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Defined Benefit and Other Postretirement Benefits - Weighted-Average Asset Allocation (Details) - Trustmark Capital Accumulation Plan [Member] - Trustmark Corporation Pension Plan for Certain Employees of Acquired Financial Institutions [Member] | Dec. 31, 2025 | Dec. 31, 2024
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Asset target allocations [Abstract] |  |
Weighted-average asset allocation (in hundredths) | 100.00% | 100.00%
Money Market Funds [Member] |  |
Asset target allocations [Abstract] |  |
Weighted-average asset allocation (in hundredths) | 5.00% | 2.00%
Exchange Traded Equity Securities Funds [Member] |  |
Asset target allocations [Abstract] |  |
Weighted-average asset allocation (in hundredths) | 30.00% | 33.00%
Exchange Traded Fixed Income Funds [Member] |  |
Asset target allocations [Abstract] |  |
Weighted-average asset allocation (in hundredths) | 55.00% | 59.00%
International Exchange Traded Funds [Member] |  |
Asset target allocations [Abstract] |  |
Weighted-average asset allocation (in hundredths) | 10.00% | 6.00%

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- Definition Percentage of actual investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(i) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 + Details
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