Shareholders' Equity - Table of Actual Regulatory Capital Amounts and Ratios (Details) $ in Thousands	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
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	$ 1,425,227	$ 1,395,844
Actual Regulatory Capital Ratio	11.29%	11.62%
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	$ 1,485,227	$ 1,455,844
Actual Regulatory Capital Ratio	11.77	12.11
Minimum Regulatory Capital Required Ratio	8.500	8.500
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	$ 1,710,700	$ 1,696,794
Actual Regulatory Capital Ratio	13.55	14.12
Minimum Regulatory Capital Required Ratio	10.500	10.500
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	$ 1,485,227	$ 1,455,844
Actual Regulatory Capital Ratio	8.73	9.33
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	$ 1,518,599	$ 1,412,015
Actual Regulatory Capital Ratio	12.03%	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	$ 1,518,599	$ 1,412,015
Actual Regulatory Capital Ratio	12.03	11.75
Minimum Regulatory Capital Required Ratio	8.500	8.500
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	$ 1,621,030	$ 1,530,044
Actual Regulatory Capital Ratio	12.84	12.73
Minimum Regulatory Capital Required Ratio	10.500	10.500
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	$ 1,518,599	$ 1,412,015
Actual Regulatory Capital Ratio	8.94	9.07
Minimum Regulatory Capital Required Ratio	4.00	4.00
Minimum Regulatory Provision to be Well-Capitalized Ratio	5.00	5.00