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Benefit Plans 1 (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Pension Plans [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Discount Rate |  | 5.15% | 5.50% |
Interest Crediting Rate |  | 4.00% | 4.25% |
Rate of Compensation Increase | [1] | 5.05% | 5.05% |
Actuarial Assumptions for Net Periodic Benefit Costs |  |  |  |
Discount Rate |  | 5.50% | 2.90% | 2.50%
Interest Crediting Rate |  | 4.25% | 4.00% | 4.00%
Expected Return on Plan Assets |  | 7.50% | 5.25% | 4.75%
Rate of Compensation Increase | [2] | 5.05% | 5.05% | 5.10%
Change in Benefit Obligation |  |  |  |
Benefit Obligation as of January 1 |  | $ 4,072.7 | $ 5,187.0 |
Service Cost |  | 94.3 | 123.1 | $ 129.2
Interest Cost |  | 219.2 | 148.2 | 137.2
Actuarial (Gain) Loss |  | 144.0 | (983.4) |
Benefit Payments |  | (368.6) | (402.2) |
Benefit Obligation as of December 31 |  | 4,161.6 | 4,072.7 | 5,187.0
Change in Fair Value of Plan Assets |  |  |  |
Fair Value of Plan Assets as of January 1 |  | 4,124.7 | 5,352.9 |
Actual Gain (Loss) on Plan Assets |  | 353.8 | (833.7) |
Company Contributions |  | 8.3 | 7.7 |
Benefit Payments |  | (368.6) | (402.2) |
Fair Value of Plan Assets as of December 31 |  | 4,118.2 | 4,124.7 | $ 5,352.9
Funded (Underfunded) Status as of December 31 |  | (43.4) | 52.0 |
Benefit Amounts Recognized on the Balance Sheets |  |  |  |
Other Noncurrent Assets - Employee Benefits and Pension Assets |  | 17.3 | 113.4 |
Other Current Liabilities - Accrued Short-term Benefit Liability |  | (6.7) | (6.3) |
Other Noncurrent Liabilities - Employee Benefits and Pension Obligations |  | (54.0) | (55.1) |
Funded (Underfunded) Status |  | (43.4) | 52.0 |
Components |  |  |  |
Net Actuarial Loss |  | 1,063.4 | 935.6 |
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 |  | 129.2 | 103.9 |
Amortization of Actuarial Gain (Loss) |  | (1.4) | (63.0) |
Change for the Year |  | $ 127.8 | $ 40.9 |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Rate of Compensation Increase | [1] | 5.05% | 5.05% |
Company Contributions |  | $ 8.3 | $ 7.7 |
Pension Plans [Member] | Regulatory Assets [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | 938.6 | 841.8 |
Pension Plans [Member] | Deferred Income Taxes [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | 26.4 | 19.9 |
Pension Plans [Member] | Net of Tax AOCI [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | $ 98.6 | $ 74.1 |
Pension Plans [Member] | AEP Texas Inc. [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Discount Rate |  | 5.15% | 5.50% |
Interest Crediting Rate |  | 4.00% | 4.25% |
Rate of Compensation Increase | [1] | 5.20% | 5.15% |
Actuarial Assumptions for Net Periodic Benefit Costs |  |  |  |
Discount Rate |  | 5.50% | 2.90% | 2.50%
Interest Crediting Rate |  | 4.25% | 4.00% | 4.00%
Expected Return on Plan Assets |  | 7.50% | 5.25% | 4.75%
Rate of Compensation Increase | [2] | 5.20% | 5.15% | 5.10%
Change in Benefit Obligation |  |  |  |
Benefit Obligation as of January 1 |  | $ 334.1 | $ 419.8 |
Service Cost |  | 8.2 | 11.1 | $ 11.8
Interest Cost |  | 18.3 | 12.1 | 11.2
Actuarial (Gain) Loss |  | 20.1 | (67.8) |
Benefit Payments |  | (37.6) | (41.1) |
Benefit Obligation as of December 31 |  | 343.1 | 334.1 | 419.8
Change in Fair Value of Plan Assets |  |  |  |
Fair Value of Plan Assets as of January 1 |  | 335.1 | 444.9 |
Actual Gain (Loss) on Plan Assets |  | 34.8 | (69.2) |
Company Contributions |  | 0.4 | 0.5 |
Benefit Payments |  | (37.6) | (41.1) |
Fair Value of Plan Assets as of December 31 |  | 332.7 | 335.1 | $ 444.9
Funded (Underfunded) Status as of December 31 |  | (10.4) | 1.0 |
Benefit Amounts Recognized on the Balance Sheets |  |  |  |
Other Noncurrent Assets - Employee Benefits and Pension Assets |  | 0.1 | 3.7 |
Other Current Liabilities - Accrued Short-term Benefit Liability |  | (0.3) | (0.4) |
Other Noncurrent Liabilities - Employee Benefits and Pension Obligations |  | 10.2 | 2.3 |
Funded (Underfunded) Status |  | (10.4) | 1.0 |
Components |  |  |  |
Net Actuarial Loss |  | 175.2 | 161.9 |
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 |  | 13.4 | 22.4 |
Amortization of Actuarial Gain (Loss) |  | (0.1) | (5.2) |
