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, 2023	Dec. 31, 2022	Dec. 31, 2021
Asset target allocations [Abstract]
Fair value of plan assets	$ 2,403	$ 2,907	$ 2,900
Level 1 [Member]
Asset target allocations [Abstract]
Fair value of plan assets	2,403	2,907
Money Market Funds [Member]
Asset target allocations [Abstract]
Fair value of plan assets	643	203
Money Market Funds [Member] | Level 1 [Member]
Asset target allocations [Abstract]
Fair value of plan assets	643	203
Exchange Traded Equity Securities Funds [Member]
Asset target allocations [Abstract]
Fair value of plan assets	861	1,379
Exchange Traded Equity Securities Funds [Member] | Level 1 [Member]
Asset target allocations [Abstract]
Fair value of plan assets	861	1,379
Exchange Traded Fixed Income Funds [Member]
Asset target allocations [Abstract]
Fair value of plan assets	690	1,135
Exchange Traded Fixed Income Funds [Member] | Level 1 [Member]
Asset target allocations [Abstract]
Fair value of plan assets	690	1,135
International Exchange Traded Funds [Member]
Asset target allocations [Abstract]
Fair value of plan assets	209	190
International Exchange Traded Funds [Member] | Level 1 [Member]
Asset target allocations [Abstract]
Fair value of plan assets	$ 209	$ 190