Segment Information - Schedule of Segment Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019		Dec. 31, 2018
Segment Reporting Information [Line Items]
Net interest income	$ 426,537	$ 426,589		$ 419,420
Provision for loan losses, net	36,113	10,839		16,988
Noninterest income	274,593	187,045	[1]	184,836	[1]
Noninterest expense	475,235	429,002		415,415
Income Before Income Taxes	189,782	173,793		171,853
Income taxes	29,757	23,333		22,269
Net Income	160,025	150,460		149,584
Selected Financial Information
Total assets	16,551,840	13,497,877		13,286,460
Depreciation and amortization	41,325	39,420		38,940
General Banking [Member]
Segment Reporting Information [Line Items]
Net interest income	420,225	419,597		412,455
Provision for loan losses, net	36,124	10,622		17,098
Noninterest income	197,691	113,756	[1]	113,930	[1]
Noninterest expense	410,744	367,976		353,174
Income Before Income Taxes	171,048	154,755		156,113
Income taxes	25,109	18,638		18,313
Net Income	145,939	136,117		137,800
Selected Financial Information
Total assets	16,226,358	13,140,467		12,896,799
Depreciation and amortization	40,351	38,634		38,181
Wealth Management [Member]
Segment Reporting Information [Line Items]
Net interest income	6,082	6,750		6,739
Provision for loan losses, net	(11)	217		(110)
Noninterest income	31,634	30,860	[1]	30,420	[1]
Noninterest expense	30,318	28,882		31,385
Income Before Income Taxes	7,409	8,511		5,884
Income taxes	1,853	2,123		1,472
Net Income	5,556	6,388		4,412
Selected Financial Information
Total assets	242,429	283,164		320,742
Depreciation and amortization	274	270		187
Insurance [Member]
Segment Reporting Information [Line Items]
Net interest income	230	242		226
Noninterest income	45,268	42,429	[1]	40,486	[1]
Noninterest expense	34,173	32,144		30,856
Income Before Income Taxes	11,325	10,527		9,856
Income taxes	2,795	2,572		2,484
Net Income	8,530	7,955		7,372
Selected Financial Information
Total assets	83,053	74,246		68,919
Depreciation and amortization	$ 700	$ 516		$ 572

[1] During the first quarter of 2020, Trustmark revised the composition of its operating segments by moving the Retail 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.