Shareholders' Equity (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Securities available for sale and transferred securities, Before tax amount [Abstract]
Unrealized holding gains (losses) arising during the period, Before tax amount				$ (4,154)	$ 17,807
Reclassification adjustment for net gains realized in net income, Before tax amount				0	(389)
Change in net unrealized holding loss on securities transferred to held to maturity, Before tax amount				3,069	2,806
Total securities available for sale and transferred securities, Before tax amount				(1,085)	20,224
Securities available for sale and transferred securities, Tax (expense) benefit [Abstract]
Unrealized holding gains (losses) arising during the period, Tax Effect				1,589	(6,811)
Reclassification adjustment for net gains realized in net income, Tax				0	149
Change in net unrealized holding loss on securities transferred to held to maturity, Tax				(1,174)	(1,073)
Total securities available for sale and transferred securities, Tax				415	(7,735)
Securities available for sale and transferred securities, Net of tax amount [Abstract]
Net unrealized holding gains (losses) on AFS Securities, net of tax at date of transfer		$ (13,951)	$ 6,767	(2,565)	10,996
Reclassification adjustment for net gains realized in net income, after tax income (expense)		0	0	0	(240)
Change in net unrealized holding loss on securities transferred to held to maturity, after tax income (expense)		1,021	910	1,895	1,733
Total securities available for sale and transferred securities, after tax income (expense)				(670)	12,489
Pension and other postretirement benefit plans, Before tax amount [Abstract]
Net change in prior service costs, before tax amount				125	125
Recognized net loss due to lump sum settlements, before tax amount				896	750
Change in net actuarial loss, before tax amount				2,437	1,805
Total pension and other postretirement benefit plans, before tax amount				3,458	2,680
Pension and other postretirement benefit plans, Tax (expense) benefit [Abstract]
Net change in prior service costs, tax (expense) benefit				(48)	(48)
Recognized net loss due to lump sum settlements, tax (expense) benefit				(343)	(287)
Change in net actuarial loss, tax (expense) benefit				(932)	(690)
Total pension and other postretirement benefit plans, tax (expense) benefit				(1,323)	(1,025)
Pension and other postretirement benefit plans, Net of tax amount [Abstract]
Net change in prior service costs, after tax income (expense)		38	38	77	77
Recognized net loss due to lump sum settlements, after tax income (expense)		296	231	553	463
Change in net actuarial loss, after tax income (expense)				1,505	1,115
Total pension and other postretirement benefit plans, after tax income (expense)				2,135	1,655
Cash Flow Hedge Derivatives, Before tax amount [Abstract]
Change in accumulated gain (loss) on effective cash flow hedge derivatives, before tax amount				(703)	(1,571)
Reclassification adjustment for loss realized in net income, before tax amount				421
Total cash flow hedge derivatives, before tax benefit				(282)
Cash Flow Hedge Derivatives, Tax (expense) benefit [Abstract]
Change in accumulated gain (loss) on effective cash flow hedge derivatives, tax (expense) benefit				269	601
Reclassification adjustment for loss realized in net income, tax (expense) benefit				(161)
Total cash flow hedge derivatives, tax (expense) benefit				108
Cash Flow Hedge Derivatives, Net of tax amount [Abstract]
Change in the accumulated gain (loss) on effective cash flow hedge derivatives, after tax amount		174	(562)	(434)	(970)
Reclassification adjustment for loss realized in net income, after tax amount		130	0	260	0
Total cash flow hedge derivatives, after tax amount				(174)
Total other comprehensive income, Before tax amount				2,091	21,333
Total other comprehensive income, Tax expense (benefit)				(800)	(8,159)
Total other comprehensive income, Net of tax				1,291	13,174
Accumulated Other Comprehensive Income (Loss) [Line Items]
Opening balance				(42,484)	(43,731)
Other comprehensive income (loss) before reclassification				1,031	13,414
