Fair Value Assets and Liabilities (Details) $ in Millions		3 Months Ended				12 Months Ended
		Mar. 31, 2017 USD ($) $ / MWh		Mar. 31, 2016 USD ($)		Dec. 31, 2016 USD ($) $ / MWh
Assets, Fair Value Disclosure
Cash and Cash Equivalents	[1]	$ 175.0				$ 210.5
Other Temporary Investments		275.0				331.7
Risk Management Assets
Risk Management Assets		395.5				383.6
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		2,333.2				2,256.2
Total Assets		3,178.7				3,182.0
Liabilities, Fair Value Disclosure
Risk Management Liabilities		413.0				369.6
Changes in the Fair Value of Net Trading Derivatives and other investments
Beginning Balance		2.5		$ 146.9		146.9
Realized Gain (Loss) Included in Net Income (or Changes in Net Assets)	[2],[3]	17.8		23.5
Unrealized Gain (Loss) Included in Net Income (or Changes in Net Assets) Relating to Assets Still Held at the Reporting Date	[2]	16.1		21.9
Realized and Unrealized Gains (Losses) Included in Other Comprehensive Income		(17.2)		1.3
Settlements		(28.8)		(42.7)
Transfers into Level 3	[4]	5.2
Transfers out of Level 3	[4]	(8.3)		10.9
Changes in Fair Value Allocated to Regulated Jurisdictions	[5]	(5.8)		(20.5)
Ending Balance		$ (18.5)		141.3		$ 2.5
Low [Member]
Level 3 Quantitative Information
Counterparty Credit Risk	[6]	0.17%				0.35%
High [Member]
Level 3 Quantitative Information
Counterparty Credit Risk	[6]	6.91%				8.24%
Weighted Average [Member]
Level 3 Quantitative Information
Counterparty Credit Risk	[6]	2.59%				3.91%
Other [Member]
Assets, Fair Value Disclosure
Cash and Cash Equivalents	[1]	$ 166.1				$ 201.8
Other Temporary Investments		15.2				32.8
Risk Management Assets
Risk Management Assets		(178.7)				(213.0)
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		7.7				11.4
Total Assets		10.3				33.0
Liabilities, Fair Value Disclosure
Risk Management Liabilities		(195.1)				(212.7)
Level 1 [Member]
Assets, Fair Value Disclosure
Cash and Cash Equivalents	[1]	8.9				8.7
Other Temporary Investments		258.5				293.8
Risk Management Assets
Risk Management Assets		1.8				6.0
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		1,352.2				1,277.4
Total Assets		1,621.4				1,585.9
Liabilities, Fair Value Disclosure
Risk Management Liabilities		5.4				8.2
Level 2 [Member]
Assets, Fair Value Disclosure
Cash and Cash Equivalents	[1]	0.0				0.0
Other Temporary Investments		1.3				5.1
Risk Management Assets
Risk Management Assets		367.0				396.7
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		973.3				967.4
Total Assets		1,341.6				1,369.2
Liabilities, Fair Value Disclosure
Risk Management Liabilities		378.8				382.7
Level 3 [Member]
Assets, Fair Value Disclosure
Cash and Cash Equivalents	[1]	0.0				0.0
Other Temporary Investments		0.0				0.0
Risk Management Assets
Risk Management Assets		205.4				193.9
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		0.0				0.0
Total Assets		205.4				193.9
Liabilities, Fair Value Disclosure
Risk Management Liabilities		223.9				191.4
2017 [Member] | Level 1 [Member]
Fair Value Measurements 1 (Textuals)
Maturity of Net Fair Value of Risk Management Contracts Prior to Cash Collateral, Assets/Liabilities		(2.0)
2017 [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				20.0
2017 [Member] | Level 3 [Member]
Fair Value Measurements 1 (Textuals)
Maturity of Net Fair Value of Risk Management Contracts Prior to Cash Collateral, Assets/Liabilities		6.0				17.0
2018 - 2020 [Member] | Level 1 [Member]
Fair Value Measurements 1 (Textuals)
Maturity of Net Fair Value of Risk Management Contracts Prior to Cash Collateral, Assets/Liabilities		(2.0)				(2.0)
2018 - 2020 [Member] | Level 2 [Member]
Fair Value Measurements 1 (Textuals)
Maturity of Net Fair Value of Risk Management Contracts Prior to Cash Collateral, Assets/Liabilities		6.0				4.0
2018 - 2020 [Member] | Level 3 [Member]
Fair Value Measurements 1 (Textuals)
Maturity of Net Fair Value of Risk Management Contracts Prior to Cash Collateral, Assets/Liabilities		24.0				28.0
2021 - 2022 [Member] | Level 2 [Member]
