Commitments, Guarantees and Contingencies (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($) MW	Apr. 25, 2019 USD ($)
Commitments, Guarantees and Contingencies (Textuals)
Utility Plant Generation Capacity | MW	2,278
Letters of Credit [Member]
Maximum Future Payments for Letters of Credit Under Uncommitted Facilities
Maximum Future Payments for Letters of Credit Issued Under the Uncommitted Facility	$ 105.8
Commitments, Guarantees and Contingencies (Textuals)
Letters of Credit Limit	1,200.0
Uncommitted Facility	305.0
Variable Rate PCBs Supported	45.0
Guarantees of Third Party Obligations [Member]
Commitments, Guarantees and Contingencies (Textuals)
Guarantees of Mine Reclamation, Amount	140.0
Mine Reclamation and Closing Liability, Noncurrent	107.0
Total Amount Collected through a Rider for Final Mine Closure and Reclamation Costs	76.0
Amount Collected through a Rider for Final Mine Closure - ARO Noncurrent	82.0
Amount Collected, Rider Mine Close Other Assets Noncurrent	6.0
Guarantees of Equity Method Investees [Member]
Commitments, Guarantees and Contingencies (Textuals)
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 Under Uncommitted Facilities
Maximum Future Payments for Letters of Credit Issued Under the Uncommitted Facility	$ 2.2
Indiana Michigan Power Co [Member]
Commitments, Guarantees and Contingencies (Textuals)
Utility Plant Generation Capacity | MW	2,278
Ohio Power Co [Member] | Letters of Credit [Member]
Maximum Future Payments for Letters of Credit Under Uncommitted Facilities
Maximum Future Payments for Letters of Credit Issued Under the Uncommitted Facility	$ 1.2
Southwestern Electric Power Co [Member] | Guarantees of Third Party Obligations [Member]
Commitments, Guarantees and Contingencies (Textuals)
Guarantees of Mine Reclamation, Amount	140.0
Mine Reclamation and Closing Liability, Noncurrent	107.0
Total Amount Collected through a Rider for Final Mine Closure and Reclamation Costs	76.0
Amount Collected through a Rider for Final Mine Closure - ARO Noncurrent	82.0
Amount Collected, Rider Mine Close Other Assets Noncurrent	6.0
June 2022 [Member] | Letters of Credit [Member]
Commitments, Guarantees and Contingencies (Textuals)
Revolving Credit Facilities	4,000.0
July 2019 [Member] | Letters of Credit [Member]
Commitments, Guarantees and Contingencies (Textuals)
Letters of Credit Outstanding, Amount	$ 46.0
Subsequent Event [Member] | Letters of Credit [Member]
Commitments, Guarantees and Contingencies (Textuals)
Uncommitted Facility		$ 50.0