ALLOWANCE FOR CREDIT LOSSES - Loans by risk grades and loan class (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Amortized cost of loans by loan type
Total loans	$ 2,936,670,000	$ 2,646,673,000
Pass
Amortized cost of loans by loan type
Total loans	2,835,768,000	2,582,970,000
Special Mention
Amortized cost of loans by loan type
Total loans	14,088,000	34,742,000
Substandard
Amortized cost of loans by loan type
Total loans	86,814,000	28,961,000
Loss or Doubtful
Amortized cost of loans by loan type
Total loans	0	0
Commercial and industrial
Amortized cost of loans by loan type
Total loans	742,957,000	527,607,000
Commercial and industrial | Loans by risk grades
Amortized cost of loans by loan type
Total loans	742,957,000
Commercial and industrial | Pass
Amortized cost of loans by loan type
Total loans	720,465,000	513,417,000
Commercial and industrial | Special Mention
Amortized cost of loans by loan type
Total loans	3,404,000	2,963,000
Commercial and industrial | Substandard
Amortized cost of loans by loan type
Total loans	19,088,000	11,227,000
Commercial real estate
Amortized cost of loans by loan type
Total loans	1,041,998,000	900,746,000
Commercial real estate | Loans by risk grades
Amortized cost of loans by loan type
Total loans	1,041,998,000
Commercial real estate | Pass
Amortized cost of loans by loan type
Total loans	1,000,503,000	876,207,000
Commercial real estate | Special Mention
Amortized cost of loans by loan type
Total loans	7,519,000	18,570,000
Commercial real estate | Substandard
Amortized cost of loans by loan type
Total loans	33,976,000	5,969,000
Construction and development
Amortized cost of loans by loan type
Total loans	522,705,000	527,812,000
Construction and development | Loans by risk grades
Amortized cost of loans by loan type
Total loans	522,705,000
Construction and development | Pass
Amortized cost of loans by loan type
Total loans	502,933,000	515,247,000
Construction and development | Special Mention
Amortized cost of loans by loan type
Total loans		12,565,000
Construction and development | Substandard
Amortized cost of loans by loan type
Total loans	19,772,000
1-4 family residential
Amortized cost of loans by loan type
Total loans	239,872,000	280,192,000
1-4 family residential | Loans by risk grades
Amortized cost of loans by loan type
Total loans	239,872,000
1-4 family residential | Pass
Amortized cost of loans by loan type
Total loans	230,654,000	274,731,000
1-4 family residential | Special Mention
Amortized cost of loans by loan type
Total loans	3,165,000	594,000
1-4 family residential | Substandard
Amortized cost of loans by loan type
Total loans	6,053,000	4,867,000
Multifamily residential
Amortized cost of loans by loan type
Total loans	258,346,000	277,209,000
Multifamily residential | Loans by risk grades
Amortized cost of loans by loan type
Total loans	258,346,000
Multifamily residential | Pass
Amortized cost of loans by loan type
Total loans	258,346,000	277,209,000
Consumer
Amortized cost of loans by loan type
Total loans	33,884,000	36,782,000
Consumer | Loans by risk grades
Amortized cost of loans by loan type
Total loans	33,884,000
Consumer | Pass
Amortized cost of loans by loan type
Total loans	33,884,000	36,566,000
Consumer | Substandard
Amortized cost of loans by loan type
Total loans		216,000
Agriculture
Amortized cost of loans by loan type
Total loans	8,670,000	9,812,000
Agriculture | Loans by risk grades
Amortized cost of loans by loan type
Total loans	8,670,000
Agriculture | Pass
Amortized cost of loans by loan type
Total loans	8,597,000	9,733,000
Agriculture | Special Mention
Amortized cost of loans by loan type
Total loans		50,000
Agriculture | Substandard
Amortized cost of loans by loan type
Total loans	73,000	29,000
Other
Amortized cost of loans by loan type
Total loans	88,238,000	86,513,000
Other | Pass
Amortized cost of loans by loan type
Total loans	80,386,000	79,860,000
Other | Substandard
Amortized cost of loans by loan type
Total loans	$ 7,852,000	$ 6,653,000