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Defined Benefit and Other Postretirement Benefits (Tables) | 12 Months Ended
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Dec. 31, 2025
Trustmark Capital Accumulation Plan [Member] |
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items] |
Plan Benefit Obligation, Plan Assets and Funded Status of the Plan | The following tables present information regarding the benefit obligation, plan assets, funded status, amounts recognized in accumulated other comprehensive loss, net periodic benefit cost and other statistical disclosures for the Continuing Plan for the periods presented ($ in thousands):
|  | December 31, |
|  | 2025 |  |  | 2024 |
Change in benefit obligation: |  |  |  |  |  |
Benefit obligation, beginning of year |  | $ | 5,531 |  |  | $ | 5,923 |
Service cost |  |  | 36 |  |  |  | 40 |
Interest cost |  |  | 275 |  |  |  | 246 |
Actuarial (gain) loss |  |  | (23 | ) |  |  | (214 | )
Benefits paid |  |  | (1,500 | ) |  |  | (464 | )
Benefit obligation, end of year |  | $ | 4,319 |  |  | $ | 5,531 |
Change in plan assets: |  |  |  |  |  |
Fair value of plan assets, beginning of year |  | $ | 2,685 |  |  | $ | 2,403 |
Actual return on plan assets |  |  | 161 |  |  |  | 233 |
Employer contributions |  |  | 299 |  |  |  | 513 |
Benefit payments |  |  | (1,500 | ) |  |  | (464 | )
Fair value of plan assets, end of year |  | $ | 1,645 |  |  | $ | 2,685 |
Funded status at end of year - net liability |  | $ | (2,674 | ) |  | $ | (2,846 | )
Amounts recognized in accumulated other comprehensive loss: |  |  |  |  |  |
Net (gain) loss - amount recognized |  | $ | (574 | ) |  | $ | (601 | )
Actuarial (gain) loss included in benefit obligation: |  |  |  |  |  |
Change in discount rate |  | $ | 120 |  |  | $ | (344 | )
Change in mortality table |  |  | — |  |  |  | — |
Other |  |  | (143 | ) |  |  | 130 |
Actuarial (gain) loss |  | $ | (23 | ) |  | $ | (214 | )
Net Periodic Benefit Cost |
|  | Years Ended December 31, |
|  | 2025 |  |  | 2024 |  |  | 2023 |
Net periodic benefit cost: |  |  |  |  |  |  |  |  |
Service cost |  | $ | 36 |  |  | $ | 40 |  |  | $ | 52 |
Interest cost |  |  | 275 |  |  |  | 246 |  |  |  | 292 |
Expected return on plan assets |  |  | (125 | ) |  |  | (96 | ) |  |  | (107 | )
Recognized net (gain) loss due to lump sum settlements |  |  | (79 | ) |  |  | (13 | ) |  |  | 25 |
Recognized net actuarial loss |  |  | (7 | ) |  |  | — |  |  |  | — |
Net periodic benefit cost |  | $ | 100 |  |  | $ | 177 |  |  | $ | 262 |
Other changes in plan assets and benefit obligation recognized in other comprehensive income (loss), before taxes: |  |  |  |  |  |  |  |  |
Net loss - Total recognized in other comprehensive income (loss) |  | $ | 27 |  |  | $ | (339 | ) |  | $ | 9 |
Total recognized in net periodic benefit cost and other comprehensive income (loss) |  | $ | 127 |  |  | $ | (162 | ) |  | $ | 271 |
Weighted-average assumptions as of end of year: |  |  |  |  |  |  |  |  |
Discount rate for benefit obligation |  |  | 4.99 | % |  |  | 5.30 | % |  |  | 4.67 | %
Discount rate for net periodic benefit cost |  |  | 5.30 | % |  |  | 4.67 | % |  |  | 4.88 | %
Expected long-term return on plan assets |  |  | 5.00 | % |  |  | 5.00 | % |  |  | 5.00 | %
Weighted-Average Asset Allocation | The weighted-average asset allocations by asset category are presented below for the Continuing Plan at December 31, 2025 and 2024.
