Shareholders' Equity (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Securities available for sale and transferred securities, Before tax amount [Abstract]
Unrealized holding gains arising during the period				$ 13,718	$ 9,415
Reclassification adjustment for net gains realized in net income, Before tax amount				0	(300)
Change in net unrealized holding loss on securities transferred to held to maturity, Before tax amount				4,747	4,444
Total securities available for sale and transferred securities, Before tax amount				18,465	13,559
Securities available for sale and transferred securities, Tax (expense) benefit [Abstract]
Unrealized holding gains arising during the period, Tax Effect				(5,248)	(3,601)
Reclassification adjustment for net gains realized in net income, Tax				0	115
Change in net unrealized holding loss on securities transferred to held to maturity, Tax				(1,816)	(1,700)
Total securities available for sale and transferred securities, Tax				(7,064)	(5,186)
Securities available for sale and transferred securities, Net of tax amount [Abstract]
Net unrealized holding gains on AFS Securities, net of tax at date of transfer		$ 11,035	$ (5,182)	8,470	5,814
Reclassification adjustment for net gains realized in net income, after tax income (expense)		0	55	0	(185)
Change in net unrealized holding loss on securities transferred to held to maturity, after tax income (expense)		1,036	1,011	2,931	2,744
Total securities available for sale and transferred securities, after tax income (expense)				11,401	8,373
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 lump sum settlements, before tax amount				1,499	2,459
Change in net actuarial loss, before tax amount				3,653	268
Total pension and other postretirement benefit plans, before tax amount				5,340	2,915
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 lump sum settlements, tax (expense) benefit				(573)	(941)
Change in net actuarial loss, tax (expense) benefit				(1,397)	(102)
Total pension and other postretirement benefit plans, tax (expense) benefit				(2,042)	(1,115)
Pension and other postretirement benefit plans, Net of tax amount [Abstract]
Net change in prior service costs, after tax income (expense)		39	39	116	116
Recognized net loss due to lump sum settlements, after tax income (expense)		373	1,055	926	1,518
Change in net actuarial loss, after tax income (expense)				2,256	166
Total pension and other postretirement benefit plans, after tax income (expense)				3,298	1,800
Cash flow hedge derivatives [Abstract]
Change in accumulated gain (loss) on effective cash flow hedge derivatives, before tax amount				(1,919)	(1,307)
Reclassification adjustment for loss realized in net income, before tax amount				632
Total cash flow hedge derivatives, before tax benefit				(1,287)
Cash flow hedge derivatives, Tax (expense) benefit [Abstract]
Change in accumulated gain (loss) on effective cash flow hedge derivatives, tax (expense) benefit				734	500
Reclassification adjustment for loss realized in net income, tax (expense) benefit				(242)
Total cash flow hedge derivatives, tax (expense) benefit				492
Cash flow hedge derivatives, Net of tax amount [Abstract]
Change in the accumulated gain (loss) on effective cash flow hedge derivatives, after tax amount		(751)	163	(1,185)	(807)
Reclassification adjustment for loss realized in net income, after tax amount		130	0	390	0
Total cash flow hedge derivatives, after tax amount				(795)
Total other comprehensive income, Before tax amount				22,518	15,167
Total other comprehensive income, Tax expense (benefit)				(8,614)	(5,801)
Total other comprehensive income, Net of tax				13,904	9,366
Accumulated Other Comprehensive Income (Loss) [Line Items]
Opening balance				(42,484)	(43,731)
Other comprehensive income (loss) before reclassification				13,514	9,551
Amounts reclassified from accumulated other comprehensive loss				390	(185)
Net other comprehensive income (loss)		12,613	(3,808)	13,904	9,366
