fair Value Significant Unobservable Input Price Per Unit | $ / MWh	[10]	145.99			145.99			263.00
Energy Contracts [Member] | Level 3 [Member] | Weighted Average [Member]
Level 3 Quantitative Information
Fair Value Significant Unobservable Input Price Per Unit | $ / MWh	[10]	34.31			34.31			36.32
Natural Gas Contracts [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets		$ 0.0			$ 0.0			$ 0.0
Liabilities, Fair Value Disclosure
Risk Management Liabilities		$ 2.3			$ 2.3			$ 0.2
Natural Gas Contracts [Member] | Level 3 [Member] | Low [Member]
Level 3 Quantitative Information
Fair Value Significant Unobservable Input Price Per Unit | $ / MMBTU	[11]	2.22			2.22			2.37
Natural Gas Contracts [Member] | Level 3 [Member] | High [Member]
Level 3 Quantitative Information
Fair Value Significant Unobservable Input Price Per Unit | $ / MMBTU	[11]	2.88			2.88			2.96
Natural Gas Contracts [Member] | Level 3 [Member] | Weighted Average [Member]
Level 3 Quantitative Information
Fair Value Significant Unobservable Input Price Per Unit | $ / MMBTU	[11]	2.49			2.49			2.62
FTRs [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets		$ 127.7			$ 127.7			$ 53.7
Liabilities, Fair Value Disclosure
Risk Management Liabilities		$ 6.8			$ 6.8			$ 4.6
FTRs [Member] | Level 3 [Member] | Low [Member]
Level 3 Quantitative Information
Fair Value Significant Unobservable Input Price Per Unit | $ / MWh	[10]	(9.40)			(9.40)			(55.62)
FTRs [Member] | Level 3 [Member] | High [Member]
Level 3 Quantitative Information
Fair Value Significant Unobservable Input Price Per Unit | $ / MWh	[10]	10.30			10.30			54.88
FTRs [Member] | Level 3 [Member] | Weighted Average [Member]
Level 3 Quantitative Information
Fair Value Significant Unobservable Input Price Per Unit | $ / MWh	[10]	0.52			0.52			0.41
Commodity Hedges [Member]
Risk Management Assets
Risk Management Assets	[7]	$ 27.3			$ 27.3			$ 22.0
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7]	61.1			61.1			65.5
Commodity Hedges [Member] | Other [Member]
Risk Management Assets
Risk Management Assets	[7]	2.8			2.8			0.0
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7]	2.8			2.8			0.0
Commodity Hedges [Member] | Level 1 [Member]
Risk Management Assets
Risk Management Assets	[7]	0.0			0.0			0.0
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7]	0.0			0.0			0.0
Commodity Hedges [Member] | Level 2 [Member]
Risk Management Assets
Risk Management Assets	[7]	18.2			18.2			17.3
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7]	24.5			24.5			23.9
Commodity Hedges [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets	[7]	6.3			6.3			4.7
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7]	33.8			33.8			41.6
Fair Value Hedges [Member]
Risk Management Assets
Risk Management Assets								2.5
Liabilities, Fair Value Disclosure
Risk Management Liabilities		27.9			27.9			8.6
Fair Value Hedges [Member] | Other [Member]
Risk Management Assets
Risk Management Assets								0.0
Liabilities, Fair Value Disclosure
Risk Management Liabilities		0.0			0.0			0.0
Fair Value Hedges [Member] | Level 1 [Member]
Risk Management Assets
Risk Management Assets								0.0
Liabilities, Fair Value Disclosure
Risk Management Liabilities		0.0			0.0			0.0
Fair Value Hedges [Member] | Level 2 [Member]
Risk Management Assets
Risk Management Assets								2.5
Liabilities, Fair Value Disclosure
Risk Management Liabilities		27.9			27.9			8.6
Fair Value Hedges [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets								0.0
Liabilities, Fair Value Disclosure
Risk Management Liabilities		0.0			0.0			0.0
AEP Texas Inc. [Member]
Assets, Fair Value Disclosure
Cash and Cash Equivalents		131.9			131.9			155.2
Spent Nuclear Fuel and Decommissioning Trusts
Total Assets		132.4			132.4			155.7
AEP Texas Inc. [Member] | Other [Member]
Assets, Fair Value Disclosure
Cash and Cash Equivalents		0.0			0.0			0.0
Spent Nuclear Fuel and Decommissioning Trusts
Total Assets		(0.1)			(0.1)			0.0
AEP Texas Inc. [Member] | Level 1 [Member]
Assets, Fair Value Disclosure
Cash and Cash Equivalents		131.9			131.9			155.2
Spent Nuclear Fuel and Decommissioning Trusts
Total Assets		131.9			131.9			155.2
AEP Texas Inc. [Member] | Level 2 [Member]
Assets, Fair Value Disclosure
Cash and Cash Equivalents		0.0			0.0			0.0
Spent Nuclear Fuel and Decommissioning Trusts
Total Assets		0.6			0.6			0.5
AEP Texas Inc. [Member] | Level 3 [Member]
Assets, Fair Value Disclosure
Cash and Cash Equivalents		0.0			0.0			0.0
Spent Nuclear Fuel and Decommissioning Trusts
Total Assets		0.0			0.0			0.0
AEP Texas Inc. [Member] | Risk Management Commodity Contracts [Member]
