FAIR VALUE - Significant Unobservable Inputs (Details) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Individually assessed loans		$ 25,063
Other real estate owned		883
Commitments to originate real estate loans for sale		14
Fair value of MSRs at end of period		$ 682
Contingent consideration	$ 2,900
Weighted Average Discount Rate [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Mortgage servicing rights, Measurement Input [Extensible List]	Weighted Average Discount Rate [Member]	Weighted Average Discount Rate [Member]
Contingent consideration, Measurement Input [Extensible List]	Weighted Average Discount Rate [Member]
Adequate Compensation [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Mortgage servicing rights, Measurement Input [Extensible List]	Adequate Compensation [Member]	Adequate Compensation [Member]
Probability Adjusted Level Of Retained Revenue [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Contingent consideration, Measurement Input [Extensible List]	Probability Adjusted Level Of Retained Revenue [Member]
Fair Value of Collateral [Member] | Estimated Cost of Disposal/Market Adjustment [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Individually assessed loans, Valuation Technique [Extensible List]	Fair Value of Collateral [Member]	Fair Value of Collateral [Member]
Individually assessed loans, Measurement Input [Extensible List]	us-gaap:MeasurementInputCostToSellMember	us-gaap:MeasurementInputCostToSellMember
Other real estate owned, Valuation Technique [Extensible List]	Fair Value of Collateral [Member]	Fair Value of Collateral [Member]
Other real estate owned, Measurement Input [Extensible List]	us-gaap:MeasurementInputCostToSellMember	us-gaap:MeasurementInputCostToSellMember
Discounted Cash Flow [Member] | Embedded Servicing Value [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Commitments to originate real estate loans for sale, Valuation Technique [Extensible List]	Discounted Cash Flow [Member]	Discounted Cash Flow [Member]
Commitments to originate real estate loans for sale, Measurement Input [Extensible List]	Embedded Servicing Value [Member]	Embedded Servicing Value [Member]
Discounted Cash Flow [Member] | Weighted Average Constant Prepayment Rate [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Mortgage servicing rights, Valuation Technique [Extensible List]	Discounted Cash Flow [Member]	Discounted Cash Flow [Member]
Mortgage servicing rights, Measurement Input [Extensible List]	Weighted Average Constant Prepayment Rate [Member]	Weighted Average Constant Prepayment Rate [Member]
Discounted Cash Flow [Member] | Weighted Average Discount Rate [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Contingent consideration, Valuation Technique [Extensible List]	Discounted Cash Flow [Member]
Minimum [Member] | Fair Value of Collateral [Member] | Estimated Cost of Disposal/Market Adjustment [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Other real estate owned, measurement input	9.0
Maximum [Member] | Fair Value of Collateral [Member] | Estimated Cost of Disposal/Market Adjustment [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Other real estate owned, measurement input	46.7
Significant Unobservable Inputs, Level 3 [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Individually assessed loans	$ 18,794
Other real estate owned	891
Commitments to originate real estate loans for sale	45
Fair value of MSRs at end of period	$ 794
Significant Unobservable Inputs, Level 3 [Member] | Discounted Cash Flow [Member] | Embedded Servicing Value [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Commitments to originate real estate loans for sale, measurement input	1.0	1.0
Significant Unobservable Inputs, Level 3 [Member] | Discounted Cash Flow [Member] | Adequate Compensation [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Mortgage servicing rights, measurement input	7	7
Significant Unobservable Inputs, Level 3 [Member] | Minimum [Member] | Weighted Average Discount Rate [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Mortgage servicing rights, measurement input	2.3
Contingent consideration, measurement input	0.8
Significant Unobservable Inputs, Level 3 [Member] | Minimum [Member] | Probability Adjusted Level Of Retained Revenue [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Contingent consideration, measurement input 2	$ 2,300
Significant Unobservable Inputs, Level 3 [Member] | Minimum [Member] | Fair Value of Collateral [Member] | Estimated Cost of Disposal/Market Adjustment [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Individually assessed loans, measurement input	9.0	9.0
Other real estate owned, measurement input	9.0	11.3
Significant Unobservable Inputs, Level 3 [Member] | Minimum [Member] | Discounted Cash Flow [Member] | Weighted Average Constant Prepayment Rate [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Mortgage servicing rights, measurement input	15.2	9.8
Significant Unobservable Inputs, Level 3 [Member] | Minimum [Member] | Discounted Cash Flow [Member] | Weighted Average Discount Rate [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Mortgage servicing rights, measurement input		1.7
Significant Unobservable Inputs, Level 3 [Member] | Maximum [Member] | Weighted Average Discount Rate [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Mortgage servicing rights, measurement input	2.8
Contingent consideration, measurement input	1.1
Significant Unobservable Inputs, Level 3 [Member] | Maximum [Member] | Probability Adjusted Level Of Retained Revenue [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Contingent consideration, measurement input 2	$ 5,800
Significant Unobservable Inputs, Level 3 [Member] | Maximum [Member] | Fair Value of Collateral [Member] | Estimated Cost of Disposal/Market Adjustment [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Individually assessed loans, measurement input	78.7	78.4
Other real estate owned, measurement input	46.7	52.9
Significant Unobservable Inputs, Level 3 [Member] | Maximum [Member] | Discounted Cash Flow [Member] | Weighted Average Constant Prepayment Rate [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Mortgage servicing rights, measurement input	24.9	18.8
Significant Unobservable Inputs, Level 3 [Member] | Maximum [Member] | Discounted Cash Flow [Member] | Weighted Average Discount Rate [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Mortgage servicing rights, measurement input		2.2
Significant Unobservable Inputs, Level 3 [Member] | Weighted Average [Member] | Weighted Average Discount Rate [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Mortgage servicing rights, measurement input	2.7
Contingent consideration, measurement input	1.0
Significant Unobservable Inputs, Level 3 [Member] | Weighted Average [Member] | Fair Value of Collateral [Member] | Estimated Cost of Disposal/Market Adjustment [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Individually assessed loans, measurement input	53.5	52.7
Other real estate owned, measurement input	33.7	34.0
Significant Unobservable Inputs, Level 3 [Member] | Weighted Average [Member] | Discounted Cash Flow [Member] | Weighted Average Constant Prepayment Rate [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Mortgage servicing rights, measurement input	16.6	17.6
Significant Unobservable Inputs, Level 3 [Member] | Weighted Average [Member] | Discounted Cash Flow [Member] | Weighted Average Discount Rate [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Mortgage servicing rights, measurement input		2.1