Shareholders' Equity (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013 Reclassification out of Accumulated Other Comprehensive Income [Member]	Mar. 31, 2012 Reclassification out of Accumulated Other Comprehensive Income [Member]	Mar. 31, 2013 Trustmark Corporation [Member] Total Capital (to Risk Weighted Assets) [Member]		Dec. 31, 2012 Trustmark Corporation [Member] Total Capital (to Risk Weighted Assets) [Member]		Mar. 31, 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]		Mar. 31, 2013 Trustmark Corporation [Member] Tier 1 Capital (to Average Assets) [Member]		Dec. 31, 2012 Trustmark Corporation [Member] Tier 1 Capital (to Average Assets) [Member]		Mar. 31, 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]	Mar. 31, 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]	Mar. 31, 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					$ 1,133,455		$ 1,157,838										$ 1,056,721	$ 1,119,438
Actual Regulatory Capital Ratio (in hundredths)					14.36%		17.22%										13.52%	16.85%
Minimum Regulatory Capital Required Amount					631,326		537,861										625,446	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]									781,807	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									1,020,170		1,043,865								945,910	1,007,775
Actual Regulatory Capital Ratio (in hundredths)									12.93%		15.53%								12.10%	15.17%
Minimum Regulatory Capital Required Amount									315,663		268,930								312,723	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]							469,084	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													1,020,170		1,043,865						945,910	1,007,775
Actual Regulatory Capital Ratio (in hundredths)													9.83%		10.97%						9.23%	10.72%
Minimum Regulatory Capital Required Amount													311,397		285,556						307,596	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]					512,660	469,974
Minimum Regulatory Provision to be Well-Capitalized Ratio (in hundredths)														[1]		[1]					5.00%	5.00%
Regulatory Capital Ratio Revision Description	11 to 16 basis points
Before-Tax Amount [Abstract]
Accumulated other comprehensive income (loss), Before - Tax, balance	5,533	5,089
Unrealized holding gains on AFS arising during period, Before - Tax	2,234	(3,103)
Adjustment for net gains realized in net income, Before - Tax	(204)	(1,050)	(204)	(1,050)
Pension and other postretirement benefit plans, Before - Tax	1,717	1,587
Accumulated other comprehensive income (loss), Before - Tax, balance	9,280	2,523
Tax Effect [Abstract]
Accumulated other comprehensive income (loss), Tax Effect, balance	(2,138)	(1,968)
Unrealized holding (gain) losses arising during period, Tax Effect	(854)	1,187
Adjustment for net gains realized in net income, Tax Effect	78	402
Pension and other postretirement benefit plans, Tax Effect, balance	(657)	(607)
Accumulated other comprehensive income (loss), Tax Effect	(3,571)	(986)
Accumulated Other Comprehensive Income (Loss) [Abstract]
Accumulated Other Comprehensive Income (Loss), Net of Tax, balance	3,395	3,121
Unrealized holding (gain) losses arising during period	1,380	(1,916)
Adjustment for net gains realized in net income	(126)	(648)	(126)	(648)
Pension and other postretirement benefit plans	1,060	980
Accumulated Other Comprehensive Income, (Loss) Net of Tax, balance	5,709	1,537
Securities available for sale:
Reclassification adjustment for net gains realized in net income, pre-tax income (expense)	204	1,050	204	1,050
Reclassification adjustment for net gains realized in net income, tax (expense) benefit			(78)	(402)
Reclassification adjustment for net gains realized in net income, after tax income (expense)	126	648	126	648
Pension and other postretirement benefit plans:
Amortization of prior service cost, pre-tax income (expense)			(63)	(62)
Recognized net actuarial loss, pre-tax income (expense)			(1,654)	(1,524)
Total pension and other postretirement benefit plans, pre-tax income (expense)			(1,717)	(1,586)
Amortization of prior service cost, tax (expense) benefit			24	24
Recognized net actuarial loss, tax (expense) benefit			633	582
Total pension and other postretirement benefit plans, tax (expense) benefit			657	606
Amortization of prior service cost, after tax income (expense)			(39)	(38)
Recognized net actuarial loss, after tax income (expense)			(1,021)	(942)
Total pension and other postretirement benefit plans, after tax income (expense)			$ (1,060)	$ (980)

[1] n/a