|  | December 31, |
|  | 2025 |  |  | 2024 |
Money market fund |  |  | 5.0 | % |  |  | 2.0 | %
Exchange traded funds: |  |  |  |  |  |
Equity securities |  |  | 30.0 | % |  |  | 33.0 | %
Fixed income |  |  | 55.0 | % |  |  | 59.0 | %
International |  |  | 10.0 | % |  |  | 6.0 | %
Total |  |  | 100.0 | % |  |  | 100.0 | %
Plan Assets Measured at Fair Value | The following tables set forth by level, within the fair value hierarchy, the Continuing Plan’s assets measured at fair value at December 31, 2025 and 2024 ($ in thousands):
|  | December 31, 2025 |
|  | Total |  |  | Level 1 |  |  | Level 2 |  |  | Level 3 |
Money market fund |  | $ | 75 |  |  | $ | 75 |  |  | $ | — |  |  | $ | — |
Exchange traded funds: |  |  |  |  |  |  |  |  |  |  |  |
Equity securities |  |  | 500 |  |  |  | 500 |  |  |  | — |  |  |  | — |
Fixed income |  |  | 905 |  |  |  | 905 |  |  |  | — |  |  |  | — |
International |  |  | 165 |  |  |  | 165 |  |  |  | — |  |  |  | — |
Total assets at fair value |  | $ | 1,645 |  |  | $ | 1,645 |  |  | $ | — |  |  | $ | — |
|  | December 31, 2024 |
|  | Total |  |  | Level 1 |  |  | Level 2 |  |  | Level 3 |
Money market fund |  | $ | 55 |  |  | $ | 55 |  |  | $ | — |  |  | $ | — |
Exchange traded funds: |  |  |  |  |  |  |  |  |  |  |  |
Equity securities |  |  | 874 |  |  |  | 874 |  |  |  | — |  |  |  | — |
Fixed income |  |  | 1,600 |  |  |  | 1,600 |  |  |  | — |  |  |  | — |
International |  |  | 156 |  |  |  | 156 |  |  |  | — |  |  |  | — |
Total assets at fair value |  | $ | 2,685 |  |  | $ | 2,685 |  |  | $ | — |  |  | $ | — |
Estimated Future Benefit Payments and Other Disclosures | The following table presents the expected benefit payments, which reflect expected future service, for the Continuing Plan ($ in thousands):
Year |  | Amount |
2026 |  | $ | 624 |
2027 |  |  | 846 |
2028 |  |  | 513 |
2029 |  |  | 374 |
2030 |  |  | 334 |
2031 - 2035 |  |  | 1,178 |
Supplemental Retirement Plan [Member] |
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items] |
Plan Benefit Obligation, Plan Assets and Funded Status of the Plan | The following tables present information regarding the benefit obligation, plan assets, funded status, amounts recognized in accumulated other comprehensive loss, net periodic benefit cost and other statistical disclosures for Trustmark’s nonqualified supplemental retirement plans for the periods presented ($ in thousands):
|  | December 31, |
|  | 2025 |  |  | 2024 |
Change in benefit obligation: |  |  |  |  |  |
Benefit obligation, beginning of year |  | $ | 38,162 |  |  | $ | 41,619 |
Service cost |  |  | 15 |  |  |  | 45 |
Interest cost |  |  | 1,921 |  |  |  | 1,851 |
Actuarial (gain) loss |  |  | 845 |  |  |  | (1,009 | )
Benefits paid |  |  | (3,868 | ) |  |  | (4,344 | )
Benefit obligation, end of year |  | $ | 37,075 |  |  | $ | 38,162 |
Change in plan assets: |  |  |  |  |  |
Fair value of plan assets, beginning of year |  | $ | — |  |  | $ | — |
Employer contributions |  |  | 3,868 |  |  |  | 4,344 |
Benefit payments |  |  | (3,868 | ) |  |  | (4,344 | )
Fair value of plan assets, end of year |  | $ | — |  |  | $ | — |
Funded status at end of year - net liability |  | $ | (37,075 | ) |  | $ | (38,162 | )
Amounts recognized in accumulated other comprehensive loss: |  |  |  |  |  |
Net loss |  | $ | 7,465 |  |  | $ | 6,880 |
Prior service cost |  |  | — |  |  |  | 15 |
Amounts recognized |  | $ | 7,465 |  |  | $ | 6,895 |
Actuarial (gain) loss included in benefit obligation: |  |  |  |  |  |
Change in discount rate |  | $ | 788 |  |  | $ | (1,794 | )
Change in mortality table |  |  | — |  |  |  | — |
Other |  |  | 57 |  |  |  | 785 |
Actuarial (gain) loss |  | $ | 845 |  |  | $ | (1,009 | )
Net Periodic Benefit Cost |
|  | Years Ended December 31, |
|  | 2025 |  |  | 2024 |  |  | 2023 |
Net periodic benefit cost: |  |  |  |  |  |  |  |  |
Service cost |  | $ | 15 |  |  | $ | 45 |  |  | $ | 69 |
Interest cost |  |  | 1,921 |  |  |  | 1,851 |  |  |  | 2,013 |
Amortization of prior service cost |  |  | 15 |  |  |  | 111 |  |  |  | 111 |
Recognized net actuarial loss |  |  | 261 |  |  |  | 346 |  |  |  | 284 |
