LOANS AND ALLOWANCE FOR LOAN LOSSES - Loans by Portfolio Segment (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Jan. 01, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Loans and Leases Receivable Disclosure [Abstract]
Loans	$ 3,657,779		$ 3,568,204
Less: Allowance for loan losses	49,006	$ 24,797	24,797	$ 27,019	$ 20,781
Total loans	3,608,773		3,543,407
Construction real estate loans
Loans and Leases Receivable Disclosure [Abstract]
Loans	581,941		644,948
Less: Allowance for loan losses	6,490	3,539	3,539	3,597	3,676
1-4 family residential real estate loans
Loans and Leases Receivable Disclosure [Abstract]
Loans	719,952		787,562
Less: Allowance for loan losses	2,270	3,833	3,833	3,844	2,445
Commercial real estate loans
Loans and Leases Receivable Disclosure [Abstract]
Loans	1,295,746		1,250,208
Less: Allowance for loan losses	35,709	9,572	9,572	13,968	10,821
Commercial loans
Loans and Leases Receivable Disclosure [Abstract]
Loans	557,122		401,521
Less: Allowance for loan losses	4,107	6,351	6,351	3,974	2,094
Municipal loans
Loans and Leases Receivable Disclosure [Abstract]
Loans	409,028		383,960
Less: Allowance for loan losses	46	570	570	525	860
Loans to individuals
Loans and Leases Receivable Disclosure [Abstract]
Loans	93,990		100,005
Less: Allowance for loan losses	$ 384	$ 932	$ 932	$ 1,111	$ 885