Acquired Loans - Changes in the Carrying Value of Acquired Loans (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018		Dec. 31, 2017	Dec. 31, 2016	Apr. 07, 2017
Carrying value of acquired loans [Abstract]
Carrying value, net, beginning		$ 257,438
Additions						$ 7,900
Accretion to interest income		9,514		$ 14,924	$ 18,405
Carrying value, net, ending		105,701		257,438
Acquired Not ASC 310-30 [Member]
Carrying value of acquired loans [Abstract]
Carrying value, net, beginning	[1]	77,868		42,743
Transfers	[1],[3]	(59,916)	[2]	(36,719)
Additions	[1],[4]			109,548
Accretion to interest income	[1]	1,019		1,578
Payments received, net	[1]	(16,234)		(39,208)
Other	[1],[5]	74		(74)
Change in allowance for loan losses, acquired loans	[1]	0		0
Carrying value, net, ending	[1]	2,811		77,868	42,743
Acquired Impaired [Member]
Carrying value of acquired loans [Abstract]
Carrying value, net, beginning		179,570		218,107
Transfers	[3]	(26,497)	[2]	0
Additions	[4]			7,899
Accretion to interest income		9,514		14,924
Payments received, net		(62,519)		(68,317)
Other	[5]	(26)		(361)
Change in allowance for loan losses, acquired loans		2,848		7,318
Carrying value, net, ending		$ 102,890		$ 179,570	$ 218,107

[1] “Acquired Not ASC 310-30” loans consist of loans that are not in scope for FASB ASC Topic 310-30.

[2] During 2018, Trustmark transferred the remaining loans acquired in the Heritage acquisition on April 11, 2015, the Bay Bank merger on March 16, 2012 and the Reliance merger on April 7, 2017 from acquired impaired loans to LHFI

[3] “Acquired Not ASC 310-30” loans transferred to LHFI due to the discount on these loans being fully amortized

[4] Loans acquired in the Reliance merger on April 7, 2017

[5] Includes miscellaneous timing adjustments as well as acquired loan terminations through foreclosure, charge-off and other terminations