Variable Interest Entities (Details) - USD ($) $ in Millions	3 Months Ended			12 Months Ended
	Mar. 31, 2016		Mar. 31, 2015	Dec. 31, 2015
Variable Interest Entities (Textuals) [Abstract]
Securitization Bonds	$ 1,863.1			$ 2,024.0
Securitized Transition Assets	$ 1,689.2			1,749.9
Percentage Ownership of "Allegheny Series" by a Nonaffiliated Company	100.00%
Protected Cell Of Energy Insurance Services, Inc. [Member]
Variable Interest Entities (Textuals) [Abstract]
Insurance Premium Expense to Protected Cell	$ 13.0		$ 14.0
Protected Cell Of Energy Insurance Services, Inc. [Member] | Current Assets [Member]
ASSETS
Assets	172.5			165.3
Protected Cell Of Energy Insurance Services, Inc. [Member] | Net Property Plant And Equipment [Member]
ASSETS
Assets	0.0			0.0
Protected Cell Of Energy Insurance Services, Inc. [Member] | Other Non Current Assets [Member]
ASSETS
Assets	2.0			1.9
Protected Cell Of Energy Insurance Services, Inc. [Member] | Total Assets [Member]
ASSETS
Assets	174.5			167.2
Protected Cell Of Energy Insurance Services, Inc. [Member] | Current Liabilities [Member]
LIABILITIES AND EQUITY
Liabilities and Equity	48.8			41.8
Protected Cell Of Energy Insurance Services, Inc. [Member] | Noncurrent Liabilities [Member]
LIABILITIES AND EQUITY
Liabilities and Equity	81.8			83.9
Protected Cell Of Energy Insurance Services, Inc. [Member] | Equity [Member]
LIABILITIES AND EQUITY
Liabilities and Equity	43.9			41.5
Protected Cell Of Energy Insurance Services, Inc. [Member] | Total Liabilities And Equity [Member]
LIABILITIES AND EQUITY
Liabilities and Equity	174.5			167.2
Transource Energy [Member]
Variable Interest Entities (Textuals) [Abstract]
Proceeds from Partnership Contribution	8.0			47.0
Transource Energy [Member] | Current Assets [Member]
ASSETS
Assets	13.6			10.8
Transource Energy [Member] | Net Property Plant And Equipment [Member]
ASSETS
Assets	253.1			227.2
Transource Energy [Member] | Other Non Current Assets [Member]
ASSETS
Assets	6.3			5.5
Transource Energy [Member] | Total Assets [Member]
ASSETS
Assets	273.0			243.5
Transource Energy [Member] | Current Liabilities [Member]
LIABILITIES AND EQUITY
Liabilities and Equity	44.5			36.6
Transource Energy [Member] | Noncurrent Liabilities [Member]
LIABILITIES AND EQUITY
Liabilities and Equity	118.7			113.0
Transource Energy [Member] | Equity [Member]
LIABILITIES AND EQUITY
Liabilities and Equity	109.8			93.9
Transource Energy [Member] | Total Liabilities And Equity [Member]
LIABILITIES AND EQUITY
Liabilities and Equity	$ 273.0			243.5
AEP Credit, Inc. [Member]
Variable Interest Entities (Textuals) [Abstract]
Minimum Percentage of Equity AEP Provides	5.00%
Percentage of Short Term Borrowing Needs in Excess of Third Party Financings	20.00%
AEP Credit, Inc. [Member] | Current Assets [Member]
ASSETS
Assets	$ 850.4			925.7
AEP Credit, Inc. [Member] | Net Property Plant And Equipment [Member]
ASSETS
Assets	0.0			0.0
AEP Credit, Inc. [Member] | Other Non Current Assets [Member]
ASSETS
Assets	7.6			6.4
AEP Credit, Inc. [Member] | Total Assets [Member]
ASSETS
Assets	858.0			932.1
AEP Credit, Inc. [Member] | Current Liabilities [Member]
LIABILITIES AND EQUITY
Liabilities and Equity	781.9			855.1
AEP Credit, Inc. [Member] | Noncurrent Liabilities [Member]
LIABILITIES AND EQUITY
Liabilities and Equity	0.4			0.3
AEP Credit, Inc. [Member] | Equity [Member]
LIABILITIES AND EQUITY
Liabilities and Equity	75.7			76.7
