Fair Value Long-term Debt, Other Temporary Investments, Nuclear Trusts (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Book Values and Fair Values of Long - term Debt
Total Long-term Debt Outstanding		$ 19,578,000		$ 19,578,000		$ 18,684,000
Long Term Debt, Fair Value		21,205,000		21,205,000		21,075,000
Other Temporary Investments
Cost		343,000		343,000		374,000
Gross Unrealized Gains		13,000		13,000		12,000
Gross Unrealized Losses		0		0		0
Estimated Fair Value		356,000		356,000		386,000
Debt and Equity Securities Within Other Temporary Investments [Abstract]
Proceeds from Investment Sales		0	$ 0	0	$ 0
Purchases of Investments		0	0	0	1,000
Gross Realized Gains on Investment Sales		0	0	0	0
Gross Realized Losses on Investment Sales		0	0	0	0
Nuclear Trust Fund Investments [Abstract]
Estimated Fair Value		2,106,000		2,106,000		2,096,000
Gross Unrealized Gains		636,000		636,000		649,000
Other-Than-Temporary Impairments		(82,000)		(82,000)		(85,000)
Securities Activity Within Decommissioning and SNF Trusts [Abstract]
Proceeds from Investment Sales		288,000	335,000	516,000	483,000
Purchases of Investments		295,000	345,000	541,000	509,000
Gross Realized Gains on Investment Sales		8,000	9,000	19,000	17,000
Gross Realized Losses on Investment Sales		6,000	8,000	10,000	9,000
Contractual Maturities, Fair Value of Debt Securities
Contractual Maturities, Fair Value of Debt Securities		2,106,000		2,106,000		2,096,000
Fair Value Measurements (Textuals) [Abstract]
Adjusted Cost of Debt Securities		877,000		877,000		903,000
Adjusted Cost of Domestic Equity Securities		540,000		540,000		524,000
Appalachian Power Co [Member]
Book Values and Fair Values of Long - term Debt
Total Long-term Debt Outstanding		3,966,647		3,966,647		3,980,274
Long Term Debt, Fair Value		4,396,429		4,396,429		4,711,210
Indiana Michigan Power Co [Member]
Book Values and Fair Values of Long - term Debt
Total Long-term Debt Outstanding		2,088,913		2,088,913		2,027,397
Long Term Debt, Fair Value		2,264,196		2,264,196		2,255,124
Nuclear Trust Fund Investments [Abstract]
Estimated Fair Value		2,106,090		2,106,090		2,095,732
Gross Unrealized Gains		635,770		635,770		649,132
Other-Than-Temporary Impairments		(82,358)		(82,358)		(85,495)
Securities Activity Within Decommissioning and SNF Trusts [Abstract]
Proceeds from Investment Sales		287,620	334,834	515,784	482,534
Purchases of Investments		294,870	344,324	540,711	508,835
Gross Realized Gains on Investment Sales		7,657	9,077	18,810	17,218
Gross Realized Losses on Investment Sales		5,885	$ 7,834	9,656	$ 8,708
Contractual Maturities, Fair Value of Debt Securities
Contractual Maturities, Fair Value of Debt Securities		2,106,090		2,106,090		2,095,732
Fair Value Measurements (Textuals) [Abstract]
Adjusted Cost of Debt Securities		877,000		877,000		903,000
Adjusted Cost of Domestic Equity Securities		540,000		540,000		524,000
Ohio Power Co [Member]
Book Values and Fair Values of Long - term Debt
Total Long-term Debt Outstanding		2,189,159		2,189,159		2,297,123
Long Term Debt, Fair Value		2,515,960		2,515,960		2,709,452
Public Service Co Of Oklahoma [Member]
Book Values and Fair Values of Long - term Debt
Total Long-term Debt Outstanding		1,290,995		1,290,995		1,041,036
Long Term Debt, Fair Value		1,417,359		1,417,359		1,216,205
Southwestern Electric Power Co [Member]
Book Values and Fair Values of Long - term Debt
Total Long-term Debt Outstanding		2,435,478		2,435,478		2,140,437
Long Term Debt, Fair Value		2,600,476		2,600,476		2,402,639
Cash [Member]
Other Temporary Investments
Cost	[1]	249,000		249,000		280,000
Gross Unrealized Gains	[1]	0		0		0
Gross Unrealized Losses	[1]	0		0		0
Estimated Fair Value	[1],[2]	249,000		249,000		280,000
Nuclear Trust Fund Investments [Abstract]
Estimated Fair Value	[3]	53,000		53,000		20,000
Contractual Maturities, Fair Value of Debt Securities
Contractual Maturities, Fair Value of Debt Securities	[3]	53,000		53,000		20,000
Cash [Member] | Indiana Michigan Power Co [Member]
