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Benefit Plans (Tables) | 12 Months Ended
--- | ---
Dec. 31, 2023 | Dec. 31, 2022
Health Care Trend Rates |
Health Care Trend Rates |  | December 31, 2023 |  | December 31, 2022
Initial |  | 7.00 | % |  | 7.50 | %
Ultimate |  | 4.50 | % |  | 4.50 | %
Year Ultimate Reached |  | 2030 |  | 2029
Reconciliation of Changes in Benefit Obligations and Fair Value of Assets |
2023 |  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
Change in Benefit Obligation |  | (in millions)
Benefit Obligation as of January 1, |  | $ | 4,072.7 |  |  | $ | 334.1 |  |  | $ | 485.7 |  |  | $ | 466.8 |  |  | $ | 363.6 |  |  | $ | 192.3 |  |  | $ | 250.7 |
Service Cost |  | 94.3 |  |  | 8.2 |  |  | 9.1 |  |  | 11.9 |  |  | 8.4 |  |  | 5.5 |  |  | 7.7 |
Interest Cost |  | 219.2 |  |  | 18.3 |  |  | 26.4 |  |  | 24.9 |  |  | 19.8 |  |  | 10.7 |  |  | 13.9 |
Actuarial Loss |  | 144.0 |  |  | 20.1 |  |  | 23.2 |  |  | 8.5 |  |  | 17.5 |  |  | 13.6 |  |  | 16.8 |
Benefit Payments |  | (368.6) |  |  | (37.6) |  |  | (40.3) |  |  | (35.1) |  |  | (30.9) |  |  | (19.9) |  |  | (27.9) |
Benefit Obligation as of December 31, |  | $ | 4,161.6 |  |  | $ | 343.1 |  |  | $ | 504.1 |  |  | $ | 477.0 |  |  | $ | 378.4 |  |  | $ | 202.2 |  |  | $ | 261.2 |
Change in Fair Value of Plan Assets |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fair Value of Plan Assets as of January 1, |  | $ | 4,124.7 |  |  | $ | 335.1 |  |  | $ | 531.7 |  |  | $ | 533.7 |  |  | $ | 406.4 |  |  | $ | 218.5 |  |  | $ | 231.3 |
Actual Gain on Plan Assets |  | 353.8 |  |  | 34.8 |  |  | 58.4 |  |  | 51.5 |  |  | 44.0 |  |  | 24.0 |  |  | 23.9 |
Company Contributions (a) |  | 8.3 |  |  | 0.4 |  |  | — |  |  | 0.5 |  |  | — |  |  | 0.1 |  |  | 0.2 |
Benefit Payments |  | (368.6) |  |  | (37.6) |  |  | (40.3) |  |  | (35.1) |  |  | (30.9) |  |  | (19.9) |  |  | (27.9) |
Fair Value of Plan Assets as of December 31, |  | $ | 4,118.2 |  |  | $ | 332.7 |  |  | $ | 549.8 |  |  | $ | 550.6 |  |  | $ | 419.5 |  |  | $ | 222.7 |  |  | $ | 227.5 |
Funded (Underfunded) Status as of December 31, |  | $ | (43.4) |  |  | $ | (10.4) |  |  | $ | 45.7 |  |  | $ | 73.6 |  |  | $ | 41.1 |  |  | $ | 20.5 |  |  | $ | (33.7) |
2022 |  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
Change in Benefit Obligation |  | (in millions)
Benefit Obligation as of January 1, |  | $ | 5,187.0 |  |  | $ | 419.8 |  |  | $ | 621.7 |  |  | $ | 612.1 |  |  | $ | 470.7 |  |  | $ | 252.6 |  |  | $ | 317.7 |
Service Cost |  | 123.1 |  |  | 11.1 |  |  | 11.4 |  |  | 16.2 |  |  | 11.2 |  |  | 7.4 |  |  | 10.6 |
Interest Cost |  | 148.2 |  |  | 12.1 |  |  | 17.5 |  |  | 17.0 |  |  | 13.3 |  |  | 7.0 |  |  | 9.1 |
Actuarial Gain |  | (983.4) |  |  | (67.8) |  |  | (123.1) |  |  | (138.0) |  |  | (97.9) |  |  | (52.9) |  |  | (57.9) |
Benefit Payments |  | (402.2) |  |  | (41.1) |  |  | (41.8) |  |  | (40.5) |  |  | (33.7) |  |  | (21.8) |  |  | (28.8) |
Benefit Obligation as of December 31, |  | $ | 4,072.7 |  |  | $ | 334.1 |  |  | $ | 485.7 |  |  | $ | 466.8 |  |  | $ | 363.6 |  |  | $ | 192.3 |  |  | $ | 250.7 |
Change in Fair Value of Plan Assets |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fair Value of Plan Assets as of January 1, |  | $ | 5,352.9 |  |  | $ | 444.9 |  |  | $ | 683.3 |  |  | $ | 681.5 |  |  | $ | 524.8 |  |  | $ | 286.2 |  |  | $ | 308.3 |
Actual (Loss) on Plan Assets |  | (833.7) |  |  | (69.2) |  |  | (109.8) |  |  | (107.4) |  |  | (84.8) |  |  | (46.0) |  |  | (48.3) |
Company Contributions (a) |  | 7.7 |  |  | 0.5 |  |  | — |  |  | 0.1 |  |  | 0.1 |  |  | 0.1 |  |  | 0.1 |
Benefit Payments |  | (402.2) |  |  | (41.1) |  |  | (41.8) |  |  | (40.5) |  |  | (33.7) |  |  | (21.8) |  |  | (28.8) |
Fair Value of Plan Assets as of December 31, |  | $ | 4,124.7 |  |  | $ | 335.1 |  |  | $ | 531.7 |  |  | $ | 533.7 |  |  | $ | 406.4 |  |  | $ | 218.5 |  |  | $ | 231.3 |
Funded (Underfunded) Status as of December 31, |  | $ | 52.0 |  |  | $ | 1.0 |  |  | $ | 46.0 |  |  | $ | 66.9 |  |  | $ | 42.8 |  |  | $ | 26.2 |  |  | $ | (19.4) |
(a)No contributions were made to the qualified pension plan for the years ended December 31, 2023 and 2022, respectively. Contributions to the non-qualified pension plans were $8 million and $8 million for the years ended December 31, 2023 and 2022, respectively. OPEB
2023 |  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
Change in Benefit Obligation |  | (in millions)
Benefit Obligation as of January 1, |  | $ | 872.6 |  |  | $ | 68.6 |  |  | $ | 140.7 |  |  | $ | 101.9 |  |  | $ | 88.9 |  |  | $ | 45.7 |  |  | $ | 55.1 |
Service Cost |  | 4.6 |  |  | 0.3 |  |  | 0.5 |  |  | 0.6 |  |  | 0.4 |  |  | 0.3 |  |  | 0.4 |
Interest Cost |  | 46.2 |  |  | 3.6 |  |  | 7.4 |  |  | 5.4 |  |  | 4.7 |  |  | 2.4 |  |  | 2.9 |
Actuarial Loss |  | 19.8 |  |  | 1.2 |  |  | 0.9 |  |  | 3.2 |  |  | 2.2 |  |  | 0.4 |  |  | 1.2 |
Benefit Payments |  | (137.8) |  |  | (10.7) |  |  | (21.6) |  |  | (18.3) |  |  | (15.0) |  |  | (7.6) |  |  | (8.8) |
