Condensed Consolidated Statements of Changes in Equity - USD ($) $ in Millions	Total	AEP Transmission Co [Member]	AEP Texas Inc. [Member]	Appalachian Power Co [Member]	Indiana Michigan Power Co [Member]	Ohio Power Co [Member]	Public Service Co Of Oklahoma [Member]	Southwestern Electric Power Co [Member]	Common Stock [Member]	Common Stock [Member] Appalachian Power Co [Member]	Common Stock [Member] Indiana Michigan Power Co [Member]	Common Stock [Member] Ohio Power Co [Member]	Common Stock [Member] Public Service Co Of Oklahoma [Member]	Common Stock [Member] Southwestern Electric Power Co [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] AEP Transmission Co [Member]	Additional Paid-in Capital [Member] AEP Texas Inc. [Member]	Additional Paid-in Capital [Member] Appalachian Power Co [Member]	Additional Paid-in Capital [Member] Indiana Michigan Power Co [Member]	Additional Paid-in Capital [Member] Ohio Power Co [Member]	Additional Paid-in Capital [Member] Public Service Co Of Oklahoma [Member]	Additional Paid-in Capital [Member] Southwestern Electric Power Co [Member]	Retained Earnings [Member]	Retained Earnings [Member] AEP Transmission Co [Member]	Retained Earnings [Member] AEP Texas Inc. [Member]	Retained Earnings [Member] Appalachian Power Co [Member]	Retained Earnings [Member] Indiana Michigan Power Co [Member]	Retained Earnings [Member] Ohio Power Co [Member]	Retained Earnings [Member] Public Service Co Of Oklahoma [Member]	Retained Earnings [Member] Southwestern Electric Power Co [Member]	Accumulated Other Comprehensive Income [Member]		Accumulated Other Comprehensive Income [Member] AEP Texas Inc. [Member]		Accumulated Other Comprehensive Income [Member] Appalachian Power Co [Member]		Accumulated Other Comprehensive Income [Member] Indiana Michigan Power Co [Member]		Accumulated Other Comprehensive Income [Member] Ohio Power Co [Member]	Accumulated Other Comprehensive Income [Member] Public Service Co Of Oklahoma [Member]	Accumulated Other Comprehensive Income [Member] Southwestern Electric Power Co [Member]		Noncontrolling Interests [Member]	Noncontrolling Interests [Member] Southwestern Electric Power Co [Member]
Beginning Balance, Shares at Dec. 31, 2016									512,000,000
Beginning Balance at Dec. 31, 2016	$ 17,420.1		$ 1,657.1	$ 3,583.5	$ 2,151.8	$ 2,117.5	$ 1,214.1	$ 2,215.2	$ 3,328.3	$ 260.4	$ 56.6	$ 321.2	$ 157.2	$ 135.7	$ 6,332.6		$ 857.9	$ 1,828.7	$ 980.9	$ 838.8	$ 364.0	$ 676.6	$ 7,892.4		$ 814.1	$ 1,502.8	$ 1,130.5	$ 954.5	$ 689.5	$ 1,411.9	$ (156.3)		$ (14.9)		$ (8.4)		$ (16.2)		$ 3.0	$ 3.4	$ (9.4)		$ 23.1	$ 0.4
Members' Equity at Dec. 31, 2016		$ 1,957.6														$ 1,455.0								$ 502.6
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock Dividends	(291.4)																						(290.3)
Common Stock Dividends				(30.0)	(31.3)	(65.0)	(17.5)	(27.5)																		(30.0)	(31.3)	(65.0)	(17.5)	(27.5)
Common Stock Dividends								(1.1)																																			(1.1)	(1.1)
Other Changes in Equity	3.5														2.9																												0.6
