Benefit Plans 3 (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
American Electric Power System Retirement Savings Plans
Cost of Company Matching Contributions	$ 81.8	$ 76.4	$ 71.8
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	$ 25.0	20.0
Noncurrent Regulatory Assets	3,527.0	3,158.8
Noncurrent Regulatory Liabilities	8,378.7	8,457.6
UMWA Withdrawal Obligation [Member]
Benefit Plans Textuals [Abstract]
Noncurrent Regulatory Assets	6.0	2.0
AEP Texas Inc. [Member]
American Electric Power System Retirement Savings Plans
Cost of Company Matching Contributions	$ 6.4	5.9	5.7
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	$ 266.8	280.6
Noncurrent Regulatory Liabilities	1,270.8	1,316.9
Appalachian Power Co [Member]
American Electric Power System Retirement Savings Plans
Cost of Company Matching Contributions	$ 7.7	7.5	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	$ 686.3	457.2
Noncurrent Regulatory Liabilities	1,224.7	1,268.7
Indiana Michigan Power Co [Member]
American Electric Power System Retirement Savings Plans
Cost of Company Matching Contributions	$ 11.3	11.0	10.5
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	$ 404.8	482.1
Noncurrent Regulatory Liabilities	2,041.9	1,891.4
Ohio Power Co [Member]
American Electric Power System Retirement Savings Plans
Cost of Company Matching Contributions	$ 7.3	6.6	6.3
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	$ 385.8	351.8
Noncurrent Regulatory Liabilities	1,005.2	1,090.9
Public Service Co Of Oklahoma [Member]
American Electric Power System Retirement Savings Plans
Cost of Company Matching Contributions	$ 4.9	4.6	4.5
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	$ 375.0	375.2
Noncurrent Regulatory Liabilities	802.2	837.2
Southwestern Electric Power Co [Member]
American Electric Power System Retirement Savings Plans
Cost of Company Matching Contributions	$ 6.7	6.2	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	$ 403.1	222.4
Noncurrent Regulatory Liabilities	863.4	892.3
Pension Plans [Member]
Accumulated Benefit Obligation
Accumulated Benefit Obligation	5,244.2	4,998.7
Underfunded Benefit Obligation
Projected Benefit Obligation	5,544.5	5,236.8	4,810.3
Accumulated Benefit Obligation	5,244.2	4,998.7
Fair Value of Plan Assets	5,556.6	5,015.4	4,695.9
Underfunded Status, Projected Benefit Obligation		(221.4)
Estimated Future Benefit Payments and Contributions
Expected Contributions and Payments During 2021	132.8
Components of Net Periodic Benefit Cost
Service Cost	111.9	95.5	97.6
Interest Cost	167.9	204.4	187.8
Expected Return on Plan Assets	(264.9)	(296.0)	(290.3)
Amortization of Prior Service Cost (Credit)	0.0	0.0	0.0
Amortization of Net Actuarial Loss	93.7	57.6	85.2
Settlements	0.0	0.0	2.6
Net Periodic Benefit Cost (Credit)	108.6	61.5	82.9
Capitalized Portion	(47.0)	(38.6)	(41.1)
Net Periodic Benefit Cost (Credit) Recognized in Expense	61.6	22.9	41.8
Pension Plans [Member] | Pension Payments [Member]
Estimated Future Benefit Payments and Contributions
2021	385.3
2022	382.8
2023	384.3
2024	384.0
2025	377.1
Years 2026 to 2030, in Total	1,763.1
Pension Plans [Member] | AEP Texas Inc. [Member]