Risk Management Assets
Risk Management Assets	[7]	0.5			0.5			0.5
AEP Texas Inc. [Member] | Risk Management Commodity Contracts [Member] | Other [Member]
Risk Management Assets
Risk Management Assets	[7]	(0.1)			(0.1)			0.0
AEP Texas Inc. [Member] | Risk Management Commodity Contracts [Member] | Level 1 [Member]
Risk Management Assets
Risk Management Assets	[7]	0.0			0.0			0.0
AEP Texas Inc. [Member] | Risk Management Commodity Contracts [Member] | Level 2 [Member]
Risk Management Assets
Risk Management Assets	[7]	0.6			0.6			0.5
AEP Texas Inc. [Member] | Risk Management Commodity Contracts [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets	[7]	0.0			0.0			0.0
Appalachian Power Co [Member]
Assets, Fair Value Disclosure
Cash and Cash Equivalents		17.7			17.7			16.3
Spent Nuclear Fuel and Decommissioning Trusts
Total Assets		80.2			80.2			42.3
Changes in the Fair Value of Net Trading Derivatives and other investments
Beginning Balance		9.1		(5.8)	24.7		1.4	1.4
Realized Gain (Loss) Included in Net Income (or Changes in Net Assets)	[1],[2]	36.0		12.2	104.7		16.9
Unrealized Gain (Loss) Included in Net Income (or Changes in Net Assets) Relating to Assets Still Held at the Reporting Date	[1]	0.0		0.0	0.0		0.0
Realized and Unrealized Gains (Losses) Included in Other Comprehensive Income		0.0		0.0	0.0		0.0
Settlements		(43.2)		(6.4)	(128.4)		(18.6)
Transfers into Level 3	[3],[4]	0.0		0.0	0.0		0.0
Transfers out of Level 3	[4]	0.0		0.0	0.0		0.0
Changes in Fair Value Allocated to Regulated Jurisdiction	[5]	58.1		41.3	59.0		41.6
Ending Balance		60.0		41.3	60.0		41.3	24.7
Appalachian Power Co [Member] | Other [Member]
Assets, Fair Value Disclosure
Cash and Cash Equivalents		0.0			0.0			0.0
Spent Nuclear Fuel and Decommissioning Trusts
Total Assets		(36.4)			(36.4)			(51.6)
Appalachian Power Co [Member] | Level 1 [Member]
Assets, Fair Value Disclosure
Cash and Cash Equivalents		17.7			17.7			16.3
Spent Nuclear Fuel and Decommissioning Trusts
Total Assets		17.9			17.9			16.3
Appalachian Power Co [Member] | Level 2 [Member]
Assets, Fair Value Disclosure
Cash and Cash Equivalents		0.0			0.0			0.0
Spent Nuclear Fuel and Decommissioning Trusts
Total Assets		37.7			37.7			52.5
Appalachian Power Co [Member] | Level 3 [Member]
Assets, Fair Value Disclosure
Cash and Cash Equivalents		0.0			0.0			0.0
Risk Management Assets
Risk Management Assets		61.0			61.0			25.1
Spent Nuclear Fuel and Decommissioning Trusts
Total Assets		61.0			61.0			25.1
Liabilities, Fair Value Disclosure
Risk Management Liabilities		1.0			1.0			0.4
Appalachian Power Co [Member] | Risk Management Commodity Contracts [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	62.5			62.5			26.0
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	1.9			1.9			1.5
Appalachian Power Co [Member] | Risk Management Commodity Contracts [Member] | Other [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	(36.4)			(36.4)			(51.6)
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	(35.6)			(35.6)			(50.1)
Appalachian Power Co [Member] | Risk Management Commodity Contracts [Member] | Level 1 [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	0.2			0.2			0.0
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	0.0			0.0			0.0
Appalachian Power Co [Member] | Risk Management Commodity Contracts [Member] | Level 2 [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	37.7			37.7			52.5
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	36.5			36.5			51.2
Appalachian Power Co [Member] | Risk Management Commodity Contracts [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	61.0			61.0			25.1
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	1.0			1.0			0.4
Appalachian Power Co [Member] | Energy Contracts [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets		1.5			1.5			0.8
Liabilities, Fair Value Disclosure
Risk Management Liabilities		$ 0.5			$ 0.5			$ 0.4
Appalachian Power Co [Member] | Energy Contracts [Member] | Level 3 [Member] | Low [Member]
Level 3 Quantitative Information
Fair Value Significant Unobservable Input Price Per Unit | $ / MWh	[10]	14.72			14.72			20.52
Appalachian Power Co [Member] | Energy Contracts [Member] | Level 3 [Member] | High [Member]
Level 3 Quantitative Information
Fair Value Significant Unobservable Input Price Per Unit | $ / MWh	[10]	63.75			63.75			195.00
Appalachian Power Co [Member] | Energy Contracts [Member] | Level 3 [Member] | Weighted Average [Member]
Level 3 Quantitative Information
Fair Value Significant Unobservable Input Price Per Unit | $ / MWh	[10]	34.64			34.64			33.80