AEP Credit, Inc. [Member] | Total Liabilities And Equity [Member]
LIABILITIES AND EQUITY
Liabilities and Equity	$ 858.0			932.1
PATH West Virginia Transmission Co, LLC [Member]
Variable Interest Entities (Textuals) [Abstract]
Percentage of Debt Capital Structure in PATH's Stipulation Agreement	50.00%
Percentage of Equity Capital Structure in PATH's Stipulation Agreement	50.00%
Percentage of Cost of Long Term Debt for PATH's Stipulation Agreement	4.70%
PATH West Virginia Transmission Co, LLC [Member] | Capital Contribution From Parent [Member]
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures [Abstract]
As Reported on the Consolidated Balance Sheet	$ 18.8			18.8
Maximum Exposure	18.8			18.8
PATH West Virginia Transmission Co, LLC [Member] | Retained Earnings [Member]
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures [Abstract]
As Reported on the Consolidated Balance Sheet	2.2			2.2
Maximum Exposure	2.2			2.2
PATH West Virginia Transmission Co, LLC [Member] | Total Investment [Member]
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures [Abstract]
As Reported on the Consolidated Balance Sheet	21.0			21.0
Maximum Exposure	21.0			21.0
AEP Texas Central Transition Funding Co [Member]
Variable Interest Entities (Textuals) [Abstract]
Securitization Bonds	1,400.0			1,500.0
Securitized Transition Assets	1,300.0			1,300.0
AEP Texas Central Transition Funding Co [Member] | Current Assets [Member]
ASSETS
Assets	139.4			234.1
AEP Texas Central Transition Funding Co [Member] | Net Property Plant And Equipment [Member]
ASSETS
Assets	0.0			0.0
AEP Texas Central Transition Funding Co [Member] | Other Non Current Assets [Member]
ASSETS
Assets	1,316.8	[1]		1,365.7	[2]
Variable Interest Entities (Textuals) [Abstract]
Intercompany Item Eliminated in Consolidation	66.6			68.2
AEP Texas Central Transition Funding Co [Member] | Total Assets [Member]
ASSETS
Assets	1,456.2			1,599.8
AEP Texas Central Transition Funding Co [Member] | Current Liabilities [Member]
LIABILITIES AND EQUITY
Liabilities and Equity	238.0			291.7
AEP Texas Central Transition Funding Co [Member] | Noncurrent Liabilities [Member]
LIABILITIES AND EQUITY
Liabilities and Equity	1,200.1			1,290.0
AEP Texas Central Transition Funding Co [Member] | Equity [Member]
LIABILITIES AND EQUITY
Liabilities and Equity	18.1			18.1
AEP Texas Central Transition Funding Co [Member] | Total Liabilities And Equity [Member]
LIABILITIES AND EQUITY
Liabilities and Equity	$ 1,456.2			1,599.8
Great Plains Energy Inc. [Member] | Transource Energy [Member]
Variable Interest Entities (Textuals) [Abstract]
Equity and Voting Ownership Percentage	13.50%
Cleco Power, LLC [Member]
Variable Interest Entities (Textuals) [Abstract]
Percentage of VIE Sales of Lignite Produced	50.00%
Appalachian Power Co [Member]
Variable Interest Entities (Textuals) [Abstract]
Securitized Transition Assets	$ 322.4			328.0
Appalachian Power Co [Member] | Billings from AEP Service Corporation [Member]
Variable Interest Entities (Textuals) [Abstract]
Billings from VIE	56.6		48.2
Appalachian Power Co [Member] | Carrying Amount in AEP Service Corporation's Accounts Payable [Member]
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures [Abstract]
As Reported on the Consolidated Balance Sheet	21.1			25.8
Maximum Exposure	21.1			25.8
Appalachian Power Co [Member] | Appalachian Consumer Rate Relief Funding [Member]