Amounts reclassified from accumulated other comprehensive loss				260	(240)
Net other comprehensive income (loss)		(11,541)	7,940	1,291	13,174
Ending balance		(41,193)	(30,557)	(41,193)	(30,557)
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		$ 1,133,094		$ 1,133,094		$ 1,069,630
Actual Regulatory Capital Ratio (in hundredths)		13.28%		13.28%		12.75%
Minimum Regulatory Capital Required Ratio (in hundredths)		4.50%		4.50%
Minimum Regulatory Provision to be Well-Capitalized Ratio (in hundredths)	[1]
Trustmark Corporation [Member] | Tier 1 Capital (to Risk Weighted Assets) [Member]
Tier 1 Capital (to Risk Weighted Assets) [Abstract]
Actual Regulatory Capital Amount		$ 1,191,523		$ 1,191,523		$ 1,129,630
Actual Regulatory Capital Ratio (in hundredths)		13.97%		13.97%		13.47%
Minimum Regulatory Capital Required Ratio (in hundredths)		6.00%		6.00%		4.00%
Minimum Regulatory Provision to be Well-Capitalized Ratio (in hundredths)	[1]
Trustmark Corporation [Member] | Total Capital (to Risk Weighted Assets) [Member]
Total Capital (to Risk Weighted Assets) [Abstract]
Actual Regulatory Capital Amount		$ 1,285,309		$ 1,285,309		$ 1,221,292
Actual Regulatory Capital Ratio (in hundredths)		15.07%		15.07%		14.56%
Minimum Regulatory Capital Required Ratio (in hundredths)		8.00%		8.00%		8.00%
Minimum Regulatory Provision to be Well-Capitalized Ratio (in hundredths)	[1]
Trustmark Corporation [Member] | Tier 1 Leverage (to Average Assets) [Member]
Tier 1 Leverage (to Average Assets) [Abstract]
Actual Regulatory Capital Amount		$ 1,191,523		$ 1,191,523		$ 1,129,630
Actual Regulatory Capital Ratio (in hundredths)		10.14%		10.14%		9.63%
Minimum Regulatory Capital Required Ratio (in hundredths)		4.00%		4.00%		4.00%
Minimum Regulatory Provision to be Well-Capitalized Ratio (in hundredths)	[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		$ 1,172,108		$ 1,172,108		$ 1,108,399
Actual Regulatory Capital Ratio (in hundredths)		13.74%		13.74%		13.24%
Minimum Regulatory Capital Required Ratio (in hundredths)		4.50%		4.50%
Minimum Regulatory Provision to be Well-Capitalized Ratio (in hundredths)		6.50%		6.50%
Trustmark National Bank [Member] | Tier 1 Capital (to Risk Weighted Assets) [Member]
Tier 1 Capital (to Risk Weighted Assets) [Abstract]
Actual Regulatory Capital Amount		$ 1,172,108		$ 1,172,108		$ 1,108,399
Actual Regulatory Capital Ratio (in hundredths)		13.74%		13.74%		13.24%
Minimum Regulatory Capital Required Ratio (in hundredths)		6.00%		6.00%		4.00%
Minimum Regulatory Provision to be Well-Capitalized Ratio (in hundredths)		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		$ 1,265,894		$ 1,265,894		$ 1,198,697
Actual Regulatory Capital Ratio (in hundredths)		14.84%		14.84%		14.32%
Minimum Regulatory Capital Required Ratio (in hundredths)		8.00%		8.00%		8.00%
Minimum Regulatory Provision to be Well-Capitalized Ratio (in hundredths)		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		$ 1,172,108		$ 1,172,108		$ 1,108,399
Actual Regulatory Capital Ratio (in hundredths)		9.99%		9.99%		9.46%
Minimum Regulatory Capital Required Ratio (in hundredths)		4.00%		4.00%		4.00%
Minimum Regulatory Provision to be Well-Capitalized Ratio (in hundredths)		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				(670)	12,729
Amounts reclassified from accumulated other comprehensive loss				0	(240)
Net other comprehensive income (loss)				(670)	12,489
Ending balance		$ (11,673)	(12,973)	(11,673)	(12,973)
Defined Benefit Pension Items [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Opening balance				(31,617)	(19,793)
Other comprehensive income (loss) before reclassification				2,135	1,655
Amounts reclassified from accumulated other comprehensive loss				0	0
Net other comprehensive income (loss)				2,135	1,655
Ending balance		(29,482)	(18,138)	(29,482)	(18,138)
Cash Flow Hedge Derivatives [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Opening balance				136	1,524
Other comprehensive income (loss) before reclassification				(434)	(970)
Amounts reclassified from accumulated other comprehensive loss				260	0
Net other comprehensive income (loss)				(174)	(970)
Ending balance		$ (38)	$ 554	$ (38)	$ 554

[1] n/a