FAIR VALUE - Valuation Methodology and Unobservable Inputs for Level 3 Assets (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2021 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($) item	Dec. 31, 2019 USD ($)
Valuation Methodology and Unobservable Inputs For Level 3 Assets Measured At Fair Value [Line Items]
Loans and Leases Receivable, Gross	$ 4,484,767		$ 4,657,183
Loans and Leases Receivable, Allowance	71,844	$ 53,609	61,408	$ 50,652
Provision for credit losses	1,477	6,600
Fair Value, Measurements, Nonrecurring [Member]
Valuation Methodology and Unobservable Inputs For Level 3 Assets Measured At Fair Value [Line Items]
Impaired loans	$ 5,539		6,765
Commercial and industrial loans
Valuation Methodology and Unobservable Inputs For Level 3 Assets Measured At Fair Value [Line Items]
Valuation Methodology	Collateral basedmeasurements
Loans and Leases Receivable, Gross	$ 1,676,464		1,791,378
Loans and Leases Receivable, Allowance	32,052	24,739	$ 28,333	25,789
Provision for credit losses	$ (540)	2,628
Commercial and industrial loans | Fair Value, Measurements, Nonrecurring [Member]
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		Discount to reflect current market conditions and ultimate collectability
Commercial and industrial loans | Fair Value, Measurements, Nonrecurring [Member] | Collateral Based Measurements | Measurement Input, Discount Rate
Valuation Methodology and Unobservable Inputs For Level 3 Assets Measured At Fair Value [Line Items]
Impaired loans	$ 4,464		$ 5,082
Commercial and industrial loans | Fair Value, Measurements, Nonrecurring [Member] | Minimum | Collateral Based Measurements | Measurement Input, Discount Rate
Valuation Methodology and Unobservable Inputs For Level 3 Assets Measured At Fair Value [Line Items]
Range of Inputs (Average) (in hundredths)	22		16
Commercial and industrial loans | Fair Value, Measurements, Nonrecurring [Member] | Maximum | Collateral Based Measurements | Measurement Input, Discount Rate
Valuation Methodology and Unobservable Inputs For Level 3 Assets Measured At Fair Value [Line Items]
Range of Inputs (Average) (in hundredths)	100		100
Commercial and industrial loans | Fair Value, Measurements, Nonrecurring [Member] | Weighted Average | Collateral Based Measurements | Measurement Input, Discount Rate
Valuation Methodology and Unobservable Inputs For Level 3 Assets Measured At Fair Value [Line Items]
Range of Inputs (Average) (in hundredths)	61		55
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 basedmeasurements
Loans and Leases Receivable, Allowance	$ 29,445	18,658	$ 22,907	15,796
Provision for credit losses	$ 2,285	2,750
Commercial real estate and multi-family residential loans | Fair Value, Measurements, Nonrecurring [Member]
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		Discount to reflect current market conditions and ultimate collectability
Commercial real estate and multi-family residential loans | Fair Value, Measurements, Nonrecurring [Member] | Collateral Based Measurements | Measurement Input, Discount Rate
Valuation Methodology and Unobservable Inputs For Level 3 Assets Measured At Fair Value [Line Items]
Impaired loans	$ 710		$ 1,211
Commercial real estate and multi-family residential loans | Fair Value, Measurements, Nonrecurring [Member] | Minimum | Collateral Based Measurements | Measurement Input, Discount Rate
Valuation Methodology and Unobservable Inputs For Level 3 Assets Measured At Fair Value [Line Items]
Range of Inputs (Average) (in hundredths)	25		21
Commercial real estate and multi-family residential loans | Fair Value, Measurements, Nonrecurring [Member] | Maximum | Collateral Based Measurements | Measurement Input, Discount Rate
Valuation Methodology and Unobservable Inputs For Level 3 Assets Measured At Fair Value [Line Items]
Range of Inputs (Average) (in hundredths)	73		74
Commercial real estate and multi-family residential loans | Fair Value, Measurements, Nonrecurring [Member] | Weighted Average | Collateral Based Measurements | Measurement Input, Discount Rate
Valuation Methodology and Unobservable Inputs For Level 3 Assets Measured At Fair Value [Line Items]
Range of Inputs (Average) (in hundredths)	67		53
Consumer 1-4 family loans
Valuation Methodology and Unobservable Inputs For Level 3 Assets Measured At Fair Value [Line Items]
Valuation Methodology	Collateral basedmeasurements
Loans and Leases Receivable, Allowance	$ 3,384	2,475	$ 2,619	$ 2,086
Provision for credit losses	$ (233)	$ 395
Consumer 1-4 family loans | Fair Value, Measurements, Nonrecurring [Member]
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		Discount to reflect current market conditions and ultimate collectability
Consumer 1-4 family loans | Fair Value, Measurements, Nonrecurring [Member] | Collateral Based Measurements | Measurement Input, Discount Rate
Valuation Methodology and Unobservable Inputs For Level 3 Assets Measured At Fair Value [Line Items]
Impaired loans	$ 322		$ 411
Consumer 1-4 family loans | Fair Value, Measurements, Nonrecurring [Member] | Minimum | Collateral Based Measurements | Measurement Input, Discount Rate
Valuation Methodology and Unobservable Inputs For Level 3 Assets Measured At Fair Value [Line Items]
Range of Inputs (Average) (in hundredths)			10
Consumer 1-4 family loans | Fair Value, Measurements, Nonrecurring [Member] | Maximum | Collateral Based Measurements | Measurement Input, Discount Rate
Valuation Methodology and Unobservable Inputs For Level 3 Assets Measured At Fair Value [Line Items]
Range of Inputs (Average) (in hundredths)			15
Consumer 1-4 family loans | Fair Value, Measurements, Nonrecurring [Member] | Weighted Average | Collateral Based Measurements | Measurement Input, Discount Rate
Valuation Methodology and Unobservable Inputs For Level 3 Assets Measured At Fair Value [Line Items]
Range of Inputs (Average) (in hundredths)	9		11
Agribusiness and Agricultural
Valuation Methodology and Unobservable Inputs For Level 3 Assets Measured At Fair Value [Line Items]
Valuation Methodology	Collateral basedmeasurements
Agribusiness and Agricultural | Fair Value, Measurements, Nonrecurring [Member]
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		Discount to reflect current market conditions and ultimate collectability
Agribusiness and Agricultural | Fair Value, Measurements, Nonrecurring [Member] | Collateral Based Measurements | Measurement Input, Discount Rate
Valuation Methodology and Unobservable Inputs For Level 3 Assets Measured At Fair Value [Line Items]
Impaired loans	$ 43		$ 61
Agribusiness and Agricultural | Fair Value, Measurements, Nonrecurring [Member] | Weighted Average | Collateral Based Measurements | Measurement Input, Discount Rate
Valuation Methodology and Unobservable Inputs For Level 3 Assets Measured At Fair Value [Line Items]
Range of Inputs (Average) (in hundredths)	70		58