BORROWINGS - Narrative (Details) - USD ($)	Mar. 15, 2022	Nov. 05, 2019	Jun. 30, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Long-term borrowings			$ 370,504,000	$ 370,205,000
FHLB availability based on pledged collateral			2,600,000,000	2,600,000,000
FHLB advances			600,000,000	550,000,000
Unsecured lines of credit, correspondent banks
Debt Instrument [Line Items]
Maximum borrowing capacity			1,000,000,000	1,600,000,000
Federal Reserve Bank Term Funding Program
Debt Instrument [Line Items]
Maximum borrowing capacity			16,600,000
Line of credit			300,000,000
Federal Home Loan Bank Advances
Debt Instrument [Line Items]
Maximum borrowing capacity			3,200,000,000	3,200,000,000
Federal Home Loan Bank Advances | Residential mortgage | Asset pledged as collateral | Federal Home Loan Bank Advances
Debt Instrument [Line Items]
Maximum borrowing capacity			1,300,000,000	1,200,000,000
Federal Home Loan Bank Advances | Commercial real estate loans | Asset pledged as collateral | Federal Home Loan Bank Advances
Debt Instrument [Line Items]
Maximum borrowing capacity			4,000,000,000	3,600,000,000
Federal Home Loan Bank Advances | Home equity lines of credit | Asset pledged as collateral | Federal Home Loan Bank Advances
Debt Instrument [Line Items]
Maximum borrowing capacity			214,000,000	214,300,000
Federal Home Loan Bank Advances | Multifamily loans | Asset pledged as collateral | Federal Home Loan Bank Advances
Debt Instrument [Line Items]
Maximum borrowing capacity			571,200,000	514,800,000
Federal Reserve and correspondent banks
Debt Instrument [Line Items]
Maximum borrowing capacity			760,800,000	718,600,000
Line of credit			$ 0	0
Subordinated Debt | Fixed Floating Rate Subordinated Notes Due 2032
Debt Instrument [Line Items]
Aggregate principal amount	$ 200,000,000
Interest rate	3.875%		3.875%
Basis spread on variable rate	1.965%
Unamortized discount (premium) and debt issuance costs, net	$ 3,100,000
Subordinated Debt | Fixed Floating Rate Subordinated Notes Due 2029
Debt Instrument [Line Items]
Interest rate		4.25%	4.25%
Basis spread on variable rate		2.62%
Unamortized discount (premium) and debt issuance costs, net		$ 2,900,000
Long-term borrowings		$ 175,000,000
Subordinated Debt | Fixed Floating Rate Subordinated Notes Due 2029 | Spread Adjustment
Debt Instrument [Line Items]
Basis spread on variable rate		0.00263%
Retail Repurchase Agreements
Debt Instrument [Line Items]
Long-term debt			$ 74,500,000	62,000,000
Federal Funds Purchased
Debt Instrument [Line Items]
Long-term debt			$ 0	$ 260,000,000