Business Segments (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Reportable Segment Information
Sales Revenue, Net		$ 3,933.3	$ 4,044.9
Revenues		3,933.3	4,044.9
NET INCOME (LOSS)		594.2	503.1
Balance Sheet Information
Total Property, Plant and Equipment		62,910.5		$ 62,036.6
Accumulated Depreciation and Amortization		16,674.2		16,397.3
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET		46,236.3		45,639.3
Assets Held for Sale		9.7		1,951.2
Total Assets		61,728.3		63,467.7
Long-term Debt Due Within One Year		2,514.2		2,878.0
Long-term Debt - Affiliated		0.0		0.0
Long-term Debt		16,722.2		17,378.4
Total Long-term Debt Outstanding		19,236.4		20,256.4
Liabilities Held for Sale		3.5		235.9
Vertically Integrated Utilities [Member]
Reportable Segment Information
Sales Revenue, Net		2,269.8	2,218.1
Revenues		2,290.4	2,245.6
NET INCOME (LOSS)		220.5	278.7
Balance Sheet Information
Total Property, Plant and Equipment		41,780.5		41,552.6
Accumulated Depreciation and Amortization		12,712.9		12,596.7
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET		29,067.6		28,955.9
Assets Held for Sale		0.0		0.0
Total Assets		37,562.2		37,428.3
Long-term Debt Due Within One Year		1,518.9		1,519.9
Long-term Debt - Affiliated		40.0		20.0
Long-term Debt		9,938.9		10,353.3
Total Long-term Debt Outstanding		11,497.8		11,893.2
Liabilities Held for Sale		0.0		0.0
Transmission And Distribution Companies [Member]
Reportable Segment Information
Sales Revenue, Net		1,066.4	1,077.3
Revenues		1,086.4	1,096.8
NET INCOME (LOSS)		119.1	107.5
Balance Sheet Information
Total Property, Plant and Equipment		14,990.4		14,762.2
Accumulated Depreciation and Amortization		3,697.8		3,655.0
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET		11,292.6		11,107.2
Assets Held for Sale		0.0		0.0
Total Assets		14,813.5		14,802.4
Long-term Debt Due Within One Year		316.4		309.4
Long-term Debt - Affiliated		0.0		0.0
Long-term Debt		4,554.4		4,672.2
Total Long-term Debt Outstanding		4,870.8		4,981.6
Liabilities Held for Sale		0.0		0.0
AEP Transmission Holdco [Member]
Reportable Segment Information
Sales Revenue, Net		27.7	29.3
Revenues		156.1	88.6
NET INCOME (LOSS)		72.8	44.7
Balance Sheet Information
Total Property, Plant and Equipment		5,665.4		5,354.0
Accumulated Depreciation and Amortization		120.7		101.4
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET		5,544.7		5,252.6
Assets Held for Sale		0.0		0.0
Total Assets		6,721.4		6,384.8
Long-term Debt Due Within One Year		130.7		0.0
Long-term Debt - Affiliated		0.0		0.0
Long-term Debt		1,931.4		2,055.7
Total Long-term Debt Outstanding		2,062.1		2,055.7
Liabilities Held for Sale		0.0		0.0
Generation And Marketing [Member]
Reportable Segment Information
Sales Revenue, Net		558.8	713.9
Revenues		591.4	748.0
NET INCOME (LOSS)		186.2	70.7
Balance Sheet Information
Total Property, Plant and Equipment		483.7		364.7
Accumulated Depreciation and Amortization		140.4		42.2
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET		343.3		322.5
Assets Held for Sale		9.7		1,951.2
Total Assets		2,194.9		3,386.1
Long-term Debt Due Within One Year		0.1		500.1
Long-term Debt - Affiliated		32.2		32.2
Long-term Debt		0.0		0.0
Total Long-term Debt Outstanding		32.3		532.3
Liabilities Held for Sale		3.5		235.9
All Other [Member]
Reportable Segment Information
Sales Revenue, Net	[1]	10.6	6.3
Revenues	[1]	26.5	24.4
NET INCOME (LOSS)	[1]	(4.4)	1.5
Balance Sheet Information
Total Property, Plant and Equipment	[1]	357.2		356.6
Accumulated Depreciation and Amortization	[1]	188.7		186.0
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET	[1]	168.5		170.6
Assets Held for Sale	[1]	0.0		0.0
Total Assets	[1]	21,233.1		20,354.8
Long-term Debt Due Within One Year	[1]	548.1		548.6
Long-term Debt - Affiliated	[1]	0.0		0.0
Long-term Debt	[1]	297.5		297.2
Total Long-term Debt Outstanding	[1]	845.6		845.8
Liabilities Held for Sale	[1]	0.0		0.0
Consolidation, Eliminations [Member]
Reportable Segment Information
Sales Revenue, Net		0.0	0.0
Revenues		(217.5)	(158.5)
NET INCOME (LOSS)		0.0	0.0
Balance Sheet Information
Total Property, Plant and Equipment	[2]	(366.7)		(353.5)
Accumulated Depreciation and Amortization	[2]	(186.3)		(184.0)
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET	[2]	(180.4)		(169.5)
Assets Held for Sale		0.0		0.0
Total Assets	[2],[3]	(20,796.8)		(18,888.7)
Long-term Debt Due Within One Year		0.0		0.0
Long-term Debt - Affiliated		(72.2)		(52.2)
Long-term Debt		0.0		0.0
Total Long-term Debt Outstanding		(72.2)		(52.2)
Liabilities Held for Sale		0.0		$ 0.0
Segment Reconciling Items [Member]
Reportable Segment Information
Sales Revenue, Net		0.0	0.0
Segment Reconciling Items [Member] | Vertically Integrated Utilities [Member]
Reportable Segment Information
Sales Revenue, Net		20.6	27.5
Segment Reconciling Items [Member] | Transmission And Distribution Companies [Member]
Reportable Segment Information
Sales Revenue, Net		20.0	19.5
Segment Reconciling Items [Member] | AEP Transmission Holdco [Member]
Reportable Segment Information
Sales Revenue, Net		128.4	59.3
Segment Reconciling Items [Member] | Generation And Marketing [Member]
Reportable Segment Information
Sales Revenue, Net		32.6	34.1
Segment Reconciling Items [Member] | All Other [Member]
Reportable Segment Information
Sales Revenue, Net	[1]	15.9	18.1
Segment Reconciling Items [Member] | Consolidation, Eliminations [Member]
Reportable Segment Information
Sales Revenue, Net		$ (217.5)	$ (158.5)

[1] Corporate and Other primarily includes the purchasing of receivables from certain AEP utility subsidiaries, Parent’s guarantee revenue received from affiliates, investment income, interest income and interest expense 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.