Net periodic benefit cost |  | $ | 2,212 |  |  | $ | 2,353 |  |  | $ | 2,477 |
Other changes in plan assets and benefit obligation recognized in other comprehensive income (loss), before taxes: |  |  |  |  |  |  |  |  |
Net (gain) loss |  | $ | 585 |  |  | $ | (1,355 | ) |  | $ | 479 |
Amortization of prior service cost |  |  | (15 | ) |  |  | (111 | ) |  |  | (111 | )
Total recognized in other comprehensive income (loss) |  | $ | 570 |  |  | $ | (1,466 | ) |  | $ | 368 |
Total recognized in net periodic benefit cost and other comprehensive income (loss) |  | $ | 2,782 |  |  | $ | 887 |  |  | $ | 2,845 |
Weighted-average assumptions as of end of year: |  |  |  |  |  |  |  |  |
Discount rate for benefit obligation |  |  | 4.99 | % |  |  | 5.30 | % |  |  | 4.67 | %
Discount rate for net periodic benefit cost |  |  | 5.30 | % |  |  | 4.67 | % |  |  | 4.88 | %
Estimated Future Benefit Payments and Other Disclosures | The following table presents the expected benefits payments for Trustmark’s supplemental retirement plans ($ in thousands):
Year |  | Amount |
2026 |  | $ | 3,856 |
2027 |  |  | 3,687 |
2028 |  |  | 3,562 |
2029 |  |  | 3,563 |
2030 |  |  | 3,465 |
2031 - 2035 |  |  | 14,656 |

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- Definition Tabular disclosure of assets, including [financial] instruments measured at fair value, by class that are measured at fair value on a recurring basis. Fair value measurements at the reporting date by the level within the fair value hierarchy in which the fair value measurements in their entirety fall, segregating fair value measurements using quoted prices in active markets for identical assets (Level 1), significant other observable inputs (Level 2), and significant unobservable inputs (Level 3). + References No definition available. + Details
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- Definition Tabular disclosure of the major categories of plan assets of pension plans and/or other employee benefit plans. This information may include, but is not limited to, the target allocation of plan assets, the fair value of each major category of plan assets, and the level within the fair value hierarchy in which the fair value measurements fall. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 715 -SubTopic 20 -Subparagraph (d)(5) -Name Accounting Standards Codification -Paragraph 1 -Section 50 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 + Details
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- Definition Tabular disclosure of the change in the benefit obligation of pension plans and/or other employee benefit plans from the beginning to the end of the period, showing separately, if applicable, the effects of the following: service cost, interest cost, contributions by plan participants, actuarial gains and losses, foreign currency exchange rate changes, benefits paid, plan amendments, business combinations, divestitures, curtailments, settlements, and special and contractual termination benefits. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 715 -SubTopic 20 -Subparagraph (a) -Name Accounting Standards Codification -Paragraph 1 -Section 50 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 + Details
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- Definition Tabular disclosure of one or more of the entity's defined benefit pension plans or one or more other defined benefit postretirement plans, separately for pension plans and other postretirement benefit plans including the entity's schedule of fair value of plan assets for defined benefit or other postretirement plans. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-5 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 1 -SubTopic 20 -Topic 715 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480482/715-20-55-17 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 3 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-3 Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 4 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-4 Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-2 + Details
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