Rate Matters Regulated Operations (Details) - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2019	Dec. 31, 2018
Public Utilities, General Disclosures [Line Items]
Gross Investment		$ 22,624.4	$ 21,699.9
Accumulated Depreciation and Amortization		18,760.2	17,986.1
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET		58,692.7	55,099.1
Materials and Supplies		613.5	579.6
Regulatory Liability, Noncurrent		8,552.8	8,540.3
Regulatory Assets, Noncurrent		3,131.4	3,310.4
Effects of Regulation Textuals [Abstract]
Secured Debt		1,059.4	1,111.4
Texas Storm Cost Securitization [Member]
Effects of Regulation Textuals [Abstract]
Secured Debt		235.0
Oklaunion Generating Station [Member] | Generating Units Probable of Abandonment [Member]
Public Utilities, General Disclosures [Line Items]
Gross Investment		106.6
Accumulated Depreciation and Amortization		80.6
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET		26.0
Oklaunion Power Station Accelerated Depreciation	[1]	21.9
Materials and Supplies		3.2
Regulatory Liability, Noncurrent		$ 5.1
Expected Retirement Date		2020
Remaining Recovery Period, Plant Depreciation		27 years
AEP Texas Inc. [Member]
Public Utilities, General Disclosures [Line Items]
Gross Investment		$ 351.8	352.1
Accumulated Depreciation and Amortization		1,742.7	1,651.2
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET		8,587.8	7,991.8
Materials and Supplies		54.6	52.8
Regulatory Liability, Noncurrent		1,325.1	1,344.3
Regulatory Assets, Noncurrent		259.6	430.0
AEP Texas Inc. [Member] | Texas Storm Cost Securitization [Member]
Effects of Regulation Textuals [Abstract]
Secured Debt		235.0
AEP Transmission Co [Member]
Public Utilities, General Disclosures [Line Items]
Accumulated Depreciation and Amortization		368.8	271.9
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET		8,898.6	7,996.2
Materials and Supplies		15.1	19.0
Regulatory Liability, Noncurrent		541.2	521.3
Regulatory Assets, Noncurrent		7.3	12.9
Appalachian Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Gross Investment		6,560.5	6,509.6
Accumulated Depreciation and Amortization		4,300.2	4,124.4
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET		10,992.1	10,668.3
Materials and Supplies		102.1	100.1
Regulatory Liability, Noncurrent		1,336.9	1,449.7
Regulatory Assets, Noncurrent		474.2	475.8
Indiana Michigan Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Gross Investment		5,002.0	4,887.2
Accumulated Depreciation and Amortization		3,280.5	3,151.6
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET		6,832.7	6,611.2
Materials and Supplies		169.9	167.3
Regulatory Liability, Noncurrent		1,809.0	1,574.5
Regulatory Assets, Noncurrent		490.2	512.5
Ohio Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Accumulated Depreciation and Amortization		2,256.1	2,218.6
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET		6,697.3	6,274.9
Materials and Supplies		48.5	42.9
Regulatory Liability, Noncurrent		1,143.6	1,221.2
Regulatory Assets, Noncurrent		372.2	387.5
Public Service Co Of Oklahoma [Member]
Public Utilities, General Disclosures [Line Items]
Gross Investment		1,569.9	1,577.0
Accumulated Depreciation and Amortization		1,558.5	1,472.9
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET		4,038.3	3,966.7
Materials and Supplies		46.2	44.8
Regulatory Liability, Noncurrent		858.9	864.7
Regulatory Assets, Noncurrent		380.7	369.0
Public Service Co Of Oklahoma [Member] | Oklaunion Generating Station [Member] | Generating Units Probable of Abandonment [Member]
Public Utilities, General Disclosures [Line Items]
Gross Investment		106.6
Accumulated Depreciation and Amortization		80.6
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET		26.0
Oklaunion Power Station Accelerated Depreciation	[1]	21.9
Materials and Supplies		3.2
Regulatory Liability, Noncurrent		$ 5.1
Expected Retirement Date		2020
Remaining Recovery Period, Plant Depreciation		27 years
Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Gross Investment		$ 4,676.1	4,672.6
Accumulated Depreciation and Amortization		2,848.2	2,808.3
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET		7,003.1	6,871.8
Materials and Supplies		69.8	67.5
Regulatory Liability, Noncurrent		918.1	923.0
Regulatory Assets, Noncurrent		223.6	230.8
Regulatory Assets Pending Final Regulatory Approval [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent	[2]	168.4	288.0
Regulatory Assets Pending Final Regulatory Approval [Member] | AEP Texas Inc. [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		2.3	152.6
Regulatory Assets Pending Final Regulatory Approval [Member] | Appalachian Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent	[2]	42.9	44.9
Regulatory Assets Pending Final Regulatory Approval [Member] | Indiana Michigan Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		10.8	3.3
Regulatory Assets Pending Final Regulatory Approval [Member] | Ohio Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		0.1	1.0
Regulatory Assets Pending Final Regulatory Approval [Member] | Public Service Co Of Oklahoma [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		21.9	6.0
Regulatory Assets Pending Final Regulatory Approval [Member] | Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		63.0	64.4