Change for the Year |  | $ 13.3 | $ 17.2 |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Rate of Compensation Increase | [1] | 5.20% | 5.15% |
Company Contributions |  | $ 0.4 | $ 0.5 |
Pension Plans [Member] | AEP Texas Inc. [Member] | Regulatory Assets [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | 163.4 | 151.2 |
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 |  | 2.7 | 2.4 |
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 |  | $ 9.1 | $ 8.3 |
Pension Plans [Member] | Appalachian Power Co [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Discount Rate |  | 5.15% | 5.50% |
Interest Crediting Rate |  | 4.00% | 4.25% |
Rate of Compensation Increase | [1] | 4.95% | 4.90% |
Actuarial Assumptions for Net Periodic Benefit Costs |  |  |  |
Discount Rate |  | 5.50% | 2.90% | 2.50%
Interest Crediting Rate |  | 4.25% | 4.00% | 4.00%
Expected Return on Plan Assets |  | 7.50% | 5.25% | 4.75%
Rate of Compensation Increase | [2] | 4.95% | 4.90% | 4.85%
Change in Benefit Obligation |  |  |  |
Benefit Obligation as of January 1 |  | $ 485.7 | $ 621.7 |
Service Cost |  | 9.1 | 11.4 | $ 11.9
Interest Cost |  | 26.4 | 17.5 | 16.4
Actuarial (Gain) Loss |  | 23.2 | (123.1) |
Benefit Payments |  | (40.3) | (41.8) |
Benefit Obligation as of December 31 |  | 504.1 | 485.7 | 621.7
Change in Fair Value of Plan Assets |  |  |  |
Fair Value of Plan Assets as of January 1 |  | 531.7 | 683.3 |
Actual Gain (Loss) on Plan Assets |  | 58.4 | (109.8) |
Company Contributions |  | 0.0 | 0.0 |
Benefit Payments |  | (40.3) | (41.8) |
Fair Value of Plan Assets as of December 31 |  | 549.8 | 531.7 | $ 683.3
Funded (Underfunded) Status as of December 31 |  | 45.7 | 46.0 |
Benefit Amounts Recognized on the Balance Sheets |  |  |  |
Other Noncurrent Assets - Employee Benefits and Pension Assets |  | 46.0 | 46.6 |
Other Current Liabilities - Accrued Short-term Benefit Liability |  | 0.0 | 0.0 |
Other Noncurrent Liabilities - Employee Benefits and Pension Obligations |  | (0.3) | (0.6) |
Funded (Underfunded) Status |  | 45.7 | 46.0 |
Components |  |  |  |
Net Actuarial Loss |  | 104.9 | 95.6 |
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 |  | 9.3 | 19.1 |
Amortization of Actuarial Gain (Loss) |  | 0.0 | (7.4) |
Change for the Year |  | $ 9.3 | $ 11.7 |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Rate of Compensation Increase | [1] | 4.95% | 4.90% |
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 |  | 102.6 | 93.6 |
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 | 0.4 |
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 |  | $ 1.9 | $ 1.6 |
Pension Plans [Member] | Indiana Michigan Power Co [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Discount Rate |  | 5.15% | 5.50% |
Interest Crediting Rate |  | 4.00% | 4.25% |
Rate of Compensation Increase | [1] | 5.05% | 5.00% |
Actuarial Assumptions for Net Periodic Benefit Costs |  |  |  |
Discount Rate |  | 5.50% | 2.90% | 2.50%
Interest Crediting Rate |  | 4.25% | 4.00% | 4.00%
Expected Return on Plan Assets |  | 7.50% | 5.25% | 4.75%
Rate of Compensation Increase | [2] | 5.05% | 5.00% | 5.00%
Change in Benefit Obligation |  |  |  |
Benefit Obligation as of January 1 |  | $ 466.8 | $ 612.1 |
Service Cost |  | 11.9 | 16.2 | $ 17.5
Interest Cost |  | 24.9 | 17.0 | 16.2
Actuarial (Gain) Loss |  | 8.5 | (138.0) |
Benefit Payments |  | (35.1) | (40.5) |
Benefit Obligation as of December 31 |  | 477.0 | 466.8 | 612.1
Change in Fair Value of Plan Assets |  |  |  |
Fair Value of Plan Assets as of January 1 |  | 533.7 | 681.5 |
Actual Gain (Loss) on Plan Assets |  | 51.5 | (107.4) |
Company Contributions |  | 0.5 | 0.1 |
Benefit Payments |  | (35.1) | (40.5) |
Fair Value of Plan Assets as of December 31 |  | 550.6 | 533.7 | $ 681.5
Funded (Underfunded) Status as of December 31 |  | 73.6 | 66.9 |
Benefit Amounts Recognized on the Balance Sheets |  |  |  |
Other Noncurrent Assets - Employee Benefits and Pension Assets |  | 74.8 | 68.5 |
Other Current Liabilities - Accrued Short-term Benefit Liability |  | 0.0 | (0.1) |
Other Noncurrent Liabilities - Employee Benefits and Pension Obligations |  | 1.2 | 1.5 |
Funded (Underfunded) Status |  | 73.6 | 66.9 |
Components |  |  |  |
Net Actuarial Loss |  | (5.8) | (6.9) |
