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Fair Value Long-term Debt, Other Temporary Investments, Nuclear Trusts (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020
Book Values and Fair Values of Long - term Debt |  |  |  |
Total Long-term Debt Outstanding |  | $ 36,801.0 | $ 34,557.6 |
Long-term Debt, Fair Value | [1] | 32,915.9 | 38,789.3 |
Other Temporary Investments |  |  |  |
Cost |  | 223.6 | 232.0 |
Gross Unrealized Gains |  | 19.4 | 36.4 |
Gross Unrealized Losses |  | 8.3 | 0.0 |
Fair Value |  | 234.7 | 268.4 |
Debt and Equity Securities Within Other Temporary Investments |  |  |  |
Proceeds From Investment Sales |  | 30.2 | 15.0 | $ 50.9
Purchases of Investments |  | 18.8 | 26.9 | 41.6
Gross Realized Gains on Investment Sales |  | 6.1 | 3.6 | 3.8
Gross Realized Losses on Investment Sales |  | 1.3 | 0.0 | 0.2
Nuclear Trust Fund Investments |  |  |  |
Fair Value |  | 3,341.2 | 3,867.0 |
Contractual Maturities, Fair Value of Debt Securities |  |  |  |
Fair Value |  | 3,341.2 | 3,867.0 |
Spent Nuclear Fuel and Decommissioning Trusts [Member] |  |  |  |
Nuclear Trust Fund Investments |  |  |  |
Gross Unrealized Gains |  | 1,467.3 | 1,974.7 |
Other-Than-Temporary Impairments |  | (28.5) | (10.1) |
Securities Activity Within the Decommissioning and SNF Trusts |  |  |  |
Proceeds from Investment Sales |  | 2,713.6 | 1,886.4 | 1,593.4
Purchases of Investments |  | 2,765.4 | 1,928.2 | 1,637.2
Gross Realized Gains on Investment Sales |  | 52.4 | 103.2 | 26.4
Gross Realized Losses on Investment Sales |  | 42.6 | 16.5 | 26.1
Contractual Maturities, Fair Value of Debt Securities |  |  |  |
Within 1 year |  | 365.2 |  |
After 1 year through 5 years |  | 425.4 |  |
After 5 years through 10 years |  | 203.0 |  |
After 10 years |  | 195.1 |  |
Fair Value Measurements (Textuals) |  |  |  |
Adjusted Cost of Debt Securities |  | 1,200.0 | 1,200.0 |
Adjusted Cost of Domestic Equity Securities |  | 654.0 | 641.0 |
AEP Texas Inc. [Member] |  |  |  |
Book Values and Fair Values of Long - term Debt |  |  |  |
Total Long-term Debt Outstanding |  | 5,657.8 | 5,180.8 |
Long-term Debt, Fair Value |  | 5,045.8 | 5,663.8 |
AEP Transmission Co [Member] |  |  |  |
Book Values and Fair Values of Long - term Debt |  |  |  |
Total Long-term Debt Outstanding |  | 4,782.8 | 4,343.9 |
Long-term Debt, Fair Value |  | 3,940.5 | 4,968.2 |
Appalachian Power Co [Member] |  |  |  |
Book Values and Fair Values of Long - term Debt |  |  |  |
Total Long-term Debt Outstanding |  | 5,410.5 | 4,938.9 |
Long-term Debt, Fair Value |  | 5,079.2 | 6,037.1 |
Indiana Michigan Power Co [Member] |  |  |  |
Book Values and Fair Values of Long - term Debt |  |  |  |
Total Long-term Debt Outstanding |  | 3,260.8 | 3,195.0 |
Long-term Debt, Fair Value |  | 2,929.0 | 3,748.0 |
Nuclear Trust Fund Investments |  |  |  |
Fair Value |  | 3,341.2 | 3,867.0 |
Contractual Maturities, Fair Value of Debt Securities |  |  |  |
Fair Value |  | 3,341.2 | 3,867.0 |
Indiana Michigan Power Co [Member] | Spent Nuclear Fuel and Decommissioning Trusts [Member] |  |  |  |
Nuclear Trust Fund Investments |  |  |  |
Gross Unrealized Gains |  | 1,467.3 | 1,974.7 |
Other-Than-Temporary Impairments |  | (28.5) | (10.1) |
