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Benefit Plans 1 (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020
Benefit Amounts Recognized on the Balance Sheets |  |  |  |
Deferred Charges and Other Noncurrent Assets - Prepaid Benefit Costs |  | $ 3,757.4 | $ 4,433.1 |
Deferred Credits and Other Noncurrent Liabilities - Accrued Long-term Benefit Liability |  | (607.3) | (603.8) |
AEP Texas Inc. [Member] |  |  |  |
Benefit Amounts Recognized on the Balance Sheets |  |  |  |
Deferred Charges and Other Noncurrent Assets - Prepaid Benefit Costs |  | 179.0 | 211.3 |
Deferred Credits and Other Noncurrent Liabilities - Accrued Long-term Benefit Liability |  | (93.2) | (73.8) |
Appalachian Power Co [Member] |  |  |  |
Benefit Amounts Recognized on the Balance Sheets |  |  |  |
Deferred Charges and Other Noncurrent Assets - Prepaid Benefit Costs |  | 138.7 | 129.2 |
Deferred Credits and Other Noncurrent Liabilities - Accrued Long-term Benefit Liability |  | (49.6) | (34.6) |
Indiana Michigan Power Co [Member] |  |  |  |
Benefit Amounts Recognized on the Balance Sheets |  |  |  |
Deferred Charges and Other Noncurrent Assets - Prepaid Benefit Costs |  | 270.5 | 316.5 |
Deferred Credits and Other Noncurrent Liabilities - Accrued Long-term Benefit Liability |  | (58.8) | (58.3) |
Ohio Power Co [Member] |  |  |  |
Benefit Amounts Recognized on the Balance Sheets |  |  |  |
Deferred Charges and Other Noncurrent Assets - Prepaid Benefit Costs |  | 578.3 | 601.1 |
Deferred Credits and Other Noncurrent Liabilities - Accrued Long-term Benefit Liability |  | (66.0) | (29.2) |
Public Service Co Of Oklahoma [Member] |  |  |  |
Benefit Amounts Recognized on the Balance Sheets |  |  |  |
Deferred Charges and Other Noncurrent Assets - Prepaid Benefit Costs |  | 20.8 | 7.9 |
Deferred Credits and Other Noncurrent Liabilities - Accrued Long-term Benefit Liability |  | (21.3) | (19.4) |
Southwestern Electric Power Co [Member] |  |  |  |
Benefit Amounts Recognized on the Balance Sheets |  |  |  |
Deferred Charges and Other Noncurrent Assets - Prepaid Benefit Costs |  | 262.0 | 251.8 |
Deferred Credits and Other Noncurrent Liabilities - Accrued Long-term Benefit Liability |  | $ (68.4) | $ (63.0) |
Pension Plans [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Discount Rate |  | 5.50% | 2.90% |
Interest Crediting Rate |  | 4.25% | 4.00% |
Rate of Compensation Increase | [1] | 5.05% | 5.10% |
Actuarial Assumptions for Net Periodic Benefit Costs |  |  |  |
Discount Rate |  | 2.90% | 2.50% | 3.25%
Interest Crediting Rate |  | 4.00% | 4.00% | 4.00%
Expected Return on Plan Assets |  | 5.25% | 4.75% | 5.75%
Rate of Compensation Increase | [2] | 5.05% | 5.10% | 5.00%
Change in Benefit Obligation |  |  |  |
Benefit Obligation as of January 1 |  | $ 5,187.0 | $ 5,544.5 |
Service Cost |  | 123.1 | 129.2 | $ 111.9
Interest Cost |  | 148.2 | 137.2 | 167.9
Actuarial (Gain) Loss |  | (983.4) | (173.9) |
Plan Amendments |  | 0.0 | 0.0 |
Benefit Payments |  | (402.2) | (450.0) |
Participant Contributions |  | 0.0 | 0.0 |
Medicare Subsidy |  | 0.0 | 0.0 |
Benefit Obligation as of December 31 |  | 4,072.7 | 5,187.0 | 5,544.5
Change in Fair Value of Plan Assets |  |  |  |
Fair Value of Plan Assets as of January 1 |  | 5,352.9 | 5,556.6 |
Actual Gain (Loss) on Plan Assets |  | (833.7) | 239.2 |
Company Contributions | [3] | 7.7 | 7.1 |
Participant Contributions |  | 0.0 | 0.0 |
Benefit Payments |  | (402.2) | (450.0) |
Fair Value of Plan Assets as of December 31 |  | 4,124.7 | 5,352.9 | $ 5,556.6
Funded (Underfunded) Status as of December 31 |  | 52.0 | 165.9 |
Benefit Amounts Recognized on the Balance Sheets |  |  |  |
Deferred Charges and Other Noncurrent Assets - Prepaid Benefit Costs |  | 113.4 | 244.3 |
Other Current Liabilities - Accrued Short-term Benefit Liability |  | (6.3) | (7.6) |
Employee Benefits and Pension Obligations - Accrued Long-term Benefit Liability |  | (55.1) | (70.8) |
Funded (Underfunded) Status |  | 52.0 | 165.9 |
Components |  |  |  |
Net Actuarial Loss |  | 935.6 | 894.7 |
Prior Service Cost (Credit) |  | 0.2 | 0.2 |
Components of Change in Amounts Included in AOCI and Regulatory Assets |  |  |  |
Actuarial (Gain) Loss During the Year |  | 103.9 | (183.4) |
Amortization of Actuarial Gain (Loss) |  | (63.0) | (101.5) |
Prior Service (Credit) Cost |  | 0.0 | 0.0 |
Amortization of Prior Service Credit (Cost) |  | 0.0 | 0.0 |
Change for the Year |  | $ 40.9 | $ (284.9) |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Rate of Compensation Increase | [1] | 5.05% | 5.10% |
Company Contributions | [3] | $ 7.7 | $ 7.1 |
Pension Plans [Member] | Regulatory Assets [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | 841.8 | 878.0 |
Pension Plans [Member] | Deferred Income Taxes [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | 19.9 | 3.6 |
Pension Plans [Member] | Net of Tax AOCI [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | $ 74.1 | $ 13.3 |
Pension Plans [Member] | AEP Texas Inc. [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Discount Rate |  | 5.50% | 2.90% |
Interest Crediting Rate |  | 4.25% | 4.00% |
Rate of Compensation Increase | [1] | 5.15% | 5.10% |
Actuarial Assumptions for Net Periodic Benefit Costs |  |  |  |
Discount Rate |  | 2.90% | 2.50% | 3.25%
Interest Crediting Rate |  | 4.00% | 4.00% | 4.00%
Expected Return on Plan Assets |  | 5.25% | 4.75% | 5.75%
Rate of Compensation Increase | [2] | 5.15% | 5.10% | 5.05%
Change in Benefit Obligation |  |  |  |
Benefit Obligation as of January 1 |  | $ 419.8 | $ 453.2 |
Service Cost |  | 11.1 | 11.8 | $ 10.0
Interest Cost |  | 12.1 | 11.2 | 13.9
Actuarial (Gain) Loss |  | (67.8) | (10.9) |
Plan Amendments |  | 0.0 | 0.0 |
Benefit Payments |  | (41.1) | (45.5) |
Participant Contributions |  | 0.0 | 0.0 |