Nuclear Trust Fund Investments [Abstract]
Estimated Fair Value	[4]	52,861		52,861		19,966
Contractual Maturities, Fair Value of Debt Securities
Contractual Maturities, Fair Value of Debt Securities	[4]	52,861		52,861		19,966
Fixed Income Funds [Member]
Nuclear Trust Fund Investments [Abstract]
Estimated Fair Value		918,000		918,000		953,000
Gross Unrealized Gains		41,000		41,000		50,000
Other-Than-Temporary Impairments		(4,000)		(4,000)		(6,000)
Contractual Maturities, Fair Value of Debt Securities
Contractual Maturities, Fair Value of Debt Securities		918,000		918,000		953,000
Fixed Income Funds [Member] | Indiana Michigan Power Co [Member]
Nuclear Trust Fund Investments [Abstract]
Estimated Fair Value		918,046		918,046		953,387
Gross Unrealized Gains		41,161		41,161		50,344
Other-Than-Temporary Impairments		(4,102)		(4,102)		(6,353)
Contractual Maturities, Fair Value of Debt Securities
Contractual Maturities, Fair Value of Debt Securities		918,046		918,046		953,387
Mutual Funds Fixed Income [Member]
Other Temporary Investments
Cost		81,000		81,000		81,000
Gross Unrealized Gains		0		0		0
Gross Unrealized Losses		0		0		0
Estimated Fair Value		81,000		81,000		81,000
Domestic [Member]
Nuclear Trust Fund Investments [Abstract]
Estimated Fair Value	[5]	1,135,000		1,135,000		1,123,000
Gross Unrealized Gains		595,000		595,000		599,000
Other-Than-Temporary Impairments		(78,000)		(78,000)		(79,000)
Contractual Maturities, Fair Value of Debt Securities
Contractual Maturities, Fair Value of Debt Securities	[5]	1,135,000		1,135,000		1,123,000
Domestic [Member] | Indiana Michigan Power Co [Member]
Nuclear Trust Fund Investments [Abstract]
Estimated Fair Value	[6]	1,135,183		1,135,183		1,122,379
Gross Unrealized Gains		594,609		594,609		598,788
Other-Than-Temporary Impairments		(78,256)		(78,256)		(79,142)
Contractual Maturities, Fair Value of Debt Securities
Contractual Maturities, Fair Value of Debt Securities	[6]	1,135,183		1,135,183		1,122,379
Mutual Funds Equity [Member]
Other Temporary Investments
Cost		13,000		13,000		13,000
Gross Unrealized Gains		13,000		13,000		12,000
Gross Unrealized Losses		0		0		0
Estimated Fair Value	[5]	26,000		26,000		25,000
Cash and Cash Equivalents [Member]
Nuclear Trust Fund Investments [Abstract]
Estimated Fair Value		53,000		53,000		20,000
Gross Unrealized Gains		0		0		0
Other-Than-Temporary Impairments		0		0		0
Contractual Maturities, Fair Value of Debt Securities
Contractual Maturities, Fair Value of Debt Securities		53,000		53,000		20,000
Cash and Cash Equivalents [Member] | Indiana Michigan Power Co [Member]
Nuclear Trust Fund Investments [Abstract]
Estimated Fair Value		52,861		52,861		19,966
Gross Unrealized Gains		0		0		0
Other-Than-Temporary Impairments		0		0		0
Contractual Maturities, Fair Value of Debt Securities
Contractual Maturities, Fair Value of Debt Securities		52,861		52,861		19,966
US Government Agencies Debt Securities [Member]
Nuclear Trust Fund Investments [Abstract]
Estimated Fair Value		786,000		786,000		697,000
Gross Unrealized Gains		37,000		37,000		45,000
Other-Than-Temporary Impairments		(3,000)		(3,000)		(5,000)
Contractual Maturities, Fair Value of Debt Securities
Contractual Maturities, Fair Value of Debt Securities		786,000		786,000		697,000
US Government Agencies Debt Securities [Member] | Indiana Michigan Power Co [Member]
Nuclear Trust Fund Investments [Abstract]
Estimated Fair Value		786,222		786,222		697,042
Gross Unrealized Gains		37,318		37,318		44,615
Other-Than-Temporary Impairments		(2,613)		(2,613)		(5,016)
Contractual Maturities, Fair Value of Debt Securities
Contractual Maturities, Fair Value of Debt Securities		786,222		786,222		697,042
Corporate Debt [Member]
Nuclear Trust Fund Investments [Abstract]
Estimated Fair Value		62,000		62,000		48,000
Gross Unrealized Gains		3,000		3,000		4,000
Other-Than-Temporary Impairments		(1,000)		(1,000)		(1,000)
Contractual Maturities, Fair Value of Debt Securities
Contractual Maturities, Fair Value of Debt Securities		62,000		62,000		48,000
