Revenue from Contracts with Customers - Summary of Noninterest Income Disaggregated by Reportable Operating Segment and Revenue Stream (Details) - USD ($) $ in Thousands		3 Months Ended			6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	[1]	Jun. 30, 2019	Jun. 30, 2018	[1]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Service charges on deposit accounts		$ 10,379	$ 10,647		$ 20,644	$ 21,504
Bank card and other fees		8,004	7,070		15,195	13,696
Mortgage banking, net		10,295	9,046		13,737	20,311
Insurance commissions		11,089	10,735		21,960	20,154
Wealth management		7,742	7,478		15,225	15,045
Other, net		2,130	2,415		4,369	3,474
Total Noninterest Income		49,639	47,391		91,130	94,184
General Banking Segment [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Service charges on deposit accounts		10,357	10,626		20,597	21,459
Bank card and other fees		7,985	7,042		15,152	13,641
Mortgage banking, net		10,295	9,046		13,737	20,311
Wealth management		97	93		188	140
Other, net		2,074	2,368		4,047	3,384
Total Noninterest Income		30,808	29,175		53,721	58,935
Wealth Management Segment [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Service charges on deposit accounts		22	21		47	45
Bank card and other fees		19	28		43	55
Wealth management		7,645	7,385		15,037	14,905
Other, net		54	46		316	89
Total Noninterest Income		7,740	7,480		15,443	15,094
Insurance Segment [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Insurance commissions		11,089	10,735		21,960	20,154
Other, net		2	1		6	1
Total Noninterest Income		11,091	10,736		21,966	20,155
Topic 606 [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Service charges on deposit accounts		10,379	10,647		20,644	21,504
Bank card and other fees		7,181	6,854		14,070	13,405
Insurance commissions		11,089	10,735		21,960	20,154
Wealth management		7,742	7,478		15,225	15,045
Other, net		2,360	1,543		4,844	2,982
Total Noninterest Income		38,751	37,257		76,743	73,090
Topic 606 [Member] | General Banking Segment [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Service charges on deposit accounts		10,357	10,626		20,597	21,459
Bank card and other fees		7,162	6,826		14,027	13,350
Wealth management		97	93		188	140
Other, net		2,333	1,526		4,577	2,950
Total Noninterest Income		19,949	19,071		39,389	37,899
Topic 606 [Member] | Wealth Management Segment [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Service charges on deposit accounts		22	21		47	45
Bank card and other fees		19	28		43	55
Wealth management		7,645	7,385		15,037	14,905
Other, net		25	16		261	31
Total Noninterest Income		7,711	7,450		15,388	15,036
Topic 606 [Member] | Insurance Segment [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Insurance commissions		11,089	10,735		21,960	20,154
Other, net		2	1		6	1
Total Noninterest Income		11,091	10,736		21,966	20,155
Not Topic 606 [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Bank card and other fees	[2]	823	216		1,125	291
Mortgage banking, net	[2]	10,295	9,046		13,737	20,311
Other, net	[2]	(230)	872		(475)	492
Total Noninterest Income	[2]	10,888	10,134		14,387	21,094
Not Topic 606 [Member] | General Banking Segment [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Bank card and other fees	[2]	823	216		1,125	291
Mortgage banking, net	[2]	10,295	9,046		13,737	20,311
Other, net	[2]	(259)	842		(530)	434
Total Noninterest Income	[2]	10,859	10,104		14,332	21,036
Not Topic 606 [Member] | Wealth Management Segment [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Other, net	[2]	29	30		55	58
Total Noninterest Income	[2]	$ 29	$ 30		$ 55	$ 58

[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] Noninterest income not in scope for FASB ASC Topic 606 includes customer derivatives revenue and miscellaneous credit card fee income within bank card and other fees; mortgage banking, net; amortization of tax credits, accretion of the FDIC indemnification asset, cash surrender value on various life insurance policies, earnings on Trustmark’s non-qualified deferred compensation plans, other partnership investments and rental income within other, net; and security gains (losses), net