Benefit Obligation as of December 31 |  | 334.1 | 419.8 | 453.2
Change in Fair Value of Plan Assets |  |  |  |
Fair Value of Plan Assets as of January 1 |  | 444.9 | 474.0 |
Actual Gain (Loss) on Plan Assets |  | (69.2) | 16.0 |
Company Contributions |  | 0.5 | 0.4 |
Participant Contributions |  | 0.0 | 0.0 |
Benefit Payments |  | (41.1) | (45.5) |
Fair Value of Plan Assets as of December 31 |  | 335.1 | 444.9 | $ 474.0
Funded (Underfunded) Status as of December 31 |  | 1.0 | 25.1 |
Benefit Amounts Recognized on the Balance Sheets |  |  |  |
Deferred Charges and Other Noncurrent Assets - Prepaid Benefit Costs |  | 3.7 | 28.7 |
Other Current Liabilities - Accrued Short-term Benefit Liability |  | (0.4) | (0.3) |
Deferred Credits and Other Noncurrent Liabilities - Accrued Long-term Benefit Liability |  | (2.3) | (3.3) |
Funded (Underfunded) Status |  | 1.0 | 25.1 |
Components |  |  |  |
Net Actuarial Loss |  | 161.9 | 144.7 |
Prior Service Cost (Credit) |  | 0.0 | 0.0 |
Components of Change in Amounts Included in AOCI and Regulatory Assets |  |  |  |
Actuarial (Gain) Loss During the Year |  | 22.4 | (7.5) |
Amortization of Actuarial Gain (Loss) |  | (5.2) | (8.3) |
Prior Service (Credit) Cost |  | 0.0 | 0.0 |
Amortization of Prior Service Credit (Cost) |  | 0.0 | 0.0 |
Change for the Year |  | $ 17.2 | $ (15.8) |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Rate of Compensation Increase | [1] | 5.15% | 5.10% |
Company Contributions |  | $ 0.5 | $ 0.4 |
Pension Plans [Member] | AEP Texas Inc. [Member] | Regulatory Assets [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | 151.2 | 136.7 |
Pension Plans [Member] | AEP Texas Inc. [Member] | Deferred Income Taxes [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | 2.4 | 1.8 |
Pension Plans [Member] | AEP Texas Inc. [Member] | Net of Tax AOCI [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | $ 8.3 | $ 6.2 |
Pension Plans [Member] | Appalachian Power Co [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Discount Rate |  | 5.50% | 2.90% |
Interest Crediting Rate |  | 4.25% | 4.00% |
Rate of Compensation Increase | [1] | 4.90% | 4.85% |
Actuarial Assumptions for Net Periodic Benefit Costs |  |  |  |
Discount Rate |  | 2.90% | 2.50% | 3.25%
Interest Crediting Rate |  | 4.00% | 4.00% | 4.00%
Expected Return on Plan Assets |  | 5.25% | 4.75% | 5.75%
Rate of Compensation Increase | [2] | 4.90% | 4.85% | 4.85%
Change in Benefit Obligation |  |  |  |
Benefit Obligation as of January 1 |  | $ 621.7 | $ 670.8 |
Service Cost |  | 11.4 | 11.9 | $ 10.5
Interest Cost |  | 17.5 | 16.4 | 20.3
Actuarial (Gain) Loss |  | (123.1) | (28.5) |
Plan Amendments |  | 0.0 | 0.0 |
Benefit Payments |  | (41.8) | (48.9) |
Participant Contributions |  | 0.0 | 0.0 |
Medicare Subsidy |  | 0.0 | 0.0 |
Benefit Obligation as of December 31 |  | 485.7 | 621.7 | 670.8
Change in Fair Value of Plan Assets |  |  |  |
Fair Value of Plan Assets as of January 1 |  | 683.3 | 701.3 |
Actual Gain (Loss) on Plan Assets |  | (109.8) | 30.9 |
Company Contributions |  | 0.0 | 0.0 |
Participant Contributions |  | 0.0 | 0.0 |
Benefit Payments |  | (41.8) | (48.9) |
Fair Value of Plan Assets as of December 31 |  | 531.7 | 683.3 | $ 701.3
Funded (Underfunded) Status as of December 31 |  | 46.0 | 61.6 |
Benefit Amounts Recognized on the Balance Sheets |  |  |  |
Employee Benefits and Pension Assets - Prepaid Benefit Costs |  | 46.6 | 62.4 |
Other Current Liabilities - Accrued Short-term Benefit Liability |  | 0.0 | 0.0 |
Employee Benefits and Pension Obligations - Accrued Long-term Benefit Liability |  | (0.6) | (0.8) |
Funded (Underfunded) Status |  | 46.0 | 61.6 |
Components |  |  |  |
Net Actuarial Loss |  | 95.6 | 83.9 |
Prior Service Cost (Credit) |  | 0.0 | 0.0 |
Components of Change in Amounts Included in AOCI and Regulatory Assets |  |  |  |
Actuarial (Gain) Loss During the Year |  | 19.1 | (30.4) |
Amortization of Actuarial Gain (Loss) |  | (7.4) | (12.0) |
Prior Service (Credit) Cost |  | 0.0 | 0.0 |
Amortization of Prior Service Credit (Cost) |  | 0.0 | 0.0 |
Change for the Year |  | $ 11.7 | $ (42.4) |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Rate of Compensation Increase | [1] | 4.90% | 4.85% |
Company Contributions |  | $ 0.0 | $ 0.0 |
Pension Plans [Member] | Appalachian Power Co [Member] | Regulatory Assets [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | 93.6 | 82.5 |
Pension Plans [Member] | Appalachian Power Co [Member] | Deferred Income Taxes [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | 0.4 | 0.3 |
Pension Plans [Member] | Appalachian Power Co [Member] | Net of Tax AOCI [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | $ 1.6 | $ 1.1 |
Pension Plans [Member] | Indiana Michigan Power Co [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Discount Rate |  | 5.50% | 2.90% |
Interest Crediting Rate |  | 4.25% | 4.00% |
Rate of Compensation Increase | [1] | 5.00% | 5.00% |
Actuarial Assumptions for Net Periodic Benefit Costs |  |  |  |
Discount Rate |  | 2.90% | 2.50% | 3.25%
Interest Crediting Rate |  | 4.00% | 4.00% | 4.00%
Expected Return on Plan Assets |  | 5.25% | 4.75% | 5.75%
Rate of Compensation Increase | [2] | 5.00% | 5.00% | 5.00%
Change in Benefit Obligation |  |  |  |
Benefit Obligation as of January 1 |  | $ 612.1 | $ 653.3 |
Service Cost |  | 16.2 | 17.5 | $ 15.4
Interest Cost |  | 17.0 | 16.2 | 19.7
Actuarial (Gain) Loss |  | (138.0) | (29.5) |
Plan Amendments |  | 0.0 | 0.0 |
Benefit Payments |  | (40.5) | (45.4) |
Participant Contributions |  | 0.0 | 0.0 |
Benefit Obligation as of December 31 |  | 466.8 | 612.1 | 653.3
Change in Fair Value of Plan Assets |  |  |  |
Fair Value of Plan Assets as of January 1 |  | 681.5 | 698.1 |
Actual Gain (Loss) on Plan Assets |  | (107.4) | 28.8 |
Company Contributions |  | 0.1 | 0.0 |