Accumulated Benefit Obligation
Accumulated Benefit Obligation	428.1	421.1
Underfunded Benefit Obligation
Projected Benefit Obligation	453.2	441.2	409.3
Accumulated Benefit Obligation	428.1	421.1
Fair Value of Plan Assets	474.0	435.1	410.7
Underfunded Status, Projected Benefit Obligation		(6.1)
Estimated Future Benefit Payments and Contributions
Expected Contributions and Payments During 2021	5.1
Components of Net Periodic Benefit Cost
Service Cost	10.0	8.6	9.2
Interest Cost	13.9	17.5	16.0
Expected Return on Plan Assets	(22.7)	(25.8)	(25.6)
Amortization of Prior Service Cost (Credit)	0.0	0.0	0.0
Amortization of Net Actuarial Loss	7.8	4.9	7.2
Net Periodic Benefit Cost (Credit)	9.0	5.2	6.8
Capitalized Portion	(5.5)	(4.5)	(4.8)
Net Periodic Benefit Cost (Credit) Recognized in Expense	3.5	0.7	2.0
Pension Plans [Member] | AEP Texas Inc. [Member] | Pension Payments [Member]
Estimated Future Benefit Payments and Contributions
2021	36.3
2022	35.9
2023	36.1
2024	35.9
2025	35.2
Years 2026 to 2030, in Total	154.1
Pension Plans [Member] | Appalachian Power Co [Member]
Accumulated Benefit Obligation
Accumulated Benefit Obligation	646.0	627.5
Underfunded Benefit Obligation
Projected Benefit Obligation	670.8	647.2	603.1
Accumulated Benefit Obligation	646.0	627.5
Fair Value of Plan Assets	701.3	637.0	593.3
Underfunded Status, Projected Benefit Obligation		(10.2)
Estimated Future Benefit Payments and Contributions
Expected Contributions and Payments During 2021	1.8
Components of Net Periodic Benefit Cost
Service Cost	10.5	9.4	9.3
Interest Cost	20.3	25.2	23.5
Expected Return on Plan Assets	(33.6)	(37.4)	(36.6)
Amortization of Prior Service Cost (Credit)	0.0	0.0	0.0
Amortization of Net Actuarial Loss	11.2	7.0	10.6
Net Periodic Benefit Cost (Credit)	8.4	4.2	6.8
Capitalized Portion	(4.5)	(4.0)	(3.8)
Net Periodic Benefit Cost (Credit) Recognized in Expense	3.9	0.2	3.0
Pension Plans [Member] | Appalachian Power Co [Member] | Pension Payments [Member]
Estimated Future Benefit Payments and Contributions
2021	44.7
2022	45.1
2023	45.1
2024	45.7
2025	44.0
Years 2026 to 2030, in Total	209.7
Pension Plans [Member] | Indiana Michigan Power Co [Member]
Accumulated Benefit Obligation
Accumulated Benefit Obligation	616.6	586.9
Underfunded Benefit Obligation
Projected Benefit Obligation	653.3	616.1	567.0
Accumulated Benefit Obligation	616.6	586.9
Fair Value of Plan Assets	698.1	630.5	583.8
Estimated Future Benefit Payments and Contributions
Expected Contributions and Payments During 2021	1.3
Components of Net Periodic Benefit Cost
Service Cost	15.4	13.4	13.6
Interest Cost	19.7	23.8	22.1
Expected Return on Plan Assets	(33.3)	(36.8)	(35.7)
Amortization of Prior Service Cost (Credit)	0.0	0.0	0.0
Amortization of Net Actuarial Loss	10.8	6.6	9.8
Net Periodic Benefit Cost (Credit)	12.6	7.0	9.8
Capitalized Portion	(4.3)	(3.4)	(5.6)
Net Periodic Benefit Cost (Credit) Recognized in Expense	8.3	3.6	4.2
Pension Plans [Member] | Indiana Michigan Power Co [Member] | Pension Payments [Member]
Estimated Future Benefit Payments and Contributions
2021	40.2
2022	42.4
2023	41.5
2024	42.7
2025	42.7
