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BENEFIT PLANS - Schedule of Obligation and Funded Status (Details) - USD ($) | 12 Months Ended
--- | ---
Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
Qualified Plans |  |  |
Change in Fair Value of Plan Assets |  |  |
Company Contributions | $ 0 | $ 0 |
Nonqualified Plans |  |  |
Change in Fair Value of Plan Assets |  |  |
Company Contributions | 14,000,000 | 8,000,000 |
Pension Plans |  |  |
Change in Benefit Obligation |  |  |
Benefit Obligation as of January 1, | 4,161,600,000 | 4,072,700,000 |
Service Cost | 100,600,000 | 94,300,000 | $ 123,100,000
Interest Cost | 207,400,000 | 219,200,000 | 148,200,000
Actuarial (Gain) Loss | (44,600,000) | 144,000,000.0 |
Settlements | (329,400,000) |  |
Benefit Payments | (223,800,000) | (368,600,000) |
Benefit Obligation as of December 31, | 3,871,800,000 | 4,161,600,000 | 4,072,700,000
Change in Fair Value of Plan Assets |  |  |
Fair Value of Plan Assets as of January 1, | 4,118,200,000 | 4,124,700,000 |
Actual Gain on Plan Assets | 87,200,000 | 353,800,000 |
Company Contributions | 14,000,000.0 | 8,300,000 |
Settlements | (329,400,000) |  |
Benefit Payments | (223,800,000) | (368,600,000) |
Fair Value of Plan Assets as of December 31, | 3,666,200,000 | 4,118,200,000 | 4,124,700,000
Funded (Underfunded) Status as of December 31, | (205,600,000) | (43,400,000) |
Pension Plans | AEP TEXAS INC. |  |  |
Change in Benefit Obligation |  |  |
Benefit Obligation as of January 1, | 343,100,000 | 334,100,000 |
Service Cost | 8,900,000 | 8,200,000 | 11,100,000
Interest Cost | 17,300,000 | 18,300,000 | 12,100,000
Actuarial (Gain) Loss | 5,500,000 | 20,100,000 |
Settlements | (34,800,000) |  |
Benefit Payments | (17,300,000) | (37,600,000) |
Benefit Obligation as of December 31, | 322,700,000 | 343,100,000 | 334,100,000
Change in Fair Value of Plan Assets |  |  |
Fair Value of Plan Assets as of January 1, | 332,700,000 | 335,100,000 |
Actual Gain on Plan Assets | 7,100,000 | 34,800,000 |
Company Contributions | 400,000 | 400,000 |
Settlements | (34,800,000) |  |
Benefit Payments | (17,300,000) | (37,600,000) |
Fair Value of Plan Assets as of December 31, | 288,100,000 | 332,700,000 | 335,100,000
Funded (Underfunded) Status as of December 31, | (34,600,000) | (10,400,000) |
Pension Plans | APPALACHIAN POWER COMPANY |  |  |
Change in Benefit Obligation |  |  |
Benefit Obligation as of January 1, | 504,100,000 | 485,700,000 |
Service Cost | 9,500,000 | 9,100,000 | 11,400,000
Interest Cost | 24,700,000 | 26,400,000 | 17,500,000
Actuarial (Gain) Loss | (12,900,000) | 23,200,000 |
Settlements | (42,000,000.0) |  |
Benefit Payments | (30,400,000) | (40,300,000) |
Benefit Obligation as of December 31, | 453,000,000.0 | 504,100,000 | 485,700,000
Change in Fair Value of Plan Assets |  |  |
Fair Value of Plan Assets as of January 1, | 549,800,000 | 531,700,000 |
Actual Gain on Plan Assets | 10,400,000 | 58,400,000 |
Company Contributions | 0 | 0 |
Settlements | (42,000,000.0) |  |
Benefit Payments | (30,400,000) | (40,300,000) |
Fair Value of Plan Assets as of December 31, | 487,800,000 | 549,800,000 | 531,700,000
Funded (Underfunded) Status as of December 31, | 34,800,000 | 45,700,000 |
Pension Plans | INDIANA MICHIGAN POWER COMPANY |  |  |
Change in Benefit Obligation |  |  |
