Parent Company Only Financial Information - Parent Only Financial Statements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Assets
Other assets	$ 577,964	$ 562,350
Total Assets	13,352,333	12,678,896
Liabilities and Shareholders' Equity:
Junior subordinated debt securities	61,856	61,856
Shareholders' equity	1,520,208	1,473,057	$ 1,419,940	$ 1,354,953
Total Liabilities and Shareholders' Equity	13,352,333	12,678,896
Expense:
Net Income	108,411	116,038	123,562
Operating Activities
Net income	108,411	116,038	123,562
Adjustments to reconcile net income to net cash provided by operating activities:
Other	2,022	4,391	16,337
Net cash provided by operating activities	147,427	171,887	211,267
Financing Activities
Cash dividends paid on common stock	(62,666)	(62,605)	(62,474)
Net cash provided by financing activities	552,192	317,168	315,200
Increase (Decrease) in cash and cash equivalents	49,955	(38,222)	(29,788)
Cash and cash equivalents at beginning of year	277,751	315,973	345,761
Cash and cash equivalents at end of year	327,706	277,751	315,973
Trustmark Corp (Parent Company Only) [Member]
Assets
Investment in banks	1,566,186	1,518,292
Other assets	16,756	17,339
Total Assets	1,582,942	1,535,631
Liabilities and Shareholders' Equity:
Accrued expense	878	718
Junior subordinated debt securities	61,856	61,856
Shareholders' equity	1,520,208	1,473,057
Total Liabilities and Shareholders' Equity	1,582,942	1,535,631
Revenue:
Dividends received from banks	65,987	64,752	64,351
Earnings of subsidiaries over distributions	44,756	53,562	60,783
Other income	60	55	55
Total Revenue	110,803	118,369	125,189
Expense:
Other expense	2,392	2,331	1,627
Total Expense	2,392	2,331	1,627
Net Income	108,411	116,038	123,562
Operating Activities
Net income	108,411	116,038	123,562
Adjustments to reconcile net income to net cash provided by operating activities:
Increase in investment in subsidiaries	(44,756)	(53,562)	(60,783)
Other	(739)	(761)	(2,158)
Net cash provided by operating activities	62,916	61,715	60,621
Financing Activities
Cash dividends paid on common stock	(62,666)	(62,605)	(62,474)
Other common stock transactions, net	(857)	(211)	(1,502)
Net cash provided by financing activities	(63,523)	(62,816)	(63,976)
Increase (Decrease) in cash and cash equivalents	(607)	(1,101)	(3,355)
Cash and cash equivalents at beginning of year	17,320	18,421	21,776
Cash and cash equivalents at end of year	$ 16,713	$ 17,320	$ 18,421