Appalachian Power Co [Member] | FTRs [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets		$ 59.5			$ 59.5			$ 24.3
Liabilities, Fair Value Disclosure
Risk Management Liabilities		$ 0.5			$ 0.5			$ 0.0
Appalachian Power Co [Member] | FTRs [Member] | Level 3 [Member] | Low [Member]
Level 3 Quantitative Information
Fair Value Significant Unobservable Input Price Per Unit | $ / MWh	[10]	0.01			0.01			(0.36)
Appalachian Power Co [Member] | FTRs [Member] | Level 3 [Member] | High [Member]
Level 3 Quantitative Information
Fair Value Significant Unobservable Input Price Per Unit | $ / MWh	[10]	8.30			8.30			7.15
Appalachian Power Co [Member] | FTRs [Member] | Level 3 [Member] | Weighted Average [Member]
Level 3 Quantitative Information
Fair Value Significant Unobservable Input Price Per Unit | $ / MWh	[10]	1.57			1.57			1.62
Indiana Michigan Power Co [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		$ 2,554.9			$ 2,554.9			$ 2,527.6
Total Assets		2,570.5			2,570.5			2,535.9
Changes in the Fair Value of Net Trading Derivatives and other investments
Beginning Balance		2.9		2.0	7.6		2.8	2.8
Realized Gain (Loss) Included in Net Income (or Changes in Net Assets)	[1],[2]	11.8		0.6	15.1		3.9
Unrealized Gain (Loss) Included in Net Income (or Changes in Net Assets) Relating to Assets Still Held at the Reporting Date	[1]	0.0		0.0	0.0		0.0
Realized and Unrealized Gains (Losses) Included in Other Comprehensive Income		0.0		0.0	0.0		0.0
Settlements		(14.6)		(2.7)	(22.1)		(6.9)
Transfers into Level 3	[3],[4]	0.0		0.0	0.0		0.0
Transfers out of Level 3	[4]	0.0		0.0	(0.3)		0.0
Changes in Fair Value Allocated to Regulated Jurisdiction	[5]	13.1		15.6	12.9		15.7
Ending Balance		13.2		15.5	13.2		15.5	7.6
Indiana Michigan Power Co [Member] | Other [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		7.7			7.7			9.7
Total Assets		(16.5)			(16.5)			(30.5)
Indiana Michigan Power Co [Member] | Level 1 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		1,508.4			1,508.4			1,469.2
Total Assets		1,508.5			1,508.5			1,469.2
Indiana Michigan Power Co [Member] | Level 2 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		1,038.8			1,038.8			1,048.7
Total Assets		1,062.9			1,062.9			1,088.1
Indiana Michigan Power Co [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets		15.6			15.6			9.1
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		0.0			0.0			0.0
Total Assets		15.6			15.6			9.1
Liabilities, Fair Value Disclosure
Risk Management Liabilities		2.4			2.4			1.5
Indiana Michigan Power Co [Member] | Risk Management Commodity Contracts [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	15.6			15.6			8.3
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	5.7			5.7			3.6
Indiana Michigan Power Co [Member] | Risk Management Commodity Contracts [Member] | Other [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	(24.2)			(24.2)			(40.2)
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	(23.7)			(23.7)			(45.5)
Indiana Michigan Power Co [Member] | Risk Management Commodity Contracts [Member] | Level 1 [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	0.1			0.1			0.0
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	0.0			0.0			0.0
Indiana Michigan Power Co [Member] | Risk Management Commodity Contracts [Member] | Level 2 [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	24.1			24.1			39.4
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	27.0			27.0			47.6
Indiana Michigan Power Co [Member] | Risk Management Commodity Contracts [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	15.6			15.6			9.1
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	2.4			2.4			1.5
Indiana Michigan Power Co [Member] | Energy Contracts [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets		0.3			0.3			0.5
Liabilities, Fair Value Disclosure
Risk Management Liabilities		$ 0.5			$ 0.5			$ 0.3
Indiana Michigan Power Co [Member] | Energy Contracts [Member] | Level 3 [Member] | Low [Member]
Level 3 Quantitative Information
Fair Value Significant Unobservable Input Price Per Unit | $ / MWh	[10]	14.72			14.72			20.52
Indiana Michigan Power Co [Member] | Energy Contracts [Member] | Level 3 [Member] | High [Member]
Level 3 Quantitative Information
Fair Value Significant Unobservable Input Price Per Unit | $ / MWh	[10]	63.75			63.75			195.00
Indiana Michigan Power Co [Member] | Energy Contracts [Member] | Level 3 [Member] | Weighted Average [Member]
Level 3 Quantitative Information
Fair Value Significant Unobservable Input Price Per Unit | $ / MWh	[10]	34.64			34.64			33.80
Indiana Michigan Power Co [Member] | FTRs [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets		$ 15.3			$ 15.3			$ 8.6
