Significant Accounting Matters (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Amounts Attributable to AEP Common Shareholders
Net Income Attributable to Noncontrolling Interests	$ 1.7	$ 1.2	$ 4.0	$ 3.2
Net Income (Loss) Available to Common Stockholders, Basic	$ 528.4	$ 375.0	$ 982.8	$ 967.2
Weighted Average Number of Basic AEP Common Shares Outstanding	492,688,342	491,790,752	492,479,035	491,751,614
Basic Earnings Per Share Attributable to AEP Common Shareholders from Continuing Operations	$ 1.07	$ 0.76	$ 2.00	$ 1.97
Weighted Average Dilutive Effect of:
Weighted Average Number of Diluted AEP Common Shares Outstanding	493,505,085	492,642,100	493,317,355	492,337,255
Diluted Earnings Per Share Attributable to AEP Common Shareholders from Continuing Operations	$ 1.07	$ 0.76	$ 1.99	$ 1.96
Organization and Summary of Significant Accounting Policies (Textuals) [Abstract]
Antidilutive Shares Outstanding			0	0
Income (Loss) from Equity Method Investments Adjustment			$ 6.0
Cash, Cash Equivalents and Restricted Cash [Abstract]
Cash and Cash Equivalents	$ 211.2		211.2		$ 214.6
Restricted Cash	176.1		176.1		198.0
Total Cash, Cash Equivalents and Restricted Cash	387.3		387.3		412.6
Total Cash, Cash Equivalents and Restricted Cash	387.3	$ 344.3	387.3	$ 344.3	412.6	$ 403.5
AEP Texas Inc. [Member]
Cash, Cash Equivalents and Restricted Cash [Abstract]
Cash and Cash Equivalents	0.1		0.1		2.0
Restricted Cash	131.9		131.9		155.2
Total Cash, Cash Equivalents and Restricted Cash	132.0		132.0		157.2
Total Cash, Cash Equivalents and Restricted Cash	132.0	129.2	132.0	129.2	157.2	146.9
AEP Transmission Co [Member]
Cash, Cash Equivalents and Restricted Cash [Abstract]
Cash and Cash Equivalents	0.0	0.0	0.0	0.0	0.0	0.0
Appalachian Power Co [Member]
Cash, Cash Equivalents and Restricted Cash [Abstract]
Cash and Cash Equivalents	2.8		2.8		2.9
Restricted Cash	17.7		17.7		16.3
Total Cash, Cash Equivalents and Restricted Cash	20.5	18.0	20.5	18.0	19.2	18.5
Indiana Michigan Power Co [Member]
Cash, Cash Equivalents and Restricted Cash [Abstract]
Cash and Cash Equivalents	1.4	1.1	1.4	1.1	1.3	1.2
Ohio Power Co [Member]
Cash, Cash Equivalents and Restricted Cash [Abstract]
Cash and Cash Equivalents	3.3		3.3		3.1
Restricted Cash	26.5		26.5		26.6
Total Cash, Cash Equivalents and Restricted Cash	29.8	29.5	29.8	29.5	29.7	30.3
Public Service Co Of Oklahoma [Member]
Cash, Cash Equivalents and Restricted Cash [Abstract]
Cash and Cash Equivalents	1.6	1.4	1.6	1.4	1.6	1.5
Southwestern Electric Power Co [Member]
Amounts Attributable to AEP Common Shareholders
Net Income Attributable to Noncontrolling Interests	1.1	0.6	2.7	1.6
Net Income (Loss) Available to Common Stockholders, Basic	37.6	24.5	49.4	40.8
Organization and Summary of Significant Accounting Policies (Textuals) [Abstract]
Income (Loss) from Equity Method Investments Adjustment			6.3
Cash, Cash Equivalents and Restricted Cash [Abstract]
Cash and Cash Equivalents	$ 2.1	$ 1.7	$ 2.1	$ 1.7	$ 1.6	$ 10.3
Restricted Stock Units and Performance Share Units [Member]
Weighted Average Dilutive Effect of:
Weighted Average Dilutive Effect of Shares	800,000	800,000	800,000	500,000
Dilutive Securities, Effect on Basic Earnings Per Share	$ (0.00)	$ (0.00)	$ (0.01)	$ (0.01)