BORROWINGS - Additional Information (Details)	1 Months Ended	3 Months Ended	12 Months Ended
	Jun. 30, 2021 USD ($)	Mar. 31, 2026 USD ($) agreement	Dec. 31, 2025 USD ($) agreement	Dec. 31, 2007 USD ($) security	Jul. 24, 2025 USD ($)
Debt Instrument [Line Items]
Prepayments of the FHLB borrowings		$ 3,500,000,000	$ 3,600,000,000
Remaining borrowing capacity		1,900,000,000	1,900,000,000
Naming applicable municipalities as beneficiaries		224,800,000	260,100,000
Loans receivable		6,434,020,000	6,493,740,000
Outstanding advances from FHLB		164,000,000	164,000,000		$ 437,000,000.0
Unamortized debt issuance costs		100,000	100,000
Open Repo borrowing at an interest rate of 3.97% and 3.93% at March 31, 2026 and December 31, 2025, respectfully. The maximum amount of the Open Repo borrowing available is $250,000.
Debt Instrument [Line Items]
Federal home loan balance		$ 250,000,000	250,000,000
Commitment term		364 days
Outstanding advances from FHLB		$ 164,000,000	164,000,000
Federal Reserve Bank Advances | Federal Reserve BIC Program
Debt Instrument [Line Items]
Federal home loan balance		206,100,000
Outstanding advances from FHLB		0	$ 0
Federal Reserve Bank Advances | Federal Reserve BIC Program | Qualifying Loans Pledged As Collateral
Debt Instrument [Line Items]
Prepayments of the FHLB borrowings		62,200,000
Loans receivable		$ 225,600,000
Subordinated Debt
Debt Instrument [Line Items]
Number of preferred trust securities | security				2
Floating rate trust preferred securities				$ 10,000,000.0
Effective percentage		5.49%	5.53%
Trust preferred securities, interest payment deferment period		5 years
Subordinated Debt | Notes Maturing In June 2031
Debt Instrument [Line Items]
Floating rate trust preferred securities	$ 85,000,000.0
Interest rate, percentage	3.25%
Proceeds from issuance of subordinated notes, net of issuance costs	$ 83,500,000
Subordinated Debt | SOFR
Debt Instrument [Line Items]
Line of credit, basis spread on variable rate (percent)		1.55%
Credit spread adjustment (as percent)		0.26161%
Subordinated Debt | SOFR | Notes Maturing In June 2031
Debt Instrument [Line Items]
Line of credit, basis spread on variable rate (percent)		2.58%
Subordinated Debt | LIBOR
Debt Instrument [Line Items]
Line of credit, basis spread on variable rate (percent)				1.55%
Line of Credit | Overnight Borrowing Agreements
Debt Instrument [Line Items]
Line of credit, outstanding amount		$ 0	$ 0
Line of Credit | Unsecured Debt
Debt Instrument [Line Items]
Number of unsecured lines of credit issued | agreement		1	1
Pledge on certain loan amount		$ 10,000,000.0	$ 10,000,000.0
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 (percent)		2.85%