LOANS - Schedule of Recorded Investment in Nonaccrual and Loans Past Due Over 90 Days on Accrual by Class of Loans (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	$ 27,434	$ 27,035
Loans Past Due Over 90 Days And Still Accruing Interest	0	654
Commercial real estate: | Nonfarm, nonresidential
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	3,460
Loans Past Due Over 90 Days And Still Accruing Interest	0
Construction and land development | Construction and land development
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual		30
Loans Past Due Over 90 Days And Still Accruing Interest			$ 0
Residential real estate: | Closed-end 1-4 family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	942	954
Loans Past Due Over 90 Days And Still Accruing Interest	0		0
Residential real estate: | Other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	2,313	1,523
Loans Past Due Over 90 Days And Still Accruing Interest	0		0
Commercial and industrial | Commercial and industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	20,719		$ 24,528
Loans Past Due Over 90 Days And Still Accruing Interest	$ 0	$ 654