Shareholders' Equity - Table of Actual Regulatory Capital Amounts and Ratios (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
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	$ 1,746,998	$ 1,729,672
Actual Regulatory Capital Ratio	11.63%	11.54%
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	$ 1,806,998	$ 1,789,672
Actual Regulatory Capital Ratio	12.03%	11.94%
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	$ 2,118,632	$ 2,094,874
Actual Regulatory Capital Ratio	14.10%	13.97%
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	$ 1,806,998	$ 1,789,672
Actual Regulatory Capital Ratio	10.11%	9.99%
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	$ 1,838,631	$ 1,828,044
Actual Regulatory Capital Ratio	12.24%	12.20%
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	$ 1,838,631	$ 1,828,044
Actual Regulatory Capital Ratio	12.24%	12.20%
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	$ 2,026,479	$ 2,009,544
Actual Regulatory Capital Ratio	13.49%	13.41%
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	$ 1,838,631	$ 1,828,044
Actual Regulatory Capital Ratio	10.29%	10.21%
Minimum Regulatory Capital Required Ratio	4.00%	4.00%
Minimum Regulatory Provision to be Well-Capitalized Ratio	5.00%	5.00%