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Benefit Plans 3 (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
American Electric Power System Retirement Savings Plans      
Cost of Company Matching Contributions $ 79.9 $ 81.8 $ 76.4
Benefit Plans Textuals [Abstract]      
Matching Contributions Provided Percentage 100.00%    
Eligible Compensation Contribution by Employee Percentage 1.00%    
Second Matching Contributions Provided Percentage 70.00%    
Second Eligible Compensation Contribution by Employee Percentage 5.00%    
Multiemployer Plans Withdrawal Obligation $ 22.0 25.0  
Noncurrent Regulatory Assets 4,142.3 [1] 3,527.0  
Noncurrent Regulatory Liabilities 8,686.3 [2] 8,378.7  
UMWA Withdrawal Obligation [Member]      
Benefit Plans Textuals [Abstract]      
Noncurrent Regulatory Assets 1.0 6.0  
AEP Texas Inc. [Member]      
American Electric Power System Retirement Savings Plans      
Cost of Company Matching Contributions $ 6.4 6.4 5.9
Benefit Plans Textuals [Abstract]      
Matching Contributions Provided Percentage 100.00%    
Eligible Compensation Contribution by Employee Percentage 1.00%    
Second Matching Contributions Provided Percentage 70.00%    
Second Eligible Compensation Contribution by Employee Percentage 5.00%    
Noncurrent Regulatory Assets $ 275.2 266.8  
Noncurrent Regulatory Liabilities 1,242.0 1,270.8  
Appalachian Power Co [Member]      
American Electric Power System Retirement Savings Plans      
Cost of Company Matching Contributions $ 7.6 7.7 7.5
Benefit Plans Textuals [Abstract]      
Matching Contributions Provided Percentage 100.00%    
Eligible Compensation Contribution by Employee Percentage 1.00%    
Second Matching Contributions Provided Percentage 70.00%    
Second Eligible Compensation Contribution by Employee Percentage 5.00%    
Noncurrent Regulatory Assets $ 757.6 686.3  
Noncurrent Regulatory Liabilities 1,238.8 1,224.7  
Indiana Michigan Power Co [Member]      
American Electric Power System Retirement Savings Plans      
Cost of Company Matching Contributions $ 10.9 11.3 11.0
Benefit Plans Textuals [Abstract]      
Matching Contributions Provided Percentage 100.00%    
Eligible Compensation Contribution by Employee Percentage 1.00%    
Second Matching Contributions Provided Percentage 70.00%    
Second Eligible Compensation Contribution by Employee Percentage 5.00%    
Noncurrent Regulatory Assets $ 410.9 404.8  
Noncurrent Regulatory Liabilities 2,447.9 2,041.9  
Ohio Power Co [Member]      
American Electric Power System Retirement Savings Plans      
Cost of Company Matching Contributions $ 7.2 7.3 6.6
Benefit Plans Textuals [Abstract]      
Matching Contributions Provided Percentage 100.00%    
Eligible Compensation Contribution by Employee Percentage 1.00%    
Second Matching Contributions Provided Percentage 70.00%    
Second Eligible Compensation Contribution by Employee Percentage 5.00%    
Noncurrent Regulatory Assets $ 293.0 385.8  
Noncurrent Regulatory Liabilities 1,020.9 1,005.2  
Public Service Co Of Oklahoma [Member]      
American Electric Power System Retirement Savings Plans      
Cost of Company Matching Contributions $ 4.6 4.9 4.6
Benefit Plans Textuals [Abstract]      