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 |  | 1.2 | 1.8 |
Amortization of Actuarial Gain (Loss) |  | (0.1) | (7.1) |
Change for the Year |  | $ 1.1 | $ (5.3) |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Rate of Compensation Increase | [1] | 5.05% | 5.00% |
Company Contributions |  | $ 0.5 | $ 0.1 |
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 |  | 6.4 | 4.8 |
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 |  | (2.6) | (2.4) |
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 |  | $ (9.6) | $ (9.3) |
Pension Plans [Member] | Ohio Power Co [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Discount Rate |  | 5.15% | 5.50% |
Interest Crediting Rate |  | 4.00% | 4.25% |
Rate of Compensation Increase | [1] | 5.45% | 5.35% |
Actuarial Assumptions for Net Periodic Benefit Costs |  |  |  |
Discount Rate |  | 5.50% | 2.90% | 2.50%
Interest Crediting Rate |  | 4.25% | 4.00% | 4.00%
Expected Return on Plan Assets |  | 7.50% | 5.25% | 4.75%
Rate of Compensation Increase | [2] | 5.45% | 5.35% | 5.30%
Change in Benefit Obligation |  |  |  |
Benefit Obligation as of January 1 |  | $ 363.6 | $ 470.7 |
Service Cost |  | 8.4 | 11.2 | $ 11.4
Interest Cost |  | 19.8 | 13.3 | 12.5
Actuarial (Gain) Loss |  | 17.5 | (97.9) |
Benefit Payments |  | (30.9) | (33.7) |
Benefit Obligation as of December 31 |  | 378.4 | 363.6 | 470.7
Change in Fair Value of Plan Assets |  |  |  |
Fair Value of Plan Assets as of January 1 |  | 406.4 | 524.8 |
Actual Gain (Loss) on Plan Assets |  | 44.0 | (84.8) |
Company Contributions |  | 0.0 | 0.1 |
Benefit Payments |  | (30.9) | (33.7) |
Fair Value of Plan Assets as of December 31 |  | 419.5 | 406.4 | $ 524.8
Funded (Underfunded) Status as of December 31 |  | 41.1 | 42.8 |
Benefit Amounts Recognized on the Balance Sheets |  |  |  |
Other Noncurrent Assets - Employee Benefits and Pension Assets |  | 41.4 | 43.1 |
Other Current Liabilities - Accrued Short-term Benefit Liability |  | 0.0 | 0.0 |
Other Noncurrent Liabilities - Employee Benefits and Pension Obligations |  | 0.3 | 0.3 |
Funded (Underfunded) Status |  | 41.1 | 42.8 |
Components |  |  |  |
Net Actuarial Loss |  | 131.9 | 124.3 |
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 |  | 7.6 | 11.7 |
Amortization of Actuarial Gain (Loss) |  | 0.0 | (5.5) |
Change for the Year |  | $ 7.6 | $ 6.2 |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Rate of Compensation Increase | [1] | 5.45% | 5.35% |
Company Contributions |  | $ 0.0 | $ 0.1 |
Pension Plans [Member] | Ohio Power Co [Member] | Regulatory Assets [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | 131.9 | 124.3 |
Pension Plans [Member] | Ohio 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] | Ohio 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] | Public Service Co Of Oklahoma [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Discount Rate |  | 5.15% | 5.50% |
Interest Crediting Rate |  | 4.00% | 4.25% |
Rate of Compensation Increase | [1] | 5.20% | 5.15% |
Actuarial Assumptions for Net Periodic Benefit Costs |  |  |  |
Discount Rate |  | 5.50% | 2.90% | 2.50%
Interest Crediting Rate |  | 4.25% | 4.00% | 4.00%
Expected Return on Plan Assets |  | 7.50% | 5.25% | 4.75%
Rate of Compensation Increase | [2] | 5.20% | 5.15% | 5.10%
Change in Benefit Obligation |  |  |  |
Benefit Obligation as of January 1 |  | $ 192.3 | $ 252.6 |
Service Cost |  | 5.5 | 7.4 | $ 8.0
Interest Cost |  | 10.7 | 7.0 | 6.7
Actuarial (Gain) Loss |  | 13.6 | (52.9) |
Benefit Payments |  | (19.9) | (21.8) |
Benefit Obligation as of December 31 |  | 202.2 | 192.3 | 252.6
Change in Fair Value of Plan Assets |  |  |  |
Fair Value of Plan Assets as of January 1 |  | 218.5 | 286.2 |
Actual Gain (Loss) on Plan Assets |  | 24.0 | (46.0) |
Company Contributions |  | 0.1 | 0.1 |
Benefit Payments |  | (19.9) | (21.8) |
Fair Value of Plan Assets as of December 31 |  | 222.7 | 218.5 | $ 286.2
Funded (Underfunded) Status as of December 31 |  | 20.5 | 26.2 |
Benefit Amounts Recognized on the Balance Sheets |  |  |  |
Other Noncurrent Assets - Employee Benefits and Pension Assets |  | 21.8 | 27.6 |
Other Current Liabilities - Accrued Short-term Benefit Liability |  | (0.1) | (0.1) |
