Shareholders' Equity (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 Reclassification out of Accumulated Other Comprehensive Income [Member]	Sep. 30, 2012 Reclassification out of Accumulated Other Comprehensive Income [Member]	Sep. 30, 2013 Trustmark Corporation [Member] Total Capital (to Risk Weighted Assets) [Member]		Dec. 31, 2012 Trustmark Corporation [Member] Total Capital (to Risk Weighted Assets) [Member]		Sep. 30, 2013 Trustmark Corporation [Member] Tier 1 Capital (to Risk Weighted Assets) [Member]		Dec. 31, 2012 Trustmark Corporation [Member] Tier 1 Capital (to Risk Weighted Assets) [Member]		Sep. 30, 2013 Trustmark Corporation [Member] Tier 1 Capital (to Average Assets) [Member]		Dec. 31, 2012 Trustmark Corporation [Member] Tier 1 Capital (to Average Assets) [Member]		Sep. 30, 2013 Trustmark National Bank [Member] Total Capital (to Risk Weighted Assets) [Member]	Dec. 31, 2012 Trustmark National Bank [Member] Total Capital (to Risk Weighted Assets) [Member]	Sep. 30, 2013 Trustmark National Bank [Member] Tier 1 Capital (to Risk Weighted Assets) [Member]	Dec. 31, 2012 Trustmark National Bank [Member] Tier 1 Capital (to Risk Weighted Assets) [Member]	Sep. 30, 2013 Trustmark National Bank [Member] Tier 1 Capital (to Average Assets) [Member]	Dec. 31, 2012 Trustmark National Bank [Member] Tier 1 Capital (to Average Assets) [Member]
Total Capital (to Risk Weighted Assets) [Abstract]
Actual Regulatory Capital Amount							$ 1,097,058		$ 1,157,838										$ 1,055,807	$ 1,119,438
Actual Regulatory Capital Ratio (in hundredths)							14.02%		17.22%										13.63%	16.85%
Minimum Regulatory Capital Required Amount							626,067		537,861										619,558	531,577
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]									774,448	664,472
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											993,155		1,043,865								954,563	1,007,775
Actual Regulatory Capital Ratio (in hundredths)											12.69%		15.53%								12.33%	15.17%
Minimum Regulatory Capital Required Amount											313,034		268,930								309,779	265,789
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]							464,669	398,683
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															993,155		1,043,865						954,563	1,007,775
Actual Regulatory Capital Ratio (in hundredths)															8.78%		10.97%						8.53%	10.72%
Minimum Regulatory Capital Required Amount															339,316		285,556						335,621	281,984
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]					559,369	469,974
Minimum Regulatory Provision to be Well-Capitalized Ratio (in hundredths)																[1]		[1]					5.00%	5.00%
Before-Tax Amount [Abstract]
Accumulated other comprehensive income (loss), Before - Tax, balance			5,533	5,089
Unrealized holding gains (losses) on AFS arising during period, Before - Tax			(98,130)	2,970
Adjustment for net gains realized in net income, Before - Tax			(378)	(1,041)	378	1,041
Pension and other postretirement benefit plans, Before - Tax			6,471	4,755	6,471	4,755
Change in accumulated gain on effective cash flow hedge derivatives			1,963
Accumulated other comprehensive income (loss), Before - Tax, balance	(84,541)	11,773	(84,541)	11,773
Tax Effect [Abstract]
Accumulated other comprehensive income (loss), Tax Effect, balance			(2,138)	(1,968)
Unrealized holding (gain) losses arising during period, Tax Effect			37,534	(1,136)
Adjustment for net gains realized in net income, Tax Effect			145	398	145	398
Pension and other postretirement benefit plans, Tax Effect, balance			(2,475)	(1,819)
Change in accumulated gain on effective cash flow hedge derivatives			(751)
Accumulated other comprehensive income (loss), Tax Effect	32,315	(4,525)	32,315	(4,525)
Accumulated Other Comprehensive Income (Loss) [Abstract]
Accumulated Other Comprehensive Income (Loss), Net of Tax, balance			3,395	3,121
Unrealized holding gains (losses) arising during the period	(17,461)	2,618	(60,596)	1,834
Adjustment for net gains realized in net income	0	0	(233)	(643)	(233)	(643)
Pension and other postretirement benefit plans	1,565	976	3,996	2,936
Change in accumulated gain on effective cash flow hedge derivatives	(242)	0	1,212	0
Accumulated Other Comprehensive Income, (Loss) Net of Tax, balance	(52,226)	7,248	(52,226)	7,248
Securities available for sale:
Reclassification adjustment for net gains realized in net income, pre-tax income (expense)			(378)	(1,041)	378	1,041
Reclassification adjustment for net gains realized in net income, tax (expense) benefit			(145)	(398)	(145)	(398)
Reclassification adjustment for net gains realized in net income, after tax income (expense)	0	0	233	643	233	643
Pension and other postretirement benefit plans:
Amortization of prior service cost, pre-tax income (expense)					(188)	(188)
Recognized net loss due to Settlement					(1,363)
Recognized net actuarial loss, pre-tax income (expense)					(4,920)	(4,567)
Total pension and other postretirement benefit plans, pre-tax income (expense)			(6,471)	(4,755)	(6,471)	(4,755)
Amortization of prior service cost, tax (expense) benefit					72	72
Recognized net loss due to settlement, tax benefit					521
Recognized net actuarial loss, tax (expense) benefit					1,882	1,747
Total pension and other postretirement benefit plans, tax (expense) benefit					2,475	1,819
Amortization of prior service cost, after tax income (expense)					(116)	(116)
Recognized net loss due to settlement after tax income (expense)					(842)
Recognized net actuarial loss, after tax income (expense)					(3,038)	(2,820)
Total pension and other postretirement benefit plans, after tax income (expense)					$ (3,996)	$ (2,936)

[1] n/a