Matching Contributions Provided Percentage 100.00%    
Eligible Compensation Contribution by Employee Percentage 1.00%    
Second Matching Contributions Provided Percentage 70.00%    
Second Eligible Compensation Contribution by Employee Percentage 5.00%    
Noncurrent Regulatory Assets $ 1,037.4 375.0  
Noncurrent Regulatory Liabilities 835.3 802.2  
Southwestern Electric Power Co [Member]      
American Electric Power System Retirement Savings Plans      
Cost of Company Matching Contributions $ 6.4 6.7 6.2
Benefit Plans Textuals [Abstract]      
Matching Contributions Provided Percentage 100.00%    
Eligible Compensation Contribution by Employee Percentage 1.00%    
Second Matching Contributions Provided Percentage 70.00%    
Second Eligible Compensation Contribution by Employee Percentage 5.00%    
Noncurrent Regulatory Assets $ 1,005.3 403.1  
Noncurrent Regulatory Liabilities 806.9 863.4  
Pension Plans [Member]      
Accumulated Benefit Obligation      
Accumulated Benefit Obligation 4,892.2 5,244.2  
Underfunded Benefit Obligation      
Projected Benefit Obligation 5,187.0 5,544.5 5,236.8
Accumulated Benefit Obligation 4,892.2 5,244.2  
Fair Value of Plan Assets 5,352.9 5,556.6 5,015.4
Estimated Future Benefit Payments and Contributions      
Expected Contributions and Payments During 2022 133.6    
Components of Net Periodic Benefit Cost      
Service Cost 129.2 111.9 95.5
Interest Cost 137.2 167.9 204.4
Expected Return on Plan Assets (229.7) (264.9) (296.0)
Amortization of Prior Service Cost (Credit) 0.0 0.0 0.0
Amortization of Net Actuarial Loss 101.5 93.7 57.6
Settlements 0.0 0.0 0.0
Net Periodic Benefit Cost (Credit) 138.2 108.6 61.5
Capitalized Portion (55.7) (47.0) (38.6)
Net Periodic Benefit Cost (Credit) Recognized in Expense 82.5 61.6 22.9
Pension Plans [Member] | Pension Payments [Member]      
Estimated Future Benefit Payments and Contributions      
2022 378.1    
2023 380.8    
2024 381.1    
2025 373.7    
2026 373.6    
Years 2027 to 2031, in Total 1,722.9    
Pension Plans [Member] | AEP Texas Inc. [Member]      
Accumulated Benefit Obligation      
Accumulated Benefit Obligation 394.7 428.1  
Underfunded Benefit Obligation      
Projected Benefit Obligation 419.8 453.2 441.2
Accumulated Benefit Obligation 394.7 428.1  
Fair Value of Plan Assets 444.9 474.0 435.1
Estimated Future Benefit Payments and Contributions      
Expected Contributions and Payments During 2022 5.9    
Components of Net Periodic Benefit Cost      
Service Cost 11.8 10.0 8.6
Interest Cost 11.2 13.9 17.5
Expected Return on Plan Assets (19.5) (22.7) (25.8)
Amortization of Prior Service Cost (Credit) 0.0 0.0 0.0
Amortization of Net Actuarial Loss 8.3 7.8 4.9
Net Periodic Benefit Cost (Credit) 11.8 9.0 5.2
Capitalized Portion (6.6) (5.5) (4.5)
Net Periodic Benefit Cost (Credit) Recognized in Expense 5.2 3.5 0.7
Pension Plans [Member] | AEP Texas Inc. [Member] | Pension Payments [Member]      
Estimated Future Benefit Payments and Contributions      
2022 36.3    
2023 35.9    
2024 35.8    
2025 34.9    
2026 34.7    
Years 2027 to 2031, in Total 145.5    
Pension Plans [Member] | Appalachian Power Co [Member]      
Accumulated Benefit Obligation      