Liabilities, Fair Value Disclosure
Risk Management Liabilities		$ 1.9			$ 1.9			$ 1.2
Indiana Michigan Power Co [Member] | FTRs [Member] | Level 3 [Member] | Low [Member]
Level 3 Quantitative Information
Fair Value Significant Unobservable Input Price Per Unit | $ / MWh	[10]	(1.50)			(1.50)			(0.36)
Indiana Michigan Power Co [Member] | FTRs [Member] | Level 3 [Member] | High [Member]
Level 3 Quantitative Information
Fair Value Significant Unobservable Input Price Per Unit | $ / MWh	[10]	5.97			5.97			5.75
Indiana Michigan Power Co [Member] | FTRs [Member] | Level 3 [Member] | Weighted Average [Member]
Level 3 Quantitative Information
Fair Value Significant Unobservable Input Price Per Unit | $ / MWh	[10]	0.77			0.77			0.86
Ohio Power Co [Member]
Assets, Fair Value Disclosure
Cash and Cash Equivalents		$ 26.5			$ 26.5
Spent Nuclear Fuel and Decommissioning Trusts
Total Assets		27.0			27.0
Changes in the Fair Value of Net Trading Derivatives and other investments
Beginning Balance		(98.5)		(124.6)	(132.4)		(119.0)	$ (119.0)
Realized Gain (Loss) Included in Net Income (or Changes in Net Assets)	[1],[2]	0.2		(0.1)	0.9		(4.3)
Unrealized Gain (Loss) Included in Net Income (or Changes in Net Assets) Relating to Assets Still Held at the Reporting Date	[1]	0.0		0.0	0.0		0.0
Realized and Unrealized Gains (Losses) Included in Other Comprehensive Income		0.0		0.0	0.0		0.0
Settlements		1.3		1.9	2.5		4.1
Transfers into Level 3	[3],[4]	0.0		0.0	0.0		0.0
Transfers out of Level 3	[4]	0.0		0.0	0.0		0.0
Changes in Fair Value Allocated to Regulated Jurisdiction	[5]	10.1		(7.7)	42.1		(11.3)
Ending Balance		(86.9)		(130.5)	$ (86.9)		(130.5)	$ (132.4)
Ohio Power Co [Member] | Low [Member]
Level 3 Quantitative Information
Counterparty Credit Risk	[6]				0.13%			0.08%
Ohio Power Co [Member] | High [Member]
Level 3 Quantitative Information
Counterparty Credit Risk	[6]				1.97%			1.90%
Ohio Power Co [Member] | Weighted Average [Member]
Level 3 Quantitative Information
Counterparty Credit Risk	[6]				1.51%			1.36%
Ohio Power Co [Member] | Other [Member]
Assets, Fair Value Disclosure
Cash and Cash Equivalents		0.0			$ 0.0
Spent Nuclear Fuel and Decommissioning Trusts
Total Assets		(0.2)			(0.2)
Ohio Power Co [Member] | Level 1 [Member]
Assets, Fair Value Disclosure
Cash and Cash Equivalents		0.0			0.0
Spent Nuclear Fuel and Decommissioning Trusts
Total Assets		0.0			0.0
Ohio Power Co [Member] | Level 2 [Member]
Assets, Fair Value Disclosure
Cash and Cash Equivalents		26.5			26.5
Spent Nuclear Fuel and Decommissioning Trusts
Total Assets		27.2			27.2
Ohio Power Co [Member] | Level 3 [Member]
Assets, Fair Value Disclosure
Cash and Cash Equivalents		0.0			0.0
Risk Management Assets
Risk Management Assets		0.0			0.0			$ 0.0
Spent Nuclear Fuel and Decommissioning Trusts
Total Assets		0.0			0.0
Liabilities, Fair Value Disclosure
Risk Management Liabilities		86.9			86.9			132.4
Ohio Power Co [Member] | Risk Management Commodity Contracts [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	0.5			0.5			0.6
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	86.8			86.8			132.4
Ohio Power Co [Member] | Risk Management Commodity Contracts [Member] | Other [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	(0.2)			(0.2)			0.0
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	(0.1)			(0.1)			0.0
Ohio Power Co [Member] | Risk Management Commodity Contracts [Member] | Level 1 [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	0.0			0.0			0.0
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	0.0			0.0			0.0
Ohio Power Co [Member] | Risk Management Commodity Contracts [Member] | Level 2 [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	0.7			0.7			0.6
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	0.0			0.0			0.0
Ohio Power Co [Member] | Risk Management Commodity Contracts [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	0.0			0.0			0.0
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	86.9			86.9			132.4
Ohio Power Co [Member] | Energy Contracts [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets		0.0			0.0			0.0
Liabilities, Fair Value Disclosure
Risk Management Liabilities		$ 86.9			$ 86.9			$ 132.4
Ohio Power Co [Member] | Energy Contracts [Member] | Level 3 [Member] | Low [Member]
Level 3 Quantitative Information
Fair Value Significant Unobservable Input Price Per Unit | $ / MWh	[10]	31.56			31.56			30.52
Ohio Power Co [Member] | Energy Contracts [Member] | Level 3 [Member] | High [Member]
Level 3 Quantitative Information
Fair Value Significant Unobservable Input Price Per Unit | $ / MWh	[10]	73.69			73.69			170.43
