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Fair Value Long-term Debt, Other Temporary Investments, Nuclear Trusts (Details) - USD ($)
3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2024
Jun. 30, 2023
Jun. 30, 2024
Jun. 30, 2023
Dec. 31, 2023
Book Values and Fair Values of Long - term Debt          
Total Long-term Debt Outstanding $ 42,062,300,000   $ 42,062,300,000   $ 40,143,200,000
Long Term Debt, Fair Value 37,897,100,000   37,897,100,000   37,325,700,000
Other Temporary Investments          
Cost 248,400,000   248,400,000   243,500,000
Gross Unrealized Gains 29,900,000   29,900,000   25,900,000
Gross Unrealized Losses (7,200,000)   (7,200,000)   (6,200,000)
Other Short-term Investments 271,100,000   271,100,000   263,200,000
Debt and Equity Securities Within Other Temporary Investments          
Proceeds from Investment Sales 0 $ 0 3,000,000.0 $ 0  
Purchases of Investments 1,500,000 1,300,000 3,000,000.0 2,300,000  
Gross Realized Gains on Investment Sales 0 0 300,000 0  
Gross Realized Losses on Investment Sales 0 0 200,000 0  
Nuclear Trust Fund Investments          
Fair Value 4,214,000,000   4,214,000,000   3,860,200,000
Securities Activity Within Decommissioning and SNF Trusts          
Payments to Acquire Investments     1,190,100,000 1,235,600,000  
Contractual Maturities, Fair Value of Debt Securities          
Fair Value 4,214,000,000   4,214,000,000   3,860,200,000
Other [Member]          
Other Temporary Investments          
Other Short-term Investments 21,900,000   21,900,000   13,900,000
Nuclear Trust Fund Investments          
Fair Value 12,600,000   12,600,000   9,000,000.0
Contractual Maturities, Fair Value of Debt Securities          
Fair Value 12,600,000   12,600,000   9,000,000.0
Spent Nuclear Fuel and Decommissioning Trusts [Member]          
Securities Activity Within Decommissioning and SNF Trusts          
Payments to Acquire Investments 598,600,000 697,000,000.0 1,187,100,000 1,233,300,000  
Contractual Maturities, Fair Value of Debt Securities          
Within 1 year 340,200,000   340,200,000    
After 1 year through 5 years 574,200,000   574,200,000    
After 5 years through 10 years 213,200,000   213,200,000    
After 10 years 264,900,000   264,900,000    
Fair Value Measurements (Textuals)          
Adjusted Cost of Debt Securities 1,400,000,000   1,400,000,000   1,400,000,000
Adjusted Cost of Domestic Equity Securities 587,000,000   587,000,000   568,000,000
Other than Temporary Impairment Losses, Investments     (27,400,000)   (41,800,000)
Proceeds from Sale of Other Investments 584,600,000 688,700,000 1,154,100,000 1,206,300,000  
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax (12,400,000)   (12,400,000)   (10,000,000.0)
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax 2,229,100,000   2,229,100,000   1,902,900,000
Spent Nuclear Fuel and Decommissioning Trusts [Member] | Gain [Member]          
Securities Activity Within Decommissioning and SNF Trusts          
Realized Investment Gains (Losses) 4,900,000 6,400,000 10,300,000 54,800,000  
Spent Nuclear Fuel and Decommissioning Trusts [Member] | Loss [Member]          
Securities Activity Within Decommissioning and SNF Trusts          
Gain (Loss) on Investments 4,200,000 3,700,000 5,400,000 12,300,000  
Cash [Member]          
Other Temporary Investments          
Cost [1] 45,400,000   45,400,000   48,900,000
Gross Unrealized Gains [1] 0   0   0
Gross Unrealized Losses [1] 0   0   0
Other Short-term Investments [1] 45,400,000   45,400,000   48,900,000
Fixed Income Funds [Member]          
Nuclear Trust Fund Investments          
Fair Value 1,392,500,000   1,392,500,000   1,406,800,000
Contractual Maturities, Fair Value of Debt Securities          
Fair Value 1,392,500,000   1,392,500,000   1,406,800,000
Fixed Income Funds [Member] | Other [Member]          
Nuclear Trust Fund Investments          
Fair Value 0   0   0
Contractual Maturities, Fair Value of Debt Securities          
Fair Value 0   0   0
Fixed Income Funds [Member] | Spent Nuclear Fuel and Decommissioning Trusts [Member]          
Fair Value Measurements (Textuals)          
Other than Temporary Impairment Losses, Investments     (27,400,000)   (41,800,000)
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax (10,600,000)   (10,600,000)   (9,100,000)
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax 15,100,000   15,100,000   33,400,000
Mutual Funds Fixed Income [Member]          
Other Temporary Investments          
Cost [2] 166,200,000   166,200,000   165,900,000
Gross Unrealized Gains [2] 0   0   0
Gross Unrealized Losses [2] (7,200,000)   (7,200,000)   (6,200,000)