Participant Contributions |  | 0.0 | 0.0 |
Benefit Payments |  | (40.5) | (45.4) |
Fair Value of Plan Assets as of December 31 |  | 533.7 | 681.5 | $ 698.1
Funded (Underfunded) Status as of December 31 |  | 66.9 | 69.4 |
Benefit Amounts Recognized on the Balance Sheets |  |  |  |
Deferred Charges and Other Noncurrent Assets - Prepaid Benefit Costs |  | 68.5 | 71.4 |
Other Current Liabilities - Accrued Short-term Benefit Liability |  | (0.1) | (0.1) |
Deferred Credits and Other Noncurrent Liabilities - Accrued Long-term Benefit Liability |  | (1.5) | (1.9) |
Funded (Underfunded) Status |  | 66.9 | 69.4 |
Components |  |  |  |
Net Actuarial Loss |  | (6.9) | (1.6) |
Prior Service Cost (Credit) |  | 0.0 | 0.0 |
Components of Change in Amounts Included in AOCI and Regulatory Assets |  |  |  |
Actuarial (Gain) Loss During the Year |  | 1.8 | (29.4) |
Amortization of Actuarial Gain (Loss) |  | (7.1) | (11.7) |
Prior Service (Credit) Cost |  | 0.0 | 0.0 |
Amortization of Prior Service Credit (Cost) |  | 0.0 | 0.0 |
Change for the Year |  | $ (5.3) | $ (41.1) |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Rate of Compensation Increase | [1] | 5.00% | 5.00% |
Company Contributions |  | $ 0.1 | $ 0.0 |
Pension Plans [Member] | Indiana Michigan Power Co [Member] | Regulatory Assets [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets | [4] | 4.8 | 3.1 |
Pension Plans [Member] | Indiana Michigan Power Co [Member] | Deferred Income Taxes [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | (2.4) | (1.0) |
Pension Plans [Member] | Indiana Michigan Power Co [Member] | Net of Tax AOCI [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | $ (9.3) | $ (3.7) |
Pension Plans [Member] | Ohio Power Co [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Discount Rate |  | 5.50% | 2.90% |
Interest Crediting Rate |  | 4.25% | 4.00% |
Rate of Compensation Increase | [1] | 5.35% | 5.30% |
Actuarial Assumptions for Net Periodic Benefit Costs |  |  |  |
Discount Rate |  | 2.90% | 2.50% | 3.25%
Interest Crediting Rate |  | 4.00% | 4.00% | 4.00%
Expected Return on Plan Assets |  | 5.25% | 4.75% | 5.75%
Rate of Compensation Increase | [2] | 5.35% | 5.30% | 5.25%
Change in Benefit Obligation |  |  |  |
Benefit Obligation as of January 1 |  | $ 470.7 | $ 510.3 |
Service Cost |  | 11.2 | 11.4 | $ 9.7
Interest Cost |  | 13.3 | 12.5 | 15.4
Actuarial (Gain) Loss |  | (97.9) | (24.1) |
Plan Amendments |  | 0.0 | 0.0 |
Benefit Payments |  | (33.7) | (39.4) |
Participant Contributions |  | 0.0 | 0.0 |
Benefit Obligation as of December 31 |  | 363.6 | 470.7 | 510.3
Change in Fair Value of Plan Assets |  |  |  |
Fair Value of Plan Assets as of January 1 |  | 524.8 | 543.1 |
Actual Gain (Loss) on Plan Assets |  | (84.8) | 21.1 |
Company Contributions |  | 0.1 | 0.0 |
Participant Contributions |  | 0.0 | 0.0 |
Benefit Payments |  | (33.7) | (39.4) |
Fair Value of Plan Assets as of December 31 |  | 406.4 | 524.8 | $ 543.1
Funded (Underfunded) Status as of December 31 |  | 42.8 | 54.1 |
Benefit Amounts Recognized on the Balance Sheets |  |  |  |
Deferred Charges and Other Noncurrent Assets - Prepaid Benefit Costs |  | 43.1 | 54.8 |
Deferred Credits and Other Noncurrent Liabilities - Accrued Long-term Benefit Liability |  | (0.3) | (0.7) |
Funded (Underfunded) Status |  | 42.8 | 54.1 |
Components |  |  |  |
Net Actuarial Loss |  | 124.3 | 118.1 |
Prior Service Cost (Credit) |  | 0.0 | 0.0 |
Components of Change in Amounts Included in AOCI and Regulatory Assets |  |  |  |
Actuarial (Gain) Loss During the Year |  | 11.7 | (22.8) |
Amortization of Actuarial Gain (Loss) |  | (5.5) | (9.1) |
Prior Service (Credit) Cost |  | 0.0 | 0.0 |
Amortization of Prior Service Credit (Cost) |  | 0.0 | 0.0 |
Change for the Year |  | $ 6.2 | $ (31.9) |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Rate of Compensation Increase | [1] | 5.35% | 5.30% |
Company Contributions |  | $ 0.1 | $ 0.0 |
Pension Plans [Member] | Ohio Power Co [Member] | Regulatory Assets [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | $ 124.3 | $ 118.1 |
Pension Plans [Member] | Public Service Co Of Oklahoma [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Discount Rate |  | 5.50% | 2.90% |
Interest Crediting Rate |  | 4.25% | 4.00% |
Rate of Compensation Increase | [1] | 5.15% | 5.10% |
Actuarial Assumptions for Net Periodic Benefit Costs |  |  |  |
Discount Rate |  | 2.90% | 2.50% | 3.25%
Interest Crediting Rate |  | 4.00% | 4.00% | 4.00%
Expected Return on Plan Assets |  | 5.25% | 4.75% | 5.75%
Rate of Compensation Increase | [2] | 5.15% | 5.10% | 5.05%
Change in Benefit Obligation |  |  |  |
Benefit Obligation as of January 1 |  | $ 252.6 | $ 279.9 |
Service Cost |  | 7.4 | 8.0 | $ 7.3
Interest Cost |  | 7.0 | 6.7 | 8.5
Actuarial (Gain) Loss |  | (52.9) | (17.2) |
Plan Amendments |  | 0.0 | 0.0 |
Benefit Payments |  | (21.8) | (24.8) |
Participant Contributions |  | 0.0 | 0.0 |
Benefit Obligation as of December 31 |  | 192.3 | 252.6 | 279.9
Change in Fair Value of Plan Assets |  |  |  |
Fair Value of Plan Assets as of January 1 |  | 286.2 | 299.8 |
Actual Gain (Loss) on Plan Assets |  | (46.0) | 11.1 |
Company Contributions |  | 0.1 | 0.1 |
Participant Contributions |  | 0.0 | 0.0 |
Benefit Payments |  | (21.8) | (24.8) |
Fair Value of Plan Assets as of December 31 |  | 218.5 | 286.2 | $ 299.8
Funded (Underfunded) Status as of December 31 |  | 26.2 | 33.6 |
Benefit Amounts Recognized on the Balance Sheets |  |  |  |
Employee Benefits and Pension Assets - Prepaid Benefit Costs |  | 27.6 | 35.5 |
Other Current Liabilities - Accrued Short-term Benefit Liability |  | (0.1) | (0.1) |
Deferred Credits and Other Noncurrent Liabilities - Accrued Long-term Benefit Liability |  | (1.3) | (1.8) |
Funded (Underfunded) Status |  | 26.2 | 33.6 |