Ohio Power Co [Member] | Energy Contracts [Member] | Level 3 [Member] | Weighted Average [Member]
Level 3 Quantitative Information
Fair Value Significant Unobservable Input Price Per Unit | $ / MWh	[10]	47.11			47.11			44.62
Public Service Co Of Oklahoma [Member]
Changes in the Fair Value of Net Trading Derivatives and other investments
Beginning Balance		$ 2.8		0.4	$ 6.2		0.7	$ 0.7
Realized Gain (Loss) Included in Net Income (or Changes in Net Assets)	[1],[2]	6.1		0.8	18.1		3.1
Unrealized Gain (Loss) Included in Net Income (or Changes in Net Assets) Relating to Assets Still Held at the Reporting Date	[1]	0.0		0.0	0.0		0.0
Realized and Unrealized Gains (Losses) Included in Other Comprehensive Income		0.0		0.0	0.0		0.0
Settlements		(8.9)		(1.3)	(24.3)		(3.8)
Transfers into Level 3	[3],[4]	0.0		0.0	0.0		0.0
Transfers out of Level 3	[4]	0.0		0.0	0.0		0.0
Changes in Fair Value Allocated to Regulated Jurisdiction	[5]	24.3		9.6	24.3		9.5
Ending Balance		24.3		9.5	24.3		9.5	6.2
Public Service Co Of Oklahoma [Member] | Risk Management Commodity Contracts [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	24.5			24.5			6.4
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	0.0			0.0			0.0
Public Service Co Of Oklahoma [Member] | Risk Management Commodity Contracts [Member] | Other [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	(0.4)			(0.4)			(0.2)
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	(0.3)			(0.3)			(0.2)
Public Service Co Of Oklahoma [Member] | Risk Management Commodity Contracts [Member] | Level 1 [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	0.0			0.0			0.0
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	0.0			0.0			0.0
Public Service Co Of Oklahoma [Member] | Risk Management Commodity Contracts [Member] | Level 2 [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	0.3			0.3			0.2
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	0.0			0.0			0.0
Public Service Co Of Oklahoma [Member] | Risk Management Commodity Contracts [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	24.6			24.6			6.4
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	0.3			0.3			0.2
Public Service Co Of Oklahoma [Member] | FTRs [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets		24.6			24.6			6.4
Liabilities, Fair Value Disclosure
Risk Management Liabilities		$ 0.3			$ 0.3			$ 0.2
Public Service Co Of Oklahoma [Member] | FTRs [Member] | Level 3 [Member] | Low [Member]
Level 3 Quantitative Information
Fair Value Significant Unobservable Input Price Per Unit | $ / MWh	[10]	(9.40)			(9.40)			(6.62)
Public Service Co Of Oklahoma [Member] | FTRs [Member] | Level 3 [Member] | High [Member]
Level 3 Quantitative Information
Fair Value Significant Unobservable Input Price Per Unit | $ / MWh	[10]	10.30			10.30			1.41
Public Service Co Of Oklahoma [Member] | FTRs [Member] | Level 3 [Member] | Weighted Average [Member]
Level 3 Quantitative Information
Fair Value Significant Unobservable Input Price Per Unit | $ / MWh	[10]	(1.23)			(1.23)			(0.76)
Southwestern Electric Power Co [Member]
Changes in the Fair Value of Net Trading Derivatives and other investments
Beginning Balance		$ 0.9		0.5	$ 5.9		0.7	$ 0.7
Realized Gain (Loss) Included in Net Income (or Changes in Net Assets)	[1],[2]	(4.0)		1.4	(4.8)		6.0
Unrealized Gain (Loss) Included in Net Income (or Changes in Net Assets) Relating to Assets Still Held at the Reporting Date	[1]	0.0		0.0	0.0		0.0
Realized and Unrealized Gains (Losses) Included in Other Comprehensive Income		0.0		0.0	0.0		0.0
Settlements		2.6		(1.9)	(1.3)		(6.8)
Transfers into Level 3	[3],[4]	0.0		0.0	0.0		0.0
Transfers out of Level 3	[4]	0.0		0.0	0.0		0.0
Changes in Fair Value Allocated to Regulated Jurisdiction	[5]	5.4		12.4	5.1		12.5
Ending Balance		4.9		$ 12.4	4.9		$ 12.4	5.9
Southwestern Electric Power Co [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets		9.5			9.5			6.7
Liabilities, Fair Value Disclosure
Risk Management Liabilities		4.6			4.6			0.8
Southwestern Electric Power Co [Member] | Risk Management Commodity Contracts [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	7.4			7.4			6.4
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	2.3			2.3			0.2
Southwestern Electric Power Co [Member] | Risk Management Commodity Contracts [Member] | Other [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	(2.4)			(2.4)			(0.6)
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	(2.3)			(2.3)			(0.6)
Southwestern Electric Power Co [Member] | Risk Management Commodity Contracts [Member] | Level 1 [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	0.0			0.0			0.0
