Shareholders' Equity - Table of Actual Regulatory Capital Amounts and Ratios (Details) - USD ($) $ in Thousands		Jun. 30, 2017	Dec. 31, 2016
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		$ 1,218,962	$ 1,209,927
Actual Regulatory Capital Ratio		11.73%	12.16%
Minimum Regulatory Capital Required Ratio		5.75%	5.125%
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		$ 1,278,714	$ 1,269,660
Actual Regulatory Capital Ratio		12.30%	12.76%
Minimum Regulatory Capital Required Ratio		7.25%	6.625%
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		$ 1,362,321	$ 1,352,322
Actual Regulatory Capital Ratio		13.11%	13.59%
Minimum Regulatory Capital Required Ratio		9.25%	8.625%
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		$ 1,278,714	$ 1,269,660
Actual Regulatory Capital Ratio		9.56%	9.90%
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		$ 1,260,808	$ 1,251,329
Actual Regulatory Capital Ratio		12.13%	12.58%
Minimum Regulatory Capital Required Ratio		5.75%	5.125%
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		$ 1,260,808	$ 1,251,329
Actual Regulatory Capital Ratio		12.13%	12.58%
Minimum Regulatory Capital Required Ratio		7.25%	6.625%
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		$ 1,344,415	$ 1,333,991
Actual Regulatory Capital Ratio		12.94%	13.41%
Minimum Regulatory Capital Required Ratio		9.25%	8.625%
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		$ 1,260,808	$ 1,251,329
Actual Regulatory Capital Ratio		9.44%	9.77%
Minimum Regulatory Capital Required Ratio		4.00%	4.00%
Minimum Regulatory Provision to be Well-Capitalized Ratio		5.00%	5.00%

[1] n/a