Rate Matters - East Companies (Details) $ in Millions	1 Months Ended	9 Months Ended
	Oct. 26, 2017 USD ($)	Sep. 30, 2017 USD ($) MW	Dec. 31, 2016 USD ($)
Public Utilities, General Disclosures [Line Items]
Construction Work in Progress		$ 3,710.0	$ 3,183.9
Appalachian Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Construction Work in Progress		493.5	390.3
Indiana Michigan Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Construction Work in Progress		478.9	654.2
Ohio Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Construction Work in Progress		$ 350.7	$ 221.5
FERC Transmission Complaint - AEP PJM Participants [Member]
Public Utilities, General Disclosures [Line Items]
Intervenor Recommended Return on Common Equity		8.32%
Approved Return on Common Equity		10.99%
Kentucky Base Rate Case - 2017 [Member]
Public Utilities, General Disclosures [Line Items]
Requested Annual Increase		$ 66.0
Requested Return on Common Equity		10.31%
Requested Annual Increase in Environmental Surcharge		$ 4.0
Adjusted Requested Annual Increase		60.0
KPCo's Regulatory Asset Related to the Retired Big Sandy, Unit 2		289.0
Indiana Base Rate Case - 2017 [Member]
Public Utilities, General Disclosures [Line Items]
Requested Annual Increase		$ 263.0
Requested Return on Common Equity		10.60%
Amount Of Annual Reduction To Customer Bills Through Credit Adjustment Rider		$ 23.0
Amount of Increase Related to Annual Depreciation Rates		78.0
Amount of Increase Related to Amortization of Regulatory Assets		11.0
Indiana Base Rate Case - 2017 [Member] | Indiana Michigan Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Requested Annual Increase		$ 263.0
Requested Return on Common Equity		10.60%
Amount Of Annual Reduction To Customer Bills Through Credit Adjustment Rider		$ 23.0
Amount of Increase Related to Annual Depreciation Rates		78.0
Amount of Increase Related to Amortization of Regulatory Assets		11.0
Michigan Base Rate Case - 2017 [Member]
Public Utilities, General Disclosures [Line Items]
Requested Annual Increase		$ 52.0
Requested Return on Common Equity		10.60%
Amount of Increase Related to Annual Depreciation Rates		$ 23.0
Amount of Increase Related to Amortization of Regulatory Assets		4.0
Michigan Base Rate Case - 2017 [Member] | Indiana Michigan Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Requested Annual Increase		$ 52.0
Requested Return on Common Equity		10.60%
Amount of Increase Related to Annual Depreciation Rates		$ 23.0
Amount of Increase Related to Amortization of Regulatory Assets		$ 4.0
Ohio Electric Security Plan Filing [Member]
Public Utilities, General Disclosures [Line Items]
Approved Return on Common Equity		10.20%
PUCO Approved Reduced Customer Credits		$ 15.0
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 Proposed in the Amended ESP Filing		10.41%
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]
Approved Return on Common Equity		10.20%
PUCO Approved Reduced Customer Credits		$ 15.0
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 Proposed in the Amended ESP Filing		10.41%
Return on Common Equity Filed in the Pending Stipulation Agreement		10.00%
Rockport Plant, Unit 2 Selective Catalytic Reduction [Member]
Public Utilities, General Disclosures [Line Items]
Projected Capital Costs		$ 274.0
Construction Work in Progress		17.0
Rockport Plant, Unit 2 Selective Catalytic Reduction [Member] | Indiana Michigan Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Projected Capital Costs		274.0
Construction Work in Progress		17.0
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
Subsequent Event [Member] | Kentucky Base Rate Case - 2017 [Member]
Public Utilities, General Disclosures [Line Items]
Proposed Lease Expense to be Deferred with a WACC Carrying Charge for Recovery	$ 100.0
Subsequent Event [Member] | Michigan Base Rate Case - 2017 [Member]
Public Utilities, General Disclosures [Line Items]
MPSC Recommended Annual Net Revenue Increase	$ 49.0
MPSC Recommended Return on Common Equity	9.80%
Subsequent Event [Member] | Michigan Base Rate Case - 2017 [Member] | Indiana Michigan Power Co [Member]
Public Utilities, General Disclosures [Line Items]
MPSC Recommended Annual Net Revenue Increase	$ 49.0
MPSC Recommended Return on Common Equity	9.80%
Subsequent Event [Member] | Ohio Electric Security Plan Filing [Member]
Public Utilities, General Disclosures [Line Items]
Intervenor Recommended Return on Common Equity	9.30%
Subsequent Event [Member] | Ohio Electric Security Plan Filing [Member] | Ohio Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Intervenor Recommended Return on Common Equity	9.30%
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
Minimum [Member] | Subsequent Event [Member] | Kentucky Base Rate Case - 2017 [Member]
Public Utilities, General Disclosures [Line Items]
Intervenor Recommended Return on Common Equity	8.60%
KPSC Recommended Annual Net Revenue Increase	$ 13.0
Minimum [Member] | Subsequent Event [Member] | Michigan Base Rate Case - 2017 [Member]
Public Utilities, General Disclosures [Line Items]
Intervenor Recommended Return on Common Equity	9.30%
Minimum [Member] | Subsequent Event [Member] | Michigan Base Rate Case - 2017 [Member] | Indiana Michigan Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Intervenor Recommended Return on Common Equity	9.30%
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
Maximum [Member] | Subsequent Event [Member] | Kentucky Base Rate Case - 2017 [Member]
Public Utilities, General Disclosures [Line Items]
Intervenor Recommended Return on Common Equity	8.85%
KPSC Recommended Annual Net Revenue Increase	$ 40.0
Maximum [Member] | Subsequent Event [Member] | Michigan Base Rate Case - 2017 [Member]
Public Utilities, General Disclosures [Line Items]
Intervenor Recommended Return on Common Equity	9.50%
Maximum [Member] | Subsequent Event [Member] | Michigan Base Rate Case - 2017 [Member] | Indiana Michigan Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Intervenor Recommended Return on Common Equity	9.50%