Variable Interest Entities (Textuals) [Abstract]
Securitization Bonds	330.0			342.0
Securitized Transition Assets	322.0			328.0
Appalachian Power Co [Member] | Appalachian Consumer Rate Relief Funding [Member] | Current Assets [Member]
ASSETS
Assets	10.8			18.5
Appalachian Power Co [Member] | Appalachian Consumer Rate Relief Funding [Member] | Net Property Plant And Equipment [Member]
ASSETS
Assets	0.0			0.0
Appalachian Power Co [Member] | Appalachian Consumer Rate Relief Funding [Member] | Other Non Current Assets [Member]
ASSETS
Assets	326.2	[3]		332.0	[4]
Variable Interest Entities (Textuals) [Abstract]
Intercompany Item Eliminated in Consolidation	3.9			4.0
Appalachian Power Co [Member] | Appalachian Consumer Rate Relief Funding [Member] | Total Assets [Member]
ASSETS
Assets	337.0			350.5
Appalachian Power Co [Member] | Appalachian Consumer Rate Relief Funding [Member] | Current Liabilities [Member]
LIABILITIES AND EQUITY
Liabilities and Equity	24.8			27.1
Appalachian Power Co [Member] | Appalachian Consumer Rate Relief Funding [Member] | Noncurrent Liabilities [Member]
LIABILITIES AND EQUITY
Liabilities and Equity	310.9			321.5
Appalachian Power Co [Member] | Appalachian Consumer Rate Relief Funding [Member] | Equity [Member]
LIABILITIES AND EQUITY
Liabilities and Equity	1.3			1.9
Appalachian Power Co [Member] | Appalachian Consumer Rate Relief Funding [Member] | Total Liabilities And Equity [Member]
LIABILITIES AND EQUITY
Liabilities and Equity	337.0			350.5
Indiana Michigan Power Co [Member] | DCC Fuel [Member]
Variable Interest Entities (Textuals) [Abstract]
Payments Made by I&M to DCC Fuel	29.0		23.0
Indiana Michigan Power Co [Member] | DCC Fuel [Member] | Current Assets [Member]
ASSETS
Assets	79.6			91.1
Indiana Michigan Power Co [Member] | DCC Fuel [Member] | Net Property Plant And Equipment [Member]
ASSETS
Assets	129.0			159.9
Indiana Michigan Power Co [Member] | DCC Fuel [Member] | Other Non Current Assets [Member]
ASSETS
Assets	67.7			84.6
Indiana Michigan Power Co [Member] | DCC Fuel [Member] | Total Assets [Member]
ASSETS
Assets	276.3			335.6
Indiana Michigan Power Co [Member] | DCC Fuel [Member] | Current Liabilities [Member]
LIABILITIES AND EQUITY
Liabilities and Equity	73.4			84.8
Indiana Michigan Power Co [Member] | DCC Fuel [Member] | Noncurrent Liabilities [Member]
LIABILITIES AND EQUITY
Liabilities and Equity	202.9			250.8
Indiana Michigan Power Co [Member] | DCC Fuel [Member] | Equity [Member]
LIABILITIES AND EQUITY
Liabilities and Equity	0.0			0.0
Indiana Michigan Power Co [Member] | DCC Fuel [Member] | Total Liabilities And Equity [Member]
LIABILITIES AND EQUITY
Liabilities and Equity	276.3			335.6
Indiana Michigan Power Co [Member] | Billings from AEP Service Corporation [Member]
Variable Interest Entities (Textuals) [Abstract]
Billings from VIE	35.0		33.5
Indiana Michigan Power Co [Member] | Billings from AEP Generating Company [Member]
Variable Interest Entities (Textuals) [Abstract]
Billings from VIE	45.0		55.0
Indiana Michigan Power Co [Member] | Carrying Amount in AEP Service Corporation's Accounts Payable [Member]
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures [Abstract]
As Reported on the Consolidated Balance Sheet	11.6			16.6
Maximum Exposure	11.6			16.6
Indiana Michigan Power Co [Member] | Carrying Amount in AEP Generating Company's Accounts Payable [Member]
