Business Segments (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Reportable Segment Information
Revenues		$ 3,892.9	$ 3,826.7	$ 7,937.8	$ 8,407.1
Income (Loss) from Continuing Operations		506.4	431.4	1,009.5	1,051.6
Income (Loss) from Discontinued Operations, Net of Tax		(2.5)	(0.1)	(2.5)	10.4
Net Income (Loss)		503.9	431.3	1,007.0	1,062.0
Balance Sheet Information
Total Property, Plant and Equipment		67,082.4		67,082.4		$ 65,481.4
Accumulated Depreciation and Amortization		19,646.2		19,646.2		19,348.2
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET		47,436.2		47,436.2		46,133.2
Total Assets		63,317.1		63,317.1		61,683.1
Long-term Debt Due Within One Year		2,006.3		2,006.3		1,831.8
Long-term Debt - Affiliated		0.0		0.0		0.0
Long-term Debt		17,537.4		17,537.4		17,740.9
Total Long-term Debt Outstanding		19,543.7		19,543.7		19,572.7
Vertically Integrated Utilities [Member]
Reportable Segment Information
Sales Revenue, Net		2,108.2	2,158.6	4,326.3	4,646.0
Revenues		2,125.9	2,182.5	4,371.5	4,687.6
Income (Loss) from Continuing Operations		210.5	207.9	489.2	508.2
Income (Loss) from Discontinued Operations, Net of Tax		0.0	0.0	0.0	0.0
Net Income (Loss)		210.5	207.9	489.2	508.2
Balance Sheet Information
Total Property, Plant and Equipment		40,710.7		40,710.7		40,130.3
Accumulated Depreciation and Amortization		12,433.1		12,433.1		12,335.0
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET		28,277.6		28,277.6		27,795.3
Total Assets		36,639.2		36,639.2		35,792.3
Long-term Debt Due Within One Year		1,232.0		1,232.0		935.4
Long-term Debt - Affiliated		20.0		20.0		20.0
Long-term Debt		10,079.9		10,079.9		9,833.0
Total Long-term Debt Outstanding		11,331.9		11,331.9		10,788.4
Transmission And Distribution Utilities [Member]
Reportable Segment Information
Sales Revenue, Net		1,076.2	1,008.0	2,153.5	2,214.3
Revenues		1,096.1	1,060.7	2,192.9	2,330.8
Income (Loss) from Continuing Operations		124.6	77.6	232.6	174.8
Income (Loss) from Discontinued Operations, Net of Tax		0.0	0.0	0.0	0.0
Net Income (Loss)		124.6	77.6	232.6	174.8
Balance Sheet Information
Total Property, Plant and Equipment		14,217.3		14,217.3		13,840.5
Accumulated Depreciation and Amortization		3,611.3		3,611.3		3,529.2
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET		10,606.0		10,606.0		10,311.3
Total Assets		14,167.3		14,167.3		14,640.2
Long-term Debt Due Within One Year		261.6		261.6		824.7
Long-term Debt - Affiliated		0.0		0.0		0.0
Long-term Debt		4,814.7		4,814.7		4,776.8
Total Long-term Debt Outstanding		5,076.3		5,076.3		5,601.5
AEP Transmission Holdco [Member]
Reportable Segment Information
Sales Revenue, Net		41.3	25.5	70.6	47.2
Revenues		161.7	99.5	250.3	157.4
Income (Loss) from Continuing Operations		95.3	65.5	140.0	101.8
Income (Loss) from Discontinued Operations, Net of Tax		0.0	0.0	0.0	0.0
Net Income (Loss)		95.3	65.5	140.0	101.8
Balance Sheet Information
Total Property, Plant and Equipment		4,529.6		4,529.6		3,977.6
Accumulated Depreciation and Amortization		75.6		75.6		52.3
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET		4,454.0		4,454.0		3,925.3
Total Assets		5,432.2		5,432.2		5,012.1
Long-term Debt Due Within One Year		0.0		0.0		0.0
Long-term Debt - Affiliated		0.0		0.0		0.0
Long-term Debt		1,660.2		1,660.2		1,648.4
Total Long-term Debt Outstanding		1,660.2		1,660.2		1,648.4
Generation And Marketing [Member]
Reportable Segment Information
Sales Revenue, Net		655.3	627.6	1,369.2	1,486.8
Revenues		683.8	800.2	1,431.8	1,970.7
Income (Loss) from Continuing Operations		49.7	81.3	120.4	268.7
Income (Loss) from Discontinued Operations, Net of Tax		0.0	0.0	0.0	0.0