Components |  |  |  |
Net Actuarial Loss |  | 38.8 | 35.0 |
Prior Service Cost (Credit) |  | 0.0 | 0.0 |
Components of Change in Amounts Included in AOCI and Regulatory Assets |  |  |  |
Actuarial (Gain) Loss During the Year |  | 6.7 | (16.0) |
Amortization of Actuarial Gain (Loss) |  | (2.9) | (4.9) |
Prior Service (Credit) Cost |  | 0.0 | 0.0 |
Amortization of Prior Service Credit (Cost) |  | 0.0 | 0.0 |
Change for the Year |  | $ 3.8 | $ (20.9) |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Rate of Compensation Increase | [1] | 5.15% | 5.10% |
Company Contributions |  | $ 0.1 | $ 0.1 |
Pension Plans [Member] | Public Service Co Of Oklahoma [Member] | Regulatory Assets [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | $ 38.8 | $ 35.0 |
Pension Plans [Member] | Southwestern Electric Power Co [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Discount Rate |  | 5.50% | 2.90% |
Interest Crediting Rate |  | 4.25% | 4.00% |
Rate of Compensation Increase | [1] | 5.00% | 4.95% |
Actuarial Assumptions for Net Periodic Benefit Costs |  |  |  |
Discount Rate |  | 2.90% | 2.50% | 3.25%
Interest Crediting Rate |  | 4.00% | 4.00% | 4.00%
Expected Return on Plan Assets |  | 5.25% | 4.75% | 5.75%
Rate of Compensation Increase | [2] | 5.00% | 4.95% | 4.90%
Change in Benefit Obligation |  |  |  |
Benefit Obligation as of January 1 |  | $ 317.7 | $ 334.5 |
Service Cost |  | 10.6 | 11.2 | $ 9.9
Interest Cost |  | 9.1 | 8.5 | 10.2
Actuarial (Gain) Loss |  | (57.9) | (3.5) |
Plan Amendments |  | 0.0 | 0.0 |
Benefit Payments |  | (28.8) | (33.0) |
Participant Contributions |  | 0.0 | 0.0 |
Benefit Obligation as of December 31 |  | 250.7 | 317.7 | 334.5
Change in Fair Value of Plan Assets |  |  |  |
Fair Value of Plan Assets as of January 1 |  | 308.3 | 326.9 |
Actual Gain (Loss) on Plan Assets |  | (48.3) | 14.3 |
Company Contributions |  | 0.1 | 0.1 |
Participant Contributions |  | 0.0 | 0.0 |
Benefit Payments |  | (28.8) | (33.0) |
Fair Value of Plan Assets as of December 31 |  | 231.3 | 308.3 | $ 326.9
Funded (Underfunded) Status as of December 31 |  | (19.4) | (9.4) |
Benefit Amounts Recognized on the Balance Sheets |  |  |  |
Deferred Charges and Other Noncurrent Assets - Prepaid Benefit Costs |  | 0.0 | 0.0 |
Other Current Liabilities - Accrued Short-term Benefit Liability |  | (0.1) | (0.1) |
Employee Benefits and Pension Obligations - Accrued Long-term Benefit Liability |  | (19.3) | (9.3) |
Funded (Underfunded) Status |  | (19.4) | (9.4) |
Components |  |  |  |
Net Actuarial Loss |  | 77.6 | 76.4 |
Prior Service Cost (Credit) |  | 0.0 | 0.0 |
Components of Change in Amounts Included in AOCI and Regulatory Assets |  |  |  |
Actuarial (Gain) Loss During the Year |  | 5.0 | (4.3) |
Amortization of Actuarial Gain (Loss) |  | (3.8) | (6.2) |
Prior Service (Credit) Cost |  | 0.0 | 0.0 |
Amortization of Prior Service Credit (Cost) |  | 0.0 | 0.0 |
Change for the Year |  | $ 1.2 | $ (10.5) |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Rate of Compensation Increase | [1] | 5.00% | 4.95% |
Company Contributions |  | $ 0.1 | $ 0.1 |
Pension Plans [Member] | Southwestern Electric Power Co [Member] | Regulatory Assets [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | 77.6 | 76.4 |
Pension Plans [Member] | Southwestern Electric Power Co [Member] | Deferred Income Taxes [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | 0.0 | 0.0 |
Pension Plans [Member] | Southwestern Electric Power Co [Member] | Net of Tax AOCI [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | $ 0.0 | 0.0 |
Pension Plans [Member] | Minimum [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Rate of Compensation Increase |  | 3.00% |  |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Rate of Compensation Increase |  | 3.00% |  |
Pension Plans [Member] | Minimum [Member] | AEP Texas Inc. [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Rate of Compensation Increase |  | 3.00% |  |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Rate of Compensation Increase |  | 3.00% |  |
Pension Plans [Member] | Minimum [Member] | Appalachian Power Co [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Rate of Compensation Increase |  | 3.00% |  |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Rate of Compensation Increase |  | 3.00% |  |
Pension Plans [Member] | Minimum [Member] | Indiana Michigan Power Co [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Rate of Compensation Increase |  | 3.00% |  |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Rate of Compensation Increase |  | 3.00% |  |
Pension Plans [Member] | Minimum [Member] | Ohio Power Co [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Rate of Compensation Increase |  | 3.00% |  |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Rate of Compensation Increase |  | 3.00% |  |
Pension Plans [Member] | Minimum [Member] | Public Service Co Of Oklahoma [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Rate of Compensation Increase |  | 3.00% |  |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Rate of Compensation Increase |  | 3.00% |  |
Pension Plans [Member] | Minimum [Member] | Southwestern Electric Power Co [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Rate of Compensation Increase |  | 3.00% |  |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Rate of Compensation Increase |  | 3.00% |  |
Pension Plans [Member] | Maximum [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Rate of Compensation Increase |  | 11.50% |  |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Rate of Compensation Increase |  | 11.50% |  |
Pension Plans [Member] | Maximum [Member] | AEP Texas Inc. [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Rate of Compensation Increase |  | 11.50% |  |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Rate of Compensation Increase |  | 11.50% |  |