Other Noncurrent Liabilities - Employee Benefits and Pension Obligations |  | 1.2 | 1.3 |
Funded (Underfunded) Status |  | 20.5 | 26.2 |
Components |  |  |  |
Net Actuarial Loss |  | 46.7 | 38.8 |
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 |  | 7.9 | 6.7 |
Amortization of Actuarial Gain (Loss) |  | 0.0 | (2.9) |
Change for the Year |  | $ 7.9 | $ 3.8 |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Rate of Compensation Increase | [1] | 5.20% | 5.15% |
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 |  | 46.7 | 38.8 |
Pension Plans [Member] | Public Service Co Of Oklahoma [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] | Public Service Co Of Oklahoma [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] | Southwestern Electric Power Co [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Discount Rate |  | 5.15% | 5.50% |
Interest Crediting Rate |  | 4.00% | 4.25% |
Rate of Compensation Increase | [1] | 5.00% | 5.00% |
Actuarial Assumptions for Net Periodic Benefit Costs |  |  |  |
Discount Rate |  | 5.50% | 2.90% | 2.50%
Interest Crediting Rate |  | 4.25% | 4.00% | 4.00%
Expected Return on Plan Assets |  | 7.50% | 5.25% | 4.75%
Rate of Compensation Increase | [2] | 5.00% | 5.00% | 4.95%
Change in Benefit Obligation |  |  |  |
Benefit Obligation as of January 1 |  | $ 250.7 | $ 317.7 |
Service Cost |  | 7.7 | 10.6 | $ 11.2
Interest Cost |  | 13.9 | 9.1 | 8.5
Actuarial (Gain) Loss |  | 16.8 | (57.9) |
Benefit Payments |  | (27.9) | (28.8) |
Benefit Obligation as of December 31 |  | 261.2 | 250.7 | 317.7
Change in Fair Value of Plan Assets |  |  |  |
Fair Value of Plan Assets as of January 1 |  | 231.3 | 308.3 |
Actual Gain (Loss) on Plan Assets |  | 23.9 | (48.3) |
Company Contributions |  | 0.2 | 0.1 |
Benefit Payments |  | (27.9) | (28.8) |
Fair Value of Plan Assets as of December 31 |  | 227.5 | 231.3 | $ 308.3
Funded (Underfunded) Status as of December 31 |  | (33.7) | (19.4) |
Benefit Amounts Recognized on the Balance Sheets |  |  |  |
Other Noncurrent Assets - Employee Benefits and Pension Assets |  | 0.0 | 0.0 |
Other Current Liabilities - Accrued Short-term Benefit Liability |  | (0.1) | (0.1) |
Other Noncurrent Liabilities - Employee Benefits and Pension Obligations |  | (33.6) | (19.3) |
Funded (Underfunded) Status |  | (33.7) | (19.4) |
Components |  |  |  |
Net Actuarial Loss |  | 89.6 | 77.6 |
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 |  | 12.1 | 5.0 |
Amortization of Actuarial Gain (Loss) |  | (0.1) | (3.8) |
Change for the Year |  | $ 12.0 | $ 1.2 |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Rate of Compensation Increase | [1] | 5.00% | 5.00% |
Company Contributions |  | $ 0.2 | $ 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 |  | 89.7 | 77.6 |
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 |  | $ (0.1) | 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 |  | $ 61.5 |  |
Benefit Obligation as of December 31 |  | 60.7 | 61.5 |
Change in Fair Value of Plan Assets |  |  |  |
Fair Value of Plan Assets as of January 1 |  | 0.0 |  |
Company Contributions |  | 8.0 | 8.0 |
Fair Value of Plan Assets as of December 31 |  | 0.0 | 0.0 |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Company Contributions |  | 8.0 | 8.0 |
Nonqualified Pension Plans [Member] | AEP Texas Inc. [Member] |  |  |  |
Change in Benefit Obligation |  |  |  |
Benefit Obligation as of January 1 |  | 2.7 |  |
Benefit Obligation as of December 31 |  |  | 2.7 |
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] | Appalachian Power Co [Member] |  |  |  |
Change in Benefit Obligation |  |  |  |
Benefit Obligation as of January 1 |  | 0.6 |  |
Benefit Obligation as of December 31 |  | 0.4 | 0.6 |
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] | Indiana Michigan Power Co [Member] |  |  |  |
Change in Benefit Obligation |  |  |  |
Benefit Obligation as of January 1 |  | 1.6 |  |
Benefit Obligation as of December 31 |  | 1.2 | 1.6 |
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] | Ohio Power Co [Member] |  |  |  |
Change in Benefit Obligation |  |  |  |
Benefit Obligation as of January 1 |  | 0.3 |  |
Benefit Obligation as of December 31 |  | 0.3 | 0.3 |
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 |  | 1.5 |  |