Benefit Obligation as of January 1, | 477,000,000.0 | 466,800,000 |
Service Cost | 13,000,000.0 | 11,900,000 | 16,200,000
Interest Cost | 23,900,000 | 24,900,000 | 17,000,000.0
Actuarial (Gain) Loss | (8,400,000) | 8,500,000 |
Settlements | (33,100,000) |  |
Benefit Payments | (22,600,000) | (35,100,000) |
Benefit Obligation as of December 31, | 449,800,000 | 477,000,000.0 | 466,800,000
Change in Fair Value of Plan Assets |  |  |
Fair Value of Plan Assets as of January 1, | 550,600,000 | 533,700,000 |
Actual Gain on Plan Assets | 11,600,000 | 51,500,000 |
Company Contributions | 0 | 500,000 |
Settlements | (33,100,000) |  |
Benefit Payments | (22,600,000) | (35,100,000) |
Fair Value of Plan Assets as of December 31, | 506,500,000 | 550,600,000 | 533,700,000
Funded (Underfunded) Status as of December 31, | 56,700,000 | 73,600,000 |
Pension Plans | OHIO POWER COMPANY |  |  |
Change in Benefit Obligation |  |  |
Benefit Obligation as of January 1, | 378,400,000 | 363,600,000 |
Service Cost | 9,200,000 | 8,400,000 | 11,200,000
Interest Cost | 18,800,000 | 19,800,000 | 13,300,000
Actuarial (Gain) Loss | (8,300,000) | 17,500,000 |
Settlements | (23,200,000) |  |
Benefit Payments | (24,200,000) | (30,900,000) |
Benefit Obligation as of December 31, | 350,700,000 | 378,400,000 | 363,600,000
Change in Fair Value of Plan Assets |  |  |
Fair Value of Plan Assets as of January 1, | 419,500,000 | 406,400,000 |
Actual Gain on Plan Assets | 8,600,000 | 44,000,000.0 |
Company Contributions | 0 | 0 |
Settlements | (23,200,000) |  |
Benefit Payments | (24,200,000) | (30,900,000) |
Fair Value of Plan Assets as of December 31, | 380,700,000 | 419,500,000 | 406,400,000
Funded (Underfunded) Status as of December 31, | 30,000,000.0 | 41,100,000 |
Pension Plans | PUBLIC SERVICE COMPANY OF OKLAHOMA |  |  |
Change in Benefit Obligation |  |  |
Benefit Obligation as of January 1, | 202,200,000 | 192,300,000 |
Service Cost | 5,900,000 | 5,500,000 | 7,400,000
Interest Cost | 10,100,000 | 10,700,000 | 7,000,000.0
Actuarial (Gain) Loss | 100,000 | 13,600,000 |
Settlements | (18,500,000) |  |
Benefit Payments | (9,600,000) | (19,900,000) |
Benefit Obligation as of December 31, | 190,200,000 | 202,200,000 | 192,300,000
Change in Fair Value of Plan Assets |  |  |
Fair Value of Plan Assets as of January 1, | 222,700,000 | 218,500,000 |
Actual Gain on Plan Assets | 5,000,000.0 | 24,000,000.0 |
Company Contributions | 100,000 | 100,000 |
Settlements | (18,500,000) |  |
Benefit Payments | (9,600,000) | (19,900,000) |
Fair Value of Plan Assets as of December 31, | 199,700,000 | 222,700,000 | 218,500,000
Funded (Underfunded) Status as of December 31, | 9,500,000 | 20,500,000 |
Pension Plans | SOUTHWESTERN ELECTRIC POWER COMPANY |  |  |
Change in Benefit Obligation |  |  |
Benefit Obligation as of January 1, | 261,200,000 | 250,700,000 |
Service Cost | 7,800,000 | 7,700,000 | 10,600,000
Interest Cost | 12,500,000 | 13,900,000 | 9,100,000
Actuarial (Gain) Loss | (11,200,000) | 16,800,000 |
Settlements | (33,100,000) |  |
Benefit Payments | (9,400,000) | (27,900,000) |
Benefit Obligation as of December 31, | 227,800,000 | 261,200,000 | 250,700,000
Change in Fair Value of Plan Assets |  |  |
Fair Value of Plan Assets as of January 1, | 227,500,000 | 231,300,000 |
