Shareholders' Equity - Table of Actual Regulatory Capital Amounts and Ratios (Details) - USD ($) $ in Thousands		Jun. 30, 2021	Dec. 31, 2020
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		$ 1,441,102	$ 1,395,844
Actual Regulatory Capital Ratio		11.76%	11.62%
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		$ 1,501,102	$ 1,455,844
Actual Regulatory Capital Ratio		12.25	12.11
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		$ 1,728,478	$ 1,696,794
Actual Regulatory Capital Ratio		14.10	14.12
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		$ 1,501,102	$ 1,455,844
Actual Regulatory Capital Ratio		9.00	9.33
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		$ 1,491,066	$ 1,412,015
Actual Regulatory Capital Ratio		12.17%	11.75%
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		$ 1,491,066	$ 1,412,015
Actual Regulatory Capital Ratio		12.17	11.75
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		$ 1,595,510	$ 1,530,044
Actual Regulatory Capital Ratio		13.02	12.73
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		$ 1,491,066	$ 1,412,015
Actual Regulatory Capital Ratio		8.96	9.07
Minimum Regulatory Capital Required Ratio		4.00	4.00
Minimum Regulatory Provision to be Well-Capitalized Ratio		5.00	5.00

[1] n/a