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	0.0			0.0			0.0
Southwestern Electric Power Co [Member] | Risk Management Commodity Contracts [Member] | Level 2 [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	0.3			0.3			0.3
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	0.0			0.0			0.0
Southwestern Electric Power Co [Member] | Risk Management Commodity Contracts [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	9.5			9.5			6.7
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	4.6			4.6			0.8
Southwestern Electric Power Co [Member] | Natural Gas Contracts [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets		0.0			0.0			0.0
Liabilities, Fair Value Disclosure
Risk Management Liabilities		$ 2.3			$ 2.3			$ 0.2
Southwestern Electric Power Co [Member] | Natural Gas Contracts [Member] | Level 3 [Member] | Low [Member]
Level 3 Quantitative Information
Fair Value Significant Unobservable Input Price Per Unit | $ / MMBTU	[11]	2.22			2.22			2.37
Southwestern Electric Power Co [Member] | Natural Gas Contracts [Member] | Level 3 [Member] | High [Member]
Level 3 Quantitative Information
Fair Value Significant Unobservable Input Price Per Unit | $ / MMBTU	[11]	2.88			2.88			2.96
Southwestern Electric Power Co [Member] | Natural Gas Contracts [Member] | Level 3 [Member] | Weighted Average [Member]
Level 3 Quantitative Information
Fair Value Significant Unobservable Input Price Per Unit | $ / MMBTU	[11]	2.49			2.49			2.62
Southwestern Electric Power Co [Member] | FTRs [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets		$ 9.5			$ 9.5			$ 6.7
Liabilities, Fair Value Disclosure
Risk Management Liabilities		$ 2.3			$ 2.3			$ 0.6
Southwestern Electric Power Co [Member] | FTRs [Member] | Level 3 [Member] | Low [Member]
Level 3 Quantitative Information
Fair Value Significant Unobservable Input Price Per Unit | $ / MWh	[10]	(9.40)			(9.40)			(6.62)
Southwestern Electric Power Co [Member] | FTRs [Member] | Level 3 [Member] | High [Member]
Level 3 Quantitative Information
Fair Value Significant Unobservable Input Price Per Unit | $ / MWh	[10]	10.30			10.30			1.41
Southwestern Electric Power Co [Member] | FTRs [Member] | Level 3 [Member] | Weighted Average [Member]
Level 3 Quantitative Information
Fair Value Significant Unobservable Input Price Per Unit | $ / MWh	[10]	(1.23)			(1.23)			(0.76)
Cash [Member]
Assets, Fair Value Disclosure
Other Short-term Investments	[13],[14]	$ 198.7			$ 198.7			$ 220.1
Cash [Member] | Other [Member]
Assets, Fair Value Disclosure
Other Short-term Investments	[13]	11.0			11.0			36.9
Cash [Member] | Level 1 [Member]
Assets, Fair Value Disclosure
Other Short-term Investments	[13]	161.2			161.2			183.2
Cash [Member] | Level 2 [Member]
Assets, Fair Value Disclosure
Other Short-term Investments	[13]	26.5			26.5			0.0
Cash [Member] | Level 3 [Member]
Assets, Fair Value Disclosure
Other Short-term Investments	[13]	0.0			0.0			0.0
Fixed Income Funds [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		1,038.8			1,038.8			1,048.7
Fixed Income Funds [Member] | Other [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		0.0			0.0			0.0
Fixed Income Funds [Member] | Level 1 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		0.0			0.0			0.0
Fixed Income Funds [Member] | Level 2 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		1,038.8			1,038.8			1,048.7
Fixed Income Funds [Member] | Level 3 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		0.0			0.0			0.0
Fixed Income Funds [Member] | Indiana Michigan Power Co [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		1,038.8			1,038.8			1,048.7
Fixed Income Funds [Member] | Indiana Michigan Power Co [Member] | Other [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		0.0			0.0			0.0
Fixed Income Funds [Member] | Indiana Michigan Power Co [Member] | Level 1 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		0.0			0.0			0.0
Fixed Income Funds [Member] | Indiana Michigan Power Co [Member] | Level 2 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		1,038.8			1,038.8			1,048.7
Fixed Income Funds [Member] | Indiana Michigan Power Co [Member] | Level 3 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		0.0			0.0			0.0
Mutual Funds Fixed Income [Member]
Assets, Fair Value Disclosure
Other Short-term Investments	[15]	103.0			103.0			102.9
Mutual Funds Fixed Income [Member] | Other [Member]
Assets, Fair Value Disclosure
Other Short-term Investments		0.0			0.0			0.0
Mutual Funds Fixed Income [Member] | Level 1 [Member]
Assets, Fair Value Disclosure
Other Short-term Investments		103.0			103.0			102.9
Mutual Funds Fixed Income [Member] | Level 2 [Member]