Fair Value Measurements 1 (Textuals)
Maturity of Net Fair Value of Risk Management Contracts Prior to Cash Collateral, Assets/Liabilities		1.0				3.0
2021 - 2022 [Member] | Level 3 [Member]
Fair Value Measurements 1 (Textuals)
Maturity of Net Fair Value of Risk Management Contracts Prior to Cash Collateral, Assets/Liabilities		14.0				11.0
2023 - 2032 [Member] | Level 2 [Member]
Fair Value Measurements 1 (Textuals)
Maturity of Net Fair Value of Risk Management Contracts Prior to Cash Collateral, Assets/Liabilities		1.0				1.0
2023 - 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		(24.0)				(31.0)
Risk Management Commodity Contracts [Member]
Risk Management Assets
Risk Management Assets	[7]	382.5	[8]			372.4	[9]
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7]	337.5	[8]			321.5	[9]
Risk Management Commodity Contracts [Member] | Other [Member]
Risk Management Assets
Risk Management Assets	[7]	(176.9)	[8]			(205.7)	[9]
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7]	(193.3)	[8]			(205.4)	[9]
Risk Management Commodity Contracts [Member] | Level 1 [Member]
Risk Management Assets
Risk Management Assets	[7]	1.8	[8]			6.0	[9]
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7]	5.4	[8]			8.2	[9]
Risk Management Commodity Contracts [Member] | Level 2 [Member]
Risk Management Assets
Risk Management Assets	[7]	353.3	[8]			379.9	[9]
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7]	340.6	[8]			352.0	[9]
Risk Management Commodity Contracts [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets	[7]	204.3	[8]			192.2	[9]
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7]	184.8	[8]			166.7	[9]
Energy Contracts [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets		199.5				183.8
Liabilities, Fair Value Disclosure
Risk Management Liabilities		$ 213.5				$ 187.1
Level 3 Quantitative Information
Forward Price Range Low | $ / MWh	[10]	9.65				6.51
Forward Price Range High | $ / MWh	[10]	92.72				86.59
Weighted Average Market Price | $ / MWh	[10]	38.24				39.40
FTRs [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets		$ 5.9				$ 10.1
Liabilities, Fair Value Disclosure
Risk Management Liabilities		$ 10.4				$ 4.3
Level 3 Quantitative Information
Forward Price Range Low | $ / MWh	[10]	(5.46)				(7.99)
Forward Price Range High | $ / MWh	[10]	7.22				8.91
Weighted Average Market Price | $ / MWh	[10]	0.50				0.86
Commodity Hedges [Member]
Risk Management Assets
Risk Management Assets	[7]	$ 13.0				$ 11.2
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7]	73.6				46.7
Commodity Hedges [Member] | Other [Member]
Risk Management Assets
Risk Management Assets	[7]	(1.8)				(7.3)
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7]	(1.8)				(7.3)
Commodity Hedges [Member] | Level 1 [Member]
Risk Management Assets
Risk Management Assets	[7]	0.0				0.0
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7]	0.0				0.0
Commodity Hedges [Member] | Level 2 [Member]
Risk Management Assets
Risk Management Assets	[7]	13.7				16.8
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7]	36.3				29.3
Commodity Hedges [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets	[7]	1.1				1.7
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7]	39.1				24.7
Fair Value Hedges [Member]
Liabilities, Fair Value Disclosure
Risk Management Liabilities		1.9				1.4
Fair Value Hedges [Member] | Other [Member]
Liabilities, Fair Value Disclosure
Risk Management Liabilities		0.0				0.0
Fair Value Hedges [Member] | Level 1 [Member]
Liabilities, Fair Value Disclosure
Risk Management Liabilities		0.0				0.0
Fair Value Hedges [Member] | Level 2 [Member]
Liabilities, Fair Value Disclosure
Risk Management Liabilities		1.9				1.4
Fair Value Hedges [Member] | Level 3 [Member]
Liabilities, Fair Value Disclosure
Risk Management Liabilities		0.0				0.0
Appalachian Power Co [Member]
Assets, Fair Value Disclosure
Cash and Cash Equivalents	[1]	8.1				15.9
Spent Nuclear Fuel and Decommissioning Trusts
Total Assets		9.4				18.5
Changes in the Fair Value of Net Trading Derivatives and other investments