Accumulated Benefit Obligation 597.4 646.0  
Underfunded Benefit Obligation      
Projected Benefit Obligation 621.7 670.8 647.2
Accumulated Benefit Obligation 597.4 646.0  
Fair Value of Plan Assets 683.3 701.3 637.0
Estimated Future Benefit Payments and Contributions      
Expected Contributions and Payments During 2022 1.4    
Components of Net Periodic Benefit Cost      
Service Cost 11.9 10.5 9.4
Interest Cost 16.4 20.3 25.2
Expected Return on Plan Assets (29.1) (33.6) (37.4)
Amortization of Prior Service Cost (Credit) 0.0 0.0 0.0
Amortization of Net Actuarial Loss 12.0 11.2 7.0
Net Periodic Benefit Cost (Credit) 11.2 8.4 4.2
Capitalized Portion (5.2) (4.5) (4.0)
Net Periodic Benefit Cost (Credit) Recognized in Expense 6.0 3.9 0.2
Pension Plans [Member] | Appalachian Power Co [Member] | Pension Payments [Member]      
Estimated Future Benefit Payments and Contributions      
2022 43.9    
2023 45.0    
2024 45.5    
2025 43.1    
2026 43.5    
Years 2027 to 2031, in Total 202.9    
Pension Plans [Member] | Indiana Michigan Power Co [Member]      
Accumulated Benefit Obligation      
Accumulated Benefit Obligation 576.4 616.6  
Underfunded Benefit Obligation      
Projected Benefit Obligation 612.1 653.3 616.1
Accumulated Benefit Obligation 576.4 616.6  
Fair Value of Plan Assets 681.5 698.1 630.5
Estimated Future Benefit Payments and Contributions      
Expected Contributions and Payments During 2022 1.1    
Components of Net Periodic Benefit Cost      
Service Cost 17.5 15.4 13.4
Interest Cost 16.2 19.7 23.8
Expected Return on Plan Assets (28.9) (33.3) (36.8)
Amortization of Prior Service Cost (Credit) 0.0 0.0 0.0
Amortization of Net Actuarial Loss 11.7 10.8 6.6
Net Periodic Benefit Cost (Credit) 16.5 12.6 7.0
Capitalized Portion (4.9) (4.3) (3.4)
Net Periodic Benefit Cost (Credit) Recognized in Expense 11.6 8.3 3.6
Pension Plans [Member] | Indiana Michigan Power Co [Member] | Pension Payments [Member]      
Estimated Future Benefit Payments and Contributions      
2022 41.3    
2023 40.9    
2024 42.1    
2025 42.0    
2026 42.2    
Years 2027 to 2031, in Total 201.8    
Pension Plans [Member] | Ohio Power Co [Member]      
Accumulated Benefit Obligation      
Accumulated Benefit Obligation 440.3 479.4  
Underfunded Benefit Obligation      
Projected Benefit Obligation 470.7 510.3 487.8
Accumulated Benefit Obligation 440.3 479.4  
Fair Value of Plan Assets 524.8 543.1 499.1
Components of Net Periodic Benefit Cost      
Service Cost 11.4 9.7 7.9
Interest Cost 12.5 15.4 19.1
Expected Return on Plan Assets (22.3) (26.3) (29.3)
Amortization of Prior Service Cost (Credit) 0.0 0.0 0.0
Amortization of Net Actuarial Loss 9.1 8.5 5.3
Net Periodic Benefit Cost (Credit) 10.7 7.3 3.0
Capitalized Portion (6.2) (5.0) (3.7)
Net Periodic Benefit Cost (Credit) Recognized in Expense 4.5 2.3 (0.7)
Pension Plans [Member] | Ohio Power Co [Member] | Pension Payments [Member]      
Estimated Future Benefit Payments and Contributions      
2022 35.1    
2023 33.7    
2024 32.9    
2025 33.0    
2026 32.4    
Years 2027 to 2031, in Total 149.1    
Pension Plans [Member] | Public Service Co Of Oklahoma [Member]      
Accumulated Benefit Obligation      
Accumulated Benefit Obligation 233.6 259.9  