Securities Activity Within the Decommissioning and SNF Trusts |  |  |  |
Proceeds from Investment Sales |  | 2,713.6 | 1,886.4 | 1,593.4
Purchases of Investments |  | 2,765.4 | 1,928.2 | 1,637.2
Gross Realized Gains on Investment Sales |  | 52.4 | 103.2 | 26.4
Gross Realized Losses on Investment Sales |  | 42.6 | 16.5 | $ 26.1
Contractual Maturities, Fair Value of Debt Securities |  |  |  |
Within 1 year |  | 365.2 |  |
After 1 year through 5 years |  | 425.4 |  |
After 5 years through 10 years |  | 203.0 |  |
After 10 years |  | 195.1 |  |
Fair Value Measurements (Textuals) |  |  |  |
Adjusted Cost of Debt Securities |  | 1,200.0 | 1,200.0 |
Adjusted Cost of Domestic Equity Securities |  | 654.0 | 641.0 |
Ohio Power Co [Member] |  |  |  |
Book Values and Fair Values of Long - term Debt |  |  |  |
Total Long-term Debt Outstanding |  | 2,970.3 | 2,968.5 |
Long-term Debt, Fair Value |  | 2,516.6 | 3,437.5 |
Public Service Co Of Oklahoma [Member] |  |  |  |
Book Values and Fair Values of Long - term Debt |  |  |  |
Total Long-term Debt Outstanding |  | 1,912.8 | 1,913.5 |
Long-term Debt, Fair Value |  | 1,635.8 | 2,163.7 |
Southwestern Electric Power Co [Member] |  |  |  |
Book Values and Fair Values of Long - term Debt |  |  |  |
Total Long-term Debt Outstanding |  | 3,391.6 | 3,395.2 |
Long-term Debt, Fair Value |  | 2,870.9 | 3,792.9 |
Cash [Member] |  |  |  |
Other Temporary Investments |  |  |  |
Cost | [2] | 47.1 | 48.0 |
Gross Unrealized Gains | [2] | 0.0 | 0.0 |
Gross Unrealized Losses | [2] | 0.0 | 0.0 |
Fair Value | [2] | 47.1 | 48.0 |
Other Cash Deposits [Member] |  |  |  |
Other Temporary Investments |  |  |  |
Cost |  | 9.0 | 10.0 |
Gross Unrealized Gains |  | 0.0 | 0.0 |
Gross Unrealized Losses |  | 0.0 | 0.0 |
Fair Value | [3] | 9.0 | 10.0 |
Mutual Funds Fixed Income [Member] |  |  |  |
Other Temporary Investments |  |  |  |
Cost | [4] | 152.4 | 154.3 |
Gross Unrealized Gains | [4] | 0.0 | 0.5 |
Gross Unrealized Losses | [4] | (8.3) | 0.0 |
Fair Value | [4] | 144.1 | 154.8 |
Mutual Funds Equity [Member] |  |  |  |
Other Temporary Investments |  |  |  |
Cost |  | 15.1 | 19.7 |
Gross Unrealized Gains |  | 19.4 | 35.9 |
Gross Unrealized Losses |  | 0.0 | 0.0 |
Fair Value |  | 34.5 | 55.6 |
Fixed Income Funds [Member] |  |  |  |
Nuclear Trust Fund Investments |  |  |  |
Fair Value |  | 1,188.7 | 1,240.4 |
Contractual Maturities, Fair Value of Debt Securities |  |  |  |
Fair Value |  | 1,188.7 | 1,240.4 |
Fixed Income Funds [Member] | Spent Nuclear Fuel and Decommissioning Trusts [Member] |  |  |  |
Nuclear Trust Fund Investments |  |  |  |
Gross Unrealized Gains |  | (10.0) | 73.4 |
Other-Than-Temporary Impairments |  | (28.5) | (10.1) |
Fixed Income Funds [Member] | Indiana Michigan Power Co [Member] |  |  |  |
Nuclear Trust Fund Investments |  |  |  |
Fair Value |  | 1,188.7 | 1,240.4 |
Contractual Maturities, Fair Value of Debt Securities |  |  |  |
Fair Value |  | 1,188.7 | 1,240.4 |
Fixed Income Funds [Member] | Indiana Michigan Power Co [Member] | Spent Nuclear Fuel and Decommissioning Trusts [Member] |  |  |  |
Nuclear Trust Fund Investments |  |  |  |
Gross Unrealized Gains |  | (10.0) | 73.4 |
Other-Than-Temporary Impairments |  | (28.5) | (10.1) |