Beginning Balance		1.4		11.7	[11]	11.7	[11]
Realized Gain (Loss) Included in Net Income (or Changes in Net Assets)	[2],[3]	5.7		15.3	[11]
Unrealized Gain (Loss) Included in Net Income (or Changes in Net Assets) Relating to Assets Still Held at the Reporting Date	[2]	0.0		0.0	[11]
Realized and Unrealized Gains (Losses) Included in Other Comprehensive Income		0.0		0.0	[11]
Settlements		(12.2)		(27.7)	[11]
Transfers into Level 3	[4],[11]	0.0
Transfers out of Level 3	[4]	0.0		0.1	[11]
Changes in Fair Value Allocated to Regulated Jurisdictions	[5]	(0.7)		3.2	[11]
Ending Balance		(5.8)		2.6	[11]	1.4
Appalachian Power Co [Member] | Other [Member]
Assets, Fair Value Disclosure
Cash and Cash Equivalents	[1]	0.1				0.1
Spent Nuclear Fuel and Decommissioning Trusts
Total Assets		(17.2)				(21.7)
Appalachian Power Co [Member] | Level 1 [Member]
Assets, Fair Value Disclosure
Cash and Cash Equivalents	[1]	8.0				15.8
Spent Nuclear Fuel and Decommissioning Trusts
Total Assets		8.0				15.8
Appalachian Power Co [Member] | Level 2 [Member]
Assets, Fair Value Disclosure
Cash and Cash Equivalents	[1]	0.0				0.0
Spent Nuclear Fuel and Decommissioning Trusts
Total Assets		16.6				20.5
Appalachian Power Co [Member] | Level 3 [Member]
Assets, Fair Value Disclosure
Cash and Cash Equivalents	[1]	0.0				0.0
Risk Management Assets
Risk Management Assets		2.0				3.9
Spent Nuclear Fuel and Decommissioning Trusts
Total Assets		2.0				3.9
Liabilities, Fair Value Disclosure
Risk Management Liabilities		7.8				2.5
Appalachian Power Co [Member] | Risk Management Commodity Contracts [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	1.3				2.6
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	6.7				1.2
Appalachian Power Co [Member] | Risk Management Commodity Contracts [Member] | Other [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	(17.3)				(21.8)
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	(17.6)				(22.0)
Appalachian Power Co [Member] | Risk Management Commodity Contracts [Member] | Level 1 [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	0.0				0.0
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	0.0				0.0
Appalachian Power Co [Member] | Risk Management Commodity Contracts [Member] | Level 2 [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	16.6				20.5
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	16.5				20.7
Appalachian Power Co [Member] | Risk Management Commodity Contracts [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	2.0				3.9
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	7.8				2.5
Appalachian Power Co [Member] | Energy Contracts [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets		0.6				0.4
Liabilities, Fair Value Disclosure
Risk Management Liabilities		$ 0.2				$ 0.4
Level 3 Quantitative Information
Forward Price Range Low | $ / MWh	[10]	19.36				19.68
Forward Price Range High | $ / MWh	[10]	46.45				48.55
Weighted Average Market Price | $ / MWh	[10]	34.61				36.34
Appalachian Power Co [Member] | FTRs [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets		$ 1.4				$ 3.5
Liabilities, Fair Value Disclosure
Risk Management Liabilities		$ 7.6				$ 2.1
Level 3 Quantitative Information
Forward Price Range Low | $ / MWh	[10]	0.04				(0.23)
Forward Price Range High | $ / MWh	[10]	4.14				8.91
Weighted Average Market Price | $ / MWh	[10]	1.34				2.37
Indiana Michigan Power Co [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		$ 2,333.2				$ 2,256.2
Total Assets		2,336.2				2,259.7
Changes in the Fair Value of Net Trading Derivatives and other investments
Beginning Balance		2.8		4.3	[11]	4.3	[11]
Realized Gain (Loss) Included in Net Income (or Changes in Net Assets)	[2],[3]	2.0		2.5	[11]
Unrealized Gain (Loss) Included in Net Income (or Changes in Net Assets) Relating to Assets Still Held at the Reporting Date	[2]	0.0		0.0	[11]
Realized and Unrealized Gains (Losses) Included in Other Comprehensive Income		0.0		0.0	[11]
Settlements		(4.3)		(4.6)	[11]
Transfers into Level 3	[4],[11]	0.0
