BORROWINGS - Additional Information (Details)	1 Months Ended	9 Months Ended	12 Months Ended
	Jun. 30, 2021 USD ($)	Sep. 30, 2023 USD ($) agreement	Dec. 31, 2022 USD ($) agreement	Dec. 31, 2007 USD ($) security
Debt Instrument [Line Items]
Prepayments of the FHLB borrowings		$ 1,800,000,000	$ 1,600,000,000
Remaining borrowing capacity		988,500,000	757,800,000
Naming applicable municipalities as beneficiaries		155,500,000	75,500,000
Loans receivable		4,492,174,000	4,275,178,000
Maximum amount of Open Repo borrowing available		0	132,396,000
Unamortized debt issuance costs		800,000	1,000,000
Federal Home Loan Bank, Advances, Open Repo Borrowings
Debt Instrument [Line Items]
Federal home loan balance		$ 250,000,000
Commitment term		364 days
Maximum amount of Open Repo borrowing available		$ 0	$ 132,396,000
Subordinated Debt
Debt Instrument [Line Items]
Number of preferred trust securities | security				2
Floating rate trust preferred securities				$ 10,000,000
Effective percentage		7.22%	6.32%
Trust preferred securities, interest payment deferment period		5 years
Subordinated Debt | SOFR
Debt Instrument [Line Items]
Line of credit, basis spread on variable rate		1.55%
Credit spread adjustment (percent)		0.26161%
Subordinated Debt | LIBOR
Debt Instrument [Line Items]
Line of credit, basis spread on variable rate				1.55%
Federal Reserve BIC Program | Federal Reserve Bank Advances
Debt Instrument [Line Items]
Federal home loan balance		$ 190,400,000
Prepayments of the FHLB borrowings		10,000,000
Loans receivable		291,700,000
Maximum amount of Open Repo borrowing available		0	$ 0
Federal Reserve's BTFP | Federal Reserve Bank Advances
Debt Instrument [Line Items]
Maximum amount of Open Repo borrowing available		$ 0	$ 0
Notes Maturing In June 2031 | Subordinated Debt
Debt Instrument [Line Items]
Floating rate trust preferred securities	$ 85,000,000
Interest rate, percentage	3.25%
Proceeds from issuance of subordinated notes, net of issuance costs	$ 83,500,000
Notes Maturing In June 2031 | Subordinated Debt | SOFR
Debt Instrument [Line Items]
Line of credit, basis spread on variable rate		2.58%
Line of Credit | Unsecured Debt
Debt Instrument [Line Items]
Number of unsecured lines of credit issued | agreement		1	1
Pledge on certain loan amount		$ 10,000,000	$ 10,000,000
Line of credit, outstanding amount		$ 0	0
Line of Credit | Unsecured Debt | SOFR
Debt Instrument [Line Items]
Line of credit, basis spread on variable rate		2.85%
Line of Credit | Overnight Borrowing Agreements
Debt Instrument [Line Items]
Line of credit, outstanding amount		$ 0	$ 0