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ALLOWANCE FOR CREDIT LOSSES - Allowance for Credit Losses and Balance of Loans Receivable (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023	Jun. 30, 2023
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, allowance for credit loss, excluding accrued interest	$ 44,455	$ 44,457	$ 44,939	$ 44,930	$ 44,867	$ 48,734
Loans individually analyzed	37,700
Financing receivable, before allowance for credit loss, fee and loan in process	5,850,449		5,748,750
Unaccreted yield adjustments	(4,274)		(15,963)
Loans receivable	5,846,175		5,732,787
Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, before allowance for credit loss, fee and loan in process	4,036,426		3,945,910
Commercial \| Multi-family mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, allowance for credit loss, excluding accrued interest	24,660	24,880	24,125	24,196	24,462	26,362
Financing receivable, before allowance for credit loss, fee and loan in process	2,733,406		2,645,851
Commercial \| Nonresidential mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, allowance for credit loss, excluding accrued interest	6,676	6,479	6,125	6,050	5,888	8,953
Financing receivable, before allowance for credit loss, fee and loan in process	988,074		948,075
Commercial \| Commercial business
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, allowance for credit loss, excluding accrued interest	1,517	1,563	1,573	1,545	1,293	1,440
Financing receivable, before allowance for credit loss, fee and loan in process	140,224		142,747
Commercial \| Construction
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, allowance for credit loss, excluding accrued interest	1,123	1,157	1,230	1,350	1,171	1,336
Financing receivable, before allowance for credit loss, fee and loan in process	174,722		209,237
Residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, allowance for credit loss, excluding accrued interest	