Shareholders' Equity (Details) (USD $)	12 Months Ended																						12 Months Ended						12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011	Dec. 31, 2011 Trustmark Corporation [Member] Total Capital (to Risk Weighted Assets) [Member]		Dec. 31, 2010 Trustmark Corporation [Member] Total Capital (to Risk Weighted Assets) [Member]		Dec. 31, 2011 Trustmark Corporation [Member] Tier 1 Capital (to Risk Weighted Assets) [Member]		Dec. 31, 2010 Trustmark Corporation [Member] Tier 1 Capital (to Risk Weighted Assets) [Member]		Dec. 31, 2011 Trustmark Corporation [Member] Tier 1 Capital (to Average Assets) [Member]		Dec. 31, 2010 Trustmark Corporation [Member] Tier 1 Capital (to Average Assets) [Member]		Dec. 31, 2011 Trustmark National Bank [Member] Total Capital (to Risk Weighted Assets) [Member]	Dec. 31, 2010 Trustmark National Bank [Member] Total Capital (to Risk Weighted Assets) [Member]	Dec. 31, 2011 Trustmark National Bank [Member] Tier 1 Capital (to Risk Weighted Assets) [Member]	Dec. 31, 2010 Trustmark National Bank [Member] Tier 1 Capital (to Risk Weighted Assets) [Member]	Dec. 31, 2011 Trustmark National Bank [Member] Tier 1 Capital (to Average Assets) [Member]	Dec. 31, 2010 Trustmark National Bank [Member] Tier 1 Capital (to Average Assets) [Member]	Dec. 31, 2009 Warrant issued to Treasury [Member]	Dec. 31, 2008 Warrant issued to Treasury [Member]	Dec. 31, 2011 Common Shares [Member]	Dec. 31, 2009 Common Shares [Member]	Dec. 31, 2008 Cumulative Preferred Stock, Series A [Member]	Dec. 31, 2009 Cumulative Preferred Stock, Series A [Member]	Dec. 31, 2009 Cumulative Preferred Stock, Series A [Member] Warrant issued to Treasury [Member]	Dec. 31, 2008 Cumulative Preferred Stock, Series A [Member] Warrant issued to Treasury [Member]
Common stock offering [Abstract]
Common shares issued (in shares)	64,142,498	63,917,591																								6,216,216
Issuance under underwriters' over-allotment option (in shares)																										810,810
Price of shares issued (in dollars per share)																										$ 18.50
Net proceeds from stock offering	$ 0	$ 0	$ 109,296,000																							$ 109,300,000
Preferred Stock and Warrant [Abstract]
Preferred Stock issued (in shares)																											215,000
Life of warrants issued, maximum (in years)																								10 Y
Common stock shares covered by warrants (in shares)																								1,647,931
Cash flows discounted using a yield curve rate, minimum (in hundredths)																											5.85%
Cash flows discounted using a yield curve rate, maximum (in hundredths)																											10.42%
Cash flows were discounted using a yield curve rate, average (in hundredths)																											8.75%
Fair value estimate, preferred shares																											182,600,000
Fair value estimate, warrants issued and outstanding																								9,000,000
Fair value estimate, Senior Preferred Stock and Warrant																														191,600,000
Proceeds from issuance Senior Preferred Stock and the Warrant																								10,100,000			204,900,000			215,000,000
Face value, Preferred Stock																												215,000,000
Repurchases [Abstract]
Repurchased shares (in shares)																							1,647,931						215,000
Repurchase price - cash	0	0	215,000,000																										215,000,000
Repurchase price - Dividend payment																													716,700
Discount reduction non-cash charge																													8,200,000
Purchase price paid for the warrant	0	0	10,000,000																				10,000,000
Total Capital (to Risk Weighted Assets) [Abstract]
Actual Regulatory Capital Amount					1,096,213,000		1,051,933,000										1,057,932,000	1,014,219,000
Actual Regulatory Capital Ratio (in hundredths)					16.67%		15.77%										16.28%	15.40%
Minimum Regulatory Capital Required Amount					526,156,000		533,774,000										519,709,000	526,894,000
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]									649,636,000	658,617,000
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									974,034,000		918,600,000								938,122,000	883,549,000
Actual Regulatory Capital Ratio (in hundredths)									14.81%		13.77%								14.44%	13.42%
Minimum Regulatory Capital Required Amount									263,078,000		266,887,000								259,855,000	263,447,000
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]							389,782,000	395,170,000
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													974,034,000		918,600,000						938,122,000	883,549,000
Actual Regulatory Capital Ratio (in hundredths)													10.43%		10.14%						10.18%	9.89%
Minimum Regulatory Capital Required Amount													280,162,000		271,867,000						276,502,000	267,967,000
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]					460,837,000	446,612,000
Minimum Regulatory Provision to be Well-Capitalized Ratio (in hundredths)														[1]		[1]					5.00%	5.00%
Dividends on common stock [Abstract]
Dividend Potential																									85,400,000
Warrant initial exercise price (per share)																								$ 19.57
Before-Tax Amount [Abstract]
Accumulated other comprehensive income (loss), before tax	(18,469,000)	(2,596,000)	(23,800,000)
Unrealized Holding Gain (Loss) on Securities Arising During Period, before Tax	39,636,000	(15,431,000)	27,639,000
Reclassification Adjustment for Sale of Securities Included in Net Income, before Tax	(80,000)	(2,329,000)	(5,467,000)
Pension and Other Postretirement Benefit Plans, Net change in Prior Service Cost Arising During Period, before Tax	(957,000)	123,000	(1,885,000)
Pension and Other Postretirement Benefit Plans, Increase (Decrease) During Period, before Tax	(15,041,000)	1,764,000	917,000
Accumulated other comprehensive income (loss), before tax	5,089,000	(18,469,000)	(2,596,000)
Tax Effect [Abstract]
Accumulated other comprehensive income (loss), tax effect	7,043,000	972,000	9,083,000
Unrealized Holding Gain (Loss) on Securities Arising During Period, Tax Effect	(15,161,000)	5,902,000	(10,572,000)
Reclassification Adjustment for Sale of Securities Included in Net Income, Tax Effect	31,000	891,000	2,091,000
Pension and Other Postretirement Benefit Plans, Increase (Decrease) in Prior Service Cost Arising During Period, Tax Effect	366,000	(47,000)	721,000
Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Tax Effect	5,753,000	(675,000)	(351,000)
Accumulated other comprehensive income (loss), tax effect	(1,968,000)	7,043,000	972,000
Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning of Period	(11,426,000)	(1,624,000)	(14,717,000)	3,121,000
Number of securities included in aggregate estimated fair value																											2
Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax	24,475,000	(9,529,000)	17,067,000
Reclassification Adjustment for Sale of Securities Included in Net Income, Net of Tax	(49,000)	(1,438,000)	(3,376,000)
Pension and Other Postretirement Benefit Plans, Increase (Decrease) in Prior Service Cost Arising During Period, Net of Tax	(591,000)	76,000	(1,164,000)
Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Net of Tax	$ (9,288,000)	$ 1,089,000	$ 566,000

[1] n/a