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, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenue From Contract With Customer [Line Items]
Service charges on deposit accounts		$ 6,397	$ 10,379	$ 16,429	$ 20,644
Bank card and other fees		7,717	8,004	13,072	15,195
Mortgage banking, net		33,745	10,295	61,228	13,737
Insurance commissions		11,868	11,089	23,418	21,960
Wealth management		7,571	7,742	16,108	15,225
Other, net		2,213	2,130	4,520	4,369
Total Noninterest Income		69,511	49,639	134,775	91,130
Topic 606 [Member]
Revenue From Contract With Customer [Line Items]
Service charges on deposit accounts		6,397	10,379	16,429	20,644
Bank card and other fees		6,557	7,181	13,289	14,070
Insurance commissions		11,868	11,089	23,418	21,960
Wealth management		7,571	7,742	16,108	15,225
Other, net		1,420	2,360	3,232	4,844
Total Noninterest Income		33,813	38,751	72,476	76,743
Not Topic 606 [Member]
Revenue From Contract With Customer [Line Items]
Bank card and other fees	[1]	1,160	823	(217)	1,125
Mortgage banking, net	[1]	33,745	10,295	61,228	13,737
Other, net	[1]	793	(230)	1,288	(475)
Total Noninterest Income	[1]	35,698	10,888	62,299	14,387
General Banking Segment [Member]
Revenue From Contract With Customer [Line Items]
Service charges on deposit accounts		6,380	10,357	16,392	20,597
Bank card and other fees		7,709	7,985	13,058	15,152
Mortgage banking, net		33,745	10,295	61,228	13,737
Wealth management		79	97	165	188
Other, net		2,138	2,074	4,384	4,047
Total Noninterest Income		50,051	30,808	95,227	53,721
General Banking Segment [Member] | Topic 606 [Member]
Revenue From Contract With Customer [Line Items]
Service charges on deposit accounts		6,380	10,357	16,392	20,597
Bank card and other fees		6,549	7,162	13,275	14,027
Wealth management		79	97	165	188
Other, net		1,354	2,333	3,118	4,577
Total Noninterest Income		14,362	19,949	32,950	39,389
General Banking Segment [Member] | Not Topic 606 [Member]
Revenue From Contract With Customer [Line Items]
Bank card and other fees	[1]	1,160	823	(217)	1,125
Mortgage banking, net	[1]	33,745	10,295	61,228	13,737
Other, net	[1]	784	(259)	1,266	(530)
Total Noninterest Income	[1]	35,689	10,859	62,277	14,332
Wealth Management Segment [Member]
Revenue From Contract With Customer [Line Items]
Service charges on deposit accounts		17	22	37	47
Bank card and other fees		8	19	14	43
Wealth management		7,492	7,645	15,943	15,037
Other, net		33	54	72	316
Total Noninterest Income		7,550	7,740	16,066	15,443
Wealth Management Segment [Member] | Topic 606 [Member]
Revenue From Contract With Customer [Line Items]
Service charges on deposit accounts		17	22	37	47
Bank card and other fees		8	19	14	43
Wealth management		7,492	7,645	15,943	15,037
Other, net		24	25	50	261
Total Noninterest Income		7,541	7,711	16,044	15,388
Wealth Management Segment [Member] | Not Topic 606 [Member]
Revenue From Contract With Customer [Line Items]
Other, net	[1]	9	29	22	55
Total Noninterest Income	[1]	9	29	22	55
Insurance Segment [Member]
Revenue From Contract With Customer [Line Items]
Insurance commissions		11,868	11,089	23,418	21,960
Other, net		42	2	64	6
Total Noninterest Income		11,910	11,091	23,482	21,966
Insurance Segment [Member] | Topic 606 [Member]
Revenue From Contract With Customer [Line Items]
Insurance commissions		11,868	11,089	23,418	21,960
Other, net		42	2	64	6
Total Noninterest Income		$ 11,910	$ 11,091	$ 23,482	$ 21,966

[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.