BORROWINGS (Details Textual) - USD ($)		3 Months Ended	12 Months Ended
	Jul. 15, 2025	Dec. 31, 2025	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Debt Instrument [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged		$ 4,500,000,000	$ 4,500,000,000	$ 3,800,000,000
Federal home loan bank unused remaining available borrowing capacity		3,200,000,000	3,200,000,000	2,600,000,000
Line of credit (less unamortized debt issuance costs of $47)		49,953,000	49,953,000	0
Interest Expense, Long-term Debt			21,300,000	5,000,000.0	$ 6,800,000
Junior Subordinated Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		61,000,000.0	61,000,000.0	61,000,000.0
Subordinated Debentures [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		300,000,000.0	$ 300,000,000.0
Capital Trust V Preferred Securities Due in 2037 [Member] | Junior Subordinated Debt [Member]
Debt Instrument [Line Items]
Basis spread on variable rate			1.48%
Debt Instrument, Face Amount		50,000,000	$ 50,000,000
Central Bancorp Capital Trust I Securities Due in 2034 [Member] | Junior Subordinated Debt [Member]
Debt Instrument [Line Items]
Basis spread on variable rate			2.44%
Debt Instrument, Face Amount		5,100,000	$ 5,100,000
Single issuer trust preferred securities issued by banks [Member] | Junior Subordinated Debt [Member]
Debt Instrument [Line Items]
Basis spread on variable rate			3.98%
Central Bancorp Capital Trust II Securities Due in 2037 [Member] | Junior Subordinated Debt [Member]
Debt Instrument [Line Items]
Basis spread on variable rate			1.65%
Debt Instrument, Face Amount		5,900,000	$ 5,900,000
Multi-Year Advance Term Loan Credit Facility | Line of Credit
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 125,000,000.0	$ 125,000,000.0
Line of credit, advance period		1 year	1 year
Debt instrument, term		2 years
Basis spread on variable rate		1.70%
Line of credit facility, interest rate at period end		5.57%	5.57%
Line of credit (less unamortized debt issuance costs of $47)		$ 50,000,000.0	$ 50,000,000.0
Interest expense on line of credit		116,000
Fixed-to-Floating Rate Subordinated Notes | Subordinated Debentures [Member]
Debt Instrument [Line Items]
Redemption of subordinated notes	$ 60,000,000.0
Federal Home Loan Bank Advances [Member]
Debt Instrument [Line Items]
Federal home loan bank unused remaining available borrowing capacity		$ 2,800,000,000	$ 2,800,000,000	$ 2,000,000,000.0