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Rate Matters East Companies (Details) - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2019
Dec. 31, 2018
Public Utilities, General Disclosures [Line Items]    
Accumulated Depreciation and Amortization $ 18,182.6 $ 17,986.1
Construction Work in Progress 4,910.9 4,393.9
AEP Transmission Co [Member]    
Public Utilities, General Disclosures [Line Items]    
Accumulated Depreciation and Amortization 306.7 271.9
Construction Work in Progress 1,812.2 1,578.3
Appalachian Power Co [Member]    
Public Utilities, General Disclosures [Line Items]    
Accumulated Depreciation and Amortization 4,174.9 4,124.4
Construction Work in Progress 524.9 490.2
Indiana Michigan Power Co [Member]    
Public Utilities, General Disclosures [Line Items]    
Accumulated Depreciation and Amortization 3,208.4 3,151.6
Construction Work in Progress 533.5 465.3
Ohio Power Co [Member]    
Public Utilities, General Disclosures [Line Items]    
Accumulated Depreciation and Amortization 2,224.1 2,218.6
Construction Work in Progress $ 461.0 $ 432.1
Virginia Legislation Affecting Earnings Reviews [Member]    
Public Utilities, General Disclosures [Line Items]    
Percent of Excess Earnings Subject to Refund 70.00%  
Basis Points Over Authorized Return on Equity Considered Excess Earnings 70.00%  
Approved Return on Common Equity 9.42%  
Virginia Legislation Affecting Earnings Reviews [Member] | Appalachian Power Co [Member]    
Public Utilities, General Disclosures [Line Items]    
Percent of Excess Earnings Subject to Refund 70.00%  
Basis Points Over Authorized Return on Equity Considered Excess Earnings 70.00%  
Approved Return on Common Equity 9.42%  
Virginia Staff Depreciation Study Request [Member]    
Public Utilities, General Disclosures [Line Items]    
Potential Increase to Total Annual Depreciation Rates $ 21.0  
Potential Increase to Annual Transmission Depreciation Rates 6.0  
Virginia Staff Depreciation Study Request [Member] | Appalachian Power Co [Member]    
Public Utilities, General Disclosures [Line Items]    
Potential Increase to Total Annual Depreciation Rates 21.0  
Potential Increase to Annual Transmission Depreciation Rates 6.0  
Virginia Tax Reform [Member]    
Public Utilities, General Disclosures [Line Items]    
Refund Due to Tax Reform 40.0  
Refund for Excess ADIT Associated with Certain Depreciable Property 9.0  
Refund for Excess ADIT Not Subject to Rate Normalization Requirements 94.0  
One Time Refund of Estimated Excess Taxes Collected 22.0  
Virginia Tax Reform [Member] | Appalachian Power Co [Member]    
Public Utilities, General Disclosures [Line Items]    
Refund Due to Tax Reform 40.0  
Refund for Excess ADIT Associated with Certain Depreciable Property 9.0  
Refund for Excess ADIT Not Subject to Rate Normalization Requirements 94.0  
One Time Refund of Estimated Excess Taxes Collected $ 22.0  
2018 West Virginia Base Rate Case [Member]    
Public Utilities, General Disclosures [Line Items]    
Approved Return on Common Equity 9.75%  
Refund for Excess ADIT Not Subject to Rate Normalization Requirements $ 24.0  
Amount of Increase Related to Annual Depreciation Rates 32.0  
Requested Annual Increase $ 115.0  
Requested Return on Equity 10.22%  
Approved Amount of Increase Related to Annual Depreciation Rates $ 18.0  
Regulatory Assets Used to Offset Tax Savings and Excess ADIT Due to Tax Reform 14.0  
Adjusted Annual Increase Request due to Tax Reform 95.0  
Approved Annual Revenue Increase $ 44.0  
2018 West Virginia Base Rate Case [Member] | Appalachian Power Co [Member]    
Public Utilities, General Disclosures [Line Items]    
Approved Return on Common Equity 9.75%  
Refund for Excess ADIT Not Subject to Rate Normalization Requirements $ 19.0  
Amount of Increase Related to Annual Depreciation Rates 28.0  
Requested Annual Increase $ 98.0  
Requested Return on Equity 10.22%  
Approved Amount of Increase Related to Annual Depreciation Rates $ 14.0  
Regulatory Assets Used to Offset Tax Savings and Excess ADIT Due to Tax Reform 12.0  
Adjusted Annual Increase Request due to Tax Reform 80.0  
Approved Annual Revenue Increase 36.0  
Michigan Tax Reform [Member]    
Public Utilities, General Disclosures [Line Items]    
Refund for Excess ADIT Associated with Certain Depreciable Property 68.0  
Refund for Excess ADIT Not Subject to Rate Normalization Requirements 37.0  
Michigan Tax Reform [Member] | Indiana Michigan Power Co [Member]    
Public Utilities, General Disclosures [Line Items]    
Refund for Excess ADIT Associated with Certain Depreciable Property 68.0  
Refund for Excess ADIT Not Subject to Rate Normalization Requirements $ 37.0  
Ohio Electric Security Plan Filing [Member]    
Public Utilities, General Disclosures [Line Items]    
Return on Common Equity Filed in the Pending Stipulation Agreement 10.00%  
Staff Calculated Overspending $ 10.0  
Ohio Electric Security Plan Filing [Member] | Ohio Power Co [Member]    
Public Utilities, General Disclosures [Line Items]    
Return on Common Equity Filed in the Pending Stipulation Agreement 10.00%  
Staff Calculated Overspending $ 10.0  
2016 SEET Filing [Member]    
Public Utilities, General Disclosures [Line Items]    
Provision for Refund 58.0  
2016 SEET Filing [Member] | Ohio Power Co [Member]    
Public Utilities, General Disclosures [Line Items]    
Provision for Refund $ 58.0  
FERC Transmission Complaint [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 $ 50.0  
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%  
Minimum [Member] | Ohio Electric Security Plan Filing [Member]    
Public Utilities, General Disclosures [Line Items]    
Rate Caps Related to the Distribution Investment Rider Range $ 215.0  
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 215.0  
Maximum [Member] | Ohio Electric Security Plan Filing [Member]    
Public Utilities, General Disclosures [Line Items]    
Rate Caps Related to the Distribution Investment Rider Range 290.0  
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 $ 290.0