Domestic [Member] |  |  |  |
Nuclear Trust Fund Investments |  |  |  |
Fair Value | [5] | 2,131.3 | 2,541.9 |
Contractual Maturities, Fair Value of Debt Securities |  |  |  |
Fair Value | [5] | 2,131.3 | 2,541.9 |
Domestic [Member] | Spent Nuclear Fuel and Decommissioning Trusts [Member] |  |  |  |
Unrealized Gain on Securities |  | 1,500.0 | 1,900.0 |
Unrealized Loss on Securities |  | 6.0 | 4.0 |
Nuclear Trust Fund Investments |  |  |  |
Gross Unrealized Gains | [6] | 1,477.3 | 1,901.3 |
Other-Than-Temporary Impairments |  | 0.0 | 0.0 |
Domestic [Member] | Indiana Michigan Power Co [Member] |  |  |  |
Nuclear Trust Fund Investments |  |  |  |
Fair Value | [5] | 2,131.3 | 2,541.9 |
Contractual Maturities, Fair Value of Debt Securities |  |  |  |
Fair Value | [5] | 2,131.3 | 2,541.9 |
Domestic [Member] | Indiana Michigan Power Co [Member] | Spent Nuclear Fuel and Decommissioning Trusts [Member] |  |  |  |
Unrealized Gain on Securities |  | 1,500.0 | 1,900.0 |
Unrealized Loss on Securities |  | 6.0 | 4.0 |
Nuclear Trust Fund Investments |  |  |  |
Gross Unrealized Gains | [6] | 1,477.3 | 1,901.3 |
Other-Than-Temporary Impairments |  | 0.0 | 0.0 |
Cash and Cash Equivalents [Member] |  |  |  |
Nuclear Trust Fund Investments |  |  |  |
Fair Value | [7] | 21.2 | 84.7 |
Contractual Maturities, Fair Value of Debt Securities |  |  |  |
Fair Value | [7] | 21.2 | 84.7 |
Cash and Cash Equivalents [Member] | Spent Nuclear Fuel and Decommissioning Trusts [Member] |  |  |  |
Nuclear Trust Fund Investments |  |  |  |
Gross Unrealized Gains |  | 0.0 | 0.0 |
Other-Than-Temporary Impairments |  | 0.0 | 0.0 |
Cash and Cash Equivalents [Member] | Indiana Michigan Power Co [Member] |  |  |  |
Nuclear Trust Fund Investments |  |  |  |
Fair Value | [7] | 21.2 | 84.7 |
Contractual Maturities, Fair Value of Debt Securities |  |  |  |
Fair Value | [7] | 21.2 | 84.7 |
Cash and Cash Equivalents [Member] | Indiana Michigan Power Co [Member] | Spent Nuclear Fuel and Decommissioning Trusts [Member] |  |  |  |
Nuclear Trust Fund Investments |  |  |  |
Gross Unrealized Gains |  | 0.0 | 0.0 |
Other-Than-Temporary Impairments |  | 0.0 | 0.0 |
US Government Agencies Debt Securities [Member] |  |  |  |
Nuclear Trust Fund Investments |  |  |  |
Fair Value |  | 1,123.8 | 1,156.4 |
Contractual Maturities, Fair Value of Debt Securities |  |  |  |
Fair Value |  | 1,123.8 | 1,156.4 |
US Government Agencies Debt Securities [Member] | Spent Nuclear Fuel and Decommissioning Trusts [Member] |  |  |  |
Nuclear Trust Fund Investments |  |  |  |
Gross Unrealized Gains |  | (3.1) | 66.3 |
Other-Than-Temporary Impairments |  | (18.8) | (7.9) |
US Government Agencies Debt Securities [Member] | Indiana Michigan Power Co [Member] |  |  |  |
Nuclear Trust Fund Investments |  |  |  |
Fair Value |  | 1,123.8 | 1,156.4 |
Contractual Maturities, Fair Value of Debt Securities |  |  |  |
Fair Value |  | 1,123.8 | 1,156.4 |
US Government Agencies Debt Securities [Member] | Indiana Michigan Power Co [Member] | Spent Nuclear Fuel and Decommissioning Trusts [Member] |  |  |  |
Nuclear Trust Fund Investments |  |  |  |
Gross Unrealized Gains |  | (3.1) | 66.3 |
Other-Than-Temporary Impairments |  | (18.8) | (7.9) |
