LOAN PERFORMANCE - Aging analysis of loan past due (Details) - USD ($)	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Aging analysis
Total past due	$ 5,386,000		$ 2,874,000
Total current loans	2,942,381,000		2,643,799,000
Total Loans	2,947,767,000		2,646,673,000
Interest income that would have been earned under the original terms of the nonaccrual loans	121,000	$ 87,000
30 to 59 days past due
Aging analysis
Total past due	5,329,000		2,071,000
60 to 89 days past due
Aging analysis
Total past due			563,000
90 days or greater past due
Aging analysis
Total past due	57,000		240,000
Commercial and industrial
Aging analysis
Total past due	1,313,000		935,000
Total current loans	836,354,000		526,672,000
Total Loans	837,667,000		527,607,000
Commercial and industrial | 30 to 59 days past due
Aging analysis
Total past due	1,256,000		664,000
Commercial and industrial | 60 to 89 days past due
Aging analysis
Total past due			31,000
Commercial and industrial | 90 days or greater past due
Aging analysis
Total past due	57,000		240,000
Commercial real estate
Aging analysis
Total past due			865,000
Total current loans	908,027,000		899,881,000
Total Loans	908,027,000		900,746,000
Commercial real estate | 30 to 59 days past due
Aging analysis
Total past due			865,000
Construction and development
Aging analysis
Total past due	386,000		532,000
Total current loans	552,493,000		527,280,000
Total Loans	552,879,000		527,812,000
Construction and development | 30 to 59 days past due
Aging analysis
Total past due	386,000
Construction and development | 60 to 89 days past due
Aging analysis
Total past due			532,000
1-4 family residential
Aging analysis
Total past due	146,000		499,000
Total current loans	272,107,000		279,693,000
Total Loans	272,253,000		280,192,000
1-4 family residential | 30 to 59 days past due
Aging analysis
Total past due	146,000		499,000
Multifamily residential
Aging analysis
Total current loans	255,273,000		277,209,000
Total Loans	255,273,000		277,209,000
Consumer
Aging analysis
Total past due	14,000		43,000
Total current loans	36,324,000		36,739,000
Total Loans	36,338,000		36,782,000
Consumer | 30 to 59 days past due
Aging analysis
Total past due	14,000		43,000
Agriculture
Aging analysis
Total past due	27,000
Total current loans	7,768,000		9,812,000
Total Loans	7,795,000		9,812,000
Agriculture | 30 to 59 days past due
Aging analysis
Total past due	27,000
Other
Aging analysis
Total past due	3,500,000
Total current loans	74,035,000		86,513,000
Total Loans	77,535,000		$ 86,513,000
Other | 30 to 59 days past due
Aging analysis
Total past due	$ 3,500,000