Segment Information - Schedule of Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended							9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018		Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018		Dec. 31, 2018
Segment Reporting Information [Line Items]
Net interest income	$ 108,466			$ 106,983				$ 320,998	$ 314,240
Provision for loan losses, net	2,899			8,206				7,180	15,043
Noninterest income	48,337			47,093	[1]			139,467	141,277	[1]
Noninterest expense	106,853			105,223				318,975	311,488
Income Before Income Taxes	47,051			40,647				134,310	128,986
Income taxes	6,016			4,394				17,796	16,090
Net Income	41,035	$ 42,140	$ 33,339	36,253		$ 39,813	$ 36,830	116,514	112,896
Selected Financial Information
Total assets	13,584,786			13,439,812				13,584,786	13,439,812		$ 13,286,460
Depreciation and amortization	10,462			9,978				29,585	29,512
General Banking [Member]
Segment Reporting Information [Line Items]
Net interest income	107,540			105,935				318,008	310,620
Provision for loan losses, net	2,895			8,212				7,179	15,054
Noninterest income	29,575			28,509	[1]			83,296	87,444	[1]
Noninterest expense	93,709			89,288				275,052	265,699
Income Before Income Taxes	40,511			36,944				119,073	117,311
Income taxes	4,432			3,460				14,033	13,162
Net Income	36,079			33,484				105,040	104,149
Selected Financial Information
Total assets	13,421,295			13,269,567				13,421,295	13,269,567
Depreciation and amortization	10,255			9,758				28,987	28,955
Wealth Management [Member]
Segment Reporting Information [Line Items]
Net interest income	854			983				2,808	3,450
Provision for loan losses, net	4			(6)				1	(11)
Noninterest income	7,685			7,817	[1]			23,128	22,911	[1]
Noninterest expense	5,191			7,795				19,346	21,759
Income Before Income Taxes	3,344			1,011				6,589	4,613
Income taxes	836			253				1,643	1,154
Net Income	2,508			758				4,946	3,459
Selected Financial Information
Total assets	90,405			104,480				90,405	104,480
Depreciation and amortization	66			65				202	120
Insurance [Member]
Segment Reporting Information [Line Items]
Net interest income	72			65				182	170
Noninterest income	11,077			10,767	[1]			33,043	30,922	[1]
Noninterest expense	7,953			8,140				24,577	24,030
Income Before Income Taxes	3,196			2,692				8,648	7,062
Income taxes	748			681				2,120	1,774
Net Income	2,448			2,011				6,528	5,288
Selected Financial Information
Total assets	73,086			65,765				73,086	65,765
Depreciation and amortization	$ 141			$ 155				$ 396	$ 437

[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.