Transfers out of Level 3	[4]	0.0		0.1	[11]
Changes in Fair Value Allocated to Regulated Jurisdictions	[5]	1.5		1.4	[11]
Ending Balance		2.0		3.7	[11]	2.8
Indiana Michigan Power Co [Member] | Other [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		7.7				11.4
Total Assets		(6.1)				(0.9)
Indiana Michigan Power Co [Member] | Level 1 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		1,352.2				1,277.4
Total Assets		1,352.2				1,277.4
Indiana Michigan Power Co [Member] | Level 2 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		973.3				967.4
Total Assets		987.9				980.2
Indiana Michigan Power Co [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets		2.2				3.0
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		0.0				0.0
Total Assets		2.2				3.0
Liabilities, Fair Value Disclosure
Risk Management Liabilities		0.2				0.2
Indiana Michigan Power Co [Member] | Risk Management Commodity Contracts [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	3.0				3.5
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	2.9				1.1
Indiana Michigan Power Co [Member] | Risk Management Commodity Contracts [Member] | Other [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	(13.8)				(12.3)
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	(14.0)				(12.4)
Indiana Michigan Power Co [Member] | Risk Management Commodity Contracts [Member] | Level 1 [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	0.0				0.0
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	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]	14.6				12.8
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	16.7				13.3
Indiana Michigan Power Co [Member] | Risk Management Commodity Contracts [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	2.2				3.0
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	0.2				0.2
Indiana Michigan Power Co [Member] | Energy Contracts [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets		0.3				0.3
Liabilities, Fair Value Disclosure
Risk Management Liabilities		$ 0.1				$ 0.2
Level 3 Quantitative Information
Forward Price Range Low | $ / MWh	[10]	19.36				19.68
Forward Price Range High | $ / MWh	[10]	46.45				48.55
Weighted Average Market Price | $ / MWh	[10]	34.61				36.34
Indiana Michigan Power Co [Member] | FTRs [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets		$ 1.9				$ 2.7
Liabilities, Fair Value Disclosure
Risk Management Liabilities		$ 0.1				$ 0.0
Level 3 Quantitative Information
Forward Price Range Low | $ / MWh	[10]	(0.33)				(7.9)
Forward Price Range High | $ / MWh	[10]	3.7				8.91
Weighted Average Market Price | $ / MWh	[10]	1.75				1.32
Ohio Power Co [Member]
Assets, Fair Value Disclosure
Cash and Cash Equivalents	[1]	$ 16.0				$ 27.2
Spent Nuclear Fuel and Decommissioning Trusts
Total Assets		16.1				27.4
Changes in the Fair Value of Net Trading Derivatives and other investments
Beginning Balance		(119.0)		15.9		15.9
Realized Gain (Loss) Included in Net Income (or Changes in Net Assets)	[2],[3]	(0.5)		(0.6)
Unrealized Gain (Loss) Included in Net Income (or Changes in Net Assets) Relating to Assets Still Held at the Reporting Date	[2]	0.0		0.0
Realized and Unrealized Gains (Losses) Included in Other Comprehensive Income		0.0		0.0
Settlements		2.1		1.4
Transfers into Level 3	[4]	0.0
Transfers out of Level 3	[4]	0.0		0.0
Changes in Fair Value Allocated to Regulated Jurisdictions	[5]	(7.2)		(27.6)
Ending Balance		$ (124.6)		(10.9)		$ (119.0)
Ohio Power Co [Member] | Low [Member]
Level 3 Quantitative Information
Counterparty Credit Risk	[6]	0.34%				0.47%
Ohio Power Co [Member] | High [Member]
Level 3 Quantitative Information
Counterparty Credit Risk	[6]	3.27%				3.40%
Ohio Power Co [Member] | Weighted Average [Member]
Level 3 Quantitative Information
Counterparty Credit Risk	[6]	2.45%				2.72%
Ohio Power Co [Member] | Other [Member]
Assets, Fair Value Disclosure
Cash and Cash Equivalents	[1]	$ 0.0				$ 27.2
Spent Nuclear Fuel and Decommissioning Trusts
Total Assets		0.0				27.0
Ohio Power Co [Member] | Level 1 [Member]
