Rate Matters - East Companies (Details)	1 Months Ended	9 Months Ended
	Oct. 25, 2018 USD ($)	Sep. 30, 2018 USD ($) MW	Dec. 31, 2017 USD ($)
Public Utilities, General Disclosures [Line Items]
Accumulated Depreciation and Amortization		$ 17,841,600,000	$ 17,167,000,000
Construction Work in Progress		4,995,500,000	4,120,700,000
Appalachian Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Accumulated Depreciation and Amortization		4,086,200,000	3,896,400,000
Construction Work in Progress		602,100,000	483,000,000
Indiana Michigan Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Accumulated Depreciation and Amortization		3,113,900,000	3,024,200,000
Construction Work in Progress		458,600,000	460,200,000
Ohio Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Accumulated Depreciation and Amortization		2,230,600,000	2,184,800,000
Construction Work in Progress		475,700,000	$ 410,100,000
Virginia Legislation Affecting Earnings Reviews [Member]
Public Utilities, General Disclosures [Line Items]
Fuel Expenses Not to be Recovered		10,000,000
Reduction in Annual Base Rates		50,000,000
Energy Efficiency Programs to be Requested from the Virginia SCC Through July, 2028 Dollars		$ 140,000,000
Energy Efficiency Programs to be Requested from the Virginia SCC Through July, 2028 MWs | MW		200
Virginia Legislation Affecting Earnings Reviews [Member] | Appalachian Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Fuel Expenses Not to be Recovered		$ 10,000,000
Reduction in Annual Base Rates		50,000,000
Energy Efficiency Programs to be Requested from the Virginia SCC Through July, 2028 Dollars		$ 140,000,000
Energy Efficiency Programs to be Requested from the Virginia SCC Through July, 2028 MWs | MW		200
2018 West Virginia Base Rate Case [Member]
Public Utilities, General Disclosures [Line Items]
Requested Annual Increase		$ 115,000,000
Requested Return on Common Equity		10.22%
Amount of Increase Related to Annual Depreciation Rates		$ 32,000,000
2018 West Virginia Base Rate Case [Member] | Appalachian Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Requested Annual Increase		$ 98,000,000
Requested Return on Common Equity		10.22%
Amount of Increase Related to Annual Depreciation Rates		$ 28,000,000
West Virginia Tax Reform [Member]
Public Utilities, General Disclosures [Line Items]
Refund Due to Tax Reform		63,000,000
Regulatory Assets Used to Offset Tax Savings and Excess ADIT Due to Tax Reform		139,000,000
Refund for Excess ADIT Not Subject to Rate Normalization Requirements		87,000,000
West Virginia Tax Reform [Member] | Appalachian Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Refund Due to Tax Reform		51,000,000
Regulatory Assets Used to Offset Tax Savings and Excess ADIT Due to Tax Reform		125,000,000
Refund for Excess ADIT Not Subject to Rate Normalization Requirements		77,000,000
Indiana Base Rate Case - 2017 [Member]
Public Utilities, General Disclosures [Line Items]
Requested Annual Increase		$ 263,000,000
Requested Return on Common Equity		10.60%
Amount Of Annual Reduction To Customer Bills Through Credit Adjustment Rider		$ 23,000,000
Amount of Increase Related to Annual Depreciation Rates		78,000,000
Amount of Increase Related to Amortization of Regulatory Assets		11,000,000
Settled Annual Increase		$ 97,000,000
Settled Return on Common Equity		9.95%
Original Sharing of Off-System Sales Margins		50.00%
Settled Sharing of Off-System Sales Margins		95.00%
Refund for Impact of Tax Reform		$ 4,000,000
Indiana Base Rate Case - 2017 [Member] | Indiana Michigan Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Requested Annual Increase		$ 263,000,000
Requested Return on Common Equity		10.60%
Amount Of Annual Reduction To Customer Bills Through Credit Adjustment Rider		$ 23,000,000
Amount of Increase Related to Annual Depreciation Rates		78,000,000
Amount of Increase Related to Amortization of Regulatory Assets		11,000,000
Settled Annual Increase		$ 97,000,000
Settled Return on Common Equity		9.95%
Original Sharing of Off-System Sales Margins		50.00%
Settled Sharing of Off-System Sales Margins		95.00%
Refund for Impact of Tax Reform		$ 4,000,000
Michigan Base Rate Case - 2017 [Member]
Public Utilities, General Disclosures [Line Items]
Requested Annual Increase		$ 52,000,000
Requested Return on Common Equity		10.60%
Amount of Increase Related to Annual Depreciation Rates		$ 23,000,000
Amount of Increase Related to Amortization of Regulatory Assets		4,000,000
ALJ Recommended Annual Increase		49,000,000
Cost of New Entry Value		$ 289
