Defined Benefit and Other Postretirement Benefits (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2015
Trustmark Capital Accumulation Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Years of service required to vest			3 years
Net periodic benefit cost [Abstract]
Service cost	$ 127	$ 123	$ 387	$ 372
Interest cost	867	1,328	2,593	3,971
Expected return on plan assets	(1,297)	(1,563)	(3,890)	(4,681)
Recognized net loss due to lump sum settlements	603	1,709	1,499	2,459
Recognized net actuarial loss (gain)	969	(1,701)	2,907	(229)
Net periodic benefit cost	1,269	(104)	3,496	1,892
Supplemental Retirement Plan [Member]
Net periodic benefit cost [Abstract]
Service cost	107	74	323	222
Interest cost	520	548	1,563	1,650
Amortization of prior service cost	63	63	188	188
Recognized net actuarial loss (gain)	246	164	745	497
Net periodic benefit cost	$ 936	$ 849	$ 2,819	$ 2,557
Subsequent Event [Member] | Trustmark Capital Accumulation Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Trustmark's minimum required contribution to Trustmark Capital Accumulation Plan					$ 0