LOANS - Past Due and Nonaccrual Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Past Due and Nonaccrual Loans
>90 Days Past Due and Accruing	$ 0	$ 343
Nonaccrual Including 90 Days or More Past Due	12,162	4,369
Total Past Due and Nonaccrual	23,775	11,078
Current	4,581,808	3,661,518
Total Loans	4,605,583	3,672,596
Interest earned on non-accrual loans	93
Accrued interest on non-accrual loans	406
30-59 Days Past Due
Past Due and Nonaccrual Loans
Total Past Due and Nonaccrual	6,588	4,465
60-89 Days Past Due
Past Due and Nonaccrual Loans
Total Past Due and Nonaccrual	5,025	1,901
Commercial Real Estate | Mortgage loans
Past Due and Nonaccrual Loans
Total Loans		1,565,687
Commercial Real Estate | Mortgage loans | Owner occupied
Past Due and Nonaccrual Loans
>90 Days Past Due and Accruing	0	0
Nonaccrual Including 90 Days or More Past Due	636	225
Total Past Due and Nonaccrual	636	1,575
Current	556,440	529,513
Total Loans	557,076	531,088
Commercial Real Estate | Mortgage loans | Owner occupied | 30-59 Days Past Due
Past Due and Nonaccrual Loans
Total Past Due and Nonaccrual	0	917
Commercial Real Estate | Mortgage loans | Owner occupied | 60-89 Days Past Due
Past Due and Nonaccrual Loans
Total Past Due and Nonaccrual	0	433
Commercial Real Estate | Mortgage loans | Non-owner occupied
Past Due and Nonaccrual Loans
>90 Days Past Due and Accruing	0	0
Nonaccrual Including 90 Days or More Past Due	6,771	512
Total Past Due and Nonaccrual	6,771	610
Current	1,074,672	1,033,989
Total Loans	1,081,443	1,034,599
Commercial Real Estate | Mortgage loans | Non-owner occupied | 30-59 Days Past Due
Past Due and Nonaccrual Loans
Total Past Due and Nonaccrual	0	98
Multi-family
Past Due and Nonaccrual Loans
Total Loans		812,174
Multi-family | Mortgage loans
Past Due and Nonaccrual Loans
>90 Days Past Due and Accruing	0	0
Nonaccrual Including 90 Days or More Past Due	0	0
Total Past Due and Nonaccrual	0	0
Current	899,730	812,174
Total Loans	899,730	812,174
Multi-family | Mortgage loans | 30-59 Days Past Due
Past Due and Nonaccrual Loans
Total Past Due and Nonaccrual	0	0
Multi-family | Mortgage loans | 60-89 Days Past Due
Past Due and Nonaccrual Loans
Total Past Due and Nonaccrual	0	0
Residential Real Estate Loans
Past Due and Nonaccrual Loans
>90 Days Past Due and Accruing	0	343
Nonaccrual Including 90 Days or More Past Due	2,897	2,743
Total Past Due and Nonaccrual	7,413	6,886
Current	427,276	486,258
Total Loans	434,689	493,144
Residential Real Estate Loans | 30-59 Days Past Due
Past Due and Nonaccrual Loans
Total Past Due and Nonaccrual	3,567	3,053
Residential Real Estate Loans | 60-89 Days Past Due
Past Due and Nonaccrual Loans
Total Past Due and Nonaccrual	949	747
Residential Real Estate Loans | Mortgage loans
Past Due and Nonaccrual Loans
Total Loans	434,689	493,144
Commercial, industrial and agricultural:
Past Due and Nonaccrual Loans
>90 Days Past Due and Accruing	0	0
Nonaccrual Including 90 Days or More Past Due	1,597	736
Total Past Due and Nonaccrual	8,380	1,730
Current	1,518,767	677,714
Total Loans	1,527,147	679,444
Commercial, industrial and agricultural: | 30-59 Days Past Due
Past Due and Nonaccrual Loans
Total Past Due and Nonaccrual	2,711	273
Commercial, industrial and agricultural: | 60-89 Days Past Due
Past Due and Nonaccrual Loans
Total Past Due and Nonaccrual	4,072	721
Real estate construction and land loans
Past Due and Nonaccrual Loans
>90 Days Past Due and Accruing	0	0
Nonaccrual Including 90 Days or More Past Due	111	123
Total Past Due and Nonaccrual	321	123
Current	82,158	97,188
Total Loans	82,479	97,311
Real estate construction and land loans | 30-59 Days Past Due
Past Due and Nonaccrual Loans
Total Past Due and Nonaccrual	210	0
Real estate construction and land loans | 60-89 Days Past Due
Past Due and Nonaccrual Loans
Total Past Due and Nonaccrual	0	0
Installment/consumer loans
Past Due and Nonaccrual Loans
>90 Days Past Due and Accruing	0	0
Nonaccrual Including 90 Days or More Past Due	150	30
Total Past Due and Nonaccrual	254	154
Current	22,765	24,682
Total Loans	23,019	24,836
Installment/consumer loans | 30-59 Days Past Due
Past Due and Nonaccrual Loans
Total Past Due and Nonaccrual	100	124
Installment/consumer loans | 60-89 Days Past Due
Past Due and Nonaccrual Loans
Total Past Due and Nonaccrual	$ 4	$ 0