Segment Information - Schedule of Segment Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018		Dec. 31, 2017
Segment Reporting Information [Line Items]
Net interest income	$ 426,589	$ 419,420		$ 407,550
Provision for loan losses, net	10,839	16,988		7,699
Noninterest income	187,045	184,836	[1]	184,663	[1],[2]
Noninterest expense	429,002	415,415		430,169
Income Before Income Taxes	173,793	171,853		154,345
Income taxes	23,333	22,269		48,715
Net Income	150,460	149,584		105,630
Selected Financial Information
Total assets	13,497,877	13,286,460		13,797,953
Depreciation and amortization	39,420	38,940		38,471
General Banking [Member]
Segment Reporting Information [Line Items]
Net interest income	422,661	415,561		402,507
Provision for loan losses, net	10,838	17,001		7,485
Noninterest income	113,755	113,930	[1]	116,044	[1],[2]
Noninterest expense	370,493	355,389		370,793
Income Before Income Taxes	155,085	157,101		140,273
Income taxes	18,721	18,560		43,427
Net Income	136,364	138,541		96,846
Selected Financial Information
Total assets	13,333,518	13,111,362		13,627,012
Depreciation and amortization	38,637	38,182		37,704
Wealth Management [Member]
Segment Reporting Information [Line Items]
Net interest income	3,686	3,633		4,809
Provision for loan losses, net	1	(13)		214
Noninterest income	30,861	30,420	[1]	30,421	[1],[2]
Noninterest expense	26,365	29,170		29,989
Income Before Income Taxes	8,181	4,896		5,027
Income taxes	2,040	1,225		1,923
Net Income	6,141	3,671		3,104
Selected Financial Information
Total assets	90,113	106,179		102,773
Depreciation and amortization	267	186		137
Insurance [Member]
Segment Reporting Information [Line Items]
Net interest income	242	226		234
Noninterest income	42,429	40,486	[1]	38,198	[1],[2]
Noninterest expense	32,144	30,856		29,387
Income Before Income Taxes	10,527	9,856		9,045
Income taxes	2,572	2,484		3,365
Net Income	7,955	7,372		5,680
Selected Financial Information
Total assets	74,246	68,919		68,168
Depreciation and amortization	$ 516	$ 572		$ 630

[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.

[2] Trustmark elected the modified retrospective approach of adoption; therefore, prior period balances are presented under legacy GAAP and may not be comparable to current year presentation.