Years 2026 to 2030, in Total	205.2
Pension Plans [Member] | Ohio Power Co [Member]
Accumulated Benefit Obligation
Accumulated Benefit Obligation	479.4	464.3
Underfunded Benefit Obligation
Projected Benefit Obligation	510.3	487.8	453.9
Accumulated Benefit Obligation	479.4	464.3
Fair Value of Plan Assets	543.1	499.1	466.1
Components of Net Periodic Benefit Cost
Service Cost	9.7	7.9	7.7
Interest Cost	15.4	19.1	17.7
Expected Return on Plan Assets	(26.3)	(29.3)	(28.8)
Amortization of Prior Service Cost (Credit)	0.0	0.0	0.0
Amortization of Net Actuarial Loss	8.5	5.3	8.0
Net Periodic Benefit Cost (Credit)	7.3	3.0	4.6
Capitalized Portion	(5.0)	(3.7)	(3.6)
Net Periodic Benefit Cost (Credit) Recognized in Expense	2.3	(0.7)	1.0
Pension Plans [Member] | Ohio Power Co [Member] | Pension Payments [Member]
Estimated Future Benefit Payments and Contributions
2021	35.4
2022	36.0
2023	34.2
2024	34.0
2025	33.3
Years 2026 to 2030, in Total	155.0
Pension Plans [Member] | Public Service Co Of Oklahoma [Member]
Accumulated Benefit Obligation
Accumulated Benefit Obligation	259.9	250.5
Underfunded Benefit Obligation
Projected Benefit Obligation	279.9	267.5	253.8
Accumulated Benefit Obligation	259.9	250.5
Fair Value of Plan Assets	299.8	276.2	261.2
Estimated Future Benefit Payments and Contributions
Expected Contributions and Payments During 2021	0.1
Components of Net Periodic Benefit Cost
Service Cost	7.3	6.5	7.0
Interest Cost	8.5	10.6	9.9
Expected Return on Plan Assets	(14.5)	(16.3)	(16.1)
Amortization of Prior Service Cost (Credit)	0.0	0.0	0.0
Amortization of Net Actuarial Loss	4.7	2.9	4.4
Net Periodic Benefit Cost (Credit)	6.0	3.7	5.2
Capitalized Portion	(2.8)	(2.4)	(2.6)
Net Periodic Benefit Cost (Credit) Recognized in Expense	3.2	1.3	2.6
Pension Plans [Member] | Public Service Co Of Oklahoma [Member] | Pension Payments [Member]
Estimated Future Benefit Payments and Contributions
2021	21.8
2022	21.2
2023	22.3
2024	21.9
2025	21.1
Years 2026 to 2030, in Total	94.8
Pension Plans [Member] | Southwestern Electric Power Co [Member]
Accumulated Benefit Obligation
Accumulated Benefit Obligation	308.5	293.2
Underfunded Benefit Obligation
Projected Benefit Obligation	334.5	314.2	291.4
Accumulated Benefit Obligation	308.5	293.2
Fair Value of Plan Assets	326.9	296.9	281.0
Underfunded Status, Projected Benefit Obligation	(7.6)	(17.3)
Estimated Future Benefit Payments and Contributions
Expected Contributions and Payments During 2021	7.1
Components of Net Periodic Benefit Cost
Service Cost	9.9	8.6	9.3
Interest Cost	10.2	12.4	11.3
Expected Return on Plan Assets	(15.7)	(17.7)	(17.3)
Amortization of Prior Service Cost (Credit)	0.0	0.0	0.0
Amortization of Net Actuarial Loss	5.7	3.4	5.1
Settlements	0.0	0.0	0.4
Net Periodic Benefit Cost (Credit)	10.1	6.7	8.8
Capitalized Portion	(3.4)	(2.9)	(3.1)
Net Periodic Benefit Cost (Credit) Recognized in Expense	6.7	3.8	5.7
Pension Plans [Member] | Southwestern Electric Power Co [Member] | Pension Payments [Member]
Estimated Future Benefit Payments and Contributions
2021	25.2
2022	25.4
2023	25.7
2024	25.7
2025	25.3
Years 2026 to 2030, in Total	115.7
