DEPOSITS - Types and Components of Deposit Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Noninterest bearing demand deposits:
Noninterest bearing demand deposits	$ 1,354,815	$ 1,040,112
Interest bearing deposits:
Total interest bearing deposits	3,577,507	3,662,657
Total deposits	4,932,322	4,702,769
Private accounts
Noninterest bearing demand deposits:
Noninterest bearing demand deposits	1,309,380	1,002,864
Interest bearing deposits:
Savings accounts	495,641	384,625
Money market demand accounts	429,687	407,461
Platinum money market accounts	381,877	353,374
Interest bearing checking accounts	835,489	699,681
NOW demand accounts	17,377	22,005
CDs of $250,000 or more	77,819	91,836
CDs under $250,000	474,503	790,053
Total interest bearing deposits	2,712,393	2,749,035
Public accounts
Noninterest bearing demand deposits:
Noninterest bearing demand deposits	45,435	37,248
Interest bearing deposits:
Savings accounts	347	337
Money market demand accounts	19,080	18,377
Platinum money market accounts	321,601	266,957
Interest bearing checking accounts	81,673	57,368
NOW demand accounts	203,638	158,804
CDs of $250,000 or more	227,201	368,351
CDs under $250,000	11,574	43,428
Total interest bearing deposits	$ 865,114	$ 913,622