Underfunded Benefit Obligation      
Projected Benefit Obligation 252.6 279.9 267.5
Accumulated Benefit Obligation 233.6 259.9  
Fair Value of Plan Assets 286.2 299.8 276.2
Estimated Future Benefit Payments and Contributions      
Expected Contributions and Payments During 2022 0.1    
Components of Net Periodic Benefit Cost      
Service Cost 8.0 7.3 6.5
Interest Cost 6.7 8.5 10.6
Expected Return on Plan Assets (12.3) (14.5) (16.3)
Amortization of Prior Service Cost (Credit) 0.0 0.0 0.0
Amortization of Net Actuarial Loss 4.9 4.7 2.9
Net Periodic Benefit Cost (Credit) 7.3 6.0 3.7
Capitalized Portion (3.4) (2.8) (2.4)
Net Periodic Benefit Cost (Credit) Recognized in Expense 3.9 3.2 1.3
Pension Plans [Member] | Public Service Co Of Oklahoma [Member] | Pension Payments [Member]      
Estimated Future Benefit Payments and Contributions      
2022 20.3    
2023 21.3    
2024 20.5    
2025 20.4    
2026 20.0    
Years 2027 to 2031, in Total 87.1    
Pension Plans [Member] | Southwestern Electric Power Co [Member]      
Accumulated Benefit Obligation      
Accumulated Benefit Obligation 292.7 308.5  
Underfunded Benefit Obligation      
Projected Benefit Obligation 317.7 334.5 314.2
Accumulated Benefit Obligation 292.7 308.5  
Fair Value of Plan Assets 308.3 326.9 296.9
Underfunded Status, Projected Benefit Obligation (9.4) (7.6)  
Estimated Future Benefit Payments and Contributions      
Expected Contributions and Payments During 2022 6.5    
Components of Net Periodic Benefit Cost      
Service Cost 11.2 9.9 8.6
Interest Cost 8.5 10.2 12.4
Expected Return on Plan Assets (13.5) (15.7) (17.7)
Amortization of Prior Service Cost (Credit) 0.0 0.0 0.0
Amortization of Net Actuarial Loss 6.2 5.7 3.4
Net Periodic Benefit Cost (Credit) 12.4 10.1 6.7
Capitalized Portion (4.1) (3.4) (2.9)
Net Periodic Benefit Cost (Credit) Recognized in Expense 8.3 6.7 3.8
Pension Plans [Member] | Southwestern Electric Power Co [Member] | Pension Payments [Member]      
Estimated Future Benefit Payments and Contributions      
2022 24.7    
2023 25.4    
2024 25.5    
2025 25.8    
2026 27.3    
Years 2027 to 2031, in Total 112.4    
Qualified Pension Plans [Member]      
Accumulated Benefit Obligation      
Accumulated Benefit Obligation 4,822.5 5,171.3  
Underfunded Benefit Obligation      
Accumulated Benefit Obligation 4,822.5 5,171.3  
Qualified Pension Plans [Member] | AEP Texas Inc. [Member]      
Accumulated Benefit Obligation      
Accumulated Benefit Obligation 391.4 424.5  
Underfunded Benefit Obligation      
Accumulated Benefit Obligation 391.4 424.5  
Qualified Pension Plans [Member] | Appalachian Power Co [Member]      
Accumulated Benefit Obligation      
Accumulated Benefit Obligation 597.0 645.8  
Underfunded Benefit Obligation      
Accumulated Benefit Obligation 597.0 645.8  
Qualified Pension Plans [Member] | Indiana Michigan Power Co [Member]      
Accumulated Benefit Obligation      
Accumulated Benefit Obligation 575.2 615.8  
Underfunded Benefit Obligation      
Accumulated Benefit Obligation 575.2 615.8  
Qualified Pension Plans [Member] | Ohio Power Co [Member]      
Accumulated Benefit Obligation      
Accumulated Benefit Obligation 440.0 479.2  
