Segment Information - Schedule of Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended					6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018		Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018		Dec. 31, 2018
Segment Reporting Information [Line Items]
Net interest income	$ 107,724		$ 105,164			$ 212,532	$ 207,257
Provision for loan losses, net	2,592		2,726			4,281	6,837
Noninterest income	49,639		47,391	[1]		91,130	94,184	[1]
Noninterest expense	106,101		103,800			212,122	206,265
Income Before Income Taxes	48,670		46,029			87,259	88,339
Income taxes	6,530		6,216			11,780	11,696
Net Income	42,140	$ 33,339	39,813		$ 36,830	75,479	76,643
Selected Financial Information
Total assets	13,548,958		13,525,265			13,548,958	13,525,265		$ 13,286,460
Depreciation and amortization	9,786		10,158			19,123	19,534
General Banking [Member]
Segment Reporting Information [Line Items]
Net interest income	106,681		103,978			210,468	204,685
Provision for loan losses, net	2,593		2,731			4,284	6,842
Noninterest income	30,808		29,175	[1]		53,721	58,935	[1]
Noninterest expense	90,684		88,421			181,343	176,411
Income Before Income Taxes	44,212		42,001			78,562	80,367
Income taxes	5,411		5,216			9,601	9,702
Net Income	38,801		36,785			68,961	70,665
Selected Financial Information
Total assets	13,365,972		13,363,465			13,365,972	13,363,465
Depreciation and amortization	9,593		9,987			18,732	19,197
Wealth Management [Member]
Segment Reporting Information [Line Items]
Net interest income	988		1,136			1,954	2,467
Provision for loan losses, net	(1)		(5)			(3)	(5)
Noninterest income	7,740		7,480	[1]		15,443	15,094	[1]
Noninterest expense	7,136		7,088			14,155	13,964
Income Before Income Taxes	1,593		1,533			3,245	3,602
Income taxes	398		384			807	901
Net Income	1,195		1,149			2,438	2,701
Selected Financial Information
Total assets	109,106		94,447			109,106	94,447
Depreciation and amortization	67		28			136	55
Insurance [Member]
Segment Reporting Information [Line Items]
Net interest income	55		50			110	105
Noninterest income	11,091		10,736	[1]		21,966	20,155	[1]
Noninterest expense	8,281		8,291			16,624	15,890
Income Before Income Taxes	2,865		2,495			5,452	4,370
Income taxes	721		616			1,372	1,093
Net Income	2,144		1,879			4,080	3,277
Selected Financial Information
Total assets	73,880		67,353			73,880	67,353
Depreciation and amortization	$ 126		$ 143			$ 255	$ 282

[1] During the first quarter of 2019, Trustmark revised the composition of its operating segments by moving the Private Banking Group from the General Banking Segment to the Wealth Management Segment as a result of a change in supervision of this group for segment reporting purposes.  The prior period amounts presented include reclassifications to conform to the current period presentation.