Qualified Pension Plans [Member]
Accumulated Benefit Obligation
Accumulated Benefit Obligation	5,171.3	4,929.0
Underfunded Benefit Obligation
Accumulated Benefit Obligation	5,171.3	4,929.0
Qualified Pension Plans [Member] | AEP Texas Inc. [Member]
Accumulated Benefit Obligation
Accumulated Benefit Obligation	424.5	417.5
Underfunded Benefit Obligation
Accumulated Benefit Obligation	424.5	417.5
Qualified Pension Plans [Member] | Appalachian Power Co [Member]
Accumulated Benefit Obligation
Accumulated Benefit Obligation	645.8	627.3
Underfunded Benefit Obligation
Accumulated Benefit Obligation	645.8	627.3
Qualified Pension Plans [Member] | Indiana Michigan Power Co [Member]
Accumulated Benefit Obligation
Accumulated Benefit Obligation	615.8	586.3
Underfunded Benefit Obligation
Accumulated Benefit Obligation	615.8	586.3
Qualified Pension Plans [Member] | Ohio Power Co [Member]
Accumulated Benefit Obligation
Accumulated Benefit Obligation	479.2	464.2
Underfunded Benefit Obligation
Accumulated Benefit Obligation	479.2	464.2
Qualified Pension Plans [Member] | Public Service Co Of Oklahoma [Member]
Accumulated Benefit Obligation
Accumulated Benefit Obligation	258.3	248.9
Underfunded Benefit Obligation
Accumulated Benefit Obligation	258.3	248.9
Qualified Pension Plans [Member] | Southwestern Electric Power Co [Member]
Accumulated Benefit Obligation
Accumulated Benefit Obligation	307.1	291.9
Underfunded Benefit Obligation
Accumulated Benefit Obligation	307.1	291.9
Nonqualified Pension Plans [Member]
Accumulated Benefit Obligation
Accumulated Benefit Obligation	72.9	69.7
Underfunded Benefit Obligation
Projected Benefit Obligation	81.4
Accumulated Benefit Obligation	72.9	69.7
Fair Value of Plan Assets	0.0	0.0
Underfunded Status, Projected Benefit Obligation	(81.4)
Underfunded Status, Accumulated Benefit Obligation	(72.9)	(69.7)
Nonqualified Pension Plans [Member] | AEP Texas Inc. [Member]
Accumulated Benefit Obligation
Accumulated Benefit Obligation	3.6	3.6
Underfunded Benefit Obligation
Projected Benefit Obligation	3.9
Accumulated Benefit Obligation	3.6	3.6
Fair Value of Plan Assets	0.0	0.0
Underfunded Status, Projected Benefit Obligation	(3.9)
Underfunded Status, Accumulated Benefit Obligation	(3.6)	(3.6)
Nonqualified Pension Plans [Member] | Appalachian Power Co [Member]
Accumulated Benefit Obligation
Accumulated Benefit Obligation	0.2	0.2
Underfunded Benefit Obligation
Projected Benefit Obligation	0.5
Accumulated Benefit Obligation	0.2	0.2
Fair Value of Plan Assets	0.0	0.0
Underfunded Status, Projected Benefit Obligation	(0.5)
Underfunded Status, Accumulated Benefit Obligation	(0.2)	(0.2)
Nonqualified Pension Plans [Member] | Indiana Michigan Power Co [Member]
Accumulated Benefit Obligation
Accumulated Benefit Obligation	0.8	0.6
Underfunded Benefit Obligation
Projected Benefit Obligation	1.7	1.5
Accumulated Benefit Obligation	0.8	0.6
Fair Value of Plan Assets	0.0	0.0
Underfunded Status, Projected Benefit Obligation	(1.7)	(1.5)
Underfunded Status, Accumulated Benefit Obligation	(0.8)	(0.6)
Nonqualified Pension Plans [Member] | Ohio Power Co [Member]
Accumulated Benefit Obligation