Pension Plans [Member] | Maximum [Member] | Appalachian Power Co [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Rate of Compensation Increase |  | 11.50% |  |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Rate of Compensation Increase |  | 11.50% |  |
Pension Plans [Member] | Maximum [Member] | Indiana Michigan Power Co [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Rate of Compensation Increase |  | 11.50% |  |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Rate of Compensation Increase |  | 11.50% |  |
Pension Plans [Member] | Maximum [Member] | Ohio Power Co [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Rate of Compensation Increase |  | 11.50% |  |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Rate of Compensation Increase |  | 11.50% |  |
Pension Plans [Member] | Maximum [Member] | Public Service Co Of Oklahoma [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Rate of Compensation Increase |  | 11.50% |  |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Rate of Compensation Increase |  | 11.50% |  |
Pension Plans [Member] | Maximum [Member] | Southwestern Electric Power Co [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Rate of Compensation Increase |  | 11.50% |  |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Rate of Compensation Increase |  | 11.50% |  |
Nonqualified Pension Plans [Member] |  |  |  |
Change in Benefit Obligation |  |  |  |
Benefit Obligation as of January 1 |  | $ 78.4 |  |
Benefit Obligation as of December 31 |  | 61.5 | 78.4 |
Change in Fair Value of Plan Assets |  |  |  |
Fair Value of Plan Assets as of January 1 |  | 0.0 |  |
Company Contributions |  | 8.0 | 7.0 |
Fair Value of Plan Assets as of December 31 |  | 0.0 | 0.0 |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Company Contributions |  | 8.0 | 7.0 |
Nonqualified Pension Plans [Member] | AEP Texas Inc. [Member] |  |  |  |
Change in Benefit Obligation |  |  |  |
Benefit Obligation as of January 1 |  | 3.6 |  |
Benefit Obligation as of December 31 |  | 2.7 | 3.6 |
Change in Fair Value of Plan Assets |  |  |  |
Fair Value of Plan Assets as of January 1 |  | 0.0 |  |
Fair Value of Plan Assets as of December 31 |  | 0.0 | 0.0 |
Nonqualified Pension Plans [Member] | Appalachian Power Co [Member] |  |  |  |
Change in Benefit Obligation |  |  |  |
Benefit Obligation as of January 1 |  | 0.8 |  |
Benefit Obligation as of December 31 |  | 0.6 | 0.8 |
Change in Fair Value of Plan Assets |  |  |  |
Fair Value of Plan Assets as of January 1 |  | 0.0 |  |
Fair Value of Plan Assets as of December 31 |  | 0.0 | 0.0 |
Nonqualified Pension Plans [Member] | Indiana Michigan Power Co [Member] |  |  |  |
Change in Benefit Obligation |  |  |  |
Benefit Obligation as of January 1 |  | 1.9 |  |
Benefit Obligation as of December 31 |  | 1.6 | 1.9 |
Change in Fair Value of Plan Assets |  |  |  |
Fair Value of Plan Assets as of January 1 |  | 0.0 |  |
Fair Value of Plan Assets as of December 31 |  | 0.0 | 0.0 |
Nonqualified Pension Plans [Member] | Ohio Power Co [Member] |  |  |  |
Change in Benefit Obligation |  |  |  |
Benefit Obligation as of January 1 |  | 0.7 |  |
Benefit Obligation as of December 31 |  | 0.3 | 0.7 |
Change in Fair Value of Plan Assets |  |  |  |
Fair Value of Plan Assets as of January 1 |  | 0.0 |  |
Fair Value of Plan Assets as of December 31 |  | 0.0 | 0.0 |
Nonqualified Pension Plans [Member] | Public Service Co Of Oklahoma [Member] |  |  |  |
Change in Benefit Obligation |  |  |  |
Benefit Obligation as of January 1 |  | 1.9 |  |
Benefit Obligation as of December 31 |  | 1.5 | 1.9 |
Change in Fair Value of Plan Assets |  |  |  |
Fair Value of Plan Assets as of January 1 |  | 0.0 |  |
Fair Value of Plan Assets as of December 31 |  | 0.0 | 0.0 |
Nonqualified Pension Plans [Member] | Southwestern Electric Power Co [Member] |  |  |  |
Change in Fair Value of Plan Assets |  |  |  |
Fair Value of Plan Assets as of January 1 |  | 0.0 |  |
Fair Value of Plan Assets as of December 31 |  | $ 231.3 | $ 0.0 |
Other Postretirement Benefit Plans [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Discount Rate |  | 5.50% | 2.90% |
Actuarial Assumptions for Net Periodic Benefit Costs |  |  |  |
Discount Rate |  | 2.90% | 2.55% | 3.30%
Expected Return on Plan Assets |  | 5.50% | 4.75% | 5.50%
Health Care Trend Rates |  |  |  |
Initial |  | 7.50% | 6.25% |
Ultimate |  | 4.50% | 4.50% |
Year Ultimate Reached |  | 2029 | 2029 |
Change in Benefit Obligation |  |  |  |
Benefit Obligation as of January 1 |  | $ 1,041.3 | $ 1,210.9 |
Service Cost |  | 7.4 | 9.5 | $ 10.0
Interest Cost |  | 29.2 | 30.5 | 39.8
Actuarial (Gain) Loss |  | (109.8) | (120.1) |
Plan Amendments |  | 0.0 | (5.4) |
Benefit Payments |  | (140.1) | (126.0) |
Participant Contributions |  | 44.1 | 41.3 |
Medicare Subsidy |  | 0.5 | 0.6 |
Benefit Obligation as of December 31 |  | 872.6 | 1,041.3 | 1,210.9
Change in Fair Value of Plan Assets |  |  |  |
Fair Value of Plan Assets as of January 1 |  | 2,044.3 | 1,946.7 |
Actual Gain (Loss) on Plan Assets |  | (403.6) | 176.5 |
Company Contributions | [3] | 4.6 | 5.8 |
Participant Contributions |  | 44.1 | 41.3 |
Benefit Payments |  | (140.1) | (126.0) |
Fair Value of Plan Assets as of December 31 |  | 1,549.3 | 2,044.3 | $ 1,946.7
Funded (Underfunded) Status as of December 31 |  | 676.7 | 1,003.0 |
Benefit Amounts Recognized on the Balance Sheets |  |  |  |
Deferred Charges and Other Noncurrent Assets - Prepaid Benefit Costs |  | 699.5 | 1,040.8 |
Other Current Liabilities - Accrued Short-term Benefit Liability |  | (2.5) | (2.7) |
Employee Benefits and Pension Obligations - Accrued Long-term Benefit Liability |  | (20.3) | (35.1) |
Funded (Underfunded) Status |  | 676.7 | 1,003.0 |
