Defined Benefit and Other Postretirement Benefits - Estimated Future Benefit Payments and Other Disclosures (Details) $ in Thousands	Dec. 31, 2017 USD ($)
Supplemental Retirement Plan [Member]
Estimated future benefit payments [Abstract]
2018	$ 3,475
2019	3,591
2020	4,047
2021	4,105
2022	4,262
2023 - 2027	19,230
Trustmark Corporation Pension Plan for Certain Employees of Acquired Financial Institutions [Member] \| Trustmark Capital Accumulation Plan [Member]
Estimated future benefit payments [Abstract]
2018	196
2019	282
2020	333
2021	394
2022	453
2023 - 2027	$ 2,961

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- Definition

Amount of benefits for defined benefit plan expected to be paid in five fiscal years after fifth fiscal year following latest fiscal year.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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- Definition

Amount of benefits for defined benefit plan expected to be paid in next fiscal year following latest fiscal year.

+ References

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- Definition

Amount of benefits for defined benefit plan expected to be paid in fifth fiscal year following latest fiscal year.

+ References

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Amount of benefits for defined benefit plan expected to be paid in fourth fiscal year following latest fiscal year.

+ References

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Amount of benefits for defined benefit plan expected to be paid in third fiscal year following latest fiscal year.

+ References

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Amount of benefits for defined benefit plan expected to be paid in second fiscal year following latest fiscal year.

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