Commitments, Guarantees and Contingencies (Details) - USD ($) $ in Millions	1 Months Ended	9 Months Ended
	Jul. 25, 2019	Sep. 30, 2019
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Payments for Environmental Liabilities	$ 7.5
Letters of Credit [Member]
Maximum Future Payments for Letters of Credit [Abstract]
Maximum Future Payments for Letters of Credit Issued Under the Uncommitted Facility		$ 204.4
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Letters of Credit Limit		1,200.0
Uncommitted Facility		405.0
Guarantees of Third Party Obligations [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Guarantees of Mine Reclamation, Amount		155.0
Estimated Final Cost Mine Reclamation		107.0
Total Amount Collected through a Rider for Final Mine Closure and Reclamation Costs		77.0
Amount Collected through a Rider for Final Mine Closure - ARO Noncurrent		83.0
Amount Collected, Rider Mine Close Other Assets Noncurrent		6.0
Guarantees of Equity Method Investees [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Maximum Potential Amount of Future Payments Associated with Guarantee		75.0
AEP Texas Inc. [Member] | Letters of Credit [Member]
Maximum Future Payments for Letters of Credit [Abstract]
Maximum Future Payments for Letters of Credit Issued Under the Uncommitted Facility		2.2
Indiana Michigan Power Co [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Payments for Environmental Liabilities	$ 7.5
Ohio Power Co [Member] | Letters of Credit [Member]
Maximum Future Payments for Letters of Credit [Abstract]
Maximum Future Payments for Letters of Credit Issued Under the Uncommitted Facility		3.6
Southwestern Electric Power Co [Member] | Guarantees of Third Party Obligations [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Guarantees of Mine Reclamation, Amount		155.0
Estimated Final Cost Mine Reclamation		107.0
Total Amount Collected through a Rider for Final Mine Closure and Reclamation Costs		77.0
Amount Collected through a Rider for Final Mine Closure - ARO Noncurrent		83.0
Amount Collected, Rider Mine Close Other Assets Noncurrent		6.0
June 2022 [Member] | Letters of Credit [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Revolving Credit Facilities		$ 4,000.0