Significant Accounting Matters (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended
		Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019
Amounts Attributable to AEP Common Shareholders
Earnings Attributable to Common Shareholders		$ 575.0	$ 495.2
Weighted Average Number of Basic AEP Common Shares Outstanding		497,058,635	494,596,869
Total Basic Earnings Per Share Attributable to AEP Common Shareholders		$ 1.16	$ 1.00
Weighted Average Dilutive Effect of:
Weighted Average Number of Diluted AEP Common Shares Outstanding		498,164,219	496,608,918
Total Diluted Earnings Per Share Attributable to AEP Common Shareholders		$ 1.15	$ 1.00
Organization and Summary of Significant Accounting Policies (Textuals)
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		0	697,000
Cash, Cash Equivalents and Restricted Cash
Cash and Cash Equivalents		$ 273.2		$ 392.7
Restricted Cash		50.8		45.6
Total Cash, Cash Equivalents and Restricted Cash		324.0	$ 1,670.8	438.3	$ 432.6
Proceeds from Issuance of Debt	[1]	1,964.6
AEP Texas Inc. [Member]
Cash, Cash Equivalents and Restricted Cash
Cash and Cash Equivalents		0.1		0.1
Restricted Cash		39.3		28.7
Total Cash, Cash Equivalents and Restricted Cash		39.4	100.2	28.8	157.8
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		4.8		5.8
Restricted Cash		11.6		16.9
Total Cash, Cash Equivalents and Restricted Cash		16.4	18.5	22.7	26.8
Indiana Michigan Power Co [Member]
Cash, Cash Equivalents and Restricted Cash
Cash and Cash Equivalents		2.8	1.8	3.3	2.0
Ohio Power Co [Member]
Cash, Cash Equivalents and Restricted Cash
Cash and Cash Equivalents		6.1		7.4
Total Cash, Cash Equivalents and Restricted Cash		6.1	3.1	7.4	3.7
Public Service Co Of Oklahoma [Member]
Cash, Cash Equivalents and Restricted Cash
Cash and Cash Equivalents		2.4	1.1	2.6	1.5
Southwestern Electric Power Co [Member]
Amounts Attributable to AEP Common Shareholders
Earnings Attributable to Common Shareholders		62.4	15.1
Cash, Cash Equivalents and Restricted Cash
Cash and Cash Equivalents		$ 18.2	$ 1.4	$ 13.2	$ 1.6
Restricted Stock Units and Performance Share Units [Member]
Weighted Average Dilutive Effect of:
Weighted Average Dilutive Effect of Shares		1,100,000	2,000,000.0
Dilutive Securities, Effect on Basic Earnings Per Share		$ (0.01)	$ 0

[1] Amounts indicated on the statements of cash flows are net of issuance costs and premium or discount and will not tie to the issuance amounts.