Defined Benefit and Other Postretirement Benefits (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 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	$ 129	$ 125	$ 260	$ 249
Interest cost	864	1,322	1,726	2,643
Expected return on plan assets	(1,297)	(1,560)	(2,593)	(3,118)
Recognized net loss due to lump sum settlements	479	375	896	750
Recognized net actuarial loss	971	736	1,938	1,472
Net periodic benefit cost	1,146	998	2,227	1,996
Supplemental Retirement Plan [Member]
Net periodic benefit cost [Abstract]
Service cost	108	75	216	148
Interest cost	519	548	1,043	1,102
Amortization of prior service cost	62	62	125	125
Recognized net actuarial loss	246	163	499	333
Net periodic benefit cost	$ 935	$ 848	$ 1,883	$ 1,708
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