Shareholders' Equity (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Securities Available for Sale and Transferred Securities [Member]	Sep. 30, 2013 Securities Available for Sale and Transferred Securities [Member]	Sep. 30, 2014 Defined Benefit Pension Items [Member]	Sep. 30, 2013 Defined Benefit Pension Items [Member]	Sep. 30, 2014 Cash Flow Hedge Derivatives [Member]	Sep. 30, 2013 Cash Flow Hedge Derivatives [Member]	Sep. 30, 2014 Trustmark Corporation [Member] Total Capital (to Risk Weighted Assets) [Member]		Dec. 31, 2013 Trustmark Corporation [Member] Total Capital (to Risk Weighted Assets) [Member]		Sep. 30, 2014 Trustmark Corporation [Member] Tier 1 Capital (to Risk Weighted Assets) [Member]		Dec. 31, 2013 Trustmark Corporation [Member] Tier 1 Capital (to Risk Weighted Assets) [Member]		Sep. 30, 2014 Trustmark Corporation [Member] Tier 1 Capital (to Average Assets) [Member]		Dec. 31, 2013 Trustmark Corporation [Member] Tier 1 Capital (to Average Assets) [Member]		Sep. 30, 2014 Trustmark National Bank [Member] Total Capital (to Risk Weighted Assets) [Member]	Dec. 31, 2013 Trustmark National Bank [Member] Total Capital (to Risk Weighted Assets) [Member]	Sep. 30, 2014 Trustmark National Bank [Member] Tier 1 Capital (to Risk Weighted Assets) [Member]	Dec. 31, 2013 Trustmark National Bank [Member] Tier 1 Capital (to Risk Weighted Assets) [Member]	Sep. 30, 2014 Trustmark National Bank [Member] Tier 1 Capital (to Average Assets) [Member]	Dec. 31, 2013 Trustmark National Bank [Member] Tier 1 Capital (to Average Assets) [Member]
Total Capital (to Risk Weighted Assets) [Abstract]
Actual Regulatory Capital Amount											$ 1,218,220		$ 1,122,904										$ 1,194,589	$ 1,076,391
Actual Regulatory Capital Ratio (in hundredths)											14.70%		14.18%										14.44%	13.74%
Minimum Regulatory Capital Required Amount											663,009		633,310										661,737	626,672
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]									827,171	783,340
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															1,116,166		1,026,858								1,094,124	982,925
Actual Regulatory Capital Ratio (in hundredths)															13.47%		12.97%								13.23%	12.55%
Minimum Regulatory Capital Required Amount															331,504		316,655								330,868	313,336
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]							496,302	470,004
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																			1,116,166		1,026,858						1,094,124	982,925
Actual Regulatory Capital Ratio (in hundredths)																			9.54%		9.06%						9.37%	8.76%
Minimum Regulatory Capital Required Amount																			467,917		453,487						467,135	448,665
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]					583,919	560,831
Minimum Regulatory Provision to be Well-Capitalized Ratio (in hundredths)																				[1]		[1]					5.00%	5.00%
Securities available for sale and transferred securities, Before tax amount: [Abstract]
Unrealized holding (losses) gains arising during the period, Before tax amount			9,415	(98,130)
Reclassification adjustment for net gains realized in net income, Before tax amount			(300)	(378)
Change in net unrealized holding loss on securities transferred to held to maturity, Before tax amount			4,444
Total securities available for sale and transferred securities, Before tax amount			13,559	(98,508)
Securities available for sale and transferred securities, Tax (expense) benefit: [Abstract]
Unrealized holding (losses) gains arising during period, Tax Effect			(3,601)	37,534
Reclassification adjustment for net gains realized in net income, Tax			115	145
Change in net unrealized holding loss on securities transferred to held to maturity, Tax			(1,700)
Total securities available for sale and transferred securities, Tax			(5,186)	37,679
Securities available for sale and transferred securities, Net of tax amount: [Abstract]
Unrealized holding (losses) gains arising during the period, after tax income (expense)	(5,182)	(17,461)	5,814	(60,596)
Reclassification adjustment for net gains realized in net income, after tax income (expense)	55	0	(185)	(233)
Change in net unrealized holding loss on securities transferred to held to maturity, after tax income (expense)	1,011	0	2,744	0
Total securities available for sale and transferred securities, after tax income (expense)			8,373	(60,829)
Pension and other postretirement benefit plans, Before tax amount: [Abstract]
Net change in prior service costs, before tax amount			188	188
Recognized net loss due to settlement, before tax amount			2,459	1,363
Recognized net actuarial loss (gain), before tax amount			268	4,920
Total pension and other postretirement benefit plans, before tax amount			2,915	6,471
Pension and other postretirement benefit plans, Tax (expense) benefit: [Abstract]
Net change in prior service costs, tax (expense) benefit			(72)	(72)
Recognized net loss due to settlement, tax (expense) benefit			(941)	(521)
Recognized net actuarial loss (gain), tax (expense) benefit			(102)	(1,882)
Total pension and other postretirement benefit plans, tax (expense) benefit			(1,115)	(2,475)
Pension and other postretirement benefit plans, Net of tax amount: [Abstract]
Net change in prior service costs, after tax income (expense)	39	38	116	116
Recognized net loss due to settlement after tax income (expense)	1,055	518	1,518	842
Recognized net actuarial loss (gain), after tax income (expense)	(949)	1,009	166	3,038
Total pension and other postretirement benefit plans, after tax income (expense)			1,800	3,996
Derivatives, Before tax amount: [Abstract]
Change in accumulated gain on effective cash flow hedge derivatives, before tax amount			(1,307)	1,963
Derivatives, Tax (expense) benefit: [Abstract]
Change in accumulated gain on effective cash flow hedge derivatives, tax (expense) benefit			500	(751)
Derivatives, Net of tax amount: [Abstract]
Change in the accumulated gain on effective cash flow hedge derivatives, after tax amount	163	(242)	(807)	1,212
Total other comprehensive income (loss), Before tax amount			15,167	(90,074)
Total other comprehensive income (loss), Tax expense (benefit)			(5,801)	34,453
Total other comprehensive income (loss), Net of tax			9,366	(55,621)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Opening balance			(43,731)	3,395	(25,462)	44,935	(19,793)	(41,540)	1,524	0
Other comprehensive income (loss) before reclassification			9,551	(55,388)	8,558	(60,596)	1,800	3,996	(807)	1,212
Amounts reclassified from accumulated other comprehensive income			(185)	(233)	(185)	(233)	0	0	0	0
Net other comprehensive income (loss)	(3,808)	(16,138)	9,366	(55,621)	8,373	(60,829)	1,800	3,996	(807)	1,212
Ending balance	$ (34,365)	$ (52,226)	$ (34,365)	$ (52,226)	$ (17,089)	$ (15,894)	$ (17,993)	$ (37,544)	$ 717	$ 1,212

[1] n/a