FAIR VALUE DISCLOSURES - Valuation Methodology and Unobservable Inputs for Level 3 Assets (Details) - Fair Value, Measurements, Nonrecurring $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)
Valuation Methodology and Unobservable Inputs For Level 3 Assets Measured At Fair Value [Line Items]
Fair Value	$ 21,333	$ 6,765
Commercial and industrial loans
Valuation Methodology and Unobservable Inputs For Level 3 Assets Measured At Fair Value [Line Items]
Valuation Methodology	Collateral based measurements	Collateral basedmeasurements
Unobservable Inputs	Discount to reflect current market conditions and ultimate collectability	Discount to reflect current market conditions and ultimate collectability
Commercial and industrial loans | Collateral Based Measurements | Measurement Input, Discount Rate
Valuation Methodology and Unobservable Inputs For Level 3 Assets Measured At Fair Value [Line Items]
Fair Value	$ 17,507	$ 5,082
Commercial and industrial loans | Average | Collateral Based Measurements | Measurement Input, Discount Rate
Valuation Methodology and Unobservable Inputs For Level 3 Assets Measured At Fair Value [Line Items]
Average	0.58	0.55
Commercial and industrial loans | Minimum | Collateral Based Measurements | Measurement Input, Discount Rate
Valuation Methodology and Unobservable Inputs For Level 3 Assets Measured At Fair Value [Line Items]
Average		0.16
Commercial and industrial loans | Maximum | Collateral Based Measurements | Measurement Input, Discount Rate
Valuation Methodology and Unobservable Inputs For Level 3 Assets Measured At Fair Value [Line Items]
Average		1
Commercial real estate and multi-family residential loans
Valuation Methodology and Unobservable Inputs For Level 3 Assets Measured At Fair Value [Line Items]
Valuation Methodology	Collateral based measurements	Collateral basedmeasurements
Unobservable Inputs	Discount to reflect current market conditions and ultimate collectability	Discount to reflect current market conditions and ultimate collectability
Commercial real estate and multi-family residential loans | Collateral Based Measurements | Measurement Input, Discount Rate
Valuation Methodology and Unobservable Inputs For Level 3 Assets Measured At Fair Value [Line Items]
Fair Value	$ 3,783	$ 1,211
Commercial real estate and multi-family residential loans | Average | Collateral Based Measurements | Measurement Input, Discount Rate
Valuation Methodology and Unobservable Inputs For Level 3 Assets Measured At Fair Value [Line Items]
Average		0.53
Commercial real estate and multi-family residential loans | Minimum | Collateral Based Measurements | Measurement Input, Discount Rate
Valuation Methodology and Unobservable Inputs For Level 3 Assets Measured At Fair Value [Line Items]
Average		0.21
Commercial real estate and multi-family residential loans | Maximum | Collateral Based Measurements | Measurement Input, Discount Rate
Valuation Methodology and Unobservable Inputs For Level 3 Assets Measured At Fair Value [Line Items]
Average		0.74
Agri-business and agricultural loans
Valuation Methodology and Unobservable Inputs For Level 3 Assets Measured At Fair Value [Line Items]
Valuation Methodology	Collateral based measurements	Collateral basedmeasurements
Unobservable Inputs	Discount to reflect current market conditions and ultimate collectability	Discount to reflect current market conditions and ultimate collectability
Agri-business and agricultural loans | Collateral Based Measurements | Measurement Input, Discount Rate
Valuation Methodology and Unobservable Inputs For Level 3 Assets Measured At Fair Value [Line Items]
Fair Value	$ 43	$ 61
Agri-business and agricultural loans | Average | Collateral Based Measurements | Measurement Input, Discount Rate
Valuation Methodology and Unobservable Inputs For Level 3 Assets Measured At Fair Value [Line Items]
Average	0.70	0.58
Consumer 1-4 family loans
Valuation Methodology and Unobservable Inputs For Level 3 Assets Measured At Fair Value [Line Items]
Valuation Methodology		Collateral basedmeasurements
Unobservable Inputs		Discount to reflect current market conditions and ultimate collectability
Consumer 1-4 family loans | Collateral Based Measurements | Measurement Input, Discount Rate
Valuation Methodology and Unobservable Inputs For Level 3 Assets Measured At Fair Value [Line Items]
Fair Value		$ 411
Consumer 1-4 family loans | Average | Collateral Based Measurements | Measurement Input, Discount Rate
Valuation Methodology and Unobservable Inputs For Level 3 Assets Measured At Fair Value [Line Items]
Average		0.11
Consumer 1-4 family loans | Minimum | Collateral Based Measurements | Measurement Input, Discount Rate
Valuation Methodology and Unobservable Inputs For Level 3 Assets Measured At Fair Value [Line Items]
Average		0.10
Consumer 1-4 family loans | Maximum | Collateral Based Measurements | Measurement Input, Discount Rate
Valuation Methodology and Unobservable Inputs For Level 3 Assets Measured At Fair Value [Line Items]
Average		0.15