Underfunded Benefit Obligation      
Accumulated Benefit Obligation 440.0 479.2  
Qualified Pension Plans [Member] | Public Service Co Of Oklahoma [Member]      
Accumulated Benefit Obligation      
Accumulated Benefit Obligation 232.1 258.3  
Underfunded Benefit Obligation      
Accumulated Benefit Obligation 232.1 258.3  
Qualified Pension Plans [Member] | Southwestern Electric Power Co [Member]      
Accumulated Benefit Obligation      
Accumulated Benefit Obligation 291.4 307.1  
Underfunded Benefit Obligation      
Accumulated Benefit Obligation 291.4 307.1  
Nonqualified Pension Plans [Member]      
Accumulated Benefit Obligation      
Accumulated Benefit Obligation 69.7 72.9  
Underfunded Benefit Obligation      
Projected Benefit Obligation 78.4 81.4  
Accumulated Benefit Obligation 69.7 72.9  
Fair Value of Plan Assets 0.0 0.0  
Underfunded Status, Projected Benefit Obligation (78.4) (81.4)  
Underfunded Status, Accumulated Benefit Obligation (69.7) (72.9)  
Nonqualified Pension Plans [Member] | AEP Texas Inc. [Member]      
Accumulated Benefit Obligation      
Accumulated Benefit Obligation 3.3 3.6  
Underfunded Benefit Obligation      
Projected Benefit Obligation 3.6 3.9  
Accumulated Benefit Obligation 3.3 3.6  
Fair Value of Plan Assets 0.0 0.0  
Underfunded Status, Projected Benefit Obligation (3.6) (3.9)  
Underfunded Status, Accumulated Benefit Obligation (3.3) (3.6)  
Nonqualified Pension Plans [Member] | Appalachian Power Co [Member]      
Accumulated Benefit Obligation      
Accumulated Benefit Obligation 0.4 0.2  
Underfunded Benefit Obligation      
Projected Benefit Obligation 0.8 0.5  
Accumulated Benefit Obligation 0.4 0.2  
Fair Value of Plan Assets 0.0 0.0  
Underfunded Status, Projected Benefit Obligation (0.8) (0.5)  
Underfunded Status, Accumulated Benefit Obligation (0.4) (0.2)  
Nonqualified Pension Plans [Member] | Indiana Michigan Power Co [Member]      
Accumulated Benefit Obligation      
Accumulated Benefit Obligation 1.2 0.8  
Underfunded Benefit Obligation      
Projected Benefit Obligation 1.9 1.7  
Accumulated Benefit Obligation 1.2 0.8  
Fair Value of Plan Assets 0.0 0.0  
Underfunded Status, Projected Benefit Obligation (1.9) (1.7)  
Underfunded Status, Accumulated Benefit Obligation (1.2) (0.8)  
Nonqualified Pension Plans [Member] | Ohio Power Co [Member]      
Accumulated Benefit Obligation      
Accumulated Benefit Obligation 0.3 0.2  
Underfunded Benefit Obligation      
Projected Benefit Obligation 0.7 0.6  
Accumulated Benefit Obligation 0.3 0.2  
Fair Value of Plan Assets 0.0 0.0  
Underfunded Status, Projected Benefit Obligation (0.7) (0.6)  
Underfunded Status, Accumulated Benefit Obligation (0.3) (0.2)  
Nonqualified Pension Plans [Member] | Public Service Co Of Oklahoma [Member]      
Accumulated Benefit Obligation      
Accumulated Benefit Obligation 1.5 1.6  
Underfunded Benefit Obligation      
Projected Benefit Obligation 1.9 2.0  
Accumulated Benefit Obligation 1.5 1.6  
Fair Value of Plan Assets 0.0 0.0  
Underfunded Status, Projected Benefit Obligation (1.9) (2.0)  
Underfunded Status, Accumulated Benefit Obligation (1.5) (1.6)  
Nonqualified Pension Plans [Member] | Southwestern Electric Power Co [Member]      
