Stock and Incentive Compensation Plans (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended						3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended				3 Months Ended		9 Months Ended						3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011 2005 Stock and Incentive Compensation Plan [Member]	Sep. 30, 2011 2005 Stock and Incentive Compensation Plan [Member] Stock option-based awards [Member]	Sep. 30, 2011 1997 Long Term Incentive Plan [Member]	Sep. 30, 2011 1997 Long Term Incentive Plan [Member] Stock option-based awards [Member]	Sep. 30, 2011 Stock option-based awards [Member]	Sep. 30, 2010 Stock option-based awards [Member]	Sep. 30, 2011 Stock option-based awards [Member]	Sep. 30, 2010 Stock option-based awards [Member]	Sep. 30, 2011 Restricted Stock [Member] Performance Based Award [Member]	Sep. 30, 2010 Restricted Stock [Member] Performance Based Award [Member]	Sep. 30, 2011 Restricted Stock [Member] Performance Based Award [Member]	Sep. 30, 2010 Restricted Stock [Member] Performance Based Award [Member]	Sep. 30, 2011 Restricted Stock [Member] Time Vested Award [Member]	Sep. 30, 2010 Restricted Stock [Member] Time Vested Award [Member]	Sep. 30, 2011 Restricted Stock [Member] Time Vested Award [Member]	Sep. 30, 2010 Restricted Stock [Member] Time Vested Award [Member]	Sep. 30, 2011 Restricted Stock [Member] Performance Based Excess Time-Vested [Member]	Sep. 30, 2011 Restricted Stock Units (RSUs) [Member]	Sep. 30, 2011 Restricted Stock Units (RSUs) [Member] Performance Based Award [Member]	Sep. 30, 2010 Restricted Stock Units (RSUs) [Member] Performance Based Award [Member]	Sep. 30, 2011 Restricted Stock Units (RSUs) [Member] Performance Based Award [Member]	Sep. 30, 2010 Restricted Stock Units (RSUs) [Member] Performance Based Award [Member]	May 10, 2011 Restricted Stock Units (RSUs) [Member] Performance Based Award [Member]	Dec. 31, 2010 Restricted Stock Units (RSUs) [Member] Performance Based Award [Member]	Jan. 27, 2009 Restricted Stock Units (RSUs) [Member] Performance Based Award [Member]	Feb. 22, 2011 Restricted Stock Units (RSUs) [Member] Performance Based Excess Time-Vested [Member]	Sep. 30, 2011 Performance Based Award [Member]	Sep. 30, 2011 Performance Based Award [Member]	Sep. 30, 2011 Time Vested Award [Member]	Sep. 30, 2011 Time Vested Award [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights description						Stock options granted under the 2005 Plan vest 20% per year and have a contractual term of seven years		Stock option awards, which were granted under the 1997 Plan, had an exercise price equal to the market price of Trustmark's stock on the date of grant, vested equally over four years with a contractual ten-year term							The restriction period for performance awards covers a three-year vesting period. These awards are recognized on the straight-line method over the requisite service period. These awards provide for excess shares, if performance measures exceed 100%. Any excess shares granted are restricted for an additional three-year vesting period.
ROATE Performance measure (in hundredths)															100.00%
TSR Performance measure (in hundredths)															100.00%
Awarded shares (in shares)																													23,123	23,123
Vested shares (in shares)																													23,123	23,123
Fair value of stock (in dollars per share)																											$ 23.65	$ 20.82
Stock options, vesting percentage per year (in hundredths)					20.00%
Stock and incentive compensation plan, contractual term (in years)					7 Y		10 Y
Vesting period							4 Y								3 Y				36 M		3 Y				2 Y
Value of one unit of performance-based restricted stock award in terms of number of shares of Trustmark's common stock (in shares)																													1
Stock and incentive plan [Roll Forward]
Outstanding/Nonvested shares or units, beginning of period									1,208,500		1,311,925											23,123									180,322	210,797	365,275	343,469
Granted									0		0											0									0	53,863	4,318	73,057
Granted - excess shares									0		0											23,123									0	0	0	84,121
Exercised or released from restriction									0		(69,525)											(46,246)									0	(84,338)	0	(126,596)
Expired									(800)		(33,400)											0									0	0	0	0
Forfeited									0		(1,300)											0									0	0	0	(4,458)
Outstanding/Nonvested shares or units, end of period									1,207,700		1,207,700											0									180,322	180,322	369,593	369,593
Compensation expense - Stock and Incentive plans: [Abstract]
Compensation expense for stock and incentive plans	$ 885	$ 1,333	$ 3,111	$ 4,177					$ 0	$ 78	$ 100	$ 355	$ 214	$ 251	$ 655	$ 752	$ 671	$ 838	$ 2,172	$ 2,580			$ 0	$ 166	$ 184	$ 490