Shareholders' Equity - Table of Actual Regulatory Capital Amounts and Ratios (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Trustmark Corporation [Member] | Common Equity Tier 1 Capital (to Risk Weighted Assets) [Member]
Common Equity Tier One Risk Based Capital [Abstract]
Actual Regulatory Capital Amount	$ 1,543,460	$ 1,521,665
Actual Regulatory Capital Ratio	10.12%	10.04%
Minimum Regulatory Capital Required Ratio	7.00%	7.00%
Minimum Regulatory Provision to be Well-Capitalized Ratio
Trustmark Corporation [Member] | Tier 1 Capital (to Risk Weighted Assets) [Member]
Tier 1 Capital (to Risk Weighted Assets) [Abstract]
Actual Regulatory Capital Amount	$ 1,603,460	$ 1,581,665
Actual Regulatory Capital Ratio	10.51%	10.44%
Minimum Regulatory Capital Required Ratio	8.50%	8.50%
Minimum Regulatory Provision to be Well-Capitalized Ratio
Trustmark Corporation [Member] | Total Capital (to Risk Weighted Assets) [Member]
Total Capital (to Risk Weighted Assets) [Abstract]
Actual Regulatory Capital Amount	$ 1,895,697	$ 1,862,246
Actual Regulatory Capital Ratio	12.42%	12.29%
Minimum Regulatory Capital Required Ratio	10.50%	10.50%
Minimum Regulatory Provision to be Well-Capitalized Ratio
Trustmark Corporation [Member] | Tier 1 Leverage (to Average Assets) [Member]
Tier 1 Leverage (to Average Assets) [Abstract]
Actual Regulatory Capital Amount	$ 1,603,460	$ 1,581,665
Actual Regulatory Capital Ratio	8.76%	8.62%
Minimum Regulatory Capital Required Ratio	4.00%	4.00%
Minimum Regulatory Provision to be Well-Capitalized Ratio
Trustmark National Bank [Member] | Common Equity Tier 1 Capital (to Risk Weighted Assets) [Member]
Common Equity Tier One Risk Based Capital [Abstract]
Actual Regulatory Capital Amount	$ 1,620,495	$ 1,602,327
Actual Regulatory Capital Ratio	10.62%	10.58%
Minimum Regulatory Capital Required Ratio	7.00%	7.00%
Minimum Regulatory Provision to be Well-Capitalized Ratio	6.50%	6.50%
Trustmark National Bank [Member] | Tier 1 Capital (to Risk Weighted Assets) [Member]
Tier 1 Capital (to Risk Weighted Assets) [Abstract]
Actual Regulatory Capital Amount	$ 1,620,495	$ 1,602,327
Actual Regulatory Capital Ratio	10.62%	10.58%
Minimum Regulatory Capital Required Ratio	8.50%	8.50%
Minimum Regulatory Provision to be Well-Capitalized Ratio	8.00%	8.00%
Trustmark National Bank [Member] | Total Capital (to Risk Weighted Assets) [Member]
Total Capital (to Risk Weighted Assets) [Abstract]
Actual Regulatory Capital Amount	$ 1,789,195	$ 1,759,426
Actual Regulatory Capital Ratio	11.73%	11.61%
Minimum Regulatory Capital Required Ratio	10.50%	10.50%
Minimum Regulatory Provision to be Well-Capitalized Ratio	10.00%	10.00%
Trustmark National Bank [Member] | Tier 1 Leverage (to Average Assets) [Member]
Tier 1 Leverage (to Average Assets) [Abstract]
Actual Regulatory Capital Amount	$ 1,620,495	$ 1,602,327
Actual Regulatory Capital Ratio	8.87%	8.75%
Minimum Regulatory Capital Required Ratio	4.00%	4.00%
Minimum Regulatory Provision to be Well-Capitalized Ratio	5.00%	5.00%