Accumulated Benefit Obligation      
Accumulated Benefit Obligation 1.3 1.4  
Underfunded Benefit Obligation      
Accumulated Benefit Obligation 1.3 1.4  
Fair Value of Plan Assets 0.0 0.0  
Underfunded Status, Accumulated Benefit Obligation (1.3) (1.4)  
Other Postretirement Benefit Plans [Member]      
Underfunded Benefit Obligation      
Projected Benefit Obligation 1,041.3 1,210.9 1,225.4
Fair Value of Plan Assets 2,044.3 1,946.7 1,781.8
Estimated Future Benefit Payments and Contributions      
Expected Contributions and Payments During 2022 3.4    
Components of Net Periodic Benefit Cost      
Service Cost 9.5 10.0 9.5
Interest Cost 30.5 39.8 50.5
Expected Return on Plan Assets (91.1) (95.6) (93.7)
Amortization of Prior Service Cost (Credit) (70.9) (69.8) (69.1)
Amortization of Net Actuarial Loss 0.0 5.9 22.1
Settlements 0.0 0.0 0.0
Net Periodic Benefit Cost (Credit) (122.0) (109.7) (80.7)
Capitalized Portion (4.1) (4.2) (3.8)
Net Periodic Benefit Cost (Credit) Recognized in Expense (126.1) (113.9) (84.5)
Other Postretirement Benefit Plans [Member] | Benefit Payments [Member]      
Estimated Future Benefit Payments and Contributions      
2022 123.9    
2023 115.4    
2024 119.4    
2025 117.9    
2026 116.0    
Years 2027 to 2031, in Total 545.1    
Other Postretirement Benefit Plans [Member] | Medicare Subsidy Receipts [Member]      
Estimated Future Benefit Payments and Contributions      
2022 0.2    
2023 0.3    
2024 0.3    
2025 0.3    
2026 0.3    
Years 2027 to 2031, in Total 1.5    
Other Postretirement Benefit Plans [Member] | AEP Texas Inc. [Member]      
Underfunded Benefit Obligation      
Projected Benefit Obligation 80.5 96.3 97.8
Fair Value of Plan Assets 168.8 162.3 148.1
Estimated Future Benefit Payments and Contributions      
Expected Contributions and Payments During 2022 0.1    
Components of Net Periodic Benefit Cost      
Service Cost 0.7 0.8 0.8
Interest Cost 2.4 3.2 4.0
Expected Return on Plan Assets (7.5) (8.0) (7.8)
Amortization of Prior Service Cost (Credit) (6.0) (5.9) (5.9)
Amortization of Net Actuarial Loss 0.0 0.5 1.8
Net Periodic Benefit Cost (Credit) (10.4) (9.4) (7.1)
Capitalized Portion (0.4) (0.4) (0.4)
Net Periodic Benefit Cost (Credit) Recognized in Expense (10.8) (9.8) (7.5)
Other Postretirement Benefit Plans [Member] | AEP Texas Inc. [Member] | Benefit Payments [Member]      
Estimated Future Benefit Payments and Contributions      
2022 9.6    
2023 9.1    
2024 9.8    
2025 9.8    
2026 9.8    
Years 2027 to 2031, in Total 44.7    
Other Postretirement Benefit Plans [Member] | AEP Texas Inc. [Member] | Medicare Subsidy Receipts [Member]      
Estimated Future Benefit Payments and Contributions      
2022 0.0    
2023 0.0    
2024 0.0    
2025 0.0    
2026 0.0    
Years 2027 to 2031, in Total 0.0    
Other Postretirement Benefit Plans [Member] | Appalachian Power Co [Member]      
Underfunded Benefit Obligation      
Projected Benefit Obligation 167.3 198.2 203.5
Fair Value of Plan Assets 302.3 293.0 271.0
Estimated Future Benefit Payments and Contributions      
Expected Contributions and Payments During 2022 1.8    
Components of Net Periodic Benefit Cost      
Service Cost 1.0 1.0 1.0
Interest Cost 4.9 6.6 8.7