Benefit Obligation as of December 31 |  | 1.4 | 1.5 |
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 |  | 231.3 |  |
Fair Value of Plan Assets as of December 31 |  | $ 227.5 | $ 231.3 |
Other Postretirement Benefit Plans [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Discount Rate |  | 5.15% | 5.50% |
Actuarial Assumptions for Net Periodic Benefit Costs |  |  |  |
Discount Rate |  | 5.50% | 2.90% | 2.55%
Expected Return on Plan Assets |  | 7.25% | 5.50% | 4.75%
Health Care Trend Rates |  |  |  |
Initial |  | 7.00% | 7.50% |
Ultimate |  | 4.50% | 4.50% |
Year Ultimate Reached |  | 2030 | 2029 |
Change in Benefit Obligation |  |  |  |
Benefit Obligation as of January 1 |  | $ 872.6 | $ 1,041.3 |
Service Cost |  | 4.6 | 7.4 | $ 9.5
Interest Cost |  | 46.2 | 29.2 | 30.5
Actuarial (Gain) Loss |  | 19.8 | (109.8) |
Benefit Payments |  | (137.8) | (140.1) |
Participant Contributions |  | 43.6 | 44.1 |
Medicare Subsidy |  | 0.5 | 0.5 |
Benefit Obligation as of December 31 |  | 849.5 | 872.6 | 1,041.3
Change in Fair Value of Plan Assets |  |  |  |
Fair Value of Plan Assets as of January 1 |  | 1,549.3 | 2,044.3 |
Actual Gain (Loss) on Plan Assets |  | 213.2 | (403.6) |
Company Contributions |  | 5.0 | 4.6 |
Participant Contributions |  | 43.6 | 44.1 |
Benefit Payments |  | (137.8) | (140.1) |
Fair Value of Plan Assets as of December 31 |  | 1,673.3 | 1,549.3 | $ 2,044.3
Funded (Underfunded) Status as of December 31 |  | 823.8 | 676.7 |
Benefit Amounts Recognized on the Balance Sheets |  |  |  |
Other Noncurrent Assets - Employee Benefits and Pension Assets |  | 838.0 | 699.5 |
Other Current Liabilities - Accrued Short-term Benefit Liability |  | (2.4) | (2.5) |
Other Noncurrent Liabilities - Employee Benefits and Pension Obligations |  | (11.8) | (20.3) |
Funded (Underfunded) Status |  | 823.8 | 676.7 |
Components |  |  |  |
Net Actuarial Loss |  | 201.5 | 300.0 |
Prior Service Cost (Credit) |  | (27.4) | (90.5) |
Components of Change in Amounts Included in AOCI and Regulatory Assets |  |  |  |
Actuarial (Gain) Loss During the Year |  | (83.7) | 403.6 |
Amortization of Actuarial Gain (Loss) |  | (14.8) |  |
Amortization of Prior Service Credit (Cost) |  | 63.1 | 71.4 |
Change for the Year |  | (35.4) | 475.0 |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Company Contributions |  | 5.0 | 4.6 |
Other Postretirement Benefit Plans [Member] | Regulatory Assets [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | 106.1 | 126.0 |
Other Postretirement Benefit Plans [Member] | Deferred Income Taxes [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | 14.3 | 17.5 |
Other Postretirement Benefit Plans [Member] | Net of Tax AOCI [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | $ 53.7 | $ 66.0 |
Other Postretirement Benefit Plans [Member] | AEP Texas Inc. [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Discount Rate |  | 5.15% | 5.50% |
Actuarial Assumptions for Net Periodic Benefit Costs |  |  |  |
Discount Rate |  | 5.50% | 2.90% | 2.55%
Expected Return on Plan Assets |  | 7.25% | 5.50% | 4.75%
Health Care Trend Rates |  |  |  |
Initial |  | 7.00% | 7.50% |
Ultimate |  | 4.50% | 4.50% |
Year Ultimate Reached |  | 2030 | 2029 |
Change in Benefit Obligation |  |  |  |
Benefit Obligation as of January 1 |  | $ 68.6 | $ 80.5 |
Service Cost |  | 0.3 | 0.5 | $ 0.7
Interest Cost |  | 3.6 | 2.2 | 2.4
Actuarial (Gain) Loss |  | 1.2 | (7.1) |
Benefit Payments |  | (10.7) | (10.9) |
Participant Contributions |  | 3.4 | 3.4 |
Medicare Subsidy |  | 0.0 | 0.0 |
Benefit Obligation as of December 31 |  | 66.4 | 68.6 | 80.5
Change in Fair Value of Plan Assets |  |  |  |
Fair Value of Plan Assets as of January 1 |  | 128.3 | 168.8 |
Actual Gain (Loss) on Plan Assets |  | 16.5 | (33.0) |
Company Contributions |  | 0.0 | 0.0 |
Participant Contributions |  | 3.4 | 3.4 |
Benefit Payments |  | (10.7) | (10.9) |
Fair Value of Plan Assets as of December 31 |  | 137.5 | 128.3 | $ 168.8
Funded (Underfunded) Status as of December 31 |  | 71.1 | 59.7 |
Benefit Amounts Recognized on the Balance Sheets |  |  |  |
Other Noncurrent Assets - Employee Benefits and Pension Assets |  | 71.1 | 59.7 |
Other Current Liabilities - Accrued Short-term Benefit Liability |  | 0.0 | 0.0 |
