Fair Value Long-term Debt, Other Temporary Investments, Nuclear Trusts (Details) - USD ($)		3 Months Ended		12 Months Ended
		Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Book Values and Fair Values of Long - term Debt
Total Long-term Debt Outstanding		$ 39,835,900,000		$ 40,143,200,000
Long Term Debt, Fair Value		36,392,200,000		37,325,700,000
Other Temporary Investments
Cost		245,900,000		243,500,000
Gross Unrealized Gains		29,000,000.0		25,900,000
Gross Unrealized Losses		(6,800,000)		(6,200,000)
Other Short-term Investments		268,100,000		263,200,000
Debt and Equity Securities Within Other Temporary Investments
Proceeds from Investment Sales		3,000,000.0	$ 0
Purchases of Investments		1,500,000	1,000,000.0
Gross Realized Gains on Investment Sales		300,000	0
Gross Realized Losses on Investment Sales		200,000	0
Nuclear Trust Fund Investments
Fair Value		4,112,600,000		3,860,200,000
Securities Activity Within Decommissioning and SNF Trusts
Payments to Acquire Investments		590,000,000.0	537,300,000
Contractual Maturities, Fair Value of Debt Securities
Fair Value		4,112,600,000		3,860,200,000
Spent Nuclear Fuel and Decommissioning Trusts [Member]
Securities Activity Within Decommissioning and SNF Trusts
Payments to Acquire Investments		588,500,000	536,300,000
Realized Investment Gains (Losses)		5,400,000	48,500,000
Gain (Loss) on Investments		1,200,000	8,600,000
Contractual Maturities, Fair Value of Debt Securities
Within 1 year		338,800,000
After 1 year through 5 years		598,000,000.0
After 5 years through 10 years		186,600,000
After 10 years		268,600,000
Fair Value Measurements (Textuals)
Adjusted Cost of Debt Securities		1,400,000,000		1,400,000,000
Adjusted Cost of Domestic Equity Securities		577,000,000		568,000,000
Other than Temporary Impairment Losses, Investments		(30,800,000)		(41,800,000)
Proceeds from Sale of Other Investments		569,500,000	517,600,000
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax		(11,300,000)		(10,000,000.0)
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax		2,138,100,000		1,902,900,000
Cash [Member]
Other Temporary Investments
Cost	[1]	51,100,000		48,900,000
Gross Unrealized Gains	[1]	0		0
Gross Unrealized Losses	[1]	0		0
Other Short-term Investments	[1]	51,100,000		48,900,000
Fixed Income Funds [Member]
Nuclear Trust Fund Investments
Fair Value		1,392,000,000		1,406,800,000
Contractual Maturities, Fair Value of Debt Securities
Fair Value		1,392,000,000		1,406,800,000
Fixed Income Funds [Member] | Spent Nuclear Fuel and Decommissioning Trusts [Member]
Fair Value Measurements (Textuals)
Other than Temporary Impairment Losses, Investments		(30,800,000)		(41,800,000)
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax		(10,200,000)		(9,100,000)
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax		19,000,000.0		33,400,000
Mutual Funds Fixed Income [Member]
Other Temporary Investments
Cost	[2]	164,700,000		165,900,000
Gross Unrealized Gains	[2]	0		0
Gross Unrealized Losses	[2]	(6,800,000)		(6,200,000)
Other Short-term Investments	[2]	157,900,000		159,700,000
Domestic [Member]
Nuclear Trust Fund Investments
Fair Value	[3]	2,695,400,000		2,436,600,000
Contractual Maturities, Fair Value of Debt Securities
Fair Value	[3]	2,695,400,000		2,436,600,000
Domestic [Member] | Spent Nuclear Fuel and Decommissioning Trusts [Member]
Fair Value Measurements (Textuals)
Other than Temporary Impairment Losses, Investments		0		0
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax		(1,100,000)		(900,000)
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax		2,119,100,000		1,869,500,000
Mutual Funds Equity [Member]
Other Temporary Investments
Cost		14,700,000		14,800,000
Gross Unrealized Gains		29,000,000.0		25,900,000
Gross Unrealized Losses		0		0
Other Short-term Investments	[3]	43,700,000		40,700,000
Cash and Cash Equivalents [Member]
Nuclear Trust Fund Investments
Fair Value	[4]	25,200,000		16,800,000
Contractual Maturities, Fair Value of Debt Securities
Fair Value	[4]	25,200,000		16,800,000
Cash and Cash Equivalents [Member] | Spent Nuclear Fuel and Decommissioning Trusts [Member]
Fair Value Measurements (Textuals)
Other than Temporary Impairment Losses, Investments		0		0
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax		0		0