Expected Return on Plan Assets (13.5) (14.4) (14.6)
Amortization of Prior Service Cost (Credit) (10.3) (10.2) (10.1)
Amortization of Net Actuarial Loss 0.0 0.9 3.7
Net Periodic Benefit Cost (Credit) (17.9) (16.1) (11.3)
Capitalized Portion (0.4) (0.4) (0.4)
Net Periodic Benefit Cost (Credit) Recognized in Expense (18.3) (16.5) (11.7)
Other Postretirement Benefit Plans [Member] | Appalachian Power Co [Member] | Benefit Payments [Member]      
Estimated Future Benefit Payments and Contributions      
2022 20.5    
2023 19.1    
2024 19.7    
2025 19.2    
2026 18.8    
Years 2027 to 2031, in Total 87.5    
Other Postretirement Benefit Plans [Member] | Appalachian Power Co [Member] | Medicare Subsidy Receipts [Member]      
Estimated Future Benefit Payments and Contributions      
2022 0.1    
2023 0.1    
2024 0.1    
2025 0.1    
2026 0.1    
Years 2027 to 2031, in Total 0.5    
Other Postretirement Benefit Plans [Member] | Indiana Michigan Power Co [Member]      
Underfunded Benefit Obligation      
Projected Benefit Obligation 118.6 141.4 142.9
Fair Value of Plan Assets 248.7 238.2 216.3
Estimated Future Benefit Payments and Contributions      
Expected Contributions and Payments During 2022 0.0    
Components of Net Periodic Benefit Cost      
Service Cost 1.3 1.4 1.4
Interest Cost 3.5 4.7 5.8
Expected Return on Plan Assets (11.1) (11.7) (11.4)
Amortization of Prior Service Cost (Credit) (9.6) (9.5) (9.4)
Amortization of Net Actuarial Loss 0.0 0.7 2.7
Net Periodic Benefit Cost (Credit) (15.9) (14.4) (10.9)
Capitalized Portion (0.4) (0.4) (0.4)
Net Periodic Benefit Cost (Credit) Recognized in Expense (16.3) (14.8) (11.3)
Other Postretirement Benefit Plans [Member] | Indiana Michigan Power Co [Member] | Benefit Payments [Member]      
Estimated Future Benefit Payments and Contributions      
2022 15.2    
2023 14.1    
2024 14.7    
2025 14.5    
2026 14.4    
Years 2027 to 2031, in Total 66.8    
Other Postretirement Benefit Plans [Member] | Indiana Michigan Power Co [Member] | Medicare Subsidy Receipts [Member]      
Estimated Future Benefit Payments and Contributions      
2022 0.0    
2023 0.0    
2024 0.0    
2025 0.0    
2026 0.0    
Years 2027 to 2031, in Total 0.0    
Other Postretirement Benefit Plans [Member] | Ohio Power Co [Member]      
Underfunded Benefit Obligation      
Projected Benefit Obligation 104.9 126.4 130.2
Fair Value of Plan Assets 220.0 213.0 197.1
Components of Net Periodic Benefit Cost      
Service Cost 0.8 0.9 0.8
Interest Cost 3.0 4.2 5.5
Expected Return on Plan Assets (9.7) (10.5) (10.8)
Amortization of Prior Service Cost (Credit) (7.2) (7.0) (6.9)
Amortization of Net Actuarial Loss 0.0 0.7 2.5
Net Periodic Benefit Cost (Credit) (13.1) (11.7) (8.9)
Capitalized Portion (0.4) (0.5) (0.4)
Net Periodic Benefit Cost (Credit) Recognized in Expense (13.5) (12.2) (9.3)
Other Postretirement Benefit Plans [Member] | Ohio Power Co [Member] | Benefit Payments [Member]      
Estimated Future Benefit Payments and Contributions      
2022 13.5    
2023 12.5    
2024 12.9    
2025 12.7    
2026 12.3    
Years 2027 to 2031, in Total 57.1    
Other Postretirement Benefit Plans [Member] | Ohio Power Co [Member] | Medicare Subsidy Receipts [Member]      
