Borrowings (Details) (USD $)	12 Months Ended									12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Long Term Federal Home Loan Bank Advances [Member]	Dec. 31, 2010 Long Term Federal Home Loan Bank Advances [Member]	Dec. 31, 2009 Long Term Federal Home Loan Bank Advances [Member]	Dec. 31, 2011 Subordinated Notes Payable [Member]	Dec. 31, 2011 Junior Subordinated Debt Securities [Member]	Aug. 25, 2006 Junior Subordinated - Republic Bancshares Capital Trust [Member]	Dec. 31, 2011 Trustmark Preferred Capital Trust I [Member]	Dec. 31, 2010 Trustmark Preferred Capital Trust I [Member]	Dec. 31, 2011 Federal Home Loan Bank Advances [Member]	Dec. 31, 2010 Federal Home Loan Bank Advances [Member]	Dec. 31, 2009 Federal Home Loan Bank Advances [Member]	Dec. 31, 2011 Serviced GNMA loans eligible for repurchase [Member]	Dec. 31, 2010 Serviced GNMA loans eligible for repurchase [Member]	Dec. 31, 2011 Treasury tax and loan service [Member]	Dec. 31, 2010 Treasury tax and loan service [Member]	Dec. 31, 2011 Other short-term borrowings [Member]	Dec. 31, 2010 Other short-term borrowings [Member]
Short-term debt [Abstract]
Short-term debt	$ 87,628,000	$ 425,343,000										$ 2,579,000	$ 350,000,000		$ 58,842,000	$ 29,739,000	$ 0	$ 20,546,000	$ 26,207,000	$ 25,058,000
Additional disclosures - Short Term Borrowings [Abstract]
Weighted-average remaining maturity (in days)												274
Weighted-average cost (in hundredths)												4.98%
Advances within a specific fixed rate range												2
Advances, lower range												585,400
Advances, upper range												1,900,000
Fair market value adjustment												93,400
Fixed interest rate, minimum (in hundredths)												4.839%
Fixed interest rate, maximum (in hundredths)												5.018%
Interest expense	43,036,000	56,195,000	87,853,000	7,000	133,000	494,000						215,000	404,000	243,000
Additional debt instrument borrowing capacity												1,900,000,000					50,000,000
Basis points spread below the Federal Funds rate																	25
Variable Interest Entity [Line Items]
Total Assets	9,727,007,000	9,553,902,000								61,900,000	61,900,000
Total Liabilities and Shareholders' Equity	9,727,007,000	9,553,902,000								61,900,000	61,900,000
Common securities	13,364,000	13,318,000								1,900,000	1,900,000
Net Income	106,841,000	100,636,000	93,047,000							38,100	45,900
Dividends paid										38,100	45,900
Debt Instrument [Line Items]
Liability assumed for securities issued to a certain bank									8,200,000
Long-Term Borrowings [Abstract]
Interest expense	43,036,000	56,195,000	87,853,000	7,000	133,000	494,000						215,000	404,000	243,000
Interest rate (in hundredths)							5.673%
Face amount of debt issued							50,000,000	60,000,000
Maturity date							Dec. 15, 2016	Sep. 30, 2036
Subordinated Notes	49,839,000	49,806,000					49,800,000
Junior subordinated debt securities	$ 61,856,000	$ 61,856,000						$ 61,900,000
Redeemable option, minimum (in years)								5Y
Variable interest rate, description								three-month LIBOR plus 1.72
Consecutive quarters that Trustmark may defer interest payments (in quarters)								20 q