Other Short-term Investments [2] 159,000,000.0   159,000,000.0   159,700,000
Mutual Funds Fixed Income [Member] | Other [Member]          
Other Temporary Investments          
Other Short-term Investments 0   0   0
Domestic [Member]          
Nuclear Trust Fund Investments          
Fair Value [3] 2,798,700,000   2,798,700,000   2,436,600,000
Contractual Maturities, Fair Value of Debt Securities          
Fair Value [3] 2,798,700,000   2,798,700,000   2,436,600,000
Domestic [Member] | Other [Member]          
Nuclear Trust Fund Investments          
Fair Value [3] 0   0   0
Contractual Maturities, Fair Value of Debt Securities          
Fair Value [3] 0   0   0
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 (1,800,000)   (1,800,000)   (900,000)
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax 2,214,000,000   2,214,000,000   1,869,500,000
Mutual Funds Equity [Member]          
Other Temporary Investments          
Cost 14,900,000   14,900,000   14,800,000
Gross Unrealized Gains 29,900,000   29,900,000   25,900,000
Gross Unrealized Losses 0   0   0
Other Short-term Investments [3] 44,800,000   44,800,000   40,700,000
Mutual Funds Equity [Member] | Other [Member]          
Other Temporary Investments          
Other Short-term Investments [3] 0   0   0
Cash and Cash Equivalents [Member]          
Nuclear Trust Fund Investments          
Fair Value [4] 22,800,000   22,800,000   16,800,000
Contractual Maturities, Fair Value of Debt Securities          
Fair Value [4] 22,800,000   22,800,000   16,800,000
Cash and Cash Equivalents [Member] | Other [Member]          
Nuclear Trust Fund Investments          
Fair Value [4] 12,600,000   12,600,000   9,000,000.0
Contractual Maturities, Fair Value of Debt Securities          
Fair Value [4] 12,600,000   12,600,000   9,000,000.0
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   0
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax 0   0   0
US Government Agencies Debt Securities [Member]          
Nuclear Trust Fund Investments          
Fair Value 1,267,800,000   1,267,800,000   1,273,000,000
Contractual Maturities, Fair Value of Debt Securities          
Fair Value 1,267,800,000   1,267,800,000   1,273,000,000
US Government Agencies Debt Securities [Member] | Other [Member]          
Nuclear Trust Fund Investments          
Fair Value 0   0   0
Contractual Maturities, Fair Value of Debt Securities          
Fair Value 0   0   0
US Government Agencies Debt Securities [Member] | Spent Nuclear Fuel and Decommissioning Trusts [Member]          
Fair Value Measurements (Textuals)          
Other than Temporary Impairment Losses, Investments     (26,600,000)   (33,200,000)
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax (3,600,000)   (3,600,000)   (3,900,000)
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax 13,800,000   13,800,000   28,600,000
Corporate Debt [Member]          
Nuclear Trust Fund Investments          
Fair Value 123,000,000.0   123,000,000.0   132,100,000
Contractual Maturities, Fair Value of Debt Securities          
Fair Value 123,000,000.0   123,000,000.0   132,100,000
Corporate Debt [Member] | Other [Member]          
Nuclear Trust Fund Investments          
Fair Value 0   0   0
Contractual Maturities, Fair Value of Debt Securities          
Fair Value 0   0   0
Corporate Debt [Member] | Spent Nuclear Fuel and Decommissioning Trusts [Member]          
Fair Value Measurements (Textuals)          
Other than Temporary Impairment Losses, Investments     (800,000)   (8,600,000)
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax (7,000,000.0)   (7,000,000.0)   (5,200,000)
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax 1,300,000   1,300,000   4,800,000
State and Local Jurisdiction [Member]          
Nuclear Trust Fund Investments          
Fair Value 1,700,000   1,700,000   1,700,000
Contractual Maturities, Fair Value of Debt Securities          
Fair Value 1,700,000   1,700,000   1,700,000
State and Local Jurisdiction [Member] | Other [Member]          
Nuclear Trust Fund Investments          
Fair Value 0   0   0
Contractual Maturities, Fair Value of Debt Securities          
Fair Value 0   0   0
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   0
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax 0   0   0
Other Cash Deposits [Member]          
Other Temporary Investments          
Cost 21,900,000 [5]   21,900,000 [5]   13,900,000
Gross Unrealized Gains 0   0   0
Gross Unrealized Losses 0   0   0
Other Short-term Investments 21,900,000 [5]   21,900,000 [5]   13,900,000
Other Cash Deposits [Member] | Other [Member]          