Estimated Future Benefit Payments and Contributions      
2022 0.0    
2023 0.0    
2024 0.0    
2025 0.0    
2026 0.0    
Years 2027 to 2031, in Total 0.0    
Other Postretirement Benefit Plans [Member] | Public Service Co Of Oklahoma [Member]      
Underfunded Benefit Obligation      
Projected Benefit Obligation 54.4 64.0 64.7
Fair Value of Plan Assets 114.0 107.8 98.0
Estimated Future Benefit Payments and Contributions      
Expected Contributions and Payments During 2022 0.0    
Components of Net Periodic Benefit Cost      
Service Cost 0.6 0.7 0.6
Interest Cost 1.6 2.1 2.6
Expected Return on Plan Assets (5.0) (5.2) (5.1)
Amortization of Prior Service Cost (Credit) (4.4) (4.4) (4.3)
Amortization of Net Actuarial Loss 0.0 0.3 1.2
Net Periodic Benefit Cost (Credit) (7.2) (6.5) (5.0)
Capitalized Portion (0.3) (0.3) (0.2)
Net Periodic Benefit Cost (Credit) Recognized in Expense (7.5) (6.8) (5.2)
Other Postretirement Benefit Plans [Member] | Public Service Co Of Oklahoma [Member] | Benefit Payments [Member]      
Estimated Future Benefit Payments and Contributions      
2022 7.1    
2023 6.7    
2024 7.0    
2025 7.0    
2026 6.8    
Years 2027 to 2031, in Total 29.7    
Other Postretirement Benefit Plans [Member] | Public Service Co Of Oklahoma [Member] | Medicare Subsidy Receipts [Member]      
Estimated Future Benefit Payments and Contributions      
2022 0.0    
2023 0.0    
2024 0.0    
2025 0.0    
2026 0.0    
Years 2027 to 2031, in Total 0.0    
Other Postretirement Benefit Plans [Member] | Southwestern Electric Power Co [Member]      
Underfunded Benefit Obligation      
Projected Benefit Obligation 65.2 77.1 77.4
Fair Value of Plan Assets 136.6 129.9 117.2
Estimated Future Benefit Payments and Contributions      
Expected Contributions and Payments During 2022 0.0    
Components of Net Periodic Benefit Cost      
Service Cost 0.8 0.8 0.8
Interest Cost 1.9 2.5 3.1
Expected Return on Plan Assets (6.1) (6.3) (5.9)
Amortization of Prior Service Cost (Credit) (5.3) (5.2) (5.2)
Amortization of Net Actuarial Loss 0.0 0.4 1.4
Net Periodic Benefit Cost (Credit) (8.7) (7.8) (5.8)
Capitalized Portion (0.3) (0.3) (0.3)
Net Periodic Benefit Cost (Credit) Recognized in Expense (9.0) $ (8.1) $ (6.1)
Other Postretirement Benefit Plans [Member] | Southwestern Electric Power Co [Member] | Benefit Payments [Member]      
Estimated Future Benefit Payments and Contributions      
2022 7.7    
2023 7.4    
2024 7.9    
2025 8.0    
2026 7.9    
Years 2027 to 2031, in Total 37.1    
Other Postretirement Benefit Plans [Member] | Southwestern Electric Power Co [Member] | Medicare Subsidy Receipts [Member]      
Estimated Future Benefit Payments and Contributions      
2022 0.0    
2023 0.0    
2024 0.0    
2025 0.0    
2026 0.0    
Years 2027 to 2031, in Total $ 0.0    
[1] 2021 amounts exclude $485 million of regulatory assets classified as Assets Held for Sale on the balance sheet. See “Disposition of KPCo and KTCo” section of Note 7 for additional information.
[2] 2021 amounts exclude $148 million of regulatory liabilities classified as Liabilities Held for Sale on the balance sheet. See “Disposition of KPCo and KTCo” section of Note 7 for additional information.