Components |  |  |  |
Net Actuarial Loss |  | 300.0 | (103.6) |
Prior Service Cost (Credit) |  | (90.5) | (161.9) |
Components of Change in Amounts Included in AOCI and Regulatory Assets |  |  |  |
Actuarial (Gain) Loss During the Year |  | 403.6 | (205.5) |
Amortization of Actuarial Gain (Loss) |  | 0.0 | 0.0 |
Prior Service (Credit) Cost |  | 0.0 | (5.5) |
Amortization of Prior Service Credit (Cost) |  | 71.4 | 70.9 |
Change for the Year |  | 475.0 | (140.1) |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Company Contributions | [3] | 4.6 | 5.8 |
Other Postretirement Benefit Plans [Member] | Regulatory Assets [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | 126.0 | (195.1) |
Other Postretirement Benefit Plans [Member] | Deferred Income Taxes [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | 17.5 | (14.7) |
Other Postretirement Benefit Plans [Member] | Net of Tax AOCI [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | $ 66.0 | $ (55.7) |
Other Postretirement Benefit Plans [Member] | AEP Texas Inc. [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Discount Rate |  | 5.50% | 2.90% |
Actuarial Assumptions for Net Periodic Benefit Costs |  |  |  |
Discount Rate |  | 2.90% | 2.55% | 3.30%
Expected Return on Plan Assets |  | 5.50% | 4.75% | 5.50%
Health Care Trend Rates |  |  |  |
Initial |  | 7.50% | 6.25% |
Ultimate |  | 4.50% | 4.50% |
Year Ultimate Reached |  | 2029 | 2029 |
Change in Benefit Obligation |  |  |  |
Benefit Obligation as of January 1 |  | $ 80.5 | $ 96.3 |
Service Cost |  | 0.5 | 0.7 | $ 0.8
Interest Cost |  | 2.2 | 2.4 | 3.2
Actuarial (Gain) Loss |  | (7.1) | (12.3) |
Plan Amendments |  | 0.0 | (0.5) |
Benefit Payments |  | (10.9) | (9.3) |
Participant Contributions |  | 3.4 | 3.2 |
Benefit Obligation as of December 31 |  | 68.6 | 80.5 | 96.3
Change in Fair Value of Plan Assets |  |  |  |
Fair Value of Plan Assets as of January 1 |  | 168.8 | 162.3 |
Actual Gain (Loss) on Plan Assets |  | (33.0) | 12.5 |
Company Contributions |  | 0.0 | 0.1 |
Participant Contributions |  | 3.4 | 3.2 |
Benefit Payments |  | (10.9) | (9.3) |
Fair Value of Plan Assets as of December 31 |  | 128.3 | 168.8 | $ 162.3
Funded (Underfunded) Status as of December 31 |  | 59.7 | 88.3 |
Benefit Amounts Recognized on the Balance Sheets |  |  |  |
Deferred Charges and Other Noncurrent Assets - Prepaid Benefit Costs |  | 59.7 | 88.3 |
Other Current Liabilities - Accrued Short-term Benefit Liability |  | 0.0 | 0.0 |
Deferred Credits and Other Noncurrent Liabilities - Accrued Long-term Benefit Liability |  | 0.0 | 0.0 |
Funded (Underfunded) Status |  | 59.7 | 88.3 |
Components |  |  |  |
Net Actuarial Loss |  | 29.7 | (5.2) |
Prior Service Cost (Credit) |  | (7.6) | (13.7) |
Components of Change in Amounts Included in AOCI and Regulatory Assets |  |  |  |
Actuarial (Gain) Loss During the Year |  | 34.9 | (17.5) |
Amortization of Actuarial Gain (Loss) |  | 0.0 | 0.0 |
Prior Service (Credit) Cost |  | 0.0 | (0.4) |
Amortization of Prior Service Credit (Cost) |  | 6.1 | 6.0 |
Change for the Year |  | 41.0 | (11.9) |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Company Contributions |  | 0.0 | 0.1 |
Other Postretirement Benefit Plans [Member] | AEP Texas Inc. [Member] | Regulatory Assets [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | 22.0 | (17.7) |
Other Postretirement Benefit Plans [Member] | AEP Texas Inc. [Member] | Deferred Income Taxes [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | 0.1 | (0.2) |
Other Postretirement Benefit Plans [Member] | AEP Texas Inc. [Member] | Net of Tax AOCI [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | $ 0.0 | $ (1.0) |
Other Postretirement Benefit Plans [Member] | Appalachian Power Co [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Discount Rate |  | 5.50% | 2.90% |
Actuarial Assumptions for Net Periodic Benefit Costs |  |  |  |
Discount Rate |  | 2.90% | 2.55% | 3.30%
Expected Return on Plan Assets |  | 5.50% | 4.75% | 5.50%
Health Care Trend Rates |  |  |  |
Initial |  | 7.50% | 6.25% |
Ultimate |  | 4.50% | 4.50% |
Year Ultimate Reached |  | 2029 | 2029 |
Change in Benefit Obligation |  |  |  |
Benefit Obligation as of January 1 |  | $ 167.3 | $ 198.2 |
Service Cost |  | 0.8 | 1.0 | $ 1.0
Interest Cost |  | 4.7 | 4.9 | 6.6
Actuarial (Gain) Loss |  | (16.2) | (21.4) |
Plan Amendments |  | 0.0 | (0.9) |
Benefit Payments |  | (23.0) | (21.3) |
Participant Contributions |  | 7.0 | 6.6 |
Medicare Subsidy |  | 0.1 | 0.2 |
Benefit Obligation as of December 31 |  | 140.7 | 167.3 | 198.2
Change in Fair Value of Plan Assets |  |  |  |
Fair Value of Plan Assets as of January 1 |  | 302.3 | 293.0 |
Actual Gain (Loss) on Plan Assets |  | (59.3) | 21.9 |
Company Contributions |  | 1.6 | 2.1 |
Participant Contributions |  | 7.0 | 6.6 |
Benefit Payments |  | (23.0) | (21.3) |
Fair Value of Plan Assets as of December 31 |  | 228.6 | 302.3 | $ 293.0
Funded (Underfunded) Status as of December 31 |  | 87.9 | 135.0 |
Benefit Amounts Recognized on the Balance Sheets |  |  |  |
Employee Benefits and Pension Assets - Prepaid Benefit Costs |  | 106.3 | 158.1 |
Other Current Liabilities - Accrued Short-term Benefit Liability |  | (1.6) | (1.8) |
Employee Benefits and Pension Obligations - Accrued Long-term Benefit Liability |  | (16.8) | (21.3) |
Funded (Underfunded) Status |  | 87.9 | 135.0 |
Components |  |  |  |
Net Actuarial Loss |  | 40.5 | (18.9) |
Prior Service Cost (Credit) |  | (13.4) | (23.8) |
Components of Change in Amounts Included in AOCI and Regulatory Assets |  |  |  |
Actuarial (Gain) Loss During the Year |  | 59.4 | (30.0) |
Amortization of Actuarial Gain (Loss) |  | 0.0 | 0.0 |
Prior Service (Credit) Cost |  | 0.0 | (0.9) |
Amortization of Prior Service Credit (Cost) |  | 10.4 | 10.3 |