Assets, Fair Value Disclosure
Other Short-term Investments		0.0			0.0			0.0
Mutual Funds Fixed Income [Member] | Level 3 [Member]
Assets, Fair Value Disclosure
Other Short-term Investments		0.0			0.0			0.0
Mutual Funds Equity [Member]
Assets, Fair Value Disclosure
Other Short-term Investments	[16]	37.5			37.5			36.7
Mutual Funds Equity [Member] | Other [Member]
Assets, Fair Value Disclosure
Other Short-term Investments	[16]	0.0			0.0			0.0
Mutual Funds Equity [Member] | Level 1 [Member]
Assets, Fair Value Disclosure
Other Short-term Investments	[16]	37.5			37.5			36.7
Mutual Funds Equity [Member] | Level 2 [Member]
Assets, Fair Value Disclosure
Other Short-term Investments	[16]	0.0			0.0			0.0
Mutual Funds Equity [Member] | Level 3 [Member]
Assets, Fair Value Disclosure
Other Short-term Investments	[16]	0.0			0.0			0.0
Cash and Cash Equivalents [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts	[17]	21.8			21.8			17.2
Cash and Cash Equivalents [Member] | Other [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts	[17]	7.7			7.7			9.7
Cash and Cash Equivalents [Member] | Level 1 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts	[17]	14.1			14.1			7.5
Cash and Cash Equivalents [Member] | Level 2 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts	[17]	0.0			0.0			0.0
Cash and Cash Equivalents [Member] | Level 3 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts	[17]	0.0			0.0			0.0
Cash and Cash Equivalents [Member] | Indiana Michigan Power Co [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts	[17]	21.8			21.8			17.2
Cash and Cash Equivalents [Member] | Indiana Michigan Power Co [Member] | Other [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts	[17]	7.7			7.7			9.7
Cash and Cash Equivalents [Member] | Indiana Michigan Power Co [Member] | Level 1 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts	[17]	14.1			14.1			7.5
Cash and Cash Equivalents [Member] | Indiana Michigan Power Co [Member] | Level 2 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts	[17]	0.0			0.0			0.0
Cash and Cash Equivalents [Member] | Indiana Michigan Power Co [Member] | Level 3 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts	[17]	0.0			0.0			0.0
US Government Agencies Debt Securities [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		958.4			958.4			981.2
US Government Agencies Debt Securities [Member] | Other [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		0.0			0.0			0.0
US Government Agencies Debt Securities [Member] | Level 1 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		0.0			0.0			0.0
US Government Agencies Debt Securities [Member] | Level 2 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		958.4			958.4			981.2
US Government Agencies Debt Securities [Member] | Level 3 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		0.0			0.0			0.0
US Government Agencies Debt Securities [Member] | Indiana Michigan Power Co [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		958.4			958.4			981.2
US Government Agencies Debt Securities [Member] | Indiana Michigan Power Co [Member] | Other [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		0.0			0.0			0.0
US Government Agencies Debt Securities [Member] | Indiana Michigan Power Co [Member] | Level 1 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		0.0			0.0			0.0
US Government Agencies Debt Securities [Member] | Indiana Michigan Power Co [Member] | Level 2 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		958.4			958.4			981.2
US Government Agencies Debt Securities [Member] | Indiana Michigan Power Co [Member] | Level 3 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		0.0			0.0			0.0
Corporate Debt [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		53.8			53.8			58.7
Corporate Debt [Member] | Other [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		0.0			0.0			0.0
Corporate Debt [Member] | Level 1 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		0.0			0.0			0.0
Corporate Debt [Member] | Level 2 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		53.8			53.8			58.7
Corporate Debt [Member] | Level 3 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		0.0			0.0			0.0
Corporate Debt [Member] | Indiana Michigan Power Co [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		53.8			53.8			58.7
Corporate Debt [Member] | Indiana Michigan Power Co [Member] | Other [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		0.0			0.0			0.0
Corporate Debt [Member] | Indiana Michigan Power Co [Member] | Level 1 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		0.0			0.0			0.0