Accumulated Benefit Obligation	0.2	0.1
Underfunded Benefit Obligation
Projected Benefit Obligation	0.6	0.4
Accumulated Benefit Obligation	0.2	0.1
Fair Value of Plan Assets	0.0	0.0
Underfunded Status, Projected Benefit Obligation	(0.6)	(0.4)
Underfunded Status, Accumulated Benefit Obligation	(0.2)	(0.1)
Nonqualified Pension Plans [Member] | Public Service Co Of Oklahoma [Member]
Accumulated Benefit Obligation
Accumulated Benefit Obligation	1.6	1.6
Underfunded Benefit Obligation
Projected Benefit Obligation	2.0	1.9
Accumulated Benefit Obligation	1.6	1.6
Fair Value of Plan Assets	0.0	0.0
Underfunded Status, Projected Benefit Obligation	(2.0)	(1.9)
Underfunded Status, Accumulated Benefit Obligation	(1.6)	(1.6)
Nonqualified Pension Plans [Member] | Southwestern Electric Power Co [Member]
Accumulated Benefit Obligation
Accumulated Benefit Obligation	1.4	1.3
Underfunded Benefit Obligation
Accumulated Benefit Obligation	1.4	1.3
Fair Value of Plan Assets	0.0	0.0
Underfunded Status, Accumulated Benefit Obligation	(1.4)	(1.3)
Other Postretirement Benefit Plans [Member]
Underfunded Benefit Obligation
Projected Benefit Obligation	1,210.9	1,225.4	1,194.5
Fair Value of Plan Assets	1,946.7	1,781.8	1,534.2
Estimated Future Benefit Payments and Contributions
Expected Contributions and Payments During 2021	3.1
Components of Net Periodic Benefit Cost
Service Cost	10.0	9.5	11.6
Interest Cost	39.8	50.5	47.4
Expected Return on Plan Assets	(95.6)	(93.7)	(102.2)
Amortization of Prior Service Cost (Credit)	(69.8)	(69.1)	(69.1)
Amortization of Net Actuarial Loss	5.9	22.1	10.5
Settlements	0.0	0.0	0.0
Net Periodic Benefit Cost (Credit)	(109.7)	(80.7)	(101.8)
Capitalized Portion	(4.2)	(3.8)	(4.9)
Net Periodic Benefit Cost (Credit) Recognized in Expense	(113.9)	(84.5)	(106.7)
Other Postretirement Benefit Plans [Member] | Benefit Payments [Member]
Estimated Future Benefit Payments and Contributions
2021	121.6
2022	122.5
2023	117.4
2024	121.9
2025	120.9
Years 2026 to 2030, in Total	573.9
Other Postretirement Benefit Plans [Member] | Medicare Subsidy Receipts [Member]
Estimated Future Benefit Payments and Contributions
2021	0.2
2022	0.2
2023	0.3
2024	0.3
2025	0.3
Years 2026 to 2030, in Total	1.5
Other Postretirement Benefit Plans [Member] | AEP Texas Inc. [Member]
Underfunded Benefit Obligation
Projected Benefit Obligation	96.3	97.8	95.9
Fair Value of Plan Assets	162.3	148.1	129.9
Estimated Future Benefit Payments and Contributions
Expected Contributions and Payments During 2021	0.1
Components of Net Periodic Benefit Cost
Service Cost	0.8	0.8	0.9
Interest Cost	3.2	4.0	3.8
Expected Return on Plan Assets	(8.0)	(7.8)	(8.6)
Amortization of Prior Service Cost (Credit)	(5.9)	(5.9)	(5.9)
Amortization of Net Actuarial Loss	0.5	1.8	0.8
Net Periodic Benefit Cost (Credit)	(9.4)	(7.1)	(9.0)
Capitalized Portion	(0.4)	(0.4)	(0.5)
Net Periodic Benefit Cost (Credit) Recognized in Expense	(9.8)	(7.5)	(9.5)
Other Postretirement Benefit Plans [Member] | AEP Texas Inc. [Member] | Benefit Payments [Member]
Estimated Future Benefit Payments and Contributions
2021	9.5
2022	9.9
2023	9.7
2024	10.3
2025	10.4
Years 2026 to 2030, in Total	48.6
