ALLOWANCE FOR CREDIT LOSSES - Charge-offs and recoveries by loan class and vintage (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment [Line Items]
Charge-offs	$ (4,560)	$ (1,458)	$ (2,108)
Recovery	969	660	2,779
Net (charge-offs) recoveries	(3,591)	(798)	671
Commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Charge-offs	(714)	(1,252)	(1,928)
Recovery	794	489	2,737
Net (charge-offs) recoveries	80	(763)	809
Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Charge-offs	(163)	(45)	(171)
Recovery	147	81	20
Net (charge-offs) recoveries	(16)	36	(151)
1-4 family residential
Financing Receivable, Recorded Investment [Line Items]
Charge-offs	(71)	(12)	(4)
Recovery	1	3	6
Net (charge-offs) recoveries	(70)	(9)	2
Consumer
Financing Receivable, Recorded Investment [Line Items]
Charge-offs	(112)	(97)	(1)
Recovery	14	71	3
Net (charge-offs) recoveries	(98)	(26)	2
Agriculture
Financing Receivable, Recorded Investment [Line Items]
Recovery	12	10	10
Net (charge-offs) recoveries	12	$ 10	$ 10
Other
Financing Receivable, Recorded Investment [Line Items]
Charge-offs	(3,500)
Recovery	1
Net (charge-offs) recoveries	(3,499)
2020.
Financing Receivable, Recorded Investment [Line Items]
Recovery	5
Net (charge-offs) recoveries	5
2020. | Consumer
Financing Receivable, Recorded Investment [Line Items]
Recovery	5
Net (charge-offs) recoveries	5
2019.
Financing Receivable, Recorded Investment [Line Items]
Charge-offs	(3,605)
Recovery	5
Net (charge-offs) recoveries	(3,600)
2019. | Commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Charge-offs	(38)
Recovery	3
Net (charge-offs) recoveries	(35)
2019. | 1-4 family residential
Financing Receivable, Recorded Investment [Line Items]
Charge-offs	(64)
Net (charge-offs) recoveries	(64)
2019. | Consumer
Financing Receivable, Recorded Investment [Line Items]
Charge-offs	(3)
Recovery	2
Net (charge-offs) recoveries	(1)
2019. | Other
Financing Receivable, Recorded Investment [Line Items]
Charge-offs	(3,500)
Net (charge-offs) recoveries	(3,500)
2018.
Financing Receivable, Recorded Investment [Line Items]
Charge-offs	(71)
Recovery	178
Net (charge-offs) recoveries	107
2018. | Commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Charge-offs	(57)
Recovery	170
Net (charge-offs) recoveries	113
2018. | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Recovery	2
Net (charge-offs) recoveries	2
2018. | Consumer
Financing Receivable, Recorded Investment [Line Items]
Charge-offs	(14)
Recovery	6
Net (charge-offs) recoveries	(8)
2017.
Financing Receivable, Recorded Investment [Line Items]
Charge-offs	(130)
Recovery	47
Net (charge-offs) recoveries	(83)
2017. | Commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Charge-offs	(35)
Recovery	46
Net (charge-offs) recoveries	11
2017. | Consumer
Financing Receivable, Recorded Investment [Line Items]
Charge-offs	(95)
Net (charge-offs) recoveries	(95)
2017. | Other
Financing Receivable, Recorded Investment [Line Items]
Recovery	1
Net (charge-offs) recoveries	1
2016.
Financing Receivable, Recorded Investment [Line Items]
Charge-offs	(42)
Recovery	41
Net (charge-offs) recoveries	(1)
2016. | Commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Charge-offs	(42)
Recovery	29
Net (charge-offs) recoveries	(13)
2016. | Agriculture
Financing Receivable, Recorded Investment [Line Items]
Recovery	12
Net (charge-offs) recoveries	12
Prior.
Financing Receivable, Recorded Investment [Line Items]
Charge-offs	(170)
Recovery	473
Net (charge-offs) recoveries	303
Prior. | Commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Recovery	326
Net (charge-offs) recoveries	326
Prior. | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Charge-offs	(163)
Recovery	145
Net (charge-offs) recoveries	(18)
Prior. | 1-4 family residential
Financing Receivable, Recorded Investment [Line Items]
Charge-offs	(7)
Recovery	1
Net (charge-offs) recoveries	(6)
Prior. | Consumer
Financing Receivable, Recorded Investment [Line Items]
Recovery	1
Net (charge-offs) recoveries	1
Revolving Loans.
Financing Receivable, Recorded Investment [Line Items]
Charge-offs	(542)
Recovery	220
Net (charge-offs) recoveries	(322)
Revolving Loans. | Commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Charge-offs	(542)
Recovery	220
Net (charge-offs) recoveries	$ (322)