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax		0		0
US Government Agencies Debt Securities [Member]
Nuclear Trust Fund Investments
Fair Value		1,267,000,000		1,273,000,000
Contractual Maturities, Fair Value of Debt Securities
Fair Value		1,267,000,000		1,273,000,000
US Government Agencies Debt Securities [Member] | Spent Nuclear Fuel and Decommissioning Trusts [Member]
Fair Value Measurements (Textuals)
Other than Temporary Impairment Losses, Investments		(25,700,000)		(33,200,000)
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax		(4,200,000)		(3,900,000)
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax		16,500,000		28,600,000
Corporate Debt [Member]
Nuclear Trust Fund Investments
Fair Value		123,300,000		132,100,000
Contractual Maturities, Fair Value of Debt Securities
Fair Value		123,300,000		132,100,000
Corporate Debt [Member] | Spent Nuclear Fuel and Decommissioning Trusts [Member]
Fair Value Measurements (Textuals)
Other than Temporary Impairment Losses, Investments		(5,100,000)		(8,600,000)
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax		(6,000,000.0)		(5,200,000)
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax		2,500,000		4,800,000
State and Local Jurisdiction [Member]
Nuclear Trust Fund Investments
Fair Value		1,700,000		1,700,000
Contractual Maturities, Fair Value of Debt Securities
Fair Value		1,700,000		1,700,000
State and Local Jurisdiction [Member] | Spent Nuclear Fuel and Decommissioning Trusts [Member]
Fair Value Measurements (Textuals)
Other than Temporary Impairment Losses, Investments		0		0
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax		0		0
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax		0		0
Other Cash Deposits [Member]
Other Temporary Investments
Cost		15,400,000		13,900,000
Gross Unrealized Gains		0		0
Gross Unrealized Losses		0		0
Other Short-term Investments		15,400,000		13,900,000
AEP Texas Inc. [Member]
Book Values and Fair Values of Long - term Debt
Total Long-term Debt Outstanding		5,878,700,000		5,889,800,000
Long Term Debt, Fair Value		5,289,700,000		5,400,700,000
AEP Transmission Co [Member]
Book Values and Fair Values of Long - term Debt
Total Long-term Debt Outstanding		5,860,700,000		5,414,400,000
Long Term Debt, Fair Value		5,066,300,000		4,796,900,000
Appalachian Power Co [Member]
Book Values and Fair Values of Long - term Debt
Total Long-term Debt Outstanding		5,670,900,000		5,588,300,000
Long Term Debt, Fair Value		5,370,800,000		5,390,100,000
Indiana Michigan Power Co [Member]
Book Values and Fair Values of Long - term Debt
Total Long-term Debt Outstanding		3,478,500,000		3,499,400,000
Long Term Debt, Fair Value		3,182,300,000		3,291,600,000
Nuclear Trust Fund Investments
Fair Value		4,112,600,000		3,860,200,000
Securities Activity Within Decommissioning and SNF Trusts
Payments to Acquire Investments		588,500,000	536,300,000
Contractual Maturities, Fair Value of Debt Securities
Fair Value		4,112,600,000		3,860,200,000
Indiana Michigan Power Co [Member] | Spent Nuclear Fuel and Decommissioning Trusts [Member]
Securities Activity Within Decommissioning and SNF Trusts
Payments to Acquire Investments		588,500,000	536,300,000
Realized Investment Gains (Losses)		5,400,000	48,500,000
Gain (Loss) on Investments		1,200,000	8,600,000
Contractual Maturities, Fair Value of Debt Securities
Within 1 year		338,800,000
After 1 year through 5 years		598,000,000.0
After 5 years through 10 years		186,600,000
After 10 years		268,600,000
Fair Value Measurements (Textuals)
Adjusted Cost of Debt Securities		1,400,000,000		1,400,000,000
Adjusted Cost of Domestic Equity Securities		577,000,000		568,000,000
Other than Temporary Impairment Losses, Investments		(30,800,000)		(41,800,000)
Proceeds from Sale of Other Investments		569,500,000	$ 517,600,000
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax		(11,300,000)		(10,000,000.0)
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax		2,138,100,000		1,902,900,000
Indiana Michigan Power Co [Member] | Fixed Income Funds [Member]
Nuclear Trust Fund Investments
Fair Value		1,392,000,000		1,406,800,000
Contractual Maturities, Fair Value of Debt Securities
Fair Value		1,392,000,000		1,406,800,000