Other Noncurrent Liabilities - Employee Benefits and Pension Obligations |  | 0.0 | 0.0 |
Funded (Underfunded) Status |  | 71.1 | 59.7 |
Components |  |  |  |
Net Actuarial Loss |  | 22.1 | 29.7 |
Prior Service Cost (Credit) |  | (2.3) | (7.6) |
Components of Change in Amounts Included in AOCI and Regulatory Assets |  |  |  |
Actuarial (Gain) Loss During the Year |  | (6.4) | 34.9 |
Amortization of Actuarial Gain (Loss) |  | (1.2) |  |
Amortization of Prior Service Credit (Cost) |  | 5.3 | 6.1 |
Change for the Year |  | (2.3) | 41.0 |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Company Contributions |  | 0.0 | 0.0 |
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 |  | 19.8 | 22.0 |
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 |  | 0.0 | 0.1 |
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 | $ 0.0 |
Other Postretirement Benefit Plans [Member] | Appalachian Power Co [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Discount Rate |  | 5.15% | 5.50% |
Actuarial Assumptions for Net Periodic Benefit Costs |  |  |  |
Discount Rate |  | 5.50% | 2.90% | 2.55%
Expected Return on Plan Assets |  | 7.25% | 5.50% | 4.75%
Health Care Trend Rates |  |  |  |
Initial |  | 7.00% | 7.50% |
Ultimate |  | 4.50% | 4.50% |
Year Ultimate Reached |  | 2030 | 2029 |
Change in Benefit Obligation |  |  |  |
Benefit Obligation as of January 1 |  | $ 140.7 | $ 167.3 |
Service Cost |  | 0.5 | 0.8 | $ 1.0
Interest Cost |  | 7.4 | 4.7 | 4.9
Actuarial (Gain) Loss |  | 0.9 | (16.2) |
Benefit Payments |  | (21.6) | (23.0) |
Participant Contributions |  | 6.6 | 7.0 |
Medicare Subsidy |  | 0.1 | 0.1 |
Benefit Obligation as of December 31 |  | 134.6 | 140.7 | 167.3
Change in Fair Value of Plan Assets |  |  |  |
Fair Value of Plan Assets as of January 1 |  | 228.6 | 302.3 |
Actual Gain (Loss) on Plan Assets |  | 28.1 | (59.3) |
Company Contributions |  | 1.3 | 1.6 |
Participant Contributions |  | 6.6 | 7.0 |
Benefit Payments |  | (21.6) | (23.0) |
Fair Value of Plan Assets as of December 31 |  | 243.0 | 228.6 | $ 302.3
Funded (Underfunded) Status as of December 31 |  | 108.4 | 87.9 |
Benefit Amounts Recognized on the Balance Sheets |  |  |  |
Other Noncurrent Assets - Employee Benefits and Pension Assets |  | 125.6 | 106.3 |
Other Current Liabilities - Accrued Short-term Benefit Liability |  | (1.6) | (1.6) |
Other Noncurrent Liabilities - Employee Benefits and Pension Obligations |  | (15.6) | (16.8) |
Funded (Underfunded) Status |  | 108.4 | 87.9 |
Components |  |  |  |
Net Actuarial Loss |  | 27.1 | 40.5 |
Prior Service Cost (Credit) |  | (4.2) | (13.4) |
Components of Change in Amounts Included in AOCI and Regulatory Assets |  |  |  |
Actuarial (Gain) Loss During the Year |  | (11.1) | 59.4 |
Amortization of Actuarial Gain (Loss) |  | (2.3) |  |
Amortization of Prior Service Credit (Cost) |  | 9.2 | 10.4 |
Change for the Year |  | (4.2) | 69.8 |
Benefit Plans (Textuals) [Abstract] |  |  |  |
Company Contributions |  | 1.3 | 1.6 |
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 |  | 13.2 | 14.7 |
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 |  | 2.0 | 2.5 |
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 |  | $ 7.7 | $ 9.9 |
Other Postretirement Benefit Plans [Member] | Indiana Michigan Power Co [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Discount Rate |  | 5.15% | 5.50% |
Actuarial Assumptions for Net Periodic Benefit Costs |  |  |  |
Discount Rate |  | 5.50% | 2.90% | 2.55%
Expected Return on Plan Assets |  | 7.25% | 5.50% | 4.75%
Health Care Trend Rates |  |  |  |
Initial |  | 7.00% | 7.50% |
Ultimate |  | 4.50% | 4.50% |
Year Ultimate Reached |  | 2030 | 2029 |
Change in Benefit Obligation |  |  |  |
Benefit Obligation as of January 1 |  | $ 101.9 | $ 118.6 |
Service Cost |  | 0.6 | 0.9 | $ 1.3
Interest Cost |  | 5.4 | 3.4 | 3.5
Actuarial (Gain) Loss |  | 3.2 | (8.7) |
Benefit Payments |  | (18.3) | (18.3) |
Participant Contributions |  | 6.0 | 6.0 |
Medicare Subsidy |  | 0.0 | 0.0 |
Benefit Obligation as of December 31 |  | 98.8 | 101.9 | 118.6
Change in Fair Value of Plan Assets |  |  |  |
Fair Value of Plan Assets as of January 1 |  | 190.5 | 248.7 |
Actual Gain (Loss) on Plan Assets |  | 26.4 | (45.9) |
