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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
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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- References

No definition available.

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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

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