Other Postretirement Benefit Plans [Member] | AEP Texas Inc. [Member] | Medicare Subsidy Receipts [Member]
Estimated Future Benefit Payments and Contributions
2021	0.0
2022	0.0
2023	0.0
2024	0.0
2025	0.0
Years 2026 to 2030, in Total	0.0
Other Postretirement Benefit Plans [Member] | Appalachian Power Co [Member]
Underfunded Benefit Obligation
Projected Benefit Obligation	198.2	203.5	205.5
Fair Value of Plan Assets	293.0	271.0	238.4
Estimated Future Benefit Payments and Contributions
Expected Contributions and Payments During 2021	1.8
Components of Net Periodic Benefit Cost
Service Cost	1.0	1.0	1.1
Interest Cost	6.6	8.7	8.2
Expected Return on Plan Assets	(14.4)	(14.6)	(16.0)
Amortization of Prior Service Cost (Credit)	(10.2)	(10.1)	(10.0)
Amortization of Net Actuarial Loss	0.9	3.7	1.9
Net Periodic Benefit Cost (Credit)	(16.1)	(11.3)	(14.8)
Capitalized Portion	(0.4)	(0.4)	(0.5)
Net Periodic Benefit Cost (Credit) Recognized in Expense	(16.5)	(11.7)	(15.3)
Other Postretirement Benefit Plans [Member] | Appalachian Power Co [Member] | Benefit Payments [Member]
Estimated Future Benefit Payments and Contributions
2021	21.1
2022	20.8
2023	19.8
2024	20.5
2025	20.0
Years 2026 to 2030, in Total	93.3
Other Postretirement Benefit Plans [Member] | Appalachian Power Co [Member] | Medicare Subsidy Receipts [Member]
Estimated Future Benefit Payments and Contributions
2021	0.1
2022	0.1
2023	0.1
2024	0.1
2025	0.1
Years 2026 to 2030, in Total	0.6
Other Postretirement Benefit Plans [Member] | Indiana Michigan Power Co [Member]
Underfunded Benefit Obligation
Projected Benefit Obligation	141.4	142.9	138.3
Fair Value of Plan Assets	238.2	216.3	187.3
Estimated Future Benefit Payments and Contributions
Expected Contributions and Payments During 2021	0.0
Components of Net Periodic Benefit Cost
Service Cost	1.4	1.4	1.6
Interest Cost	4.7	5.8	5.4
Expected Return on Plan Assets	(11.7)	(11.4)	(12.3)
Amortization of Prior Service Cost (Credit)	(9.5)	(9.4)	(9.5)
Amortization of Net Actuarial Loss	0.7	2.7	1.2
Net Periodic Benefit Cost (Credit)	(14.4)	(10.9)	(13.6)
Capitalized Portion	(0.4)	(0.4)	(0.7)
Net Periodic Benefit Cost (Credit) Recognized in Expense	(14.8)	(11.3)	(14.3)
Other Postretirement Benefit Plans [Member] | Indiana Michigan Power Co [Member] | Benefit Payments [Member]
Estimated Future Benefit Payments and Contributions
2021	15.1
2022	15.3
2023	14.7
2024	15.3
2025	15.1
Years 2026 to 2030, in Total	70.9
Other Postretirement Benefit Plans [Member] | Indiana Michigan Power Co [Member] | Medicare Subsidy Receipts [Member]
Estimated Future Benefit Payments and Contributions
2021	0.0
2022	0.0
2023	0.0
2024	0.0
2025	0.0
Years 2026 to 2030, in Total	0.0
Other Postretirement Benefit Plans [Member] | Ohio Power Co [Member]
Underfunded Benefit Obligation
Projected Benefit Obligation	126.4	130.2	129.5
Fair Value of Plan Assets	213.0	197.1	175.4
Components of Net Periodic Benefit Cost
Service Cost	0.9	0.8	0.9
Interest Cost	4.2	5.5	5.1
Expected Return on Plan Assets	(10.5)	(10.8)	(11.7)
Amortization of Prior Service Cost (Credit)	(7.0)	(6.9)	(6.9)
Amortization of Net Actuarial Loss	0.7	2.5	1.1