Change for the Year |  | 69.8 | (20.6) |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Company Contributions |  | 1.6 | 2.1 |
Other Postretirement Benefit Plans [Member] | Appalachian Power Co [Member] | Regulatory Assets [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | 14.7 | (19.8) |
Other Postretirement Benefit Plans [Member] | Appalachian Power Co [Member] | Deferred Income Taxes [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | 2.5 | (4.9) |
Other Postretirement Benefit Plans [Member] | Appalachian Power Co [Member] | Net of Tax AOCI [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | $ 9.9 | $ (18.0) |
Other Postretirement Benefit Plans [Member] | Indiana Michigan Power Co [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Discount Rate |  | 5.50% | 2.90% |
Actuarial Assumptions for Net Periodic Benefit Costs |  |  |  |
Discount Rate |  | 2.90% | 2.55% | 3.30%
Expected Return on Plan Assets |  | 5.50% | 4.75% | 5.50%
Health Care Trend Rates |  |  |  |
Initial |  | 7.50% | 6.25% |
Ultimate |  | 4.50% | 4.50% |
Year Ultimate Reached |  | 2029 | 2029 |
Change in Benefit Obligation |  |  |  |
Benefit Obligation as of January 1 |  | $ 118.6 | $ 141.4 |
Service Cost |  | 0.9 | 1.3 | $ 1.4
Interest Cost |  | 3.4 | 3.5 | 4.7
Actuarial (Gain) Loss |  | (8.7) | (16.8) |
Plan Amendments |  | 0.0 | (0.7) |
Benefit Payments |  | (18.3) | (15.3) |
Participant Contributions |  | 6.0 | 5.2 |
Benefit Obligation as of December 31 |  | 101.9 | 118.6 | 141.4
Change in Fair Value of Plan Assets |  |  |  |
Fair Value of Plan Assets as of January 1 |  | 248.7 | 238.2 |
Actual Gain (Loss) on Plan Assets |  | (45.9) | 20.6 |
Company Contributions |  | 0.0 | 0.0 |
Participant Contributions |  | 6.0 | 5.2 |
Benefit Payments |  | (18.3) | (15.3) |
Fair Value of Plan Assets as of December 31 |  | 190.5 | 248.7 | $ 238.2
Funded (Underfunded) Status as of December 31 |  | 88.6 | 130.1 |
Benefit Amounts Recognized on the Balance Sheets |  |  |  |
Deferred Charges and Other Noncurrent Assets - Prepaid Benefit Costs |  | 88.6 | 130.1 |
Other Current Liabilities - Accrued Short-term Benefit Liability |  | 0.0 | 0.0 |
Deferred Credits and Other Noncurrent Liabilities - Accrued Long-term Benefit Liability |  | 0.0 | 0.0 |
Funded (Underfunded) Status |  | 88.6 | 130.1 |
Components |  |  |  |
Net Actuarial Loss |  | 40.2 | (10.7) |
Prior Service Cost (Credit) |  | (12.4) | (22.1) |
Components of Change in Amounts Included in AOCI and Regulatory Assets |  |  |  |
Actuarial (Gain) Loss During the Year |  | 50.9 | (26.3) |
Amortization of Actuarial Gain (Loss) |  | 0.0 | 0.0 |
Prior Service (Credit) Cost |  | 0.0 | (0.7) |
Amortization of Prior Service Credit (Cost) |  | 9.7 | 9.6 |
Change for the Year |  | 60.6 | (17.4) |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Company Contributions |  | 0.0 | 0.0 |
Other Postretirement Benefit Plans [Member] | Indiana Michigan Power Co [Member] | Regulatory Assets [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets | [4] | 22.1 | (30.7) |
Other Postretirement Benefit Plans [Member] | Indiana Michigan Power Co [Member] | Deferred Income Taxes [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | 1.2 | (0.4) |
Other Postretirement Benefit Plans [Member] | Indiana Michigan Power Co [Member] | Net of Tax AOCI [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | $ 4.5 | $ (1.7) |
Other Postretirement Benefit Plans [Member] | Ohio Power Co [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Discount Rate |  | 5.50% | 2.90% |
Actuarial Assumptions for Net Periodic Benefit Costs |  |  |  |
Discount Rate |  | 2.90% | 2.55% | 3.30%
Expected Return on Plan Assets |  | 5.50% | 4.75% | 5.50%
Health Care Trend Rates |  |  |  |
Initial |  | 7.50% | 6.25% |
Ultimate |  | 4.50% | 4.50% |
Year Ultimate Reached |  | 2029 | 2029 |
Change in Benefit Obligation |  |  |  |
Benefit Obligation as of January 1 |  | $ 104.9 | $ 126.4 |
Service Cost |  | 0.6 | 0.8 | $ 0.9
Interest Cost |  | 3.0 | 3.0 | 4.2
Actuarial (Gain) Loss |  | (8.9) | (15.6) |
Plan Amendments |  | 0.0 | (0.6) |
Benefit Payments |  | (15.5) | (13.6) |
Participant Contributions |  | 4.8 | 4.5 |
Benefit Obligation as of December 31 |  | 88.9 | 104.9 | 126.4
Change in Fair Value of Plan Assets |  |  |  |
Fair Value of Plan Assets as of January 1 |  | 220.0 | 213.0 |
Actual Gain (Loss) on Plan Assets |  | (43.1) | 16.1 |
Company Contributions |  | 0.0 | 0.0 |
Participant Contributions |  | 4.8 | 4.5 |
Benefit Payments |  | (15.5) | (13.6) |
Fair Value of Plan Assets as of December 31 |  | 166.2 | 220.0 | $ 213.0
Funded (Underfunded) Status as of December 31 |  | 77.3 | 115.1 |
Benefit Amounts Recognized on the Balance Sheets |  |  |  |
Deferred Charges and Other Noncurrent Assets - Prepaid Benefit Costs |  | 77.3 | 115.1 |
Deferred Credits and Other Noncurrent Liabilities - Accrued Long-term Benefit Liability |  | 0.0 | 0.0 |
Funded (Underfunded) Status |  | 77.3 | 115.1 |
Components |  |  |  |
Net Actuarial Loss |  | 27.6 | (18.5) |
Prior Service Cost (Credit) |  | (9.2) | (16.3) |
Components of Change in Amounts Included in AOCI and Regulatory Assets |  |  |  |
Actuarial (Gain) Loss During the Year |  | 46.1 | (22.1) |
Amortization of Actuarial Gain (Loss) |  | 0.0 | 0.0 |
Prior Service (Credit) Cost |  | 0.0 | (0.6) |
Amortization of Prior Service Credit (Cost) |  | 7.1 | 7.2 |
Change for the Year |  | 53.2 | (15.5) |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Company Contributions |  | 0.0 | 0.0 |
Other Postretirement Benefit Plans [Member] | Ohio Power Co [Member] | Regulatory Assets [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | $ 18.4 | $ (34.8) |
Other Postretirement Benefit Plans [Member] | Public Service Co Of Oklahoma [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Discount Rate |  | 5.50% | 2.90% |