Assets, Fair Value Disclosure
Cash and Cash Equivalents	[1]	16.0				0.0
Spent Nuclear Fuel and Decommissioning Trusts
Total Assets		16.0				0.0
Ohio Power Co [Member] | Level 2 [Member]
Assets, Fair Value Disclosure
Cash and Cash Equivalents	[1]	0.0				0.0
Spent Nuclear Fuel and Decommissioning Trusts
Total Assets		0.1				0.4
Ohio Power Co [Member] | Level 3 [Member]
Assets, Fair Value Disclosure
Cash and Cash Equivalents	[1]	0.0				0.0
Risk Management Assets
Risk Management Assets		0.0				0.0
Spent Nuclear Fuel and Decommissioning Trusts
Total Assets		0.0				0.0
Liabilities, Fair Value Disclosure
Risk Management Liabilities		124.6				119.0
Ohio Power Co [Member] | Risk Management Commodity Contracts [Member]
Risk Management Assets
Risk Management Assets		0.1				0.2	[7],[12]
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	124.6				119.0
Ohio Power Co [Member] | Risk Management Commodity Contracts [Member] | Other [Member]
Risk Management Assets
Risk Management Assets		0.0				(0.2)	[7],[12]
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	0.0				0.0
Ohio Power Co [Member] | Risk Management Commodity Contracts [Member] | Level 1 [Member]
Risk Management Assets
Risk Management Assets		0.0				0.0	[7],[12]
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	0.0				0.0
Ohio Power Co [Member] | Risk Management Commodity Contracts [Member] | Level 2 [Member]
Risk Management Assets
Risk Management Assets		0.1				0.4	[7],[12]
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	0.0				0.0
Ohio Power Co [Member] | Risk Management Commodity Contracts [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets		0.0				0.0	[7],[12]
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	124.6				119.0
Ohio Power Co [Member] | Energy Contracts [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets		0.0				0.0
Liabilities, Fair Value Disclosure
Risk Management Liabilities		$ 124.6				$ 119.0
Level 3 Quantitative Information
Forward Price Range Low | $ / MWh	[10]	28.17				30.14
Forward Price Range High | $ / MWh	[10]	70.98				71.85
Weighted Average Market Price | $ / MWh	[10]	46.04				47.45
Public Service Co Of Oklahoma [Member]
Changes in the Fair Value of Net Trading Derivatives and other investments
Beginning Balance		$ 0.7		0.6		$ 0.6
Realized Gain (Loss) Included in Net Income (or Changes in Net Assets)	[2],[3]	2.2		(0.8)
Unrealized Gain (Loss) Included in Net Income (or Changes in Net Assets) Relating to Assets Still Held at the Reporting Date	[2]	0.0		0.0
Realized and Unrealized Gains (Losses) Included in Other Comprehensive Income		0.0		0.0
Settlements		(2.6)		0.5
Transfers into Level 3	[4]	0.0
Transfers out of Level 3	[4]	0.0		0.0
Changes in Fair Value Allocated to Regulated Jurisdictions	[5]	0.1		0.3
Ending Balance		0.4		0.6		0.7
Public Service Co Of Oklahoma [Member] | Risk Management Commodity Contracts [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	0.5				0.8
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	0.0
Public Service Co Of Oklahoma [Member] | Risk Management Commodity Contracts [Member] | Other [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	(0.1)				(0.1)
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	(0.1)
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
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	0.0
Public Service Co Of Oklahoma [Member] | Risk Management Commodity Contracts [Member] | Level 2 [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	0.1				0.2
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	0.0
Public Service Co Of Oklahoma [Member] | Risk Management Commodity Contracts [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	0.5				0.7
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	0.1
Public Service Co Of Oklahoma [Member] | FTRs [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets		0.5				0.7
Liabilities, Fair Value Disclosure
Risk Management Liabilities		$ 0.1				$ 0.0
Level 3 Quantitative Information
Forward Price Range Low | $ / MWh	[10]	(3.51)				(7.99)