Participant Contributions |  | 43.6 |  |  | 3.4 |  |  | 6.6 |  |  | 6.0 |  |  | 4.7 |  |  | 2.5 |  |  | 2.9 |
Medicare Subsidy |  | 0.5 |  |  | — |  |  | 0.1 |  |  | — |  |  | — |  |  | — |  |  | — |
Benefit Obligation as of December 31, |  | $ | 849.5 |  |  | $ | 66.4 |  |  | $ | 134.6 |  |  | $ | 98.8 |  |  | $ | 85.9 |  |  | $ | 43.7 |  |  | $ | 53.7 |
Change in Fair Value of Plan Assets |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fair Value of Plan Assets as of January 1, |  | $ | 1,549.3 |  |  | $ | 128.3 |  |  | $ | 228.6 |  |  | $ | 190.5 |  |  | $ | 166.2 |  |  | $ | 85.4 |  |  | $ | 103.0 |
Actual Gain on Plan Assets |  | 213.2 |  |  | 16.5 |  |  | 28.1 |  |  | 26.4 |  |  | 21.9 |  |  | 9.9 |  |  | 14.0 |
Company Contributions |  | 5.0 |  |  | — |  |  | 1.3 |  |  | — |  |  | — |  |  | — |  |  | — |
Participant Contributions |  | 43.6 |  |  | 3.4 |  |  | 6.6 |  |  | 6.0 |  |  | 4.7 |  |  | 2.5 |  |  | 2.9 |
Benefit Payments |  | (137.8) |  |  | (10.7) |  |  | (21.6) |  |  | (18.3) |  |  | (15.0) |  |  | (7.6) |  |  | (8.8) |
Fair Value of Plan Assets as of December 31, |  | $ | 1,673.3 |  |  | $ | 137.5 |  |  | $ | 243.0 |  |  | $ | 204.6 |  |  | $ | 177.8 |  |  | $ | 90.2 |  |  | $ | 111.1 |
Funded Status as of December 31, |  | $ | 823.8 |  |  | $ | 71.1 |  |  | $ | 108.4 |  |  | $ | 105.8 |  |  | $ | 91.9 |  |  | $ | 46.5 |  |  | $ | 57.4 |
2022 |  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
Change in Benefit Obligation |  | (in millions)
Benefit Obligation as of January 1, |  | $ | 1,041.3 |  |  | $ | 80.5 |  |  | $ | 167.3 |  |  | $ | 118.6 |  |  | $ | 104.9 |  |  | $ | 54.4 |  |  | $ | 65.2 |
Service Cost |  | 7.4 |  |  | 0.5 |  |  | 0.8 |  |  | 0.9 |  |  | 0.6 |  |  | 0.4 |  |  | 0.6 |
Interest Cost |  | 29.2 |  |  | 2.2 |  |  | 4.7 |  |  | 3.4 |  |  | 3.0 |  |  | 1.5 |  |  | 1.8 |
Actuarial Gain |  | (109.8) |  |  | (7.1) |  |  | (16.2) |  |  | (8.7) |  |  | (8.9) |  |  | (5.2) |  |  | (6.6) |
Benefit Payments |  | (140.1) |  |  | (10.9) |  |  | (23.0) |  |  | (18.3) |  |  | (15.5) |  |  | (7.9) |  |  | (8.8) |
Participant Contributions |  | 44.1 |  |  | 3.4 |  |  | 7.0 |  |  | 6.0 |  |  | 4.8 |  |  | 2.5 |  |  | 2.9 |
Medicare Subsidy |  | 0.5 |  |  | — |  |  | 0.1 |  |  | — |  |  | — |  |  | — |  |  | — |
Benefit Obligation as of December 31, |  | $ | 872.6 |  |  | $ | 68.6 |  |  | $ | 140.7 |  |  | $ | 101.9 |  |  | $ | 88.9 |  |  | $ | 45.7 |  |  | $ | 55.1 |
Change in Fair Value of Plan Assets |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fair Value of Plan Assets as of January 1, |  | $ | 2,044.3 |  |  | $ | 168.8 |  |  | $ | 302.3 |  |  | $ | 248.7 |  |  | $ | 220.0 |  |  | $ | 114.0 |  |  | $ | 136.6 |
Actual Loss on Plan Assets |  | (403.6) |  |  | (33.0) |  |  | (59.3) |  |  | (45.9) |  |  | (43.1) |  |  | (23.2) |  |  | (27.7) |
Company Contributions |  | 4.6 |  |  | — |  |  | 1.6 |  |  | — |  |  | — |  |  | — |  |  | — |
Participant Contributions |  | 44.1 |  |  | 3.4 |  |  | 7.0 |  |  | 6.0 |  |  | 4.8 |  |  | 2.5 |  |  | 2.9 |
Benefit Payments |  | (140.1) |  |  | (10.9) |  |  | (23.0) |  |  | (18.3) |  |  | (15.5) |  |  | (7.9) |  |  | (8.8) |
Fair Value of Plan Assets as of December 31, |  | $ | 1,549.3 |  |  | $ | 128.3 |  |  | $ | 228.6 |  |  | $ | 190.5 |  |  | $ | 166.2 |  |  | $ | 85.4 |  |  | $ | 103.0 |
Funded Status as of December 31, |  | $ | 676.7 |  |  | $ | 59.7 |  |  | $ | 87.9 |  |  | $ | 88.6 |  |  | $ | 77.3 |  |  | $ | 39.7 |  |  | $ | 47.9 |
Benefit Amounts Recognized on the Balance Sheets | Amounts Included on the Balance Sheets Related to Funded Status Pension Plans
December 31, 2023 |  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
|  | (in millions)
Other Noncurrent Assets - Employee Benefits and Pension Assets |  | $ | 17.3 |  |  | $ | 0.1 |  |  | $ | 46.0 |  |  | $ | 74.8 |  |  | $ | 41.4 |  |  | $ | 21.8 |  |  | $ | — |
Other Current Liabilities – Accrued Short-term Benefit Liability |  | (6.7) |  |  | (0.3) |  |  | — |  |  | — |  |  | — |  |  | (0.1) |  |  | (0.1) |
Other Noncurrent Liabilities – Accrued Long-term Benefit Liability |  | (54.0) |  |  | (10.2) |  |  | (0.3) |  |  | (1.2) |  |  | (0.3) |  |  | (1.2) |  |  | (33.6) |
Funded (Underfunded) Status |  | $ | (43.4) |  |  | $ | (10.4) |  |  | $ | 45.7 |  |  | $ | 73.6 |  |  | $ | 41.1 |  |  | $ | 20.5 |  |  | $ | (33.7) |
December 31, 2022 |  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
|  | (in millions)
Other Noncurrent Assets - Employee Benefits and Pension Assets |  | $ | 113.4 |  |  | $ | 3.7 |  |  | $ | 46.6 |  |  | $ | 68.5 |  |  | $ | 43.1 |  |  | $ | 27.6 |  |  | $ | — |
Other Current Liabilities – Accrued Short-term Benefit Liability |  | (6.3) |  |  | (0.4) |  |  | — |  |  | (0.1) |  |  | — |  |  | (0.1) |  |  | (0.1) |
Other Noncurrent Liabilities – Accrued Long-term Benefit Liability |  | (55.1) |  |  | (2.3) |  |  | (0.6) |  |  | (1.5) |  |  | (0.3) |  |  | (1.3) |  |  | (19.3) |