Actual Gain on Plan Assets | 3,600,000 | 23,900,000 |
Company Contributions | 200,000 | 200,000 |
Settlements | (33,100,000) |  |
Benefit Payments | (9,400,000) | (27,900,000) |
Fair Value of Plan Assets as of December 31, | 188,800,000 | 227,500,000 | 231,300,000
Funded (Underfunded) Status as of December 31, | (39,000,000.0) | (33,700,000) |
OPEB |  |  |
Change in Benefit Obligation |  |  |
Benefit Obligation as of January 1, | 849,500,000 | 872,600,000 |
Service Cost | 4,500,000 | 4,600,000 | 7,400,000
Interest Cost | 42,000,000.0 | 46,200,000 | 29,200,000
Actuarial (Gain) Loss | (192,300,000) | 19,800,000 |
Special/Contractual Termination Benefits | 3,500,000 |  |
Benefit Payments | (105,800,000) | (137,800,000) |
Participant Contributions | 44,900,000 | 43,600,000 |
Medicare Subsidy | 300,000 | 500,000 |
Benefit Obligation as of December 31, | 646,600,000 | 849,500,000 | 872,600,000
Change in Fair Value of Plan Assets |  |  |
Fair Value of Plan Assets as of January 1, | 1,673,300,000 | 1,549,300,000 |
Actual Gain on Plan Assets | 159,200,000 | 213,200,000 |
Company Contributions | 4,300,000 | 5,000,000.0 |
Participant Contributions | 44,900,000 | 43,600,000 |
Benefit Payments | (105,800,000) | (137,800,000) |
Fair Value of Plan Assets as of December 31, | 1,775,900,000 | 1,673,300,000 | 1,549,300,000
Funded (Underfunded) Status as of December 31, | 1,129,300,000 | 823,800,000 |
OPEB | AEP TEXAS INC. |  |  |
Change in Benefit Obligation |  |  |
Benefit Obligation as of January 1, | 66,400,000 | 68,600,000 |
Service Cost | 300,000 | 300,000 | 500,000
Interest Cost | 3,300,000 | 3,600,000 | 2,200,000
Actuarial (Gain) Loss | (15,400,000) | 1,200,000 |
Special/Contractual Termination Benefits | 400,000 |  |
Benefit Payments | (8,300,000) | (10,700,000) |
Participant Contributions | 3,500,000 | 3,400,000 |
Medicare Subsidy | 0 | 0 |
Benefit Obligation as of December 31, | 50,200,000 | 66,400,000 | 68,600,000
Change in Fair Value of Plan Assets |  |  |
Fair Value of Plan Assets as of January 1, | 137,500,000 | 128,300,000 |
Actual Gain on Plan Assets | 14,000,000.0 | 16,500,000 |
Company Contributions | 0 | 0 |
Participant Contributions | 3,500,000 | 3,400,000 |
Benefit Payments | (8,300,000) | (10,700,000) |
Fair Value of Plan Assets as of December 31, | 146,700,000 | 137,500,000 | 128,300,000
Funded (Underfunded) Status as of December 31, | 96,500,000 | 71,100,000 |
OPEB | APPALACHIAN POWER COMPANY |  |  |
Change in Benefit Obligation |  |  |
Benefit Obligation as of January 1, | 134,600,000 | 140,700,000 |
Service Cost | 500,000 | 500,000 | 800,000
Interest Cost | 6,600,000 | 7,400,000 | 4,700,000
Actuarial (Gain) Loss | (30,400,000) | 900,000 |
Special/Contractual Termination Benefits | 600,000 |  |
Benefit Payments | (16,700,000) | (21,600,000) |
Participant Contributions | 6,800,000 | 6,600,000 |
Medicare Subsidy | 100,000 | 100,000 |
Benefit Obligation as of December 31, | 102,100,000 | 134,600,000 | 140,700,000
Change in Fair Value of Plan Assets |  |  |
Fair Value of Plan Assets as of January 1, | 243,000,000.0 | 228,600,000 |
Actual Gain on Plan Assets | 22,500,000 | 28,100,000 |
Company Contributions | 800,000 | 1,300,000 |
Participant Contributions | 6,800,000 | 6,600,000 |
Benefit Payments | (16,700,000) | (21,600,000) |
