Shareholders' Equity - Table of Actual Regulatory Capital Amounts and Ratios (Details) - USD ($) $ in Thousands		Sep. 30, 2016	Dec. 31, 2015
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		$ 1,194,729	$ 1,161,598
Actual Regulatory Capital Ratio		12.35%	12.57%
Minimum Regulatory Capital Required Ratio		5.125%	4.50%
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		$ 1,254,453	$ 1,220,535
Actual Regulatory Capital Ratio		12.97%	13.21%
Minimum Regulatory Capital Required Ratio		6.625%	6.00%
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		$ 1,336,704	$ 1,300,146
Actual Regulatory Capital Ratio		13.82%	14.07%
Minimum Regulatory Capital Required Ratio		8.625%	8.00%
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		$ 1,254,453	$ 1,220,535
Actual Regulatory Capital Ratio		9.92%	10.03%
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		$ 1,235,923	$ 1,201,113
Actual Regulatory Capital Ratio		12.78%	13.00%
Minimum Regulatory Capital Required Ratio		5.125%	4.50%
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		$ 1,235,923	$ 1,201,113
Actual Regulatory Capital Ratio		12.78%	13.00%
Minimum Regulatory Capital Required Ratio		6.625%	6.00%
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		$ 1,318,174	$ 1,280,724
Actual Regulatory Capital Ratio		13.63%	13.86%
Minimum Regulatory Capital Required Ratio		8.625%	8.00%
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		$ 1,235,923	$ 1,201,113
Actual Regulatory Capital Ratio		9.79%	9.89%
Minimum Regulatory Capital Required Ratio		4.00%	4.00%
Minimum Regulatory Provision to be Well-Capitalized Ratio		5.00%	5.00%

[1] n/a