Funded (Underfunded) Status |  | $ | 52.0 |  |  | $ | 1.0 |  |  | $ | 46.0 |  |  | $ | 66.9 |  |  | $ | 42.8 |  |  | $ | 26.2 |  |  | $ | (19.4) |
OPEB
December 31, 2023 |  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
|  | (in millions)
Other Noncurrent Assets - Employee Benefits and Pension Assets |  | $ | 838.0 |  |  | $ | 71.1 |  |  | $ | 125.6 |  |  | $ | 105.8 |  |  | $ | 91.9 |  |  | $ | 46.5 |  |  | $ | 57.4 |
Other Current Liabilities – Accrued Short-term Benefit Liability |  | (2.4) |  |  | — |  |  | (1.6) |  |  | — |  |  | — |  |  | — |  |  | — |
Other Noncurrent Liabilities – Accrued Long-term Benefit Liability |  | (11.8) |  |  | — |  |  | (15.6) |  |  | — |  |  | — |  |  | — |  |  | — |
Funded Status |  | $ | 823.8 |  |  | $ | 71.1 |  |  | $ | 108.4 |  |  | $ | 105.8 |  |  | $ | 91.9 |  |  | $ | 46.5 |  |  | $ | 57.4 |
December 31, 2022 |  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
|  | (in millions)
Other Noncurrent Assets - Employee Benefits and Pension Assets |  | $ | 699.5 |  |  | $ | 59.7 |  |  | $ | 106.3 |  |  | $ | 88.6 |  |  | $ | 77.3 |  |  | $ | 39.7 |  |  | $ | 47.9 |
Other Current Liabilities – Accrued Short-term Benefit Liability |  | (2.5) |  |  | — |  |  | (1.6) |  |  | — |  |  | — |  |  | — |  |  | — |
Other Noncurrent Liabilities – Accrued Long-term Benefit Liability |  | (20.3) |  |  | — |  |  | (16.8) |  |  | — |  |  | — |  |  | — |  |  | — |
Funded Status |  | $ | 676.7 |  |  | $ | 59.7 |  |  | $ | 87.9 |  |  | $ | 88.6 |  |  | $ | 77.3 |  |  | $ | 39.7 |  |  | $ | 47.9 |
Amounts Included in AOCI and Regulatory Assets |
December 31, 2023 |  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
Components |  | (in millions)
Net Actuarial (Gain) Loss |  | $ | 1,063.4 |  |  | $ | 175.2 |  |  | $ | 104.9 |  |  | $ | (5.8) |  |  | $ | 131.9 |  |  | $ | 46.7 |  |  | $ | 89.6 |
Prior Service Cost |  | 0.2 |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |
Recorded as |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory Assets |  | $ | 938.6 |  |  | $ | 163.4 |  |  | $ | 102.6 |  |  | $ | 6.4 |  |  | $ | 131.9 |  |  | $ | 46.7 |  |  | $ | 89.7 |
Deferred Income Taxes |  | 26.4 |  |  | 2.7 |  |  | 0.4 |  |  | (2.6) |  |  | — |  |  | — |  |  | — |
Net of Tax AOCI |  | 98.6 |  |  | 9.1 |  |  | 1.9 |  |  | (9.6) |  |  | — |  |  | — |  |  | (0.1) |
December 31, 2023 |  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
Components |  | (in millions)
Net Actuarial Loss |  | $ | 201.5 |  |  | $ | 22.1 |  |  | $ | 27.1 |  |  | $ | 28.7 |  |  | $ | 18.1 |  |  | $ | 17.5 |  |  | $ | 18.4 |
Prior Service Credit |  | (27.4) |  |  | (2.3) |  |  | (4.2) |  |  | (3.7) |  |  | (2.9) |  |  | (1.6) |  |  | (2.1) |
Recorded as |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory Assets |  | $ | 106.1 |  |  | $ | 19.8 |  |  | $ | 13.2 |  |  | $ | 19.0 |  |  | $ | 15.2 |  |  | $ | 15.9 |  |  | $ | 10.2 |
Deferred Income Taxes |  | 14.3 |  |  | — |  |  | 2.0 |  |  | 1.3 |  |  | — |  |  | — |  |  | 1.3 |
Net of Tax AOCI |  | 53.7 |  |  | — |  |  | 7.7 |  |  | 4.7 |  |  | — |  |  | — |  |  | 4.8 |
December 31, 2022 |  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
Components |  | (in millions)
Net Actuarial (Gain) Loss |  | $ | 935.6 |  |  | $ | 161.9 |  |  | $ | 95.6 |  |  | $ | (6.9) |  |  | $ | 124.3 |  |  | $ | 38.8 |  |  | $ | 77.6 |
Prior Service Cost |  | 0.2 |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |
Recorded as |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory Assets |  | $ | 841.8 |  |  | $ | 151.2 |  |  | $ | 93.6 |  |  | $ | 4.8 |  |  | $ | 124.3 |  |  | $ | 38.8 |  |  | $ | 77.6 |
Deferred Income Taxes |  | 19.9 |  |  | 2.4 |  |  | 0.4 |  |  | (2.4) |  |  | — |  |  | — |  |  | — |
Net of Tax AOCI |  | 74.1 |  |  | 8.3 |  |  | 1.6 |  |  | (9.3) |  |  | — |  |  | — |  |  | — |
December 31, 2022 |  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
Components |  | (in millions)
Net Actuarial Loss |  | $ | 300.0 |  |  | $ | 29.7 |  |  | $ | 40.5 |  |  | $ | 40.2 |  |  | $ | 27.6 |  |  | $ | 22.0 |  |  | $ | 25.0 |
Prior Service Credit |  | (90.5) |  |  | (7.6) |  |  | (13.4) |  |  | (12.4) |  |  | (9.2) |  |  | (5.6) |  |  | (7.0) |
Recorded as |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory Assets |  | $ | 126.0 |  |  | $ | 22.0 |  |  | $ | 14.7 |  |  | $ | 22.1 |  |  | $ | 18.4 |  |  | $ | 16.4 |  |  | $ | 11.2 |
Deferred Income Taxes |  | 17.5 |  |  | 0.1 |  |  | 2.5 |  |  | 1.2 |  |  | — |  |  | — |  |  | 1.5 |
Net of Tax AOCI |  | 66.0 |  |  | — |  |  | 9.9 |  |  | 4.5 |  |  | — |  |  | — |  |  | 5.3 |
Components of Change in Amounts Included in AOCI and Regulatory Assets |
December 31, 2023 |  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
Components |  | (in millions)
Actuarial Loss During the Year |  | $ | 129.2 |  |  | $ | 13.4 |  |  | $ | 9.3 |  |  | $ | 1.2 |  |  | $ | 7.6 |  |  | $ | 7.9 |  |  | $ | 12.1 |
Amortization of Actuarial Loss |  | (1.4) |  |  | (0.1) |  |  | — |  |  | (0.1) |  |  | — |  |  | — |  |  | (0.1) |