Other Temporary Investments          
Other Short-term Investments [7] 21,900,000 [6]   21,900,000 [6]   13,900,000
Other Cash Deposits [Member] | AEP OnSite Partners          
Other Temporary Investments          
Other Short-term Investments 300,000   300,000    
AEP Texas Inc. [Member]          
Book Values and Fair Values of Long - term Debt          
Total Long-term Debt Outstanding 6,489,700,000   6,489,700,000   5,889,800,000
Long Term Debt, Fair Value 5,779,100,000   5,779,100,000   5,400,700,000
AEP Transmission Co [Member]          
Book Values and Fair Values of Long - term Debt          
Total Long-term Debt Outstanding 5,861,500,000   5,861,500,000   5,414,400,000
Long Term Debt, Fair Value 4,867,600,000   4,867,600,000   4,796,900,000
Appalachian Power Co [Member]          
Book Values and Fair Values of Long - term Debt          
Total Long-term Debt Outstanding 5,672,000,000   5,672,000,000   5,588,300,000
Long Term Debt, Fair Value 5,267,700,000   5,267,700,000   5,390,100,000
Indiana Michigan Power Co [Member]          
Book Values and Fair Values of Long - term Debt          
Total Long-term Debt Outstanding 3,540,300,000   3,540,300,000   3,499,400,000
Long Term Debt, Fair Value 3,159,400,000   3,159,400,000   3,291,600,000
Nuclear Trust Fund Investments          
Fair Value 4,214,000,000   4,214,000,000   3,860,200,000
Securities Activity Within Decommissioning and SNF Trusts          
Payments to Acquire Investments     1,187,100,000 1,233,300,000  
Contractual Maturities, Fair Value of Debt Securities          
Fair Value 4,214,000,000   4,214,000,000   3,860,200,000
Indiana Michigan Power Co [Member] | Other [Member]          
Nuclear Trust Fund Investments          
Fair Value 12,600,000   12,600,000   9,000,000.0
Contractual Maturities, Fair Value of Debt Securities          
Fair Value 12,600,000   12,600,000   9,000,000.0
Indiana Michigan Power Co [Member] | Spent Nuclear Fuel and Decommissioning Trusts [Member]          
Securities Activity Within Decommissioning and SNF Trusts          
Payments to Acquire Investments 598,600,000 697,000,000.0 1,187,100,000 1,233,300,000  
Contractual Maturities, Fair Value of Debt Securities          
Within 1 year 340,200,000   340,200,000    
After 1 year through 5 years 574,200,000   574,200,000    
After 5 years through 10 years 213,200,000   213,200,000    
After 10 years 264,900,000   264,900,000    
Fair Value Measurements (Textuals)          
Adjusted Cost of Debt Securities 1,400,000,000   1,400,000,000   1,400,000,000
Adjusted Cost of Domestic Equity Securities 587,000,000   587,000,000   568,000,000
Other than Temporary Impairment Losses, Investments     (27,400,000)   (41,800,000)
Proceeds from Sale of Other Investments 584,600,000 688,700,000 1,154,100,000 1,206,300,000  
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax (12,400,000)   (12,400,000)   (10,000,000.0)
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax 2,229,100,000   2,229,100,000   1,902,900,000
Indiana Michigan Power Co [Member] | Spent Nuclear Fuel and Decommissioning Trusts [Member] | Gain [Member]          
Securities Activity Within Decommissioning and SNF Trusts          
Realized Investment Gains (Losses) 4,900,000 6,400,000 10,300,000 54,800,000  
Indiana Michigan Power Co [Member] | Spent Nuclear Fuel and Decommissioning Trusts [Member] | Loss [Member]          
Securities Activity Within Decommissioning and SNF Trusts          
Gain (Loss) on Investments 4,200,000 $ 3,700,000 5,400,000 $ 12,300,000  
Indiana Michigan Power Co [Member] | Fixed Income Funds [Member]          
Nuclear Trust Fund Investments          
Fair Value 1,392,500,000   1,392,500,000   1,406,800,000
Contractual Maturities, Fair Value of Debt Securities          
Fair Value 1,392,500,000   1,392,500,000   1,406,800,000
Indiana Michigan Power Co [Member] | Fixed Income Funds [Member] | Other [Member]          
Nuclear Trust Fund Investments          
Fair Value 0   0   0
Contractual Maturities, Fair Value of Debt Securities          
Fair Value 0   0   0
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     (27,400,000)   (41,800,000)
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax (10,600,000)   (10,600,000)   (9,100,000)
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax 15,100,000   15,100,000   33,400,000
Indiana Michigan Power Co [Member] | Domestic [Member]          
Nuclear Trust Fund Investments          
Fair Value [3] 2,798,700,000   2,798,700,000   2,436,600,000
Contractual Maturities, Fair Value of Debt Securities          
Fair Value [3] 2,798,700,000   2,798,700,000   2,436,600,000