Corporate Debt [Member] | Indiana Michigan Power Co [Member]
Nuclear Trust Fund Investments [Abstract]
Estimated Fair Value		61,654		61,654		47,792
Gross Unrealized Gains		2,851		2,851		4,523
Other-Than-Temporary Impairments		(1,115)		(1,115)		(1,018)
Contractual Maturities, Fair Value of Debt Securities
Contractual Maturities, Fair Value of Debt Securities		61,654		61,654		47,792
State and Local Jurisdiction [Member]
Nuclear Trust Fund Investments [Abstract]
Estimated Fair Value		70,000		70,000		208,000
Gross Unrealized Gains		1,000		1,000		1,000
Other-Than-Temporary Impairments		0		0		0
Contractual Maturities, Fair Value of Debt Securities
Contractual Maturities, Fair Value of Debt Securities		70,000		70,000		208,000
State and Local Jurisdiction [Member] | Indiana Michigan Power Co [Member]
Nuclear Trust Fund Investments [Abstract]
Estimated Fair Value		70,170		70,170		208,553
Gross Unrealized Gains		992		992		1,206
Other-Than-Temporary Impairments		(374)		(374)		(319)
Contractual Maturities, Fair Value of Debt Securities
Contractual Maturities, Fair Value of Debt Securities		70,170		70,170		$ 208,553
Within One Year [Member]
Nuclear Trust Fund Investments [Abstract]
Estimated Fair Value		141,000		141,000
Contractual Maturities, Fair Value of Debt Securities
Contractual Maturities, Fair Value of Debt Securities		141,000		141,000
Within One Year [Member] | Indiana Michigan Power Co [Member]
Nuclear Trust Fund Investments [Abstract]
Estimated Fair Value		140,990		140,990
Contractual Maturities, Fair Value of Debt Securities
Contractual Maturities, Fair Value of Debt Securities		140,990		140,990
One Year To Five Year [Member]
Nuclear Trust Fund Investments [Abstract]
Estimated Fair Value		376,000		376,000
Contractual Maturities, Fair Value of Debt Securities
Contractual Maturities, Fair Value of Debt Securities		376,000		376,000
One Year To Five Year [Member] | Indiana Michigan Power Co [Member]
Nuclear Trust Fund Investments [Abstract]
Estimated Fair Value		375,637		375,637
Contractual Maturities, Fair Value of Debt Securities
Contractual Maturities, Fair Value of Debt Securities		375,637		375,637
Five Year To Ten Year [Member]
Nuclear Trust Fund Investments [Abstract]
Estimated Fair Value		186,000		186,000
Contractual Maturities, Fair Value of Debt Securities
Contractual Maturities, Fair Value of Debt Securities		186,000		186,000
Five Year To Ten Year [Member] | Indiana Michigan Power Co [Member]
Nuclear Trust Fund Investments [Abstract]
Estimated Fair Value		186,505		186,505
Contractual Maturities, Fair Value of Debt Securities
Contractual Maturities, Fair Value of Debt Securities		186,505		186,505
After Ten Year [Member]
Nuclear Trust Fund Investments [Abstract]
Estimated Fair Value		215,000		215,000
Contractual Maturities, Fair Value of Debt Securities
Contractual Maturities, Fair Value of Debt Securities		215,000		215,000
After Ten Year [Member] | Indiana Michigan Power Co [Member]
Nuclear Trust Fund Investments [Abstract]
Estimated Fair Value		214,914		214,914
Contractual Maturities, Fair Value of Debt Securities
Contractual Maturities, Fair Value of Debt Securities		$ 214,914		$ 214,914

[1] Primarily represents amounts held for the repayment of debt.

[2] Amounts in ''Other'' column primarily represent cash deposits in bank accounts with financial institutions or with third parties. Level 1 and Level 2 amounts primarily represent investments in money market funds.

[3] Amounts in ''Other'' column primarily represent accrued interest receivables from financial institutions. Level 1 amounts primarily represent investments in money market funds.

[4] Amounts in “Other” column primarily represent accrued interest receivables from financial institutions. Level 1 amounts primarily represent investments in money market funds.

[5] Amounts represent publicly traded equity securities and equity-based mutual funds.

[6] Amounts represent publicly traded equity securities and equity-based mutual funds.