Change for the Year Ended December 31, |  | $ | 127.8 |  |  | $ | 13.3 |  |  | $ | 9.3 |  |  | $ | 1.1 |  |  | $ | 7.6 |  |  | $ | 7.9 |  |  | $ | 12.0 |
December 31, 2023 |  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
Components |  | (in millions)
Actuarial Gain During the Year |  | $ | (83.7) |  |  | $ | (6.4) |  |  | $ | (11.1) |  |  | $ | (9.6) |  |  | $ | (7.9) |  |  | $ | (3.7) |  |  | $ | (5.6) |
Amortization of Actuarial Loss |  | (14.8) |  |  | (1.2) |  |  | (2.3) |  |  | (1.9) |  |  | (1.6) |  |  | (0.8) |  |  | (1.0) |
Amortization of Prior Service Credit |  | 63.1 |  |  | 5.3 |  |  | 9.2 |  |  | 8.7 |  |  | 6.3 |  |  | 4.0 |  |  | 4.9 |
Change for the Year Ended December 31, |  | $ | (35.4) |  |  | $ | (2.3) |  |  | $ | (4.2) |  |  | $ | (2.8) |  |  | $ | (3.2) |  |  | $ | (0.5) |  |  | $ | (1.7) |
December 31, 2022 |  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
Components |  | (in millions)
Actuarial Loss During the Year |  | $ | 103.9 |  |  | $ | 22.4 |  |  | $ | 19.1 |  |  | $ | 1.8 |  |  | $ | 11.7 |  |  | $ | 6.7 |  |  | $ | 5.0 |
Amortization of Actuarial Loss |  | (63.0) |  |  | (5.2) |  |  | (7.4) |  |  | (7.1) |  |  | (5.5) |  |  | (2.9) |  |  | (3.8) |
Change for the Year Ended December 31, |  | $ | 40.9 |  |  | $ | 17.2 |  |  | $ | 11.7 |  |  | $ | (5.3) |  |  | $ | 6.2 |  |  | $ | 3.8 |  |  | $ | 1.2 |
December 31, 2022 |  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
Components |  | (in millions)
Actuarial Loss During the Year |  | $ | 403.6 |  |  | $ | 34.9 |  |  | $ | 59.4 |  |  | $ | 50.9 |  |  | $ | 46.1 |  |  | $ | 24.1 |  |  | $ | 28.5 |
Amortization of Prior Service Credit |  | 71.4 |  |  | 6.1 |  |  | 10.4 |  |  | 9.7 |  |  | 7.1 |  |  | 4.4 |  |  | 5.3 |
Change for the Year Ended December 31, |  | $ | 475.0 |  |  | $ | 41.0 |  |  | $ | 69.8 |  |  | $ | 60.6 |  |  | $ | 53.2 |  |  | $ | 28.5 |  |  | $ | 33.8 |
Allocated Assets of Investments |
|  | Pension Plan |  | OPEB
|  | December 31,
Company |  | 2023 |  | 2022 |  | 2023 |  | 2022
AEP Texas |  | 8.1 | % |  | 8.1 | % |  | 8.2 | % |  | 8.3 | %
APCo |  | 13.4 | % |  | 12.9 | % |  | 14.5 | % |  | 14.8 | %
I&M |  | 13.4 | % |  | 12.9 | % |  | 12.2 | % |  | 12.3 | %
OPCo |  | 10.2 | % |  | 9.9 | % |  | 10.6 | % |  | 10.7 | %
PSO |  | 5.4 | % |  | 5.3 | % |  | 5.4 | % |  | 5.5 | %
SWEPCo |  | 5.5 | % |  | 5.6 | % |  | 6.6 | % |  | 6.6 | %
Accumulated Benefit Obligation |
Accumulated Benefit Obligation |  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
|  | (in millions)
Qualified Pension Plan |  | $ | 3,878.7 |  |  | $ | 321.1 |  |  | $ | 485.6 |  |  | $ | 450.3 |  |  | $ | 354.0 |  |  | $ | 186.6 |  |  | $ | 241.9 |
Nonqualified Pension Plans |  | 54.8 |  |  | 2.1 |  |  | 0.1 |  |  | 0.7 |  |  | 0.1 |  |  | 1.2 |  |  | 1.0 |
Total as of December 31, 2023 |  | $ | 3,933.5 |  |  | $ | 323.2 |  |  | $ | 485.7 |  |  | $ | 451.0 |  |  | $ | 354.1 |  |  | $ | 187.8 |  |  | $ | 242.9 |
Accumulated Benefit Obligation |  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
|  | (in millions)
Qualified Pension Plan |  | $ | 3,827.4 |  |  | $ | 315.4 |  |  | $ | 470.1 |  |  | $ | 443.8 |  |  | $ | 344.1 |  |  | $ | 179.1 |  |  | $ | 234.0 |
Nonqualified Pension Plans |  | 55.6 |  |  | 2.5 |  |  | 0.3 |  |  | 1.2 |  |  | 0.1 |  |  | 1.2 |  |  | 1.1 |
Total as of December 31, 2022 |  | $ | 3,883.0 |  |  | $ | 317.9 |  |  | $ | 470.4 |  |  | $ | 445.0 |  |  | $ | 344.2 |  |  | $ | 180.3 |  |  | $ | 235.1 |
Underfunded Projected Benefit Obligation |
| AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
| (in millions)
Projected Benefit Obligation | $ | 60.7 |  |  | $ | 343.1 |  |  | $ | 0.4 |  |  | $ | 1.2 |  |  | $ | 0.3 |  |  | $ | 1.4 |  |  | $ | 261.2 |
Fair Value of Plan Assets | — |  |  | 332.7 |  |  | — |  |  | — |  |  | — |  |  | — |  |  | 227.5 |
Underfunded Projected Benefit Obligation as of December 31, 2023 | $ | (60.7) |  |  | $ | (10.4) |  |  | $ | (0.4) |  |  | $ | (1.2) |  |  | $ | (0.3) |  |  | $ | (1.4) |  |  | $ | (33.7) |
| AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
| (in millions)
Projected Benefit Obligation | $ | 61.5 |  |  | $ | 2.7 |  |  | $ | 0.6 |  |  | $ | 1.6 |  |  | $ | 0.3 |  |  | $ | 1.5 |  |  | $ | 250.7 |
Fair Value of Plan Assets | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | 231.3 |
Underfunded Projected Benefit Obligation as of December 31, 2022 | $ | (61.5) |  |  | $ | (2.7) |  |  | $ | (0.6) |  |  | $ | (1.6) |  |  | $ | (0.3) |  |  | $ | (1.5) |  |  | $ | (19.4) |
Underfunded Accumulated Benefit Obligation |
| AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
| (in millions)
Accumulated Benefit Obligation | $ | 54.8 |  |  | $ | 2.1 |  |  | $ | 0.1 |  |  | $ | 0.7 |  |  | $ | 0.1 |  |  | $ | 1.2 |  |  | $ | 242.9 |
Fair Value of Plan Assets | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | 227.5 |
