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, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenue From Contract With Customer [Line Items]
Service charges on deposit accounts		$ 7,577	$ 11,065	$ 24,006	$ 31,709
Bank card and other fees		8,843	8,349	21,915	23,544
Mortgage banking, net		36,439	8,171	97,667	21,908
Insurance commissions		11,562	11,072	34,980	33,032
Wealth management		7,679	7,691	23,787	22,916
Other, net		1,601	1,989	6,121	6,358
Total Noninterest Income		73,701	48,337	208,476	139,467
Topic 606 [Member]
Revenue From Contract With Customer [Line Items]
Service charges on deposit accounts		7,577	11,065	24,006	31,709
Bank card and other fees		7,026	6,966	20,315	21,036
Insurance commissions		11,562	11,072	34,980	33,032
Wealth management		7,679	7,691	23,787	22,916
Other, net		1,546	1,819	4,778	6,663
Total Noninterest Income		35,390	38,613	107,866	115,356
Not Topic 606 [Member]
Revenue From Contract With Customer [Line Items]
Bank card and other fees	[1]	1,817	1,383	1,600	2,508
Mortgage banking, net	[1]	36,439	8,171	97,667	21,908
Other, net	[1]	55	170	1,343	(305)
Total Noninterest Income	[1]	38,311	9,724	100,610	24,111
General Banking Segment [Member]
Revenue From Contract With Customer [Line Items]
Service charges on deposit accounts		7,557	11,041	23,949	31,638
Bank card and other fees		8,836	8,342	21,894	23,494
Mortgage banking, net		36,439	8,171	97,667	21,908
Wealth management		54	92	219	280
Other, net		1,536	1,930	5,920	5,977
Total Noninterest Income		54,422	29,576	149,649	83,297
General Banking Segment [Member] | Topic 606 [Member]
Revenue From Contract With Customer [Line Items]
Service charges on deposit accounts		7,557	11,041	23,949	31,638
Bank card and other fees		7,019	6,959	20,294	20,986
Wealth management		54	92	219	280
Other, net		1,496	1,792	4,614	6,369
Total Noninterest Income		16,126	19,884	49,076	59,273
General Banking Segment [Member] | Not Topic 606 [Member]
Revenue From Contract With Customer [Line Items]
Bank card and other fees	[1]	1,817	1,383	1,600	2,508
Mortgage banking, net	[1]	36,439	8,171	97,667	21,908
Other, net	[1]	40	138	1,306	(392)
Total Noninterest Income	[1]	38,296	9,692	100,573	24,024
Wealth Management Segment [Member]
Revenue From Contract With Customer [Line Items]
Service charges on deposit accounts		20	24	57	71
Bank card and other fees		7	7	21	50
Wealth management		7,625	7,599	23,568	22,636
Other, net		42	54	114	370
Total Noninterest Income		7,694	7,684	23,760	23,127
Wealth Management Segment [Member] | Topic 606 [Member]
Revenue From Contract With Customer [Line Items]
Service charges on deposit accounts		20	24	57	71
Bank card and other fees		7	7	21	50
Wealth management		7,625	7,599	23,568	22,636
Other, net		27	22	77	283
Total Noninterest Income		7,679	7,652	23,723	23,040
Wealth Management Segment [Member] | Not Topic 606 [Member]
Revenue From Contract With Customer [Line Items]
Other, net	[1]	15	32	37	87
Total Noninterest Income	[1]	15	32	37	87
Insurance Segment [Member]
Revenue From Contract With Customer [Line Items]
Insurance commissions		11,562	11,072	34,980	33,032
Other, net		23	5	87	11
Total Noninterest Income		11,585	11,077	35,067	33,043
Insurance Segment [Member] | Topic 606 [Member]
Revenue From Contract With Customer [Line Items]
Insurance commissions		11,562	11,072	34,980	33,032
Other, net		23	5	87	11
Total Noninterest Income		$ 11,585	$ 11,077	$ 35,067	$ 33,043

[1] 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.