Asset Retirement Obligation - Arkansas, Louisiana [Member] | Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		6.8	5.3
Cook Plant Study Costs [Member] | Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Indiana Michigan Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		10.7	0.0
Kentucky Deferred Purchase Power Expenses [Member] | Regulatory Assets Currently Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		26.2	14.5
Oklaunion Power Station Accelerated Depreciation [Member] | Regulatory Assets Currently Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		21.9	5.5
Oklaunion Power Station Accelerated Depreciation [Member] | Regulatory Assets Currently Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Public Service Co Of Oklahoma [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		21.9	5.5
Other Regulatory Assets Pending Final Regulatory Approval [Member] | Regulatory Assets Currently Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		5.4	9.3
Other Regulatory Assets Pending Final Regulatory Approval [Member] | Regulatory Assets Currently Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		0.3	0.3
Other Regulatory Assets Pending Final Regulatory Approval [Member] | Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		26.8	20.7
Other Regulatory Assets Pending Final Regulatory Approval [Member] | Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Appalachian Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		0.0	0.6
Other Regulatory Assets Pending Final Regulatory Approval [Member] | Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Indiana Michigan Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		0.1	3.3
Other Regulatory Assets Pending Final Regulatory Approval [Member] | Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Ohio Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		0.1	1.0
Other Regulatory Assets Pending Final Regulatory Approval [Member] | Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Public Service Co Of Oklahoma [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		0.0	0.5
Other Regulatory Assets Pending Final Regulatory Approval [Member] | Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		4.2	3.6
Plant Retirement Costs - Asset Retirement Obligation Costs [Member] | Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		37.8	35.3
Plant Retirement Costs - Asset Retirement Obligation Costs [Member] | Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Appalachian Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		37.8	35.3
Plant Retirement Costs - Materials and Supplies [Member] | Regulatory Assets Currently Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Appalachian Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		5.1	9.0
Plant Retirement Costs - Unrecovered Plant [Member] | Regulatory Assets Pending Final Regulatory Approval [Member]
Public Utilities, General Disclosures [Line Items]
Accumulated Depreciation and Amortization		91.0
Effects of Regulation Textuals [Abstract]
Cost of Removal		17.0
Plant Retirement Costs - Unrecovered Plant [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Appalachian Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Accumulated Depreciation and Amortization		91.0
Effects of Regulation Textuals [Abstract]
Cost of Removal		17.0
Plant Retirement Costs - Unrecovered Plant [Member] | Regulatory Assets Currently Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		50.3	50.3
Plant Retirement Costs - Unrecovered Plant [Member] | Regulatory Assets Currently Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		50.3	50.3
Rate Case Expense - Texas [Member] | Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		1.4	4.9
Rate Case Expense [Member] | Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | AEP Texas Inc. [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		2.3	0.2
Storm Costs [Member] | Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent	[3]	0.0	152.4
Storm Costs [Member] | Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | AEP Texas Inc. [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent	[3]	$ 0.0	$ 152.4

[1] In October 2018, PSO changed depreciation rates to utilize the 2020 end-of-life and defer depreciation expense to a regulatory asset for the amount in excess of the previously OCC-approved depreciation rates for Oklaunion Power Station. See “2018 Oklahoma Base Rate Case” discussion below for additional information.

[2] In 2015, APCo recorded a $91 million reduction, before cost of removal of $17 million, to accumulated depreciation related to the remaining net book value of plants retired in 2015, primarily in its Virginia jurisdiction. These plants were normal retirements at the end of their depreciable lives under the group composite method of depreciation. APCo’s recovery of the remaining Virginia net book value for the retired plants will be considered in the Virginia SCC’s 2020 triennial review of APCo’s generation and distribution base rates.

[3] In September 2019, AEP Texas securitized $235 million of storm-related costs. As a result of the securitization, the regulatory asset balance was transferred to Securitized Assets on the balance sheets. See “Texas Storm Cost Securitization” discussion below for additional information.