Revenue from Contracts with Customers - Summary of Noninterest Income Disaggregated by Reportable Operating Segment and Revenue Stream (Details) - USD ($) $ in Thousands		3 Months Ended			9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	[1]	Sep. 30, 2019	Sep. 30, 2018	[1]
Revenue From Contract With Customer [Line Items]
Service charges on deposit accounts		$ 11,065	$ 11,075		$ 31,709	$ 32,579
Bank card and other fees		8,349	7,459		23,544	21,155
Mortgage banking, net		8,171	8,647		21,908	28,958
Insurance commissions		11,072	10,765		33,032	30,919
Wealth management		7,691	7,789		22,916	22,834
Other, net		1,989	1,358		6,358	4,832
Total Noninterest Income		48,337	47,093		139,467	141,277
General Banking Segment [Member]
Revenue From Contract With Customer [Line Items]
Service charges on deposit accounts		11,041	11,054		31,638	32,513
Bank card and other fees		8,342	7,434		23,494	21,075
Mortgage banking, net		8,171	8,647		21,908	28,958
Wealth management		92	70		280	210
Other, net		1,929	1,304		5,976	4,688
Total Noninterest Income		29,575	28,509		83,296	87,444
Wealth Management Segment [Member]
Revenue From Contract With Customer [Line Items]
Service charges on deposit accounts		24	21		71	66
Bank card and other fees		7	25		50	80
Wealth management		7,599	7,719		22,636	22,624
Other, net		55	52		371	141
Total Noninterest Income		7,685	7,817		23,128	22,911
Insurance Segment [Member]
Revenue From Contract With Customer [Line Items]
Insurance commissions		11,072	10,765		33,032	30,919
Other, net		5	2		11	3
Total Noninterest Income		11,077	10,767		33,043	30,922
Topic 606 [Member]
Revenue From Contract With Customer [Line Items]
Service charges on deposit accounts		11,065	11,075		31,709	32,579
Bank card and other fees		6,966	6,523		21,036	19,928
Insurance commissions		11,072	10,765		33,032	30,919
Wealth management		7,691	7,789		22,916	22,834
Other, net		1,819	1,690		6,663	4,672
Total Noninterest Income		38,613	37,842		115,356	110,932
Topic 606 [Member] | General Banking Segment [Member]
Revenue From Contract With Customer [Line Items]
Service charges on deposit accounts		11,041	11,054		31,638	32,513
Bank card and other fees		6,959	6,498		20,986	19,848
Wealth management		92	70		280	210
Other, net		1,791	1,670		6,368	4,620
Total Noninterest Income		19,883	19,292		59,272	57,191
Topic 606 [Member] | Wealth Management Segment [Member]
Revenue From Contract With Customer [Line Items]
Service charges on deposit accounts		24	21		71	66
Bank card and other fees		7	25		50	80
Wealth management		7,599	7,719		22,636	22,624
Other, net		23	18		284	49
Total Noninterest Income		7,653	7,783		23,041	22,819
Topic 606 [Member] | Insurance Segment [Member]
Revenue From Contract With Customer [Line Items]
Insurance commissions		11,072	10,765		33,032	30,919
Other, net		5	2		11	3
Total Noninterest Income		11,077	10,767		33,043	30,922
Not Topic 606 [Member]
Revenue From Contract With Customer [Line Items]
Bank card and other fees	[2]	1,383	936		2,508	1,227
Mortgage banking, net	[2]	8,171	8,647		21,908	28,958
Other, net	[2]	170	(332)		(305)	160
Total Noninterest Income	[2]	9,724	9,251		24,111	30,345
Not Topic 606 [Member] | General Banking Segment [Member]
Revenue From Contract With Customer [Line Items]
Bank card and other fees	[2]	1,383	936		2,508	1,227
Mortgage banking, net	[2]	8,171	8,647		21,908	28,958
Other, net	[2]	138	(366)		(392)	68
Total Noninterest Income	[2]	9,692	9,217		24,024	30,253
Not Topic 606 [Member] | Wealth Management Segment [Member]
Revenue From Contract With Customer [Line Items]
Other, net	[2]	32	34		87	92
Total Noninterest Income	[2]	$ 32	$ 34		$ 87	$ 92

[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