Defined Benefit and Other Postretirement Benefits (Details) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Years of service required to vest			3 years
Trustmark Capital Accumulation Plan [Member]
Net periodic benefit cost [Abstract]
Service cost	$ 148,000	$ 139,000	$ 298,000	$ 279,000
Interest cost	1,264,000	945,000	2,254,000	1,890,000
Expected return on plan assets	(2,059,000)	(1,400,000)	(3,600,000)	(2,800,000)
Recognized net loss due to Settlement	525,000	0	525,000	0
Recognized net actuarial loss	1,374,000	1,309,000	2,768,000	2,619,000
Net periodic benefit cost	1,252,000	993,000	2,245,000	1,988,000
Period of average interest rate before MAP-21			2 years
Period of average interest rate after MAP-21			25 years
Lump sum settlement	525,000
Pension funding contributions cap percentage (in hundredths)			115.00%
Pension funding contributions floor percentage (in hundredths)			85.00%
Minimum required contribution			1,500,000
Voluntary contribution					1,500,000
Supplemental Retirement Plan [Member]
Net periodic benefit cost [Abstract]
Service cost	149,000	170,000	298,000	340,000
Interest cost	484,000	516,000	968,000	1,033,000
Amortization of prior service credits	63,000	63,000	126,000	125,000
Recognized net actuarial loss	259,000	215,000	518,000	430,000
Net periodic benefit cost	$ 955,000	$ 964,000	$ 1,910,000	$ 1,928,000