Revenue from Contracts with Customers - Summary of Noninterest Income Disaggregated by Reportable Operating Segment and Revenue Stream (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Service charges on deposit accounts		$ 10,857	$ 10,832	[1]
Bank card and other fees		6,626	6,500	[1]
Mortgage banking, net		11,265	10,185	[1]
Insurance commissions		9,419	9,212	[1]
Wealth management		7,567	7,413	[1]
Other, net		1,059	1,891	[1]
Total Noninterest Income		46,793	46,033	[1]
Topic 606 [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Service charges on deposit accounts		10,857	10,832	[1]
Bank card and other fees		6,552	6,476	[1]
Insurance commissions		9,419	9,212	[1]
Wealth management		7,567	7,413	[1]
Other, net		1,441	2,344	[1]
Total Noninterest Income		35,836	36,277	[1]
Not Topic 606 [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Bank card and other fees	[2]	74	24	[1]
Mortgage banking, net	[2]	11,265	10,185	[1]
Other, net	[2]	(382)	(453)	[1]
Total Noninterest Income	[2]	10,957	9,756	[1]
General Banking Division [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Service charges on deposit accounts		10,857	10,832	[1]
Bank card and other fees		6,604	6,496	[1]
Mortgage banking, net		11,265	10,185	[1]
Wealth management		47	63	[1]
Other, net		1,036	1,864	[1]
Total Noninterest Income		29,809	29,440	[1]
General Banking Division [Member] | Topic 606 [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Service charges on deposit accounts		10,857	10,832	[1]
Bank card and other fees		6,530	6,472	[1]
Wealth management		47	63	[1]
Other, net		1,440	2,340	[1]
Total Noninterest Income		18,874	19,707	[1]
General Banking Division [Member] | Not Topic 606 [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Bank card and other fees	[2]	74	24	[1]
Mortgage banking, net	[2]	11,265	10,185	[1]
Other, net	[2]	(404)	(476)	[1]
Total Noninterest Income	[2]	10,935	9,733	[1]
Wealth Management Division [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Bank card and other fees		22	4	[1]
Wealth management		7,520	7,350	[1]
Other, net		23	23	[1]
Total Noninterest Income		7,565	7,377	[1]
Wealth Management Division [Member] | Topic 606 [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Bank card and other fees		22	4	[1]
Wealth management		7,520	7,350	[1]
Other, net		1
Total Noninterest Income		7,543	7,354	[1]
Wealth Management Division [Member] | Not Topic 606 [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Other, net	[2]	22	23	[1]
Total Noninterest Income	[2]	22	23	[1]
Insurance Division [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Insurance commissions		9,419	9,212	[1]
Other, net	[1]		4
Total Noninterest Income		9,419	9,216	[1]
Insurance Division [Member] | Topic 606 [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Insurance commissions		9,419	9,212	[1]
Other, net	[1]		4
Total Noninterest Income		$ 9,419	$ 9,216	[1]

[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.

[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.