Capital Contributions from Parent		125.5	200.0													125.5	200.0
Net Income (Loss)																							592.2							16.3
Net Income Attributable to Noncontrolling Interests	2.0							1.0																																			2.0	1.0
Net Income (Loss)	594.2	57.0	33.3	110.6	68.4	86.2	4.8	17.3																57.0	33.3	110.6	68.4	86.2	4.8
Other Comprehensive Income (Loss)	(14.7)		0.3	(0.5)	0.3	(0.2)	(0.2)	0.3																							(14.7)		0.3		(0.5)		0.3		(0.2)	(0.2)	0.3
Ending Balance at Mar. 31, 2017	$ 17,711.7		1,890.7	3,663.6	2,189.2	2,138.5	$ 1,201.2	2,204.2	$ 3,328.3	260.4	56.6	321.2	157.2	135.7	6,335.5		1,057.9	1,828.7	980.9	838.8	364.0	676.6	8,194.3		847.4	1,583.4	1,167.6	975.7	676.8	1,400.7	(171.0)		(14.6)		(8.9)		(15.9)		2.8	3.2	(9.1)		24.6	0.3
Members' Equity at Mar. 31, 2017		2,140.1														1,580.5								559.6
Ending Balance, Shares at Mar. 31, 2017									512,000,000
Beginning Balance, Shares at Dec. 31, 2017	512,210,644						10,482,000		512,200,000
Beginning Balance at Dec. 31, 2017	$ 18,313.6		2,169.9	3,804.5	2,217.6	2,310.3	$ 1,215.3	2,234.5	$ 3,329.4	260.4	56.6	321.2	157.2	135.7	6,398.7		1,057.9	1,828.7	980.9	838.8	364.0	676.6	8,626.7		1,124.6	1,714.1	1,192.2	1,148.4	691.5	1,426.6	(67.8)		(12.6)		1.3		(12.1)		1.9	2.6	(4.0)		26.6	(0.4)
Members' Equity at Dec. 31, 2017		2,605.3														1,816.6								788.7
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Common Stock, Value	32.2								$ 3.3						28.9
Issuance of Common Stock, Shares									500,000
Common Stock Dividends	(306.1)																						(305.5)
Common Stock Dividends				(40.0)	(33.5)	(112.5)	(12.5)	(20.0)																		(40.0)	(33.5)	(112.5)	(12.5)	(20.0)
Common Stock Dividends								(0.8)																																			(0.6)	(0.8)
Other Changes in Equity	16.9														16.9
Capital Contributions from Parent		65.0	100.0													65.0	100.0
ASU 2018-02 Adoption	(3.0)		(0.9)	0.4	2.4	0.4	0.5	(1.3)															14.0		1.8	0.1	(0.3)			(0.4)	(17.0)	[1]	(2.7)	[1]	0.3	[1]	(2.7)	[1]	0.4	0.5	(0.9)	[1]
ASU 2016-01 Adoption	0.0																						11.9								(11.9)	[1]
Net Income (Loss)																							454.4							11.8
Net Income Attributable to Noncontrolling Interests	2.3							1.6																																			2.3	1.6
Net Income (Loss)	456.7	85.9	46.8	125.5	64.2	79.6	(7.2)	13.4																85.9	46.8	125.5	64.2	79.6	(7.2)
Other Comprehensive Income (Loss)	1.3		0.3	(1.0)	0.4	(0.3)	(0.2)	0.1																							1.3		0.3		(1.0)		0.4		(0.3)	(0.2)	0.1
Ending Balance at Mar. 31, 2018	$ 18,511.6		$ 2,316.1	$ 3,889.4	$ 2,246.3	$ 2,277.5	$ 1,195.9	$ 2,225.9	$ 3,332.7	$ 260.4	$ 56.6	$ 321.2	$ 157.2	$ 135.7	$ 6,444.5		$ 1,157.9	$ 1,828.7	$ 980.9	$ 838.8	$ 364.0	$ 676.6	$ 8,801.5		$ 1,173.2	$ 1,799.7	$ 1,223.2	$ 1,115.5	$ 671.8	$ 1,418.0	$ (95.4)		$ (15.0)		$ 0.6		$ (14.4)		$ 2.0	$ 2.9	$ (4.8)		$ 28.3	$ 0.4
Members' Equity at Mar. 31, 2018		$ 2,756.2														$ 1,881.6								$ 874.6
Ending Balance, Shares at Mar. 31, 2018	512,716,170						10,482,000		512,700,000

[1] See Note 2 - New Accounting Pronouncements for additional information.