Company Contributions |  | 0.0 | 0.0 |
Participant Contributions |  | 6.0 | 6.0 |
Benefit Payments |  | (18.3) | (18.3) |
Fair Value of Plan Assets as of December 31 |  | 204.6 | 190.5 | $ 248.7
Funded (Underfunded) Status as of December 31 |  | 105.8 | 88.6 |
Benefit Amounts Recognized on the Balance Sheets |  |  |  |
Other Noncurrent Assets - Employee Benefits and Pension Assets |  | 105.8 | 88.6 |
Other Current Liabilities - Accrued Short-term Benefit Liability |  | 0.0 | 0.0 |
Other Noncurrent Liabilities - Employee Benefits and Pension Obligations |  | 0.0 | 0.0 |
Funded (Underfunded) Status |  | 105.8 | 88.6 |
Components |  |  |  |
Net Actuarial Loss |  | 28.7 | 40.2 |
Prior Service Cost (Credit) |  | (3.7) | (12.4) |
Components of Change in Amounts Included in AOCI and Regulatory Assets |  |  |  |
Actuarial (Gain) Loss During the Year |  | (9.6) | 50.9 |
Amortization of Actuarial Gain (Loss) |  | (1.9) |  |
Amortization of Prior Service Credit (Cost) |  | 8.7 | 9.7 |
Change for the Year |  | (2.8) | 60.6 |
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 |  | 19.0 | 22.1 |
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 |  | 1.3 | 1.2 |
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 |  | $ 4.7 | $ 4.5 |
Other Postretirement Benefit Plans [Member] | Ohio Power Co [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Discount Rate |  | 5.15% | 5.50% |
Actuarial Assumptions for Net Periodic Benefit Costs |  |  |  |
Discount Rate |  | 5.50% | 2.90% | 2.55%
Expected Return on Plan Assets |  | 7.25% | 5.50% | 4.75%
Health Care Trend Rates |  |  |  |
Initial |  | 7.00% | 7.50% |
Ultimate |  | 4.50% | 4.50% |
Year Ultimate Reached |  | 2030 | 2029 |
Change in Benefit Obligation |  |  |  |
Benefit Obligation as of January 1 |  | $ 88.9 | $ 104.9 |
Service Cost |  | 0.4 | 0.6 | $ 0.8
Interest Cost |  | 4.7 | 3.0 | 3.0
Actuarial (Gain) Loss |  | 2.2 | (8.9) |
Benefit Payments |  | (15.0) | (15.5) |
Participant Contributions |  | 4.7 | 4.8 |
Medicare Subsidy |  | 0.0 | 0.0 |
Benefit Obligation as of December 31 |  | 85.9 | 88.9 | 104.9
Change in Fair Value of Plan Assets |  |  |  |
Fair Value of Plan Assets as of January 1 |  | 166.2 | 220.0 |
Actual Gain (Loss) on Plan Assets |  | 21.9 | (43.1) |
Company Contributions |  | 0.0 | 0.0 |
Participant Contributions |  | 4.7 | 4.8 |
Benefit Payments |  | (15.0) | (15.5) |
Fair Value of Plan Assets as of December 31 |  | 177.8 | 166.2 | $ 220.0
Funded (Underfunded) Status as of December 31 |  | 91.9 | 77.3 |
Benefit Amounts Recognized on the Balance Sheets |  |  |  |
Other Noncurrent Assets - Employee Benefits and Pension Assets |  | 91.9 | 77.3 |
Other Current Liabilities - Accrued Short-term Benefit Liability |  | 0.0 | 0.0 |
Other Noncurrent Liabilities - Employee Benefits and Pension Obligations |  | 0.0 | 0.0 |
Funded (Underfunded) Status |  | 91.9 | 77.3 |
Components |  |  |  |
Net Actuarial Loss |  | 18.1 | 27.6 |
Prior Service Cost (Credit) |  | (2.9) | (9.2) |
Components of Change in Amounts Included in AOCI and Regulatory Assets |  |  |  |
Actuarial (Gain) Loss During the Year |  | (7.9) | 46.1 |
Amortization of Actuarial Gain (Loss) |  | (1.6) |  |
Amortization of Prior Service Credit (Cost) |  | 6.3 | 7.1 |
Change for the Year |  | (3.2) | 53.2 |
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 |  | 15.2 | 18.4 |
Other Postretirement Benefit Plans [Member] | Ohio 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 |
Other Postretirement Benefit Plans [Member] | Ohio 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 |
Other Postretirement Benefit Plans [Member] | Public Service Co Of Oklahoma [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Discount Rate |  | 5.15% | 5.50% |
Actuarial Assumptions for Net Periodic Benefit Costs |  |  |  |
Discount Rate |  | 5.50% | 2.90% | 2.55%
Expected Return on Plan Assets |  | 7.25% | 5.50% | 4.75%
Health Care Trend Rates |  |  |  |
Initial |  | 7.00% | 7.50% |
Ultimate |  | 4.50% | 4.50% |
Year Ultimate Reached |  | 2030 | 2029 |
Change in Benefit Obligation |  |  |  |
Benefit Obligation as of January 1 |  | $ 45.7 | $ 54.4 |
Service Cost |  | 0.3 | 0.4 | $ 0.6
Interest Cost |  | 2.4 | 1.5 | 1.6
Actuarial (Gain) Loss |  | 0.4 | (5.2) |