Indiana Michigan Power Co [Member] | Fixed Income Funds [Member] | Spent Nuclear Fuel and Decommissioning Trusts [Member]
Fair Value Measurements (Textuals)
Other than Temporary Impairment Losses, Investments		(30,800,000)		(41,800,000)
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax		(10,200,000)		(9,100,000)
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax		19,000,000.0		33,400,000
Indiana Michigan Power Co [Member] | Domestic [Member]
Nuclear Trust Fund Investments
Fair Value	[3]	2,695,400,000		2,436,600,000
Contractual Maturities, Fair Value of Debt Securities
Fair Value	[3]	2,695,400,000		2,436,600,000
Indiana Michigan Power Co [Member] | Domestic [Member] | Spent Nuclear Fuel and Decommissioning Trusts [Member]
Fair Value Measurements (Textuals)
Other than Temporary Impairment Losses, Investments		0		0
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax		(1,100,000)		(900,000)
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax		2,119,100,000		1,869,500,000
Indiana Michigan Power Co [Member] | Cash and Cash Equivalents [Member]
Nuclear Trust Fund Investments
Fair Value	[4]	25,200,000		16,800,000
Contractual Maturities, Fair Value of Debt Securities
Fair Value	[4]	25,200,000		16,800,000
Indiana Michigan Power Co [Member] | Cash and Cash Equivalents [Member] | Spent Nuclear Fuel and Decommissioning Trusts [Member]
Fair Value Measurements (Textuals)
Other than Temporary Impairment Losses, Investments		0		0
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax		0		0
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax		0		0
Indiana Michigan Power Co [Member] | US Government Agencies Debt Securities [Member]
Nuclear Trust Fund Investments
Fair Value		1,267,000,000		1,273,000,000
Contractual Maturities, Fair Value of Debt Securities
Fair Value		1,267,000,000		1,273,000,000
Indiana Michigan Power Co [Member] | US Government Agencies Debt Securities [Member] | Spent Nuclear Fuel and Decommissioning Trusts [Member]
Fair Value Measurements (Textuals)
Other than Temporary Impairment Losses, Investments		(25,700,000)		(33,200,000)
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax		(4,200,000)		(3,900,000)
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax		16,500,000		28,600,000
Indiana Michigan Power Co [Member] | Corporate Debt [Member]
Nuclear Trust Fund Investments
Fair Value		123,300,000		132,100,000
Contractual Maturities, Fair Value of Debt Securities
Fair Value		123,300,000		132,100,000
Indiana Michigan Power Co [Member] | Corporate Debt [Member] | Spent Nuclear Fuel and Decommissioning Trusts [Member]
Fair Value Measurements (Textuals)
Other than Temporary Impairment Losses, Investments		(5,100,000)		(8,600,000)
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax		(6,000,000.0)		(5,200,000)
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax		2,500,000		4,800,000
Indiana Michigan Power Co [Member] | State and Local Jurisdiction [Member]
Nuclear Trust Fund Investments
Fair Value		1,700,000		1,700,000
Contractual Maturities, Fair Value of Debt Securities
Fair Value		1,700,000		1,700,000
Indiana Michigan Power Co [Member] | State and Local Jurisdiction [Member] | Spent Nuclear Fuel and Decommissioning Trusts [Member]
Fair Value Measurements (Textuals)
Other than Temporary Impairment Losses, Investments		0		0
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax		0		0
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax		0		0
Ohio Power Co [Member]
Book Values and Fair Values of Long - term Debt
Total Long-term Debt Outstanding		3,367,400,000		3,366,800,000
Long Term Debt, Fair Value		2,912,100,000		2,992,100,000
Public Service Co Of Oklahoma [Member]
Book Values and Fair Values of Long - term Debt
Total Long-term Debt Outstanding		2,384,900,000		2,384,600,000
Long Term Debt, Fair Value		2,130,200,000		2,154,300,000
Southwestern Electric Power Co [Member]
Book Values and Fair Values of Long - term Debt
Total Long-term Debt Outstanding		3,647,600,000		3,646,900,000
Long Term Debt, Fair Value		$ 3,170,600,000		$ 3,209,700,000

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

[2] Primarily short and intermediate maturities which may be sold and do not contain maturity dates.

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

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