Forward Price Range High | $ / MWh	[10]	3.13				1.03
Weighted Average Market Price | $ / MWh	[10]	(0.40)				(0.36)
Southwestern Electric Power Co [Member]
Assets, Fair Value Disclosure
Cash and Cash Equivalents	[1]	$ 10.3				$ 10.3
Spent Nuclear Fuel and Decommissioning Trusts
Total Assets		10.9				11.2
Changes in the Fair Value of Net Trading Derivatives and other investments
Beginning Balance		0.7		0.8		0.8
Realized Gain (Loss) Included in Net Income (or Changes in Net Assets)	[2],[3]	4.5		4.6
Unrealized Gain (Loss) Included in Net Income (or Changes in Net Assets) Relating to Assets Still Held at the Reporting Date	[2]	0.0		0.0
Realized and Unrealized Gains (Losses) Included in Other Comprehensive Income		0.0		0.0
Settlements		(4.9)		(4.9)
Transfers into Level 3	[4]	0.0
Transfers out of Level 3	[4]	0.0		0.0
Changes in Fair Value Allocated to Regulated Jurisdictions	[5]	0.2		0.2
Ending Balance		0.5		$ 0.7		0.7
Southwestern Electric Power Co [Member] | Other [Member]
Assets, Fair Value Disclosure
Cash and Cash Equivalents	[1]	1.4				1.6
Spent Nuclear Fuel and Decommissioning Trusts
Total Assets		1.3				1.4
Southwestern Electric Power Co [Member] | Level 1 [Member]
Assets, Fair Value Disclosure
Cash and Cash Equivalents	[1]	8.9				8.7
Spent Nuclear Fuel and Decommissioning Trusts
Total Assets		8.9				8.7
Southwestern Electric Power Co [Member] | Level 2 [Member]
Assets, Fair Value Disclosure
Cash and Cash Equivalents	[1]	0.0				0.0
Spent Nuclear Fuel and Decommissioning Trusts
Total Assets		0.1				0.3
Southwestern Electric Power Co [Member] | Level 3 [Member]
Assets, Fair Value Disclosure
Cash and Cash Equivalents	[1]	0.0				0.0
Spent Nuclear Fuel and Decommissioning Trusts
Total Assets		0.6				0.8
Southwestern Electric Power Co [Member] | Risk Management Commodity Contracts [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	0.6				0.9
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	0.4				0.3
Southwestern Electric Power Co [Member] | Risk Management Commodity Contracts [Member] | Other [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	(0.1)				(0.2)
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	(0.1)				(0.1)
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
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	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]	0.1				0.3
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	0.4				0.3
Southwestern Electric Power Co [Member] | Risk Management Commodity Contracts [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets	[7],[12]	0.6				0.8
Liabilities, Fair Value Disclosure
Risk Management Liabilities	[7],[12]	0.1				0.1
Southwestern Electric Power Co [Member] | FTRs [Member] | Level 3 [Member]
Risk Management Assets
Risk Management Assets		0.6				0.8
Liabilities, Fair Value Disclosure
Risk Management Liabilities		$ 0.1				$ 0.1
Level 3 Quantitative Information
Forward Price Range Low | $ / MWh	[10]	(3.51)				(7.99)
Forward Price Range High | $ / MWh	[10]	3.13				1.03
Weighted Average Market Price | $ / MWh	[10]	(0.40)				(0.36)
Cash [Member]
Assets, Fair Value Disclosure
Other Temporary Investments	[1],[13]	$ 152.7				$ 211.7
Cash [Member] | Other [Member]
Assets, Fair Value Disclosure
Other Temporary Investments	[1]	15.2				32.8
Cash [Member] | Level 1 [Member]
Assets, Fair Value Disclosure
Other Temporary Investments	[1]	136.2				173.8
Cash [Member] | Level 2 [Member]
Assets, Fair Value Disclosure
Other Temporary Investments	[1]	1.3				5.1
Cash [Member] | Level 3 [Member]
Assets, Fair Value Disclosure
Other Temporary Investments	[1]	0.0				0.0
Fixed Income Funds [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		973.3				967.4
Fixed Income Funds [Member] | Other [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		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
Fixed Income Funds [Member] | Level 2 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		973.3				967.4
