Parent Company Only Financial Information - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Financial Statements Captions [Line Items]
Income taxes paid	$ 7,371	$ 24,836	$ 16,321
Interest paid	41,472	24,312	20,733
Trustmark Corp (Parent Company Only) [Member]
Condensed Financial Statements Captions [Line Items]
Income taxes paid	7,400	24,800	16,300
Interest paid	$ 283	$ 600	$ 837