Fair Value of Plan Assets as of December 31, | 256,400,000 | 243,000,000.0 | 228,600,000
Funded (Underfunded) Status as of December 31, | 154,300,000 | 108,400,000 |
OPEB | INDIANA MICHIGAN POWER COMPANY |  |  |
Change in Benefit Obligation |  |  |
Benefit Obligation as of January 1, | 98,800,000 | 101,900,000 |
Service Cost | 600,000 | 600,000 | 900,000
Interest Cost | 4,800,000 | 5,400,000 | 3,400,000
Actuarial (Gain) Loss | (24,700,000) | 3,200,000 |
Special/Contractual Termination Benefits | 400,000 |  |
Benefit Payments | (13,400,000) | (18,300,000) |
Participant Contributions | 6,000,000.0 | 6,000,000.0 |
Medicare Subsidy | 0 | 0 |
Benefit Obligation as of December 31, | 72,500,000 | 98,800,000 | 101,900,000
Change in Fair Value of Plan Assets |  |  |
Fair Value of Plan Assets as of January 1, | 204,600,000 | 190,500,000 |
Actual Gain on Plan Assets | 14,700,000 | 26,400,000 |
Company Contributions | 0 | 0 |
Participant Contributions | 6,000,000.0 | 6,000,000.0 |
Benefit Payments | (13,400,000) | (18,300,000) |
Fair Value of Plan Assets as of December 31, | 211,900,000 | 204,600,000 | 190,500,000
Funded (Underfunded) Status as of December 31, | 139,400,000 | 105,800,000 |
OPEB | OHIO POWER COMPANY |  |  |
Change in Benefit Obligation |  |  |
Benefit Obligation as of January 1, | 85,900,000 | 88,900,000 |
Service Cost | 400,000 | 400,000 | 600,000
Interest Cost | 4,200,000 | 4,700,000 | 3,000,000.0
Actuarial (Gain) Loss | (20,700,000) | 2,200,000 |
Special/Contractual Termination Benefits | 300,000 |  |
Benefit Payments | (11,300,000) | (15,000,000.0) |
Participant Contributions | 4,600,000 | 4,700,000 |
Medicare Subsidy | 0 | 0 |
Benefit Obligation as of December 31, | 63,400,000 | 85,900,000 | 88,900,000
Change in Fair Value of Plan Assets |  |  |
Fair Value of Plan Assets as of January 1, | 177,800,000 | 166,200,000 |
Actual Gain on Plan Assets | 14,100,000 | 21,900,000 |
Company Contributions | 0 | 0 |
Participant Contributions | 4,600,000 | 4,700,000 |
Benefit Payments | (11,300,000) | (15,000,000.0) |
Fair Value of Plan Assets as of December 31, | 185,200,000 | 177,800,000 | 166,200,000
Funded (Underfunded) Status as of December 31, | 121,800,000 | 91,900,000 |
OPEB | PUBLIC SERVICE COMPANY OF OKLAHOMA |  |  |
Change in Benefit Obligation |  |  |
Benefit Obligation as of January 1, | 43,700,000 | 45,700,000 |
Service Cost | 300,000 | 300,000 | 400,000
Interest Cost | 2,100,000 | 2,400,000 | 1,500,000
Actuarial (Gain) Loss | (10,400,000) | 400,000 |
Special/Contractual Termination Benefits | 100,000 |  |
Benefit Payments | (5,800,000) | (7,600,000) |
Participant Contributions | 2,600,000 | 2,500,000 |
Medicare Subsidy | 0 | 0 |
Benefit Obligation as of December 31, | 32,600,000 | 43,700,000 | 45,700,000
Change in Fair Value of Plan Assets |  |  |
Fair Value of Plan Assets as of January 1, | 90,200,000 | 85,400,000 |
Actual Gain on Plan Assets | 8,300,000 | 9,900,000 |
Company Contributions | 0 | 0 |
Participant Contributions | 2,600,000 | 2,500,000 |
Benefit Payments | (5,800,000) | (7,600,000) |
Fair Value of Plan Assets as of December 31, | 95,300,000 | 90,200,000 | 85,400,000
Funded (Underfunded) Status as of December 31, | 62,700,000 | 46,500,000 |
OPEB | SOUTHWESTERN ELECTRIC POWER COMPANY |  |  |
Change in Benefit Obligation |  |  |
