Acquired Loans - Changes in the Carrying Value of Acquired Loans (Details) - USD ($) $ in Thousands		3 Months Ended		12 Months Ended
		Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Carrying value of acquired loans [Abstract]
Carrying value, net, beginning		$ 105,701
Accretion to interest income		1,563	$ 3,268
Carrying value, net, ending		91,904		$ 105,701
Acquired Not ASC 310-30 [Member]
Carrying value of acquired loans [Abstract]
Carrying value, net, beginning	[1]	2,811	77,868	77,868
Transfers	[1],[2]	(2,926)		(59,916)
Accretion to interest income	[1]	115		1,019
Payments received, net	[1]	0		(16,234)
Other	[1],[3]	0		74
Change in allowance for loan losses, acquired loans	[1]	0		0
Carrying value, net, ending	[1]	0		2,811
Acquired Impaired [Member]
Carrying value of acquired loans [Abstract]
Carrying value, net, beginning		102,890	$ 179,570	179,570
Transfers	[4]	0		(26,497)
Accretion to interest income		1,563		9,514
Payments received, net		(12,548)		(62,519)
Other	[3]	65		(26)
Change in allowance for loan losses, acquired loans		(66)		2,848
Carrying value, net, ending		$ 91,904		$ 102,890

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

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

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

[4] During 2018, Trustmark transferred the remaining loans acquired in the Heritage, Bay Bank and Reliance acquisitions from acquired impaired loans to LHFI.