Segment Information - Schedule of Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017		Jun. 30, 2018	Jun. 30, 2017		Dec. 31, 2017
Segment Reporting Information [Line Items]
Net interest income	$ 105,164	$ 102,004		$ 207,257	$ 199,594
Provision for loan losses, net	2,726	357		6,837	1,514
Noninterest income	47,391	50,190	[1]	94,184	96,223	[1]
Noninterest expense	103,800	122,075		206,265	224,132
Income Before Income Taxes	46,029	29,762		88,339	70,171
Income taxes	6,216	5,727		11,696	14,888
Net Income	39,813	24,035		76,643	55,283
Selected Financial Information
Total assets	13,525,265	13,909,138		13,525,265	13,909,138		$ 13,797,953
Depreciation and amortization	10,158	9,698		19,534	18,729
General Banking [Member]
Segment Reporting Information [Line Items]
Net interest income	104,894	101,794		206,515	199,205
Provision for loan losses, net	2,726	357		6,837	1,514
Noninterest income	29,221	32,820	[1]	59,030	62,260	[1]
Noninterest expense	89,026	108,249		177,573	195,606
Income Before Income Taxes	42,363	26,008		81,135	64,345
Income taxes	5,307	4,273		9,894	12,642
Net Income	37,056	21,735		71,241	51,703
Selected Financial Information
Total assets	13,451,422	13,837,564		13,451,422	13,837,564
Depreciation and amortization	9,989	9,497		19,200	18,333
Wealth Management [Member]
Segment Reporting Information [Line Items]
Net interest income	220	155		637	284
Noninterest income	7,434	7,624	[1]	14,999	15,001	[1]
Noninterest expense	6,483	6,369		12,802	13,570
Income Before Income Taxes	1,171	1,410		2,834	1,715
Income taxes	293	541		709	657
Net Income	878	869		2,125	1,058
Selected Financial Information
Total assets	6,490	7,014		6,490	7,014
Depreciation and amortization	26	37		52	74
Insurance [Member]
Segment Reporting Information [Line Items]
Net interest income	50	55		105	105
Noninterest income	10,736	9,746	[1]	20,155	18,962	[1]
Noninterest expense	8,291	7,457		15,890	14,956
Income Before Income Taxes	2,495	2,344		4,370	4,111
Income taxes	616	913		1,093	1,589
Net Income	1,879	1,431		3,277	2,522
Selected Financial Information
Total assets	67,353	64,560		67,353	64,560
Depreciation and amortization	$ 143	$ 164		$ 282	$ 322

[1] 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.