SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)		3 Months Ended	12 Months Ended
	Jan. 01, 2020 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2020 USD ($) subsidary segment	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Property Plant And Equipment [Line Items]
Number of subsidiaries | subsidary			6
Goodwill impairment			$ 0
Number of operating segments | segment			1
Number of reportable operating segments | segment			1
Reclassification of certain tax effects from accumulated other comprehensive income					$ (486,000)
Provision for credit losses			$ 13,200,000	$ 1,250,000	$ 2,250,000
Decrease to retained earnings			113,449,000	98,239,000
Retained earnings, net of tax				955,000
Operating lease right of use asset			13,291,000	11,554,000
Operating lease liability			$ 13,539,000	$ 11,675,000
Accounting Standards Update 2018-02
Property Plant And Equipment [Line Items]
Change in Accounting Principle, Accounting Standards Update, Early Adoption [true false]			true
Change In Accounting Principle Accounting Standards Update Adoption Date			Jan. 01, 2020
Accounting Standards Update 2018-02 | Accumulated Other Comprehensive Income (Loss)
Property Plant And Equipment [Line Items]
Reclassification of certain tax effects from accumulated other comprehensive income		$ (486,000)
Accounting Standards Update 2018-02 | Retained Earnings
Property Plant And Equipment [Line Items]
Reclassification of certain tax effects from accumulated other comprehensive income		486,000
Accounting Standards Update 2017-04
Property Plant And Equipment [Line Items]
Change In Accounting Principle Accounting Standards Update Adoption Date			Jan. 01, 2020
Change In Accounting Principle Accounting Standards Update Adopted			true
Change In Accounting Principle Accounting Standards Update Immaterial Effect			true
Accounting Standards Update 2016-13
Property Plant And Equipment [Line Items]
Change In Accounting Principle Accounting Standards Update Adoption Date			Jan. 01, 2020
Change In Accounting Principle Accounting Standards Update Adopted			true
Increase to allowance for credit losses	$ 4,548,000
Increase to allowance for credit losses, percent	28.10%
Provision for credit losses			$ 13,200,000
Accounting Standards Update 2016-13 | Impact of adoption of ASC 326 | Revision of Prior Period, Adjustment
Property Plant And Equipment [Line Items]
Decrease to retained earnings			(3,593,000)
Retained earnings, net of tax			$ 955,000
Accounting Standards Update 2016-02
Property Plant And Equipment [Line Items]
Change In Accounting Principle Accounting Standards Update Adoption Date			Jan. 01, 2019
Change In Accounting Principle Accounting Standards Update Adopted			true
Change In Accounting Principle Accounting Standards Update Immaterial Effect			false
Operating lease right of use asset		12,000,000.0
Operating lease liability		$ 12,000,000.0
Accounting Standards Update 2014-09
Property Plant And Equipment [Line Items]
Change In Accounting Principle Accounting Standards Update Adoption Date			Jan. 01, 2018
Change In Accounting Principle Accounting Standards Update Adopted			true
Change In Accounting Principle Accounting Standards Update Immaterial Effect			true
Change in Accounting Principle, Accounting Standards Update, Transition Option Elected [Extensible List]			us-gaap:AccountingStandardsUpdate201409RetrospectiveMember
Core Deposits
Property Plant And Equipment [Line Items]
Core deposit amortization period			10 years