Actuarial Assumptions for Net Periodic Benefit Costs |  |  |  |
Discount Rate |  | 2.90% | 2.55% | 3.30%
Expected Return on Plan Assets |  | 5.50% | 4.75% | 5.50%
Health Care Trend Rates |  |  |  |
Initial |  | 7.50% | 6.25% |
Ultimate |  | 4.50% | 4.50% |
Year Ultimate Reached |  | 2029 | 2029 |
Change in Benefit Obligation |  |  |  |
Benefit Obligation as of January 1 |  | $ 54.4 | $ 64.0 |
Service Cost |  | 0.4 | 0.6 | $ 0.7
Interest Cost |  | 1.5 | 1.6 | 2.1
Actuarial (Gain) Loss |  | (5.2) | (6.8) |
Plan Amendments |  | 0.0 | (0.3) |
Benefit Payments |  | (7.9) | (7.0) |
Participant Contributions |  | 2.5 | 2.3 |
Benefit Obligation as of December 31 |  | 45.7 | 54.4 | 64.0
Change in Fair Value of Plan Assets |  |  |  |
Fair Value of Plan Assets as of January 1 |  | 114.0 | 107.8 |
Actual Gain (Loss) on Plan Assets |  | (23.2) | 10.9 |
Company Contributions |  | 0.0 | 0.0 |
Participant Contributions |  | 2.5 | 2.3 |
Benefit Payments |  | (7.9) | (7.0) |
Fair Value of Plan Assets as of December 31 |  | 85.4 | 114.0 | $ 107.8
Funded (Underfunded) Status as of December 31 |  | 39.7 | 59.6 |
Benefit Amounts Recognized on the Balance Sheets |  |  |  |
Employee Benefits and Pension Assets - Prepaid Benefit Costs |  | 39.7 | 59.6 |
Other Current Liabilities - Accrued Short-term Benefit Liability |  | 0.0 | 0.0 |
Deferred Credits and Other Noncurrent Liabilities - Accrued Long-term Benefit Liability |  | 0.0 | 0.0 |
Funded (Underfunded) Status |  | 39.7 | 59.6 |
Components |  |  |  |
Net Actuarial Loss |  | 22.0 | (2.1) |
Prior Service Cost (Credit) |  | (5.6) | (10.0) |
Components of Change in Amounts Included in AOCI and Regulatory Assets |  |  |  |
Actuarial (Gain) Loss During the Year |  | 24.1 | (12.6) |
Amortization of Actuarial Gain (Loss) |  | 0.0 | 0.0 |
Prior Service (Credit) Cost |  | 0.0 | (0.3) |
Amortization of Prior Service Credit (Cost) |  | 4.4 | 4.4 |
Change for the Year |  | 28.5 | (8.5) |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Company Contributions |  | 0.0 | 0.0 |
Other Postretirement Benefit Plans [Member] | Public Service Co Of Oklahoma [Member] | Regulatory Assets [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | $ 16.4 | $ (12.1) |
Other Postretirement Benefit Plans [Member] | Southwestern Electric Power Co [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Discount Rate |  | 5.50% | 2.90% |
Actuarial Assumptions for Net Periodic Benefit Costs |  |  |  |
Discount Rate |  | 2.90% | 2.55% | 3.30%
Expected Return on Plan Assets |  | 5.50% | 4.75% | 5.50%
Health Care Trend Rates |  |  |  |
Initial |  | 7.50% | 6.25% |
Ultimate |  | 4.50% | 4.50% |
Year Ultimate Reached |  | 2029 | 2029 |
Change in Benefit Obligation |  |  |  |
Benefit Obligation as of January 1 |  | $ 65.2 | $ 77.1 |
Service Cost |  | 0.6 | 0.8 | $ 0.8
Interest Cost |  | 1.8 | 1.9 | 2.5
Actuarial (Gain) Loss |  | (6.6) | (9.2) |
Plan Amendments |  | 0.0 | (0.4) |
Benefit Payments |  | (8.8) | (7.6) |
Participant Contributions |  | 2.9 | 2.6 |
Benefit Obligation as of December 31 |  | 55.1 | 65.2 | 77.1
Change in Fair Value of Plan Assets |  |  |  |
Fair Value of Plan Assets as of January 1 |  | 136.6 | 129.9 |
Actual Gain (Loss) on Plan Assets |  | (27.7) | 11.7 |
Company Contributions |  | 0.0 | 0.0 |
Participant Contributions |  | 2.9 | 2.6 |
Benefit Payments |  | (8.8) | (7.6) |
Fair Value of Plan Assets as of December 31 |  | 103.0 | 136.6 | $ 129.9
Funded (Underfunded) Status as of December 31 |  | 47.9 | 71.4 |
Benefit Amounts Recognized on the Balance Sheets |  |  |  |
Deferred Charges and Other Noncurrent Assets - Prepaid Benefit Costs |  | 47.9 | 71.4 |
Other Current Liabilities - Accrued Short-term Benefit Liability |  | 0.0 | 0.0 |
Employee Benefits and Pension Obligations - Accrued Long-term Benefit Liability |  | 0.0 | 0.0 |
Funded (Underfunded) Status |  | 47.9 | 71.4 |
Components |  |  |  |
Net Actuarial Loss |  | 25.0 | (3.5) |
Prior Service Cost (Credit) |  | (7.0) | (12.3) |
Components of Change in Amounts Included in AOCI and Regulatory Assets |  |  |  |
Actuarial (Gain) Loss During the Year |  | 28.5 | (15.0) |
Amortization of Actuarial Gain (Loss) |  | 0.0 | 0.0 |
Prior Service (Credit) Cost |  | 0.0 | (0.4) |
Amortization of Prior Service Credit (Cost) |  | 5.3 | 5.3 |
Change for the Year |  | 33.8 | (10.1) |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Company Contributions |  | 0.0 | 0.0 |
Other Postretirement Benefit Plans [Member] | Southwestern Electric Power Co [Member] | Regulatory Assets [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | 11.2 | (8.9) |
Other Postretirement Benefit Plans [Member] | Southwestern Electric Power Co [Member] | Deferred Income Taxes [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | 1.5 | (1.4) |
Other Postretirement Benefit Plans [Member] | Southwestern Electric Power Co [Member] | Net of Tax AOCI [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | $ 5.3 | $ (5.5) |
[1] | Rates are for base pay only. In addition, an amount is added to reflect target incentive compensation for exempt employees and overtime and incentive pay for nonexempt employees.
[2] | Rates are for base pay only. In addition, an amount is added to reflect target incentive compensation for exempt employees and overtime and incentive pay for nonexempt employees.
[3] | No contributions were made to the qualified pension plan for the years ended December 31, 2022 and 2021, respectively. Contributions to the non-qualified pension plans were $8 million and $7 million for the years ended December 31, 2022 and 2021, respectively.
[4] | Recorded as a Regulatory Asset as of December 31, 2022 and recorded as a Regulatory Liability as of December 31, 2021.

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