Corporate Debt [Member] |  |  |  |
Nuclear Trust Fund Investments |  |  |  |
Fair Value |  | 61.6 | 76.7 |
Contractual Maturities, Fair Value of Debt Securities |  |  |  |
Fair Value |  | 61.6 | 76.7 |
Corporate Debt [Member] | Spent Nuclear Fuel and Decommissioning Trusts [Member] |  |  |  |
Nuclear Trust Fund Investments |  |  |  |
Gross Unrealized Gains |  | (7.0) | 6.7 |
Other-Than-Temporary Impairments |  | (9.6) | (2.1) |
Corporate Debt [Member] | Indiana Michigan Power Co [Member] |  |  |  |
Nuclear Trust Fund Investments |  |  |  |
Fair Value |  | 61.6 | 76.7 |
Contractual Maturities, Fair Value of Debt Securities |  |  |  |
Fair Value |  | 61.6 | 76.7 |
Corporate Debt [Member] | Indiana Michigan Power Co [Member] | Spent Nuclear Fuel and Decommissioning Trusts [Member] |  |  |  |
Nuclear Trust Fund Investments |  |  |  |
Gross Unrealized Gains |  | (7.0) | 6.7 |
Other-Than-Temporary Impairments |  | (9.6) | (2.1) |
State and Local Jurisdiction |  |  |  |
Nuclear Trust Fund Investments |  |  |  |
Fair Value |  | 3.3 | 7.3 |
Contractual Maturities, Fair Value of Debt Securities |  |  |  |
Fair Value |  | 3.3 | 7.3 |
State and Local Jurisdiction | Spent Nuclear Fuel and Decommissioning Trusts [Member] |  |  |  |
Nuclear Trust Fund Investments |  |  |  |
Gross Unrealized Gains |  | 0.1 | 0.4 |
Other-Than-Temporary Impairments |  | (0.1) | (0.1) |
State and Local Jurisdiction | Indiana Michigan Power Co [Member] |  |  |  |
Nuclear Trust Fund Investments |  |  |  |
Fair Value |  | 3.3 | 7.3 |
Contractual Maturities, Fair Value of Debt Securities |  |  |  |
Fair Value |  | 3.3 | 7.3 |
State and Local Jurisdiction | Indiana Michigan Power Co [Member] | Spent Nuclear Fuel and Decommissioning Trusts [Member] |  |  |  |
Nuclear Trust Fund Investments |  |  |  |
Gross Unrealized Gains |  | 0.1 | 0.4 |
Other-Than-Temporary Impairments |  | (0.1) | (0.1) |
Equity units [Member] |  |  |  |
Book Values and Fair Values of Long - term Debt |  |  |  |
Long-term Debt, Fair Value |  | $ 877.0 | $ 1,700.0 |
[1] | The fair value amounts include debt related to AEP’s Equity Units and had a fair value of $877 million and $1.7 billion as of December 31, 2022 and 2021, respectively. See “Equity Units” section of Note 14 for additional information.
[2] | Primarily represents amounts held for the repayment of debt.
[3] | Amounts in “Other” column primarily represent cash deposits in bank accounts with financial institutions or third-parties. Level 1 and Level 2 amounts primarily represent investments in money market funds.
[4] | Primarily short and intermediate maturities which may be sold and do not contain maturity dates.
[5] | Amounts represent publicly-traded equity securities and equity-based mutual funds.
[6] | Amount reported as Gross Unrealized Gains includes unrealized gains of $1.5 billion and $1.9 billion and unrealized losses of $6 million and $4 million as of December 31, 2022 and 2021, respectively.
[7] | Amounts in “Other” column primarily represent accrued interest receivables from financial institutions. Level 1 amounts primarily represent investments in money market funds.

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