Underfunded Accumulated Benefit Obligation as of December 31, 2023 | $ | (54.8) |  |  | $ | (2.1) |  |  | $ | (0.1) |  |  | $ | (0.7) |  |  | $ | (0.1) |  |  | $ | (1.2) |  |  | $ | (15.4) |
| AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
| (in millions)
Accumulated Benefit Obligation | $ | 55.6 |  |  | $ | 2.5 |  |  | $ | 0.3 |  |  | $ | 1.2 |  |  | $ | 0.1 |  |  | $ | 1.2 |  |  | $ | 235.1 |
Fair Value of Plan Assets | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | 231.3 |
Underfunded Accumulated Benefit Obligation as of December 31, 2022 | $ | (55.6) |  |  | $ | (2.5) |  |  | $ | (0.3) |  |  | $ | (1.2) |  |  | $ | (0.1) |  |  | $ | (1.2) |  |  | $ | (3.8) |
Estimated Contributions and Payments to the Pension and OPEB Plans |
|  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
|  | (in millions)
Pension Plans |  | $ | 6.7 |  |  | $ | 0.3 |  |  | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | 0.1 |  |  | $ | 0.1 |
OPEB |  | 3.0 |  |  | — |  |  | 1.6 |  |  | — |  |  | — |  |  | — |  |  | — |
Estimated Payments Expected to be Made by the Pension and OPEB Plans |
Pension Plans |  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
|  | (in millions)
2024 |  | $ | 369.5 |  |  | $ | 36.7 |  |  | $ | 43.9 |  |  | $ | 39.0 |  |  | $ | 32.6 |  |  | $ | 19.7 |  |  | $ | 24.4 |
2025 |  | 361.8 |  |  | 34.3 |  |  | 43.3 |  |  | 39.7 |  |  | 32.7 |  |  | 19.2 |  |  | 25.8 |
2026 |  | 365.7 |  |  | 34.5 |  |  | 44.1 |  |  | 39.7 |  |  | 32.5 |  |  | 19.4 |  |  | 26.1 |
2027 |  | 361.9 |  |  | 32.2 |  |  | 42.6 |  |  | 39.8 |  |  | 32.4 |  |  | 19.3 |  |  | 25.3 |
2028 |  | 357.8 |  |  | 32.2 |  |  | 43.5 |  |  | 39.4 |  |  | 31.3 |  |  | 19.0 |  |  | 23.7 |
Years 2029 to 2033, in Total |  | 1,657.6 |  |  | 133.5 |  |  | 200.0 |  |  | 189.4 |  |  | 144.5 |  |  | 81.0 |  |  | 105.6 |
OPEB Benefit Payments |  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
|  | (in millions)
2024 |  | $ | 117.2 |  |  | $ | 9.4 |  |  | $ | 18.8 |  |  | $ | 15.2 |  |  | $ | 12.6 |  |  | $ | 6.7 |  |  | $ | 7.8 |
2025 |  | 122.6 |  |  | 10.0 |  |  | 19.4 |  |  | 15.7 |  |  | 13.0 |  |  | 7.1 |  |  | 8.3 |
2026 |  | 122.4 |  |  | 10.2 |  |  | 19.3 |  |  | 15.7 |  |  | 12.8 |  |  | 7.0 |  |  | 8.3 |
2027 |  | 121.5 |  |  | 10.2 |  |  | 19.1 |  |  | 15.4 |  |  | 12.7 |  |  | 6.8 |  |  | 8.1 |
2028 |  | 120.2 |  |  | 9.9 |  |  | 19.0 |  |  | 15.0 |  |  | 12.5 |  |  | 6.5 |  |  | 8.2 |
Years 2029 to 2033, in Total |  | 566.1 |  |  | 45.2 |  |  | 88.3 |  |  | 69.7 |  |  | 57.6 |  |  | 30.2 |  |  | 38.8 |
OPEB Medicare Subsidy Receipts |  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
|  | (in millions)
2024 |  | $ | 0.3 |  |  | $ | — |  |  | $ | 0.1 |  |  | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | — |
2025 |  | 0.3 |  |  | — |  |  | 0.1 |  |  | — |  |  | — |  |  | — |  |  | — |
2026 |  | 0.3 |  |  | — |  |  | 0.1 |  |  | — |  |  | — |  |  | — |  |  | — |
2027 |  | 0.3 |  |  | — |  |  | 0.1 |  |  | — |  |  | — |  |  | — |  |  | — |
2028 |  | 0.3 |  |  | — |  |  | 0.1 |  |  | — |  |  | — |  |  | — |  |  | — |
Years 2029 to 2033, in Total |  | 1.5 |  |  | — |  |  | 0.5 |  |  | — |  |  | — |  |  | — |  |  | — |
Components of Net Periodic Benefit Cost |
2023 |  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
|  | (in millions)
Service Cost |  | $ | 94.3 |  |  | $ | 8.2 |  |  | $ | 9.1 |  |  | $ | 11.9 |  |  | $ | 8.4 |  |  | $ | 5.5 |  |  | $ | 7.7 |
Interest Cost |  | 219.2 |  |  | 18.3 |  |  | 26.4 |  |  | 24.9 |  |  | 19.8 |  |  | 10.7 |  |  | 13.9 |
Expected Return on Plan Assets |  | (339.2) |  |  | (28.1) |  |  | (44.6) |  |  | (44.2) |  |  | (34.0) |  |  | (18.3) |  |  | (19.4) |
Amortization of Net Actuarial Loss |  | 1.4 |  |  | 0.1 |  |  | — |  |  | 0.1 |  |  | — |  |  | — |  |  | 0.1 |
Net Periodic Benefit Cost (Credit) |  | (24.3) |  |  | (1.5) |  |  | (9.1) |  |  | (7.3) |  |  | (5.8) |  |  | (2.1) |  |  | 2.3 |
Capitalized Portion |  | (43.6) |  |  | (4.7) |  |  | (4.2) |  |  | (3.6) |  |  | (4.7) |  |  | (2.5) |  |  | (3.0) |
Net Periodic Benefit Credit Recognized in Expense |  | $ | (67.9) |  |  | $ | (6.2) |  |  | $ | (13.3) |  |  | $ | (10.9) |  |  | $ | (10.5) |  |  | $ | (4.6) |  |  | $ | (0.7) |
2022 |  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
|  | (in millions)
Service Cost |  | $ | 123.1 |  |  | $ | 11.1 |  |  | $ | 11.4 |  |  | $ | 16.2 |  |  | $ | 11.2 |  |  | $ | 7.4 |  |  | $ | 10.6 |
Interest Cost |  | 148.2 |  |  | 12.1 |  |  | 17.5 |  |  | 17.0 |  |  | 13.3 |  |  | 7.0 |  |  | 9.1 |
Expected Return on Plan Assets |  | (253.4) |  |  | (21.0) |  |  | (32.3) |  |  | (32.4) |  |  | (24.8) |  |  | (13.4) |  |  | (14.6) |
Amortization of Net Actuarial Loss |  | 63.0 |  |  | 5.2 |  |  | 7.4 |  |  | 7.1 |  |  | 5.5 |  |  | 2.9 |  |  | 3.8 |
Net Periodic Benefit Cost |  | 80.9 |  |  | 7.4 |  |  | 4.0 |  |  | 7.9 |  |  | 5.2 |  |  | 3.9 |  |  | 8.9 |
Capitalized Portion |  | (53.8) |  |  | (6.2) |  |  | (5.0) |  |  | (4.6) |  |  | (6.1) |  |  | (3.2) |  |  | (4.0) |
