Defined Benefit and Other Postretirement Benefits (Details) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Net periodic benefit cost [Abstract]
Years of service required to vest (in years)			3Y
Trustmark Capital Accumulation Plan [Member]
Net periodic benefit cost [Abstract]
Service cost	$ 139,000	$ 137,000	$ 279,000	$ 274,000
Interest cost	945,000	1,115,000	1,890,000	2,230,000
Expected return on plan assets	(1,400,000)	(1,471,000)	(2,800,000)	(2,942,000)
Recognized net actuarial loss	1,309,000	1,037,000	2,618,000	2,074,000
Net periodic benefit cost	993,000	818,000	1,987,000	1,636,000
Contribution					1,000,000
Minimum required contribution	3,000,000		3,000,000
Supplemental Retirement Plan [Member]
Net periodic benefit cost [Abstract]
Service cost	170,000	147,000	340,000	294,000
Interest cost	516,000	569,000	1,033,000	1,138,000
Amortization of prior service cost	63,000	59,000	125,000	118,000
Recognized net actuarial loss	215,000	124,000	430,000	248,000
Net periodic benefit cost	$ 964,000	$ 899,000	$ 1,928,000	$ 1,798,000