Net Periodic Benefit Cost (Credit)	(11.7)	(8.9)	(11.5)
Capitalized Portion	(0.5)	(0.4)	(0.4)
Net Periodic Benefit Cost (Credit) Recognized in Expense	(12.2)	(9.3)	(11.9)
Other Postretirement Benefit Plans [Member] | Ohio Power Co [Member] | Benefit Payments [Member]
Estimated Future Benefit Payments and Contributions
2021	13.7
2022	13.9
2023	13.2
2024	13.7
2025	13.4
Years 2026 to 2030, in Total	61.7
Other Postretirement Benefit Plans [Member] | Ohio Power Co [Member] | Medicare Subsidy Receipts [Member]
Estimated Future Benefit Payments and Contributions
2021	0.0
2022	0.0
2023	0.0
2024	0.0
2025	0.0
Years 2026 to 2030, in Total	0.0
Other Postretirement Benefit Plans [Member] | Public Service Co Of Oklahoma [Member]
Underfunded Benefit Obligation
Projected Benefit Obligation	64.0	64.7	62.3
Fair Value of Plan Assets	107.8	98.0	84.3
Estimated Future Benefit Payments and Contributions
Expected Contributions and Payments During 2021	0.0
Components of Net Periodic Benefit Cost
Service Cost	0.7	0.6	0.7
Interest Cost	2.1	2.6	2.5
Expected Return on Plan Assets	(5.2)	(5.1)	(5.6)
Amortization of Prior Service Cost (Credit)	(4.4)	(4.3)	(4.3)
Amortization of Net Actuarial Loss	0.3	1.2	0.5
Net Periodic Benefit Cost (Credit)	(6.5)	(5.0)	(6.2)
Capitalized Portion	(0.3)	(0.2)	(0.3)
Net Periodic Benefit Cost (Credit) Recognized in Expense	(6.8)	(5.2)	(6.5)
Other Postretirement Benefit Plans [Member] | Public Service Co Of Oklahoma [Member] | Benefit Payments [Member]
Estimated Future Benefit Payments and Contributions
2021	6.4
2022	6.7
2023	6.6
2024	6.9
2025	6.9
Years 2026 to 2030, in Total	32.1
Other Postretirement Benefit Plans [Member] | Public Service Co Of Oklahoma [Member] | Medicare Subsidy Receipts [Member]
Estimated Future Benefit Payments and Contributions
2021	0.0
2022	0.0
2023	0.0
2024	0.0
2025	0.0
Years 2026 to 2030, in Total	0.0
Other Postretirement Benefit Plans [Member] | Southwestern Electric Power Co [Member]
Underfunded Benefit Obligation
Projected Benefit Obligation	77.1	77.4	72.7
Fair Value of Plan Assets	129.9	117.2	98.5
Estimated Future Benefit Payments and Contributions
Expected Contributions and Payments During 2021	0.0
Components of Net Periodic Benefit Cost
Service Cost	0.8	0.8	0.9
Interest Cost	2.5	3.1	2.8
Expected Return on Plan Assets	(6.3)	(5.9)	(6.4)
Amortization of Prior Service Cost (Credit)	(5.2)	(5.2)	(5.2)
Amortization of Net Actuarial Loss	0.4	1.4	0.6
Settlements	0.0	0.0	0.0
Net Periodic Benefit Cost (Credit)	(7.8)	(5.8)	(7.3)
Capitalized Portion	(0.3)	(0.3)	(0.3)
Net Periodic Benefit Cost (Credit) Recognized in Expense	(8.1)	$ (6.1)	$ (7.6)
Other Postretirement Benefit Plans [Member] | Southwestern Electric Power Co [Member] | Benefit Payments [Member]
Estimated Future Benefit Payments and Contributions
2021	7.5
2022	7.8
2023	7.6
2024	8.2
2025	8.2
Years 2026 to 2030, in Total	39.1
Other Postretirement Benefit Plans [Member] | Southwestern Electric Power Co [Member] | Medicare Subsidy Receipts [Member]
Estimated Future Benefit Payments and Contributions
2021	0.0
2022	0.0
2023	0.0
2024	0.0
2025	0.0
Years 2026 to 2030, in Total	$ 0.0