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures [Abstract]
As Reported on the Consolidated Balance Sheet	13.0			17.0
Ohio Power Co [Member]
Variable Interest Entities (Textuals) [Abstract]
Securitized Transition Assets	79.9			85.9
Ohio Power Co [Member] | Billings from AEP Service Corporation [Member]
Variable Interest Entities (Textuals) [Abstract]
Billings from VIE	44.5		39.2
Ohio Power Co [Member] | Carrying Amount in AEP Service Corporation's Accounts Payable [Member]
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures [Abstract]
As Reported on the Consolidated Balance Sheet	14.9			23.3
Maximum Exposure	14.9			23.3
Ohio Power Co [Member] | Ohio Phase-In-Recovery Funding [Member]
Variable Interest Entities (Textuals) [Abstract]
Securitization Bonds	163.0			185.0
Securitized Transition Assets	80.0			86.0
Ohio Power Co [Member] | Ohio Phase-In-Recovery Funding [Member] | Current Assets [Member]
ASSETS
Assets	18.8			31.2
Ohio Power Co [Member] | Ohio Phase-In-Recovery Funding [Member] | Net Property Plant And Equipment [Member]
ASSETS
Assets	0.0			0.0
Ohio Power Co [Member] | Ohio Phase-In-Recovery Funding [Member] | Other Non Current Assets [Member]
ASSETS
Assets	150.6	[5]		162.0	[6]
Variable Interest Entities (Textuals) [Abstract]
Intercompany Item Eliminated in Consolidation	70.7			76.1
Ohio Power Co [Member] | Ohio Phase-In-Recovery Funding [Member] | Total Assets [Member]
ASSETS
Assets	169.4			193.2
Ohio Power Co [Member] | Ohio Phase-In-Recovery Funding [Member] | Current Liabilities [Member]
LIABILITIES AND EQUITY
Liabilities and Equity	46.2			47.3
Ohio Power Co [Member] | Ohio Phase-In-Recovery Funding [Member] | Noncurrent Liabilities [Member]
LIABILITIES AND EQUITY
Liabilities and Equity	121.9			144.6
Ohio Power Co [Member] | Ohio Phase-In-Recovery Funding [Member] | Equity [Member]
LIABILITIES AND EQUITY
Liabilities and Equity	1.3			1.3
Ohio Power Co [Member] | Ohio Phase-In-Recovery Funding [Member] | Total Liabilities And Equity [Member]
LIABILITIES AND EQUITY
Liabilities and Equity	169.4			193.2
Public Service Co Of Oklahoma [Member] | Billings from AEP Service Corporation [Member]
Variable Interest Entities (Textuals) [Abstract]
Billings from VIE	28.5		23.5
Public Service Co Of Oklahoma [Member] | Carrying Amount in AEP Service Corporation's Accounts Payable [Member]
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures [Abstract]
As Reported on the Consolidated Balance Sheet	9.1			12.6
Maximum Exposure	9.1			12.6
Southwestern Electric Power Co [Member] | Sabine Mining Co [Member]
Variable Interest Entities (Textuals) [Abstract]
Billings from VIE	41.0		42.0
Southwestern Electric Power Co [Member] | Sabine Mining Co [Member] | Current Assets [Member]
ASSETS
Assets	59.6			61.7
Southwestern Electric Power Co [Member] | Sabine Mining Co [Member] | Net Property Plant And Equipment [Member]
ASSETS
Assets	140.4			147.0
Southwestern Electric Power Co [Member] | Sabine Mining Co [Member] | Other Non Current Assets [Member]
ASSETS
Assets	62.8			61.8
Southwestern Electric Power Co [Member] | Sabine Mining Co [Member] | Total Assets [Member]
ASSETS
Assets	262.8			270.5
Southwestern Electric Power Co [Member] | Sabine Mining Co [Member] | Current Liabilities [Member]
LIABILITIES AND EQUITY
Liabilities and Equity	37.3			47.7
Southwestern Electric Power Co [Member] | Sabine Mining Co [Member] | Noncurrent Liabilities [Member]
LIABILITIES AND EQUITY
