Shareholders' Equity - Table of Actual Regulatory Capital Amounts and Ratios (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
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	$ 1,443,971	$ 1,413,672
Actual Regulatory Capital Ratio	9.76%	9.74%
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	$ 1,503,971	$ 1,473,672
Actual Regulatory Capital Ratio	10.17%	10.15%
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	$ 1,767,798	$ 1,729,499
Actual Regulatory Capital Ratio	11.95%	11.91%
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	$ 1,503,971	$ 1,473,672
Actual Regulatory Capital Ratio	8.29%	8.47%
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	$ 1,530,429	$ 1,501,889
Actual Regulatory Capital Ratio	10.35%	10.34%
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	$ 1,530,429	$ 1,501,889
Actual Regulatory Capital Ratio	10.35%	10.34%
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	$ 1,670,939	$ 1,634,454
Actual Regulatory Capital Ratio	11.30%	11.26%
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	$ 1,530,429	$ 1,501,889
Actual Regulatory Capital Ratio	8.46%	8.65%
Minimum Regulatory Capital Required Ratio	4.00%	4.00%
Minimum Regulatory Provision to be Well-Capitalized Ratio	5.00%	5.00%