Fixed Income Funds [Member] | Level 3 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		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		973.3				967.4
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
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
Fixed Income Funds [Member] | Indiana Michigan Power Co [Member] | Level 2 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		973.3				967.4
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
Mutual Funds Fixed Income [Member]
Assets, Fair Value Disclosure
Other Temporary Investments	[14]	92.3				91.7
Mutual Funds Fixed Income [Member] | Other [Member]
Assets, Fair Value Disclosure
Other Temporary Investments		0.0				0.0
Mutual Funds Fixed Income [Member] | Level 1 [Member]
Assets, Fair Value Disclosure
Other Temporary Investments		92.3				91.7
Mutual Funds Fixed Income [Member] | Level 2 [Member]
Assets, Fair Value Disclosure
Other Temporary Investments		0.0				0.0
Mutual Funds Fixed Income [Member] | Level 3 [Member]
Assets, Fair Value Disclosure
Other Temporary Investments		0.0				0.0
Mutual Funds Equity [Member]
Assets, Fair Value Disclosure
Other Temporary Investments	[15]	30.0				28.3
Mutual Funds Equity [Member] | Other [Member]
Assets, Fair Value Disclosure
Other Temporary Investments	[15]	0.0				0.0
Mutual Funds Equity [Member] | Level 1 [Member]
Assets, Fair Value Disclosure
Other Temporary Investments	[15]	30.0				28.3
Mutual Funds Equity [Member] | Level 2 [Member]
Assets, Fair Value Disclosure
Other Temporary Investments	[15]	0.0				0.0
Mutual Funds Equity [Member] | Level 3 [Member]
Assets, Fair Value Disclosure
Other Temporary Investments	[15]	0.0				0.0
Cash and Cash Equivalents [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts	[16]	16.6				18.7
Cash and Cash Equivalents [Member] | Other [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts	[16]	7.7				11.4
Cash and Cash Equivalents [Member] | Level 1 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts	[16]	8.9				7.3
Cash and Cash Equivalents [Member] | Level 2 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts	[16]	0.0				0.0
Cash and Cash Equivalents [Member] | Level 3 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts	[16]	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	[16]	16.6				18.7
Cash and Cash Equivalents [Member] | Indiana Michigan Power Co [Member] | Other [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts	[16]	7.7				11.4
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	[16]	8.9				7.3
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	[16]	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	[16]	0.0				0.0
US Government Agencies Debt Securities [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		814.2				785.4
US Government Agencies Debt Securities [Member] | Other [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		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
US Government Agencies Debt Securities [Member] | Level 2 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		814.2				785.4
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
US Government Agencies Debt Securities [Member] | Indiana Michigan Power Co [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		814.2				785.4
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
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
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		814.2				785.4
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
Corporate Debt [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		57.2				60.9
Corporate Debt [Member] | Other [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		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
Corporate Debt [Member] | Level 2 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		57.2				60.9
Corporate Debt [Member] | Level 3 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		0.0				0.0
Corporate Debt [Member] | Indiana Michigan Power Co [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		57.2				60.9
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
