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Defined Benefit and Other Postretirement Benefits - Plan Assets Measured at Fair Value (Details) - Trustmark Capital Accumulation Plan [Member] - Trustmark Corporation Pension Plan for Certain Employees of Acquired Financial Institutions [Member] - USD ($) $ in Thousands | Dec. 31, 2025 | Dec. 31, 2024 | Dec. 31, 2023
--- | --- | --- | ---
Asset target allocations [Abstract] |  |  |
Fair value of plan assets | $ 1,645 | $ 2,685 | $ 2,403
Level 1 [Member] |  |  |
Asset target allocations [Abstract] |  |  |
Fair value of plan assets |  | 2,685 |
Money Market Funds [Member] |  |  |
Asset target allocations [Abstract] |  |  |
Fair value of plan assets | 75 | 55 |
Money Market Funds [Member] | Level 1 [Member] |  |  |
Asset target allocations [Abstract] |  |  |
Fair value of plan assets | 75 | 55 |
Exchange Traded Equity Securities Funds [Member] |  |  |
Asset target allocations [Abstract] |  |  |
Fair value of plan assets | 500 | 874 |
Exchange Traded Equity Securities Funds [Member] | Level 1 [Member] |  |  |
Asset target allocations [Abstract] |  |  |
Fair value of plan assets | 500 | 874 |
Exchange Traded Fixed Income Funds [Member] |  |  |
Asset target allocations [Abstract] |  |  |
Fair value of plan assets | 905 | 1,600 |
Exchange Traded Fixed Income Funds [Member] | Level 1 [Member] |  |  |
Asset target allocations [Abstract] |  |  |
Fair value of plan assets | 905 | 1,600 |
International Exchange Traded Funds [Member] |  |  |
Asset target allocations [Abstract] |  |  |
Fair value of plan assets | 165 | 156 |
International Exchange Traded Funds [Member] | Level 1 [Member] |  |  |
Asset target allocations [Abstract] |  |  |
Fair value of plan assets | $ 165 | $ 156 |

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