Condensed Consolidated Statements of Changes in Equity - USD ($) $ in Millions	Total	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] 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] 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] 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 at Dec. 31, 2014	$ 16,824.5	$ 3,366.9	$ 1,954.0	$ 1,980.2	$ 1,028.2	$ 2,097.2	$ 3,313.3	$ 260.4	$ 56.6	$ 321.2	$ 157.2	$ 135.7	$ 6,203.4	$ 1,809.6	$ 980.9	$ 838.8	$ 364.0	$ 674.6	$ 7,406.6	$ 1,291.9	$ 930.8	$ 814.6	$ 502.0	$ 1,294.0	$ (103.1)	$ 5.0	$ (14.3)	$ 5.6	$ 5.0	$ (7.5)	$ 4.3	$ 0.4
Beginning Balance, Shares at Dec. 31, 2014							509,700,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Common Stock, Value	67.9						$ 9.1						58.8
Issuance of Common Stock, Shares							1,400,000
Common Stock Dividends	(783.4)																		(780.3)
Common Stock Dividends		(181.3)	(90.0)	(156.3)		(90.0)														(181.3)	(90.0)	(156.3)		(90.0)
Common Stock Dividends						(3.1)																									(3.1)	(3.1)
Other Changes in Equity	24.6												19.6																		5.0
Net Income (Loss)	1,577.5					185.3													1,577.5					185.3
Net Income Attributable to Noncontrolling Interests	4.1					3.0																									4.1	3.0
Net Income (Loss)	1,581.6	275.4	179.9	184.7	85.5	188.3														275.4	179.9	184.7	85.5
Other Comprehensive Income (Loss)	(10.8)	(1.5)	0.8	(1.0)	(0.5)	0.8																			(10.8)	(1.5)	0.8	(1.0)	(0.5)	0.8
Contribution of Mutual Energy SWEPCo, LLC from Parent						2.0												2.0
Pension and OPEB Adjustment Related to Mitchell Plant	5.1																								5.1
Ending Balance at Sep. 30, 2015	17,709.5	3,459.5	2,044.7	2,007.6	1,113.2	2,195.2	$ 3,322.4	260.4	56.6	321.2	157.2	135.7	6,281.8	1,809.6	980.9	838.8	364.0	676.6	8,203.8	1,386.0	1,020.7	843.0	587.5	1,389.3	(108.8)	3.5	(13.5)	4.6	4.5	(6.7)	10.3	0.3
Ending Balance, Shares at Sep. 30, 2015							511,100,000
Beginning Balance at Dec. 31, 2015	$ 17,904.9	3,475.0	2,036.4	1,986.6	$ 1,119.9	2,169.7	$ 3,324.0	260.4	56.6	321.2	157.2	135.7	6,296.5	1,828.7	980.9	838.8	364.0	676.6	8,398.3	1,388.7	1,015.6	822.3	594.5	1,366.3	(127.1)	(2.8)	(16.7)	4.3	4.2	(9.4)	13.2	0.5
Beginning Balance, Shares at Dec. 31, 2015	511,389,173				10,482,000		511,400,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Common Stock, Value	$ 34.2						$ 4.3						29.9
Issuance of Common Stock, Shares							600,000
Common Stock Dividends	(829.8)																		(826.4)
Common Stock Dividends		(225.0)	(93.8)	(150.0)		(90.0)														(225.0)	(93.8)	(150.0)		(90.0)
Common Stock Dividends						(3.5)																									(3.4)	(3.5)
Other Changes in Equity	9.6												3.6																		6.0
Net Income (Loss)	237.5					149.9													237.5					149.9
Net Income Attributable to Noncontrolling Interests	5.3					3.3																									5.3	3.3
Net Income (Loss)	242.8	303.8	201.4	244.7	$ 97.4	153.2														303.8	201.4	244.7	97.4
Other Comprehensive Income (Loss)	(18.7)	(1.6)	1.0	(1.0)	(0.6)	0.8																			(18.7)	(1.6)	1.0	(1.0)	(0.6)	0.8
Contribution of Mutual Energy SWEPCo, LLC from Parent						0.0
Ending Balance at Sep. 30, 2016	$ 17,343.0	$ 3,552.2	$ 2,145.0	$ 2,080.3	$ 1,216.7	$ 2,230.2	$ 3,328.3	$ 260.4	$ 56.6	$ 321.2	$ 157.2	$ 135.7	$ 6,330.0	$ 1,828.7	$ 980.9	$ 838.8	$ 364.0	$ 676.6	$ 7,809.4	$ 1,467.5	$ 1,123.2	$ 917.0	$ 691.9	$ 1,426.2	$ (145.8)	$ (4.4)	$ (15.7)	$ 3.3	$ 3.6	$ (8.6)	$ 21.1	$ 0.3
Ending Balance, Shares at Sep. 30, 2016	512,046,044				10,482,000		512,000,000