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
Corporate Debt [Member] | Indiana Michigan Power Co [Member] | Level 2 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		57.2				60.9
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
State and Local Jurisdiction [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		101.9				121.1
State and Local Jurisdiction [Member] | Other [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		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
State and Local Jurisdiction [Member] | Level 2 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		101.9				121.1
State and Local Jurisdiction [Member] | Level 3 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts		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		101.9				121.1
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
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
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		101.9				121.1
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
Domestic [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts	[15]	1,343.3				1,270.1
Domestic [Member] | Other [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts	[15]	0.0				0.0
Domestic [Member] | Level 1 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts	[15]	1,343.3				1,270.1
Domestic [Member] | Level 2 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts	[15]	0.0				0.0
Domestic [Member] | Level 3 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts	[15]	0.0				0.0
Domestic [Member] | Indiana Michigan Power Co [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts	[15]	1,343.3				1,270.1
Domestic [Member] | Indiana Michigan Power Co [Member] | Other [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts	[15]	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	[15]	1,343.3				1,270.1
Domestic [Member] | Indiana Michigan Power Co [Member] | Level 2 [Member]
Spent Nuclear Fuel and Decommissioning Trusts
Spent Nuclear Fuel and Decommissioning Trusts	[15]	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	[15]	$ 0.0				$ 0.0

[1] 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.

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

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

[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 assets/liabilities.

[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 March 31, 2017 maturity of the net fair value of risk management contracts prior to cash collateral, assets/(liabilities), is as follows: Level 1 matures $(2) million in 2017 and $(2) million in periods 2018-2020; Level 2 matures $5 million in 2017, $6 million in periods 2018-2020, $1 million in periods 2021-2022 and $1 million in periods 2023-2032; Level 3 matures $6 million in 2017, $24 million in periods 2018-2020, $14 million in periods 2021-2022 and $(24) million in periods 2023-2032. Risk management commodity contracts are substantially comprised of power contracts.

[9] The December 31, 2016 maturity of the net fair value of risk management contracts prior to cash collateral, assets/(liabilities), is as follows: Level 1 matures $(2) million in 2018-2020; Level 2 matures $20 million in 2017, $4 million in periods 2018-2020, $3 million in periods 2021-2022 and $1 million in periods 2023-2032; Level 3 matures $17 million in 2017, $28 million in periods 2018-2020, $11 million in periods 2021-2022 and $(31) million in periods 2023-2032. Risk management commodity contracts are substantially comprised of power contracts.

[10] Represents market prices in dollars per MWh.

[11] Includes both affiliated and nonaffiliated transactions.

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

[13] Primarily represents amounts held for the repayment of debt.(b)Primarily short and intermediate maturities which may be sold and do not contain maturity dates.

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

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

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