Liabilities and Equity	225.1			222.3
Southwestern Electric Power Co [Member] | Sabine Mining Co [Member] | Equity [Member]
LIABILITIES AND EQUITY
Liabilities and Equity	0.4			0.5
Southwestern Electric Power Co [Member] | Sabine Mining Co [Member] | Total Liabilities And Equity [Member]
LIABILITIES AND EQUITY
Liabilities and Equity	262.8			$ 270.5
Southwestern Electric Power Co [Member] | Dolet Hills Lignite Co, LLC [Member]
Variable Interest Entities (Textuals) [Abstract]
Billings from VIE	$ 15.0		15.0
Percentage of VIE Sales of Lignite Produced	50.00%
Percentage of DHLCs Debt Guaranteed by Each SWEPCo and CLECO	50.00%
Percentage of Management Fee Received by SWEPCo from DHLC				100.00%
Southwestern Electric Power Co [Member] | Dolet Hills Lignite Co, LLC [Member] | Capital Contribution From Parent [Member]
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures [Abstract]
As Reported on the Consolidated Balance Sheet	$ 7.6			$ 7.6
Maximum Exposure	7.6			7.6
Southwestern Electric Power Co [Member] | Dolet Hills Lignite Co, LLC [Member] | Retained Earnings [Member]
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures [Abstract]
As Reported on the Consolidated Balance Sheet	8.7			7.7
Maximum Exposure	8.7			7.7
Southwestern Electric Power Co [Member] | Dolet Hills Lignite Co, LLC [Member] | SWEPCo's Guarantee Of Debt [Member]
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures [Abstract]
As Reported on the Consolidated Balance Sheet	0.0			0.0
Maximum Exposure	87.4			82.9
Southwestern Electric Power Co [Member] | Dolet Hills Lignite Co, LLC [Member] | Total Investment [Member]
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures [Abstract]
As Reported on the Consolidated Balance Sheet	16.3			15.3
Maximum Exposure	103.7			98.2
Southwestern Electric Power Co [Member] | Billings from AEP Service Corporation [Member]
Variable Interest Entities (Textuals) [Abstract]
Billings from VIE	36.7		$ 31.5
Southwestern Electric Power Co [Member] | Carrying Amount in AEP Service Corporation's Accounts Payable [Member]
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures [Abstract]
As Reported on the Consolidated Balance Sheet	12.6			16.4
Maximum Exposure	$ 12.6			$ 16.4
AEP Generating Co [Member] | Rockport Generating Plant (Unit No. 1) [Member]
Variable Interest Entities (Textuals) [Abstract]
Jointly Owned Utility Plant, Proportionate Ownership Share	50.00%
AEP Generating Co [Member] | Rockport Generating Plant (Unit No. 2) [Member]
Variable Interest Entities (Textuals) [Abstract]
Percentage Interest in Rockport Plant Unit 2 Lease				50.00%
AEP Generating Co [Member] | Lawrenceburg Generating Station [Member]
Variable Interest Entities (Textuals) [Abstract]
Jointly Owned Utility Plant, Proportionate Ownership Share				100.00%
Transource Energy [Member]
Variable Interest Entities (Textuals) [Abstract]
Equity and Voting Ownership Percentage	86.50%

[1] Includes an intercompany item eliminated in consolidation of $66.6 million.

[2] Includes an intercompany item eliminated in consolidation of $68.2 million.

[3] Includes an intercompany item eliminated in consolidation of $3.9 million.

[4] Includes an intercompany item eliminated in consolidation of $4.0 million.

[5] Includes an intercompany item eliminated in consolidation of $70.7 million.

[6] Includes an intercompany item eliminated in consolidation of $76.1 million.