Benefit Payments |  | (7.6) | (7.9) |
Participant Contributions |  | 2.5 | 2.5 |
Medicare Subsidy |  | 0.0 | 0.0 |
Benefit Obligation as of December 31 |  | 43.7 | 45.7 | 54.4
Change in Fair Value of Plan Assets |  |  |  |
Fair Value of Plan Assets as of January 1 |  | 85.4 | 114.0 |
Actual Gain (Loss) on Plan Assets |  | 9.9 | (23.2) |
Company Contributions |  | 0.0 | 0.0 |
Participant Contributions |  | 2.5 | 2.5 |
Benefit Payments |  | (7.6) | (7.9) |
Fair Value of Plan Assets as of December 31 |  | 90.2 | 85.4 | $ 114.0
Funded (Underfunded) Status as of December 31 |  | 46.5 | 39.7 |
Benefit Amounts Recognized on the Balance Sheets |  |  |  |
Other Noncurrent Assets - Employee Benefits and Pension Assets |  | 46.5 | 39.7 |
Other Current Liabilities - Accrued Short-term Benefit Liability |  | 0.0 | 0.0 |
Other Noncurrent Liabilities - Employee Benefits and Pension Obligations |  | 0.0 | 0.0 |
Funded (Underfunded) Status |  | 46.5 | 39.7 |
Components |  |  |  |
Net Actuarial Loss |  | 17.5 | 22.0 |
Prior Service Cost (Credit) |  | (1.6) | (5.6) |
Components of Change in Amounts Included in AOCI and Regulatory Assets |  |  |  |
Actuarial (Gain) Loss During the Year |  | (3.7) | 24.1 |
Amortization of Actuarial Gain (Loss) |  | (0.8) |  |
Amortization of Prior Service Credit (Cost) |  | 4.0 | 4.4 |
Change for the Year |  | (0.5) | 28.5 |
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 |  | 15.9 | 16.4 |
Other Postretirement Benefit Plans [Member] | Public Service Co Of Oklahoma [Member] | Deferred Income Taxes [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | 0.0 | 0.0 |
Other Postretirement Benefit Plans [Member] | Public Service Co Of Oklahoma [Member] | Net of Tax AOCI [Member] |  |  |  |
Recorded as |  |  |  |
Total of Amounts Included in AOCI, Income Tax Expense and Regulatory Assets |  | $ 0.0 | $ 0.0 |
Other Postretirement Benefit Plans [Member] | Southwestern Electric Power Co [Member] |  |  |  |
Actuarial Assumptions for Benefit Obligations |  |  |  |
Discount Rate |  | 5.15% | 5.50% |
Actuarial Assumptions for Net Periodic Benefit Costs |  |  |  |
Discount Rate |  | 5.50% | 2.90% | 2.55%
Expected Return on Plan Assets |  | 7.25% | 5.50% | 4.75%
Health Care Trend Rates |  |  |  |
Initial |  | 7.00% | 7.50% |
Ultimate |  | 4.50% | 4.50% |
Year Ultimate Reached |  | 2030 | 2029 |
Change in Benefit Obligation |  |  |  |
Benefit Obligation as of January 1 |  | $ 55.1 | $ 65.2 |
Service Cost |  | 0.4 | 0.6 | $ 0.8
Interest Cost |  | 2.9 | 1.8 | 1.9
Actuarial (Gain) Loss |  | 1.2 | (6.6) |
Benefit Payments |  | (8.8) | (8.8) |
Participant Contributions |  | 2.9 | 2.9 |
Medicare Subsidy |  | 0.0 | 0.0 |
Benefit Obligation as of December 31 |  | 53.7 | 55.1 | 65.2
Change in Fair Value of Plan Assets |  |  |  |
Fair Value of Plan Assets as of January 1 |  | 103.0 | 136.6 |
Actual Gain (Loss) on Plan Assets |  | 14.0 | (27.7) |
Company Contributions |  | 0.0 | 0.0 |
Participant Contributions |  | 2.9 | 2.9 |
Benefit Payments |  | (8.8) | (8.8) |
Fair Value of Plan Assets as of December 31 |  | 111.1 | 103.0 | $ 136.6
Funded (Underfunded) Status as of December 31 |  | 57.4 | 47.9 |
Benefit Amounts Recognized on the Balance Sheets |  |  |  |
Other Noncurrent Assets - Employee Benefits and Pension Assets |  | 57.4 | 47.9 |
Other Current Liabilities - Accrued Short-term Benefit Liability |  | 0.0 | 0.0 |
Other Noncurrent Liabilities - Employee Benefits and Pension Obligations |  | 0.0 | 0.0 |
Funded (Underfunded) Status |  | 57.4 | 47.9 |
Components |  |  |  |
Net Actuarial Loss |  | 18.4 | 25.0 |
Prior Service Cost (Credit) |  | (2.1) | (7.0) |
Components of Change in Amounts Included in AOCI and Regulatory Assets |  |  |  |
Actuarial (Gain) Loss During the Year |  | (5.6) | 28.5 |
Amortization of Actuarial Gain (Loss) |  | (1.0) |  |
Amortization of Prior Service Credit (Cost) |  | 4.9 | 5.3 |
Change for the Year |  | (1.7) | 33.8 |
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 |  | 10.2 | 11.2 |
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 |  | 1.3 | 1.5 |
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 |  | $ 4.8 | $ 5.3 |
[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.

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