Shareholders' Equity (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2012 Total Capital (to Risk Weighted Assets) [Member] Trustmark Corporation [Member]		Dec. 31, 2011 Total Capital (to Risk Weighted Assets) [Member] Trustmark Corporation [Member]		Mar. 31, 2012 Total Capital (to Risk Weighted Assets) [Member] Trustmark National Bank [Member]	Dec. 31, 2011 Total Capital (to Risk Weighted Assets) [Member] Trustmark National Bank [Member]	Mar. 31, 2012 Tier 1 Capital (to Risk Weighted Assets) [Member] Trustmark Corporation [Member]		Dec. 31, 2011 Tier 1 Capital (to Risk Weighted Assets) [Member] Trustmark Corporation [Member]		Mar. 31, 2012 Tier 1 Capital (to Risk Weighted Assets) [Member] Trustmark National Bank [Member]	Dec. 31, 2011 Tier 1 Capital (to Risk Weighted Assets) [Member] Trustmark National Bank [Member]	Mar. 31, 2012 Tier 1 Capital (to Average Assets) [Member] Trustmark Corporation [Member]		Dec. 31, 2011 Tier 1 Capital (to Average Assets) [Member] Trustmark Corporation [Member]		Mar. 31, 2012 Tier 1 Capital (to Average Assets) [Member] Trustmark National Bank [Member]	Dec. 31, 2011 Tier 1 Capital (to Average Assets) [Member] Trustmark National Bank [Member]
Total Capital (to Risk Weighted Assets) [Abstract]
Actual Regulatory Capital Amount			$ 1,121,259		$ 1,096,213		$ 1,083,298	$ 1,057,932
Actual Regulatory Capital Ratio (in hundredths)			16.72%		16.67%		16.33%	16.28%
Minimum Regulatory Capital Required Amount			536,562		526,156		530,549	519,709
Minimum Regulatory Capital Required Ratio (in hundredths)			8.00%		8.00%		8.00%	8.00%
Minimum Regulatory Provision to be Well-Capitalized Amount				[1]		[1]	663,186	649,636
Minimum Regulatory Provision to be Well-Capitalized Ratio (in hundredths)				[1]		[1]	10.00%	10.00%
Tier 1 Capital (to Risk Weighted Assets) [Abstract]
Actual Regulatory Capital Amount									997,447		974,034		961,735	938,122
Actual Regulatory Capital Ratio (in hundredths)									14.87%		14.81%		14.50%	14.44%
Minimum Regulatory Capital Required Amount									268,281		263,078		265,274	259,855
Minimum Regulatory Capital Required Ratio (in hundredths)									4.00%		4.00%		4.00%	4.00%
Minimum Regulatory Provision to be Well-Capitalized Amount										[1]		[1]	397,911	389,782
Minimum Regulatory Provision to be Well-Capitalized Ratio (in hundredths)										[1]		[1]	6.00%	6.00%
Tier 1 Capital (to Average Assets) [Abstract]
Actual Regulatory Capital Amount															997,447		974,034		961,735	938,122
Actual Regulatory Capital Ratio (in hundredths)															10.55%		10.43%		10.31%	10.18%
Minimum Regulatory Capital Required Amount															283,574		280,162		279,918	276,502
Minimum Regulatory Capital Required Ratio (in hundredths)															3.00%		3.00%		3.00%	3.00%
Minimum Regulatory Provision to be Well-Capitalized Amount																[1]		[1]	466,530	460,837
Minimum Regulatory Provision to be Well-Capitalized Ratio (in hundredths)																[1]		[1]	5.00%	5.00%
Other Comprehensive Income (Loss) before Tax [Abstract]
Accumulated other comprehensive income (loss), before tax	5,089	(18,469)
Unrealized Holding Gain (Loss) on AFS Arising During Period, before Tax	(3,103)	(1,531)
Adjustment for net gains realized in net income, before tax	(1,050)	(7)
Pension and other postretirement benefit plans, before tax	1,587	1,219
Accumulated other comprehensive income (loss), before tax	2,523	(18,788)
Other Comprehensive Income (Loss), Tax [Abstract]
Accumulated other comprehensive income (loss), tax effect	(1,968)	7,043
Unrealized Holding Gain (Loss) on AFS Arising During Period, Tax Effect	1,187	585
Adjustment for net gains realized in net income, tax effect	402	3
Pension and other postretirement benefit plans, tax effect	(607)	(466)
Accumulated other comprehensive income (loss), tax effect	(986)	7,165
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss), Net of Tax	3,121	(11,426)
Unrealized holding gain (loss) on AFS arising during period, net of tax	(1,916)	(946)
Adjustment for net gains realized in net income, net of tax	(648)	(4)
Pension and other postretirement benefit plans, net of tax	980	753
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ 1,537	$ (11,623)

[1] n/a