ALLOWANCE FOR CREDIT LOSSES AND CREDIT QUALITY - Additional Information (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2021 USD ($) loan	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($) borrower loan	Jun. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Financing Receivable, Allowance for Credit Loss [Line Items]
Loan amount of credit quality analysis			$ 250,000
Loans receivable before allowance for credit loss	$ 4,353,709,000		4,353,709,000
Loans modified In troubled debt restructured loans		$ 2,400,000		$ 2,400,000
Increase in allowance for loan loss		2,300,000
Charge-offs recorded for new troubled debt restructurings		$ 0		$ 666,000
Financing receivable, loan portfolio, deferrals, COVID-19			$ 36,900,000
Financing receivable, loan portfolio, deferrals, COVID-19, percentage of loan portfolio (as a percent)			0.80%
30-89 Days Past Due
Financing Receivable, Allowance for Credit Loss [Line Items]
Number of loans past due | loan	0		0
PPP | Pass
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans receivable before allowance for credit loss	$ 194,200,000		$ 194,200,000
Total consumer loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans modified In troubled debt restructured loans	$ 5,800,000		$ 5,800,000
Loans modified In troubled debt restructured loans					$ 5,500,000
Number of loans modified as troubled debt restructurings | loan	0		0
Financing receivable, loan portfolio, deferrals, COVID-19, borrowers | borrower			0
Total commercial loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing receivable, loan portfolio, deferrals, COVID-19, borrowers | borrower			8
Loans under first deferral action			$ 14,200,000
Loans under second deferral action			253,000
Loans under third deferral action			20,000,000.0
Loans under fourth deferral action			$ 2,500,000
Borrowers percentage			0.64