Corporate Debt [Member] | Indiana Michigan Power Co [Member] | Level 2 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		53.8			53.8			58.7
Corporate Debt [Member] | Indiana Michigan Power Co [Member] | Level 3 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		0.0			0.0			0.0
State and Local Jurisdiction [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		26.6			26.6			8.8
State and Local Jurisdiction [Member] | Other [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		0.0			0.0			0.0
State and Local Jurisdiction [Member] | Level 1 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		0.0			0.0			0.0
State and Local Jurisdiction [Member] | Level 2 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		26.6			26.6			8.8
State and Local Jurisdiction [Member] | Level 3 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		0.0			0.0			0.0
State and Local Jurisdiction [Member] | Indiana Michigan Power Co [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		26.6			26.6			8.8
State and Local Jurisdiction [Member] | Indiana Michigan Power Co [Member] | Other [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		0.0			0.0			0.0
State and Local Jurisdiction [Member] | Indiana Michigan Power Co [Member] | Level 1 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		0.0			0.0			0.0
State and Local Jurisdiction [Member] | Indiana Michigan Power Co [Member] | Level 2 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		26.6			26.6			8.8
State and Local Jurisdiction [Member] | Indiana Michigan Power Co [Member] | Level 3 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		0.0			0.0			0.0
Domestic [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts	[16]	1,494.3			1,494.3			1,461.7
Domestic [Member] | Other [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts	[16]	0.0			0.0			0.0
Domestic [Member] | Level 1 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts	[16]	1,494.3			1,494.3			1,461.7
Domestic [Member] | Level 2 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts	[16]	0.0			0.0			0.0
Domestic [Member] | Level 3 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts	[16]	0.0			0.0			0.0
Domestic [Member] | Indiana Michigan Power Co [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts	[16]	1,494.3			1,494.3			1,461.7
Domestic [Member] | Indiana Michigan Power Co [Member] | Other [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts	[16]	0.0			0.0			0.0
Domestic [Member] | Indiana Michigan Power Co [Member] | Level 1 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts	[16]	1,494.3			1,494.3			1,461.7
Domestic [Member] | Indiana Michigan Power Co [Member] | Level 2 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts	[16]	0.0			0.0			0.0
Domestic [Member] | Indiana Michigan Power Co [Member] | Level 3 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts	[16]	$ 0.0			$ 0.0			$ 0.0

[1] Included in revenues on the statements of income.

[2] Represents the change in fair value between the beginning of the reporting period and the settlement of the risk management commodity contract.

[3] Represents existing assets or liabilities that were previously categorized as Level 2.

[4] Transfers are recognized based on their value at the beginning of the reporting period that the transfer occurred.

[5] Relates to the net gains (losses) of those contracts that are not reflected on the statements of income. These net gains (losses) are recorded as regulatory liabilities/assets or accounts payable.

[6] Represents prices of credit default swaps used to calculate counterparty credit risk, reported in basis points.

[7] 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.’’

[8] 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.

[9] 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.

[10] Represents market prices in dollars per MWh.

[11] Represents market prices in dollars per MMBtu.

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

[13] Amounts in “Other’’ column primarily represent cash deposits in bank accounts with financial institutions or with third parties. Level 1 and Level 2 amounts primarily represent investments in money market funds.

[14] Primarily represents amounts held for the repayment of debt.

[15] Primarily short and intermediate maturities which may be sold and do not contain maturity dates.

[16] Amounts represent publicly traded equity securities and equity-based mutual funds.

[17] Amounts in “Other’’ column primarily represent accrued interest receivables from financial institutions. Level 1 amounts primarily represent investments in money market funds.