Indiana Michigan Power Co [Member] | Domestic [Member] | Other [Member]          
Nuclear Trust Fund Investments          
Fair Value [3] 0   0   0
Contractual Maturities, Fair Value of Debt Securities          
Fair Value [3] 0   0   0
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 (1,800,000)   (1,800,000)   (900,000)
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax 2,214,000,000   2,214,000,000   1,869,500,000
Indiana Michigan Power Co [Member] | Cash and Cash Equivalents [Member]          
Nuclear Trust Fund Investments          
Fair Value [4] 22,800,000   22,800,000   16,800,000
Contractual Maturities, Fair Value of Debt Securities          
Fair Value [4] 22,800,000   22,800,000   16,800,000
Indiana Michigan Power Co [Member] | Cash and Cash Equivalents [Member] | Other [Member]          
Nuclear Trust Fund Investments          
Fair Value [4] 12,600,000   12,600,000   9,000,000.0
Contractual Maturities, Fair Value of Debt Securities          
Fair Value [4] 12,600,000   12,600,000   9,000,000.0
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   0
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax 0   0   0
Indiana Michigan Power Co [Member] | US Government Agencies Debt Securities [Member]          
Nuclear Trust Fund Investments          
Fair Value 1,267,800,000   1,267,800,000   1,273,000,000
Contractual Maturities, Fair Value of Debt Securities          
Fair Value 1,267,800,000   1,267,800,000   1,273,000,000
Indiana Michigan Power Co [Member] | US Government Agencies Debt Securities [Member] | Other [Member]          
Nuclear Trust Fund Investments          
Fair Value 0   0   0
Contractual Maturities, Fair Value of Debt Securities          
Fair Value 0   0   0
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     (26,600,000)   (33,200,000)
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax (3,600,000)   (3,600,000)   (3,900,000)
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax 13,800,000   13,800,000   28,600,000
Indiana Michigan Power Co [Member] | Corporate Debt [Member]          
Nuclear Trust Fund Investments          
Fair Value 123,000,000.0   123,000,000.0   132,100,000
Contractual Maturities, Fair Value of Debt Securities          
Fair Value 123,000,000.0   123,000,000.0   132,100,000
Indiana Michigan Power Co [Member] | Corporate Debt [Member] | Other [Member]          
Nuclear Trust Fund Investments          
Fair Value 0   0   0
Contractual Maturities, Fair Value of Debt Securities          
Fair Value 0   0   0
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     (800,000)   (8,600,000)
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax (7,000,000.0)   (7,000,000.0)   (5,200,000)
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax 1,300,000   1,300,000   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   1,700,000
Contractual Maturities, Fair Value of Debt Securities          
Fair Value 1,700,000   1,700,000   1,700,000
Indiana Michigan Power Co [Member] | State and Local Jurisdiction [Member] | Other [Member]          
Nuclear Trust Fund Investments          
Fair Value 0   0   0
Contractual Maturities, Fair Value of Debt Securities          
Fair Value 0   0   0
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   0
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax 0   0   0
Ohio Power Co [Member]          
Book Values and Fair Values of Long - term Debt          
Total Long-term Debt Outstanding 3,714,300,000   3,714,300,000   3,366,800,000
Long Term Debt, Fair Value 3,182,200,000   3,182,200,000   2,992,100,000
Public Service Co Of Oklahoma [Member]          
Book Values and Fair Values of Long - term Debt          
Total Long-term Debt Outstanding 2,385,200,000   2,385,200,000   2,384,600,000
Long Term Debt, Fair Value 2,084,500,000   2,084,500,000   2,154,300,000
Southwestern Electric Power Co [Member]          
Book Values and Fair Values of Long - term Debt          
Total Long-term Debt Outstanding 3,648,300,000   3,648,300,000   3,646,900,000
Long Term Debt, Fair Value $ 3,114,400,000   $ 3,114,400,000   $ 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.
[5] Excludes Other Cash Deposits of $0.3 million classified as Assets Held for Sale on the balance sheets. See ”Planned Disposition of AEP OnSite Partners” section of Note 6 for additional information.
[6] Excludes Other Cash Deposits of $0.3 million classified as Assets Held for Sale on the balance sheets. See ”Planned Disposition of AEP OnSite Partners” section of Note 6 for additional information.
[7] 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.