Shareholders' Equity - Table of Actual Regulatory Capital Amounts and Ratios (Details) - USD ($) $ in Thousands		Mar. 31, 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		$ 1,425,283	$ 1,425,227
Actual Regulatory Capital Ratio		11.23%	11.29%
Minimum Regulatory Capital Required Ratio		7.00%	7.00%
Minimum Regulatory Provision to be Well-Capitalized Ratio	[1]
Trustmark Corporation [Member] | Tier 1 Capital (to Risk Weighted Assets) [Member]
Tier 1 Capital (to Risk Weighted Assets) [Abstract]
Actual Regulatory Capital Amount		$ 1,485,283	$ 1,485,227
Actual Regulatory Capital Ratio		11.70%	11.77%
Minimum Regulatory Capital Required Ratio		8.50%	8.50%
Minimum Regulatory Provision to be Well-Capitalized Ratio	[1]
Trustmark Corporation [Member] | Total Capital (to Risk Weighted Assets) [Member]
Total Capital (to Risk Weighted Assets) [Abstract]
Actual Regulatory Capital Amount		$ 1,717,144	$ 1,710,700
Actual Regulatory Capital Ratio		13.53%	13.55%
Minimum Regulatory Capital Required Ratio		10.50%	10.50%
Minimum Regulatory Provision to be Well-Capitalized Ratio	[1]
Trustmark Corporation [Member] | Tier 1 Leverage (to Average Assets) [Member]
Tier 1 Leverage (to Average Assets) [Abstract]
Actual Regulatory Capital Amount		$ 1,485,283	$ 1,485,227
Actual Regulatory Capital Ratio		8.66%	8.73%
Minimum Regulatory Capital Required Ratio		4.00%	4.00%
Minimum Regulatory Provision to be Well-Capitalized Ratio	[1]
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		$ 1,516,646	$ 1,518,599
Actual Regulatory Capital Ratio		11.95%	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		$ 1,516,646	$ 1,518,599
Actual Regulatory Capital Ratio		11.95%	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		$ 1,625,410	$ 1,621,030
Actual Regulatory Capital Ratio		12.81%	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		$ 1,516,646	$ 1,518,599
Actual Regulatory Capital Ratio		8.86%	8.94%
Minimum Regulatory Capital Required Ratio		4.00%	4.00%
Minimum Regulatory Provision to be Well-Capitalized Ratio		5.00%	5.00%

[1] n/a