Significant Accounting Matters (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Amounts Attributable to AEP Common Shareholders
Earnings Attributable to Common Shareholders	$ 495.2	$ 572.8
Weighted Average Number of Basic AEP Common Shares Outstanding	494,596,869	493,309,076
Total Basic Earnings Per Share Attributable to AEP Common Shareholders	$ 1.00	$ 1.16
Weighted Average Dilutive Effect of:
Weighted Average Number of Diluted AEP Common Shares Outstanding	496,608,918	494,484,144
Total Diluted Earnings Per Share Attributable to AEP Common Shareholders	$ 1.00	$ 1.16
Organization and Summary of Significant Accounting Policies (Textuals)
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	697,000	0
Cash, Cash Equivalents and Restricted Cash
Cash and Cash Equivalents	$ 1,554.6		$ 246.8
Restricted Cash	116.2		185.8
Total Cash, Cash Equivalents and Restricted Cash	1,670.8	$ 363.1	432.6	$ 444.1
AEP Texas Inc. [Member]
Cash, Cash Equivalents and Restricted Cash
Cash and Cash Equivalents	0.1		3.1
Restricted Cash	100.1		154.7
Total Cash, Cash Equivalents and Restricted Cash	100.2	100.7	157.8	159.8
AEP Transmission Co [Member]
Cash, Cash Equivalents and Restricted Cash
Cash and Cash Equivalents	0.0	0.0	0.0	0.0
Appalachian Power Co [Member]
Cash, Cash Equivalents and Restricted Cash
Cash and Cash Equivalents	2.8		3.3
Restricted Cash	15.7		23.5
Total Cash, Cash Equivalents and Restricted Cash	18.5	21.2	26.8	29.8
Indiana Michigan Power Co [Member]
Cash, Cash Equivalents and Restricted Cash
Cash and Cash Equivalents	1.8	1.7	2.0	2.4
Ohio Power Co [Member]
Cash, Cash Equivalents and Restricted Cash
Cash and Cash Equivalents	3.1		3.7
Total Cash, Cash Equivalents and Restricted Cash	3.1	19.8	3.7	32.5
Public Service Co Of Oklahoma [Member]
Cash, Cash Equivalents and Restricted Cash
Cash and Cash Equivalents	1.1	1.5	1.5	2.0
Southwestern Electric Power Co [Member]
Amounts Attributable to AEP Common Shareholders
Earnings Attributable to Common Shareholders	15.1	27.8
Cash, Cash Equivalents and Restricted Cash
Cash and Cash Equivalents	$ 1.4	$ 22.1	$ 1.6	$ 24.5
Restricted Stock Units and Performance Share Units [Member]
Weighted Average Dilutive Effect of:
Weighted Average Dilutive Effect of Shares	2,000,000.0	1,200,000
Dilutive Securities, Effect on Basic Earnings Per Share	$ 0	$ 0