Ending balance		(28,580)	(34,365)	(28,580)	(34,365)
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		$ 1,147,861		$ 1,147,861		$ 1,069,630
Actual Regulatory Capital Ratio		13.00%		13.00%		12.75%
Minimum Regulatory Capital Required Ratio		4.50%		4.50%			[1]
Minimum Regulatory Provision to be Well-Capitalized Ratio	[1]
Trustmark Corporation [Member] | Tier 1 Capital (to Risk Weighted Assets) [Member]
Tier 1 Capital (to Risk Weighted Assets) [Abstract]
Actual Regulatory Capital Amount		$ 1,206,574		$ 1,206,574		$ 1,129,630
Actual Regulatory Capital Ratio		13.66%		13.66%		13.47%
Minimum Regulatory Capital Required Ratio		6.00%		6.00%		4.00%
Minimum Regulatory Provision to be Well-Capitalized Ratio	[1]
Trustmark Corporation [Member] | Total Capital (to Risk Weighted Assets) [Member]
Total Capital (to Risk Weighted Assets) [Abstract]
Actual Regulatory Capital Amount		$ 1,294,358		$ 1,294,358		$ 1,221,292
Actual Regulatory Capital Ratio		14.66%		14.66%		14.56%
Minimum Regulatory Capital Required Ratio		8.00%		8.00%		8.00%
Minimum Regulatory Provision to be Well-Capitalized Ratio	[1]
Trustmark Corporation [Member] | Tier 1 Leverage (to Average Assets) [Member]
Tier 1 Leverage (to Average Assets) [Abstract]
Actual Regulatory Capital Amount		$ 1,206,574		$ 1,206,574		$ 1,129,630
Actual Regulatory Capital Ratio		10.09%		10.09%		9.63%
Minimum Regulatory Capital Required Ratio		4.00%		4.00%		4.00%
Minimum Regulatory Provision to be Well-Capitalized Ratio	[1]
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		$ 1,186,875		$ 1,186,875		$ 1,108,399
Actual Regulatory Capital Ratio		13.44%		13.44%		13.24%
Minimum Regulatory Capital Required Ratio		4.50%		4.50%			[1]
Minimum Regulatory Provision to be Well-Capitalized Ratio		6.50%		6.50%			[1]
Trustmark National Bank [Member] | Tier 1 Capital (to Risk Weighted Assets) [Member]
Tier 1 Capital (to Risk Weighted Assets) [Abstract]
Actual Regulatory Capital Amount		$ 1,186,875		$ 1,186,875		$ 1,108,399
Actual Regulatory Capital Ratio		13.44%		13.44%		13.24%
Minimum Regulatory Capital Required Ratio		6.00%		6.00%		4.00%
Minimum Regulatory Provision to be Well-Capitalized Ratio		8.00%		8.00%		6.00%
Trustmark National Bank [Member] | Total Capital (to Risk Weighted Assets) [Member]
Total Capital (to Risk Weighted Assets) [Abstract]
Actual Regulatory Capital Amount		$ 1,274,659		$ 1,274,659		$ 1,198,697
Actual Regulatory Capital Ratio		14.43%		14.43%		14.32%
Minimum Regulatory Capital Required Ratio		8.00%		8.00%		8.00%
Minimum Regulatory Provision to be Well-Capitalized Ratio		10.00%		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		$ 1,186,875		$ 1,186,875		$ 1,108,399
Actual Regulatory Capital Ratio		9.94%		9.94%		9.46%
Minimum Regulatory Capital Required Ratio		4.00%		4.00%		4.00%
Minimum Regulatory Provision to be Well-Capitalized Ratio		5.00%		5.00%		5.00%
Securities Available for Sale and Transferred Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Opening balance				$ (11,003)	(25,462)
Other comprehensive income (loss) before reclassification				11,401	8,558
Amounts reclassified from accumulated other comprehensive loss				0	(185)
Net other comprehensive income (loss)				11,401	8,373
Ending balance		$ 398	(17,089)	398	(17,089)
Defined Benefit Pension Items [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Opening balance				(31,617)	(19,793)
Other comprehensive income (loss) before reclassification				3,298	1,800
Amounts reclassified from accumulated other comprehensive loss				0	0
Net other comprehensive income (loss)				3,298	1,800
Ending balance		(28,319)	(17,993)	(28,319)	(17,993)
Cash Flow Hedge Derivatives [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Opening balance				136	1,524
Other comprehensive income (loss) before reclassification				(1,185)	(807)
Amounts reclassified from accumulated other comprehensive loss				390	0
Net other comprehensive income (loss)				(795)	(807)
Ending balance		$ (659)	$ 717	$ (659)	$ 717

[1] n/a