Defined Benefit and Other Postretirement Benefits (Details) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
Trustmark Capital Accumulation Plan [Member]
Net periodic benefit cost [Abstract]
Service cost	$ 137,000	$ 137,000	$ 274,000	$ 274,000
Interest cost	1,115,000	1,195,000	2,230,000	2,389,000
Expected return on plan assets	(1,471,000)	(1,481,000)	(2,942,000)	(2,963,000)
Recognized net actuarial loss	1,037,000	849,000	2,074,000	1,699,000
Net periodic benefit cost	818,000	700,000	1,636,000	1,399,000
Years of service required to vest (in years)					3 Y
Voluntary contribution					1,900,000
Supplemental Retirement Plan [Member]
Net periodic benefit cost [Abstract]
Service cost	147,000	190,000	294,000	377,000
Interest cost	569,000	561,000	1,138,000	1,121,000
Amortization of prior service cost	59,000	39,000	118,000	76,000
Recognized net actuarial loss	124,000	89,000	248,000	178,000
Net periodic benefit cost	$ 899,000	$ 879,000	$ 1,798,000	$ 1,752,000