Net Income (Loss)		49.7	81.3	120.4	268.7
Balance Sheet Information
Total Property, Plant and Equipment		7,561.1		7,561.1		7,461.3
Accumulated Depreciation and Amortization		3,459.1		3,459.1		3,367.0
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET		4,102.0		4,102.0		4,094.3
Total Assets		5,437.3		5,437.3		5,414.5
Long-term Debt Due Within One Year		511.7		511.7		71.6
Long-term Debt - Affiliated		32.2		32.2		32.2
Long-term Debt		135.3		135.3		639.5
Total Long-term Debt Outstanding		679.2		679.2		743.3
All Other [Member]
Reportable Segment Information
Sales Revenue, Net	[1]	11.9	7.0	18.2	12.8
Revenues	[1]	29.9	23.9	54.3	50.1
Income (Loss) from Continuing Operations	[1]	26.3	(0.9)	27.3	(1.9)
Income (Loss) from Discontinued Operations, Net of Tax	[1]	(2.5)	(0.1)	(2.5)	10.4
Net Income (Loss)	[1]	23.8	(1.0)	24.8	8.5
Balance Sheet Information
Total Property, Plant and Equipment	[1]	361.0		361.0		350.9
Accumulated Depreciation and Amortization	[1]	186.9		186.9		176.9
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET	[1]	174.1		174.1		174.0
Total Assets	[1]	22,302.0		22,302.0		21,907.4
Long-term Debt Due Within One Year	[1]	1.0		1.0		0.1
Long-term Debt - Affiliated	[1]	0.0		0.0		0.0
Long-term Debt	[1]	847.3		847.3		843.2
Total Long-term Debt Outstanding	[1]	848.3		848.3		843.3
Consolidation, Eliminations [Member]
Reportable Segment Information
Sales Revenue, Net		0.0	0.0	0.0	0.0
Revenues		(204.5)	(340.1)	(363.0)	(789.5)
Income (Loss) from Continuing Operations		0.0	0.0	0.0	0.0
Income (Loss) from Discontinued Operations, Net of Tax		0.0	0.0	0.0	0.0
Net Income (Loss)		0.0	0.0	0.0	0.0
Balance Sheet Information
Total Property, Plant and Equipment	[2]	(297.3)		(297.3)		(279.2)
Accumulated Depreciation and Amortization	[2]	(119.8)		(119.8)		(112.2)
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET	[2]	(177.5)		(177.5)		(167.0)
Total Assets	[2],[3]	(20,660.9)		(20,660.9)		(21,083.4)
Long-term Debt Due Within One Year		0.0		0.0		0.0
Long-term Debt - Affiliated		(52.2)		(52.2)		(52.2)
Long-term Debt		0.0		0.0		0.0
Total Long-term Debt Outstanding		(52.2)		(52.2)		$ (52.2)
Segment Reconciling Items [Member] | Vertically Integrated Utilities [Member]
Reportable Segment Information
Sales Revenue, Net		17.7	23.9	45.2	41.6
Segment Reconciling Items [Member] | Transmission And Distribution Utilities [Member]
Reportable Segment Information
Sales Revenue, Net		19.9	52.7	39.4	116.5
Segment Reconciling Items [Member] | AEP Transmission Holdco [Member]
Reportable Segment Information
Sales Revenue, Net		120.4	74.0	179.7	110.2
Segment Reconciling Items [Member] | Generation And Marketing [Member]
Reportable Segment Information
Sales Revenue, Net		28.5	172.6	62.6	483.9
Segment Reconciling Items [Member] | All Other [Member]
Reportable Segment Information
Sales Revenue, Net	[1]	18.0	16.9	36.1	37.3
Segment Reconciling Items [Member] | Consolidation, Eliminations [Member]
Reportable Segment Information
Sales Revenue, Net		$ (204.5)	$ (340.1)	$ (363.0)	$ (789.5)

[1] Corporate and Other primarily includes the purchasing of receivables from certain AEP utility subsidiaries. This segment also includes Parent’s guarantee revenue received from affiliates, investment income, interest income, interest expense and discontinued operations of AEPRO and other nonallocated costs.

[2] Includes eliminations due to an intercompany capital lease.

[3] Reconciling Adjustments for Total Assets primarily include the elimination of intercompany advances to affiliates and intercompany accounts receivable along with the elimination of AEP’s investments in subsidiary companies.