Net Periodic Benefit Cost (Credit) Recognized in Expense |  | $ | 27.1 |  |  | $ | 1.2 |  |  | $ | (1.0) |  |  | $ | 3.3 |  |  | $ | (0.9) |  |  | $ | 0.7 |  |  | $ | 4.9 |
2021 |  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
|  | (in millions)
Service Cost |  | $ | 129.2 |  |  | $ | 11.8 |  |  | $ | 11.9 |  |  | $ | 17.5 |  |  | $ | 11.4 |  |  | $ | 8.0 |  |  | $ | 11.2 |
Interest Cost |  | 137.2 |  |  | 11.2 |  |  | 16.4 |  |  | 16.2 |  |  | 12.5 |  |  | 6.7 |  |  | 8.5 |
Expected Return on Plan Assets |  | (229.7) |  |  | (19.5) |  |  | (29.1) |  |  | (28.9) |  |  | (22.3) |  |  | (12.3) |  |  | (13.5) |
Amortization of Net Actuarial Loss |  | 101.5 |  |  | 8.3 |  |  | 12.0 |  |  | 11.7 |  |  | 9.1 |  |  | 4.9 |  |  | 6.2 |
Net Periodic Benefit Cost |  | 138.2 |  |  | 11.8 |  |  | 11.2 |  |  | 16.5 |  |  | 10.7 |  |  | 7.3 |  |  | 12.4 |
Capitalized Portion |  | (55.7) |  |  | (6.6) |  |  | (5.2) |  |  | (4.9) |  |  | (6.2) |  |  | (3.4) |  |  | (4.1) |
Net Periodic Benefit Cost Recognized in Expense |  | $ | 82.5 |  |  | $ | 5.2 |  |  | $ | 6.0 |  |  | $ | 11.6 |  |  | $ | 4.5 |  |  | $ | 3.9 |  |  | $ | 8.3 |
OPEB
2023 |  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
|  | (in millions)
Service Cost |  | $ | 4.6 |  |  | $ | 0.3 |  |  | $ | 0.5 |  |  | $ | 0.6 |  |  | $ | 0.4 |  |  | $ | 0.3 |  |  | $ | 0.4 |
Interest Cost |  | 46.2 |  |  | 3.6 |  |  | 7.4 |  |  | 5.4 |  |  | 4.7 |  |  | 2.4 |  |  | 2.9 |
Expected Return on Plan Assets |  | (109.6) |  |  | (9.0) |  |  | (16.1) |  |  | (13.5) |  |  | (11.8) |  |  | (5.9) |  |  | (7.2) |
Amortization of Prior Service Credit |  | (63.1) |  |  | (5.3) |  |  | (9.2) |  |  | (8.7) |  |  | (6.3) |  |  | (4.0) |  |  | (4.9) |
Amortization of Net Actuarial Loss |  | 14.8 |  |  | 1.2 |  |  | 2.3 |  |  | 1.9 |  |  | 1.6 |  |  | 0.8 |  |  | 1.0 |
Net Periodic Benefit Credit |  | (107.1) |  |  | (9.2) |  |  | (15.1) |  |  | (14.3) |  |  | (11.4) |  |  | (6.4) |  |  | (7.8) |
Capitalized Portion |  | (2.1) |  |  | (0.2) |  |  | (0.2) |  |  | (0.2) |  |  | (0.2) |  |  | (0.1) |  |  | (0.2) |
Net Periodic Benefit Credit Recognized in Expense |  | $ | (109.2) |  |  | $ | (9.4) |  |  | $ | (15.3) |  |  | $ | (14.5) |  |  | $ | (11.6) |  |  | $ | (6.5) |  |  | $ | (8.0) |
2022 |  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
|  | (in millions)
Service Cost |  | $ | 7.4 |  |  | $ | 0.5 |  |  | $ | 0.8 |  |  | $ | 0.9 |  |  | $ | 0.6 |  |  | $ | 0.4 |  |  | $ | 0.6 |
Interest Cost |  | 29.2 |  |  | 2.2 |  |  | 4.7 |  |  | 3.4 |  |  | 3.0 |  |  | 1.5 |  |  | 1.8 |
Expected Return on Plan Assets |  | (110.0) |  |  | (9.1) |  |  | (16.3) |  |  | (13.7) |  |  | (12.0) |  |  | (6.1) |  |  | (7.3) |
Amortization of Prior Service Credit |  | (71.4) |  |  | (6.1) |  |  | (10.4) |  |  | (9.7) |  |  | (7.1) |  |  | (4.4) |  |  | (5.3) |
Net Periodic Benefit Credit |  | (144.8) |  |  | (12.5) |  |  | (21.2) |  |  | (19.1) |  |  | (15.5) |  |  | (8.6) |  |  | (10.2) |
Capitalized Portion |  | (3.2) |  |  | (0.3) |  |  | (0.4) |  |  | (0.3) |  |  | (0.3) |  |  | (0.2) |  |  | (0.2) |
Net Periodic Benefit Credit Recognized in Expense |  | $ | (148.0) |  |  | $ | (12.8) |  |  | $ | (21.6) |  |  | $ | (19.4) |  |  | $ | (15.8) |  |  | $ | (8.8) |  |  | $ | (10.4) |
2021 |  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
|  | (in millions)
Service Cost |  | $ | 9.5 |  |  | $ | 0.7 |  |  | $ | 1.0 |  |  | $ | 1.3 |  |  | $ | 0.8 |  |  | $ | 0.6 |  |  | $ | 0.8 |
Interest Cost |  | 30.5 |  |  | 2.4 |  |  | 4.9 |  |  | 3.5 |  |  | 3.0 |  |  | 1.6 |  |  | 1.9 |
Expected Return on Plan Assets |  | (91.1) |  |  | (7.5) |  |  | (13.5) |  |  | (11.1) |  |  | (9.7) |  |  | (5.0) |  |  | (6.1) |
Amortization of Prior Service Credit |  | (70.9) |  |  | (6.0) |  |  | (10.3) |  |  | (9.6) |  |  | (7.2) |  |  | (4.4) |  |  | (5.3) |
Net Periodic Benefit Credit |  | (122.0) |  |  | (10.4) |  |  | (17.9) |  |  | (15.9) |  |  | (13.1) |  |  | (7.2) |  |  | (8.7) |
Capitalized Portion |  | (4.1) |  |  | (0.4) |  |  | (0.4) |  |  | (0.4) |  |  | (0.4) |  |  | (0.3) |  |  | (0.3) |
Net Periodic Benefit Credit Recognized in Expense |  | $ | (126.1) |  |  | $ | (10.8) |  |  | $ | (18.3) |  |  | $ | (16.3) |  |  | $ | (13.5) |  |  | $ | (7.5) |  |  | $ | (9.0) |
Cost for Matching Contributions to the Retirement Savings Plans |
Year Ended December 31, |  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
|  | (in millions)
2023 |  | $ | 87.9 |  |  | $ | 7.1 |  |  | $ | 8.4 |  |  | $ | 11.0 |  |  | $ | 8.2 |  |  | $ | 5.3 |  |  | $ | 6.7 |
2022 |  | 81.9 |  |  | 6.5 |  |  | 7.8 |  |  | 11.1 |  |  | 7.7 |  |  | 4.7 |  |  | 6.4 |
2021 |  | 79.9 |  |  | 6.4 |  |  | 7.6 |  |  | 10.9 |  |  | 7.2 |  |  | 4.6 |  |  | 6.4 |
Benefit Obligations [Member] |  |
Actuarial Assumptions |
|  | Pension Plans |  | OPEB
|  | December 31,
Assumption |  | 2023 |  | 2022 |  | 2023 |  | 2022
Discount Rate |  | 5.15 | % |  | 5.50 | % |  | 5.15 | % |  | 5.50 | %
Interest Crediting Rate |  | 4.00 | % |  | 4.25 | % |  | NA |  | NA
NA Not applicable.
