Shareholders' Equity - Table of Actual Regulatory Capital Amounts and Ratios (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
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	$ 1,439,352	$ 1,425,227
Actual Regulatory Capital Ratio	11.01%	11.29%
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	$ 1,499,352	$ 1,485,227
Actual Regulatory Capital Ratio	11.47%	11.77%
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	$ 1,734,106	$ 1,710,700
Actual Regulatory Capital Ratio	13.26%	13.55%
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	$ 1,499,352	$ 1,485,227
Actual Regulatory Capital Ratio	8.80%	8.73%
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	$ 1,529,578	$ 1,518,599
Actual Regulatory Capital Ratio	11.70%	12.03%
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	$ 1,529,578	$ 1,518,599
Actual Regulatory Capital Ratio	11.70%	12.03%
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	$ 1,641,180	$ 1,621,030
Actual Regulatory Capital Ratio	12.55%	12.84%
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	$ 1,529,578	$ 1,518,599
Actual Regulatory Capital Ratio	9.00%	8.94%
Minimum Regulatory Capital Required Ratio	4.00%	4.00%
Minimum Regulatory Provision to be Well-Capitalized Ratio	5.00%	5.00%