ALJ Recommended Return on Common Equity		9.80%
Alternate Supplier Cap		10.00%
Reduced Capacity Charge Pretax Loss		$ 9,000,000
Approved Annual Revenue Increase		$ 50,000,000
Approved Return On Equity		9.90%
Michigan Base Rate Case - 2017 [Member] | Indiana Michigan Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Requested Annual Increase		$ 52,000,000
Requested Return on Common Equity		10.60%
Amount of Increase Related to Annual Depreciation Rates		$ 23,000,000
Amount of Increase Related to Amortization of Regulatory Assets		4,000,000
ALJ Recommended Annual Increase		49,000,000
Cost of New Entry Value		$ 289
ALJ Recommended Return on Common Equity		9.80%
Alternate Supplier Cap		10.00%
Reduced Capacity Charge Pretax Loss		$ 9,000,000
Approved Annual Revenue Increase		$ 50,000,000
Approved Return On Equity		9.90%
Michigan Tax Reform [Member]
Public Utilities, General Disclosures [Line Items]
Refund Due to Tax Reform		$ 9,000,000
Michigan Tax Reform [Member] | Indiana Michigan Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Refund Due to Tax Reform		9,000,000
Rockport Plant, Unit 2 Selective Catalytic Reduction [Member]
Public Utilities, General Disclosures [Line Items]
Projected Capital Costs		274,000,000
Approved Capital Costs		274,000,000
Rockport Plant, Unit 2 Selective Catalytic Reduction [Member] | Indiana Michigan Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Projected Capital Costs		274,000,000
Approved Capital Costs		274,000,000
Kentucky Base Rate Case - 2017 [Member]
Public Utilities, General Disclosures [Line Items]
KPSC Order Annual Revenue Increase		$ 12,000,000
KPSC Order Return on Common Equity		9.70%
KPSC Order Annual Revenue Reduction due to Tax Reform		$ 14,000,000
KPSC Order Deferral of Rockport Plant Unit Power Agreement Expenses		$ 50,000,000
Recovery/Return of certain PJM OATT Expenses Above/Below Corresponding Level Recovered in Rates		80.00%
KPCo Request for Additional Revenue Increase		$ 2,300,000
KPSC Order Additional Annual Revenue Increase		765,000
Kentucky Tax Reform [Member]
Public Utilities, General Disclosures [Line Items]
Refund for Excess ADIT Associated with Certain Depreciable Property		82,000,000
Refund for Excess ADIT Not Subject to Rate Normalization Requirements		93,000,000
Ohio Electric Security Plan Filing [Member]
Public Utilities, General Disclosures [Line Items]
PUCO Approved Reduced Customer Credits		$ 15,000,000
Solar Energy Projects To Be Developed And Implemented By 2021 As Proposed In Stipulation Agreement | MW		400
Wind Energy Projects To Be Developed And Implemented By 2021 As Proposed In Stipulation Agreement | MW		500
Percentage of Output to be Received from Solar and Wind Projects as Proposed in Stipulation Agreement		100.00%
Maximum Ownership Percentage of Solar and Wind Projects as Proposed in Stipulation Agreement		50.00%
Return on Common Equity Filed in the Pending Stipulation Agreement		10.00%
Ohio Electric Security Plan Filing [Member] | Ohio Power Co [Member]
Public Utilities, General Disclosures [Line Items]
PUCO Approved Reduced Customer Credits		$ 15,000,000
Solar Energy Projects To Be Developed And Implemented By 2021 As Proposed In Stipulation Agreement | MW		400
Wind Energy Projects To Be Developed And Implemented By 2021 As Proposed In Stipulation Agreement | MW		500
Percentage of Output to be Received from Solar and Wind Projects as Proposed in Stipulation Agreement		100.00%
Maximum Ownership Percentage of Solar and Wind Projects as Proposed in Stipulation Agreement		50.00%
Return on Common Equity Filed in the Pending Stipulation Agreement		10.00%
2016 SEET Filing [Member]
Public Utilities, General Disclosures [Line Items]
Provision for Refund		$ 58,000,000
Intervenor Recommended Refund to Customers		53,000,000
2016 SEET Filing [Member] | Ohio Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Provision for Refund		58,000,000
Intervenor Recommended Refund to Customers		53,000,000
PJM Transmission Rates [Member]
Public Utilities, General Disclosures [Line Items]
Amount of RTEP Refunds Recorded to Customer Accounts Receivable		134,000,000
Amount of RTEP Refunds Recorded to Deferred Charges and Other Noncurrent Assets		$ 75,000,000
FERC Transmission Complaint - AEP PJM Participants [Member]
Public Utilities, General Disclosures [Line Items]
Approved Return on Common Equity		10.99%
Intervenor Recommended Return on Common Equity		8.32%
Return On Common Equity Per Settlement Agreement		9.85%
Return on Common Equity Inclusive of RTO Per Settlement Agreement		10.35%