Assumption – Rate of Compensation Increase (a) - Pension Plans
|  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
December 31, 2023 |  | 5.05 | % |  | 5.20 | % |  | 4.95 | % |  | 5.05 | % |  | 5.45 | % |  | 5.20 | % |  | 5.00 | %
December 31, 2022 |  | 5.05 | % |  | 5.15 | % |  | 4.90 | % |  | 5.00 | % |  | 5.35 | % |  | 5.15 | % |  | 5.00 | %
(a)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. |
Benefit Costs [Member] |  |
Actuarial Assumptions |
|  | Pension Plans |  | OPEB
|  | Year Ended December 31,
Assumption |  | 2023 |  | 2022 |  | 2021 |  | 2023 |  | 2022 |  | 2021
Discount Rate |  | 5.50 | % |  | 2.90 | % |  | 2.50 | % |  | 5.50 | % |  | 2.90 | % |  | 2.55 | %
Interest Crediting Rate |  | 4.25 | % |  | 4.00 | % |  | 4.00 | % |  | NA |  | NA |  | NA
Expected Return on Plan Assets |  | 7.50 | % |  | 5.25 | % |  | 4.75 | % |  | 7.25 | % |  | 5.50 | % |  | 4.75 | %
NA Not applicable.
Assumption – Rate of Compensation Increase (a) - Pension Plans
|  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
December 31, 2023 |  | 5.05 | % |  | 5.20 | % |  | 4.95 | % |  | 5.05 | % |  | 5.45 | % |  | 5.20 | % |  | 5.00 | %
December 31, 2022 |  | 5.05 | % |  | 5.15 | % |  | 4.90 | % |  | 5.00 | % |  | 5.35 | % |  | 5.15 | % |  | 5.00 | %
December 31, 2021 |  | 5.10 | % |  | 5.10 | % |  | 4.85 | % |  | 5.00 | % |  | 5.30 | % |  | 5.10 | % |  | 4.95 | %
(a)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. |
Pension Plans [Member] |  |
Assets within Fair Value Hierarchy |
Asset Class |  | Level 1 |  | Level 2 |  | Level 3 |  | Other |  | Total |  | Year End Allocation
|  | (in millions) |  |
Equities (a): |  |  |  |  |  |  |  |  |  |  |  |
Domestic |  | $ | 411.3 |  |  | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | 411.3 |  |  | 10.0 | %
International |  | 389.8 |  |  | — |  |  | — |  |  | — |  |  | 389.8 |  |  | 9.5 | %
Common Collective Trusts (b) |  | — |  |  | — |  |  | — |  |  | 420.9 |  |  | 420.9 |  |  | 10.2 | %
Subtotal – Equities |  | 801.1 |  |  | — |  |  | — |  |  | 420.9 |  |  | 1,222.0 |  |  | 29.7 | %
Fixed Income (a): |  |  |  |  |  |  |  |  |  |  |  |
United States Government and Agency Securities |  | 8.3 |  |  | 1,099.2 |  |  | — |  |  | — |  |  | 1,107.5 |  |  | 26.9 | %
Corporate Debt |  | — |  |  | 894.8 |  |  | — |  |  | — |  |  | 894.8 |  |  | 21.7 | %
Foreign Debt |  | — |  |  | 167.1 |  |  | — |  |  | — |  |  | 167.1 |  |  | 4.1 | %
State and Local Government |  | — |  |  | 38.7 |  |  | — |  |  | — |  |  | 38.7 |  |  | 0.9 | %
Other – Asset Backed |  | — |  |  | 1.3 |  |  | — |  |  | — |  |  | 1.3 |  |  | — | %
Subtotal – Fixed Income |  | 8.3 |  |  | 2,201.1 |  |  | — |  |  | — |  |  | 2,209.4 |  |  | 53.6 | %
Infrastructure (b) |  | — |  |  | — |  |  | — |  |  | 101.4 |  |  | 101.4 |  |  | 2.5 | %
Real Estate (b) |  | — |  |  | — |  |  | — |  |  | 239.3 |  |  | 239.3 |  |  | 5.8 | %
Alternative Investments (b) |  | — |  |  | — |  |  | — |  |  | 241.8 |  |  | 241.8 |  |  | 5.8 | %
Cash and Cash Equivalents (b) |  | — |  |  | 51.0 |  |  | — |  |  | 33.8 |  |  | 84.8 |  |  | 2.1 | %
Other – Pending Transactions and Accrued Income (c) |  | — |  |  | — |  |  | 0.1 |  |  | 19.4 |  |  | 19.5 |  |  | 0.5 | %
Total |  | $ | 809.4 |  |  | $ | 2,252.1 |  |  | $ | 0.1 |  |  | $ | 1,056.6 |  |  | $ | 4,118.2 |  |  | 100.0 | %
(a)Includes investment securities loaned to borrowers under the securities lending program. See the “Investments Held in Trust for Future Liabilities” section of Note 1 for additional information. (b)Amounts in “Other” column represent investments for which fair value is measured using net asset value per-share. (c)Amounts in “Other” column primarily represent accrued interest, dividend receivables and transactions pending settlement.