Benefit Obligation as of January 1, | 53,700,000 | 55,100,000 |
Service Cost | 400,000 | 400,000 | 600,000
Interest Cost | 2,700,000 | 2,900,000 | 1,800,000
Actuarial (Gain) Loss | (11,500,000) | 1,200,000 |
Special/Contractual Termination Benefits | 300,000 |  |
Benefit Payments | (7,400,000) | (8,800,000) |
Participant Contributions | 3,300,000 | 2,900,000 |
Medicare Subsidy | 0 | 0 |
Benefit Obligation as of December 31, | 41,500,000 | 53,700,000 | 55,100,000
Change in Fair Value of Plan Assets |  |  |
Fair Value of Plan Assets as of January 1, | 111,100,000 | 103,000,000.0 |
Actual Gain on Plan Assets | 14,200,000 | 14,000,000.0 |
Company Contributions | 0 | 0 |
Participant Contributions | 3,300,000 | 2,900,000 |
Benefit Payments | (7,400,000) | (8,800,000) |
Fair Value of Plan Assets as of December 31, | 121,200,000 | 111,100,000 | $ 103,000,000.0
Funded (Underfunded) Status as of December 31, | $ 79,700,000 | $ 57,400,000 |

X
- Definition Amount of increase (decrease) in plan assets of defined benefit plan from actual return (loss) determined by change in fair value of plan assets adjusted for contributions, benefit payments, and other expenses. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 17 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480482/715-20-55-17 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 + Details
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- Definition Amount of gain (loss) from change in actuarial assumptions which (increases) decreases benefit obligation of defined benefit plan. Assumptions include, but are not limited to, interest, mortality, employee turnover, salary, and temporary deviation from substantive plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (a)(4) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 + Details
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- Definition Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 + Details
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- Definition Amount of payment to participant of defined benefit plan which decreases benefit obligation. For pension plan, payment includes, but is not limited to, pension benefits and death benefits. For other postretirement plan, payment includes, but is not limited to, prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 60 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480266/715-60-50-4 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (a)(6) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 + Details
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- Definition Amount of payment, which decreases benefit obligation of defined benefit plan, for irrevocable action relieving primary responsibility for benefit obligation and eliminating risk for obligation and assets used to effect settlement. Transaction constituting settlement includes, but is not limited to, making lump-sum cash payment to participant in exchange for their rights to receive specified benefits and purchasing nonparticipating annuity contract. Excludes decreases to benefit obligation for remeasurement due to settlement. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (a)(10) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 + Details
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