RTO Incentive Adder Per Settlement Agreement		0.50%
One Time Refund to Customers Per Settlement Agreement		$ 50,000,000
Increased Cap on Equity Portion of the Capital Structure Per Settlement Agreement		55.00%
Original Cap on Equity Portion of the Capital Structure Prior to Settlement Agreement		50.00%
Second Intervenor Recommended Return on Common Equity		8.48%
Second Intervenor Recommended One Time Refund to Customers		$ 184,000,000
FERC Trial Staff Recommended Return on Common Equity		8.41%
FERC Trial Staff Recommended One Time Refund to Customers		$ 175,000,000
Subsequent Event [Member] | Virginia Tax Reform [Member]
Public Utilities, General Disclosures [Line Items]
Refund for Excess ADIT Not Subject to Rate Normalization Requirements to Offset Fuel	$ 55,000,000
Refund Due to Tax Reform	7,000,000
Refund for Current Year Tax Reform Rate Change	39,000,000
Refund for Excess ADIT Associated with Certain Depreciable Property	7,000,000
Refund for Excess ADIT Not Subject to Rate Normalization Requirements	11,000,000
Subsequent Event [Member] | Virginia Tax Reform [Member] | Appalachian Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Refund for Excess ADIT Not Subject to Rate Normalization Requirements to Offset Fuel	55,000,000
Refund Due to Tax Reform	7,000,000
Refund for Current Year Tax Reform Rate Change	39,000,000
Refund for Excess ADIT Associated with Certain Depreciable Property	7,000,000
Refund for Excess ADIT Not Subject to Rate Normalization Requirements	11,000,000
Subsequent Event [Member] | 2018 West Virginia Base Rate Case [Member]
Public Utilities, General Disclosures [Line Items]
Adjusted Annual Increase Request due to Tax Reform	95,000,000
Staff Recommended Annual Increase	$ 2,000,000
Staff Recommended Return on Common Equity	9.25%
Intervenor Recommended Annual Decrease	$ 14,000,000
Intervenor Recommended Return on Common Equity	8.75%
Subsequent Event [Member] | 2018 West Virginia Base Rate Case [Member] | Appalachian Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Adjusted Annual Increase Request due to Tax Reform	$ 80,000,000
Staff Recommended Annual Increase	$ 2,000,000
Staff Recommended Return on Common Equity	9.25%
Intervenor Recommended Annual Decrease	$ 14,000,000
Intervenor Recommended Return on Common Equity	8.75%
Subsequent Event [Member] | Michigan Tax Reform [Member]
Public Utilities, General Disclosures [Line Items]
Refund for Current Year Tax Reform Rate Change	$ 3,000,000
Refund for Excess ADIT Associated with Certain Depreciable Property	68,000,000
Refund for Excess ADIT Not Subject to Rate Normalization Requirements	37,000,000
Subsequent Event [Member] | Michigan Tax Reform [Member] | Indiana Michigan Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Refund for Current Year Tax Reform Rate Change	3,000,000
Refund for Excess ADIT Associated with Certain Depreciable Property	68,000,000
Refund for Excess ADIT Not Subject to Rate Normalization Requirements	37,000,000
Subsequent Event [Member] | Ohio Tax Reform [Member]
Public Utilities, General Disclosures [Line Items]
Refund Due to Tax Reform	20,000,000
Regulatory Assets Used to Offset Tax Savings and Excess ADIT Due to Tax Reform	48,000,000
Refund for Excess ADIT Associated with Certain Depreciable Property	278,000,000
Refund for Excess ADIT Not Subject to Rate Normalization Requirements	129,000,000
Subsequent Event [Member] | Ohio Tax Reform [Member] | Ohio Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Refund Due to Tax Reform	20,000,000
Regulatory Assets Used to Offset Tax Savings and Excess ADIT Due to Tax Reform	48,000,000
Refund for Excess ADIT Associated with Certain Depreciable Property	278,000,000
Refund for Excess ADIT Not Subject to Rate Normalization Requirements	$ 129,000,000
Minimum [Member] | Ohio Electric Security Plan Filing [Member]
Public Utilities, General Disclosures [Line Items]
Rate Caps Related to the Distribution Investment Rider Range		215,000,000
Minimum [Member] | Ohio Electric Security Plan Filing [Member] | Ohio Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Rate Caps Related to the Distribution Investment Rider Range		215,000,000
Maximum [Member] | Ohio Electric Security Plan Filing [Member]
Public Utilities, General Disclosures [Line Items]
Rate Caps Related to the Distribution Investment Rider Range		290,000,000
Maximum [Member] | Ohio Electric Security Plan Filing [Member] | Ohio Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Rate Caps Related to the Distribution Investment Rider Range		$ 290,000,000