Asset Class |  | Level 1 |  | Level 2 |  | Level 3 |  | Other |  | Total |  | Year End Allocation
|  | (in millions) |  |
Equities (a): |  |  |  |  |  |  |  |  |  |  |  |
Domestic |  | $ | 347.6 |  |  | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | 347.6 |  |  | 8.4 | %
International |  | 398.4 |  |  | — |  |  | — |  |  | — |  |  | 398.4 |  |  | 9.7 | %
Common Collective Trusts (b) |  | — |  |  | — |  |  | — |  |  | 379.9 |  |  | 379.9 |  |  | 9.2 | %
Subtotal – Equities |  | 746.0 |  |  | — |  |  | — |  |  | 379.9 |  |  | 1,125.9 |  |  | 27.3 | %
Fixed Income (a): |  |  |  |  |  |  |  |  |  |  |  |
United States Government and Agency Securities |  | (0.6) |  |  | 1,071.4 |  |  | — |  |  | — |  |  | 1,070.8 |  |  | 26.0 | %
Corporate Debt |  | — |  |  | 891.7 |  |  | — |  |  | — |  |  | 891.7 |  |  | 21.6 | %
Foreign Debt |  | — |  |  | 140.2 |  |  | — |  |  | — |  |  | 140.2 |  |  | 3.4 | %
State and Local Government |  | — |  |  | 37.0 |  |  | — |  |  | — |  |  | 37.0 |  |  | 0.9 | %
Other – Asset Backed |  | — |  |  | 0.8 |  |  | — |  |  | — |  |  | 0.8 |  |  | — | %
Subtotal – Fixed Income |  | (0.6) |  |  | 2,141.1 |  |  | — |  |  | — |  |  | 2,140.5 |  |  | 51.9 | %
Infrastructure (b) |  | — |  |  | — |  |  | — |  |  | 109.2 |  |  | 109.2 |  |  | 2.6 | %
Real Estate (b) |  | — |  |  | — |  |  | — |  |  | 276.9 |  |  | 276.9 |  |  | 6.7 | %
Alternative Investments (b) |  | — |  |  | — |  |  | — |  |  | 319.7 |  |  | 319.7 |  |  | 7.8 | %
Cash and Cash Equivalents (b) |  | — |  |  | 64.9 |  |  | — |  |  | 58.3 |  |  | 123.2 |  |  | 3.0 | %
Other – Pending Transactions and Accrued Income (c) |  | — |  |  | — |  |  | — |  |  | 29.3 |  |  | 29.3 |  |  | 0.7 | %
Total |  | $ | 745.4 |  |  | $ | 2,206.0 |  |  | $ | — |  |  | $ | 1,173.3 |  |  | $ | 4,124.7 |  |  | 100.0 | %
(a)Includes investment securities loaned to borrowers under the securities lending program. See the “Investments Held in Trust for Future Liabilities” section of Note 1 for additional information. (b)Amounts in “Other” column represent investments for which fair value is measured using net asset value per-share. (c)Amounts in “Other” column primarily represent accrued interest, dividend receivables and transactions pending settlement. |
Other Postretirement Benefit Plans [Member] |  |
Assets within Fair Value Hierarchy |
Asset Class |  | Level 1 |  | Level 2 |  | Level 3 |  | Other |  | Total |  | Year End Allocation
|  | (in millions) |  |
Equities: |  |  |  |  |  |  |  |  |  |  |  |
Domestic |  | $ | 540.6 |  |  | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | 540.6 |  |  | 32.3 | %
International |  | 288.4 |  |  | — |  |  | — |  |  | — |  |  | 288.4 |  |  | 17.2 | %
Common Collective Trusts (a) |  | — |  |  | — |  |  | — |  |  | 131.6 |  |  | 131.6 |  |  | 7.9 | %
Subtotal – Equities |  | 829.0 |  |  | — |  |  | — |  |  | 131.6 |  |  | 960.6 |  |  | 57.4 | %
Fixed Income: |  |  |  |  |  |  |  |  |  |  |  |
Common Collective Trust – Debt (a) |  | — |  |  | — |  |  | — |  |  | 146.7 |  |  | 146.7 |  |  | 8.8 | %
United States Government and Agency Securities |  | 1.4 |  |  | 163.3 |  |  | — |  |  | — |  |  | 164.7 |  |  | 9.8 | %
Corporate Debt |  | — |  |  | 149.0 |  |  | — |  |  | — |  |  | 149.0 |  |  | 8.9 | %
Foreign Debt |  | — |  |  | 28.6 |  |  | — |  |  | — |  |  | 28.6 |  |  | 1.7 | %
State and Local Government |  | 41.5 |  |  | 7.8 |  |  | — |  |  | — |  |  | 49.3 |  |  | 3.0 | %
Other – Asset Backed |  | — |  |  | 0.2 |  |  | — |  |  | — |  |  | 0.2 |  |  | — | %
Subtotal – Fixed Income |  | 42.9 |  |  | 348.9 |  |  | — |  |  | 146.7 |  |  | 538.5 |  |  | 32.2 | %
Trust Owned Life Insurance: |  |  |  |  |  |  |  |  |  |  |  |
International Equities |  | — |  |  | 22.3 |  |  | — |  |  | — |  |  | 22.3 |  |  | 1.3 | %
United States Bonds |  | — |  |  | 130.0 |  |  | — |  |  | — |  |  | 130.0 |  |  | 7.8 | %
Subtotal – Trust Owned Life Insurance |  | — |  |  | 152.3 |  |  | — |  |  | — |  |  | 152.3 |  |  | 9.1 | %
Cash and Cash Equivalents (a) |  | 25.9 |  |  | — |  |  | — |  |  | 2.9 |  |  | 28.8 |  |  | 1.7 | %
Other – Pending Transactions and Accrued Income (b) |  | — |  |  | — |  |  | — |  |  | (6.9) |  |  | (6.9) |  |  | (0.4) | %
Total |  | $ | 897.8 |  |  | $ | 501.2 |  |  | $ | — |  |  | $ | 274.3 |  |  | $ | 1,673.3 |  |  | 100.0 | %
(a)Amounts in “Other” column represent investments for which fair value is measured using net asset value per-share. (b)Amounts in “Other” column primarily represent accrued interest, dividend receivables and transactions pending settlement.
Asset Class |  | Level 1 |  | Level 2 |  | Level 3 |  | Other |  | Total |  | Year End Allocation
|  | (in millions) |  |
Equities: |  |  |  |  |  |  |  |  |  |  |  |
Domestic |  | $ | 414.1 |  |  | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | 414.1 |  |  | 26.7 | %
International |  | 265.0 |  |  | — |  |  | — |  |  | — |  |  | 265.0 |  |  | 17.1 | %
Common Collective Trusts (a) |  | — |  |  | — |  |  | — |  |  | 169.1 |  |  | 169.1 |  |  | 10.9 | %
Subtotal – Equities |  | 679.1 |  |  | — |  |  | — |  |  | 169.1 |  |  | 848.2 |  |  | 54.7 | %
Fixed Income: |  |  |  |  |  |  |  |  |  |  |  |
Common Collective Trust – Debt (a) |  | — |  |  | — |  |  | — |  |  | 120.3 |  |  | 120.3 |  |  | 7.8 | %
United States Government and Agency Securities |  | 0.1 |  |  | 155.8 |  |  | — |  |  | — |  |  | 155.9 |  |  | 10.1 | %
Corporate Debt |  | — |  |  | 141.5 |  |  | — |  |  | — |  |  | 141.5 |  |  | 9.1 | %
Foreign Debt |  | — |  |  | 21.0 |  |  | — |  |  | — |  |  | 21.0 |  |  | 1.4 | %
State and Local Government |  | 62.9 |  |  | 7.8 |  |  | — |  |  | — |  |  | 70.7 |  |  | 4.6 | %
Subtotal – Fixed Income |  | 63.0 |  |  | 326.1 |  |  | — |  |  | 120.3 |  |  | 509.4 |  |  | 33.0 | %
Trust Owned Life Insurance: |  |  |  |  |  |  |  |  |  |  |  |
International Equities |  | — |  |  | 46.7 |  |  | — |  |  | — |  |  | 46.7 |  |  | 3.0 | %
United States Bonds |  | — |  |  | 110.3 |  |  | — |  |  | — |  |  | 110.3 |  |  | 7.1 | %
Subtotal – Trust Owned Life Insurance |  | — |  |  | 157.0 |  |  | — |  |  | — |  |  | 157.0 |  |  | 10.1 | %
Cash and Cash Equivalents (a) |  | 23.2 |  |  | — |  |  | — |  |  | 6.7 |  |  | 29.9 |  |  | 1.9 | %
Other – Pending Transactions and Accrued Income (b) |  | — |  |  | — |  |  | — |  |  | 4.8 |  |  | 4.8 |  |  | 0.3 | %
Total |  | $ | 765.3 |  |  | $ | 483.1 |  |  | $ | — |  |  | $ | 300.9 |  |  | $ | 1,549.3 |  |  | 100.0 | %
(a)Amounts in “Other” column represent investments for which fair value is measured using net asset value per-share. (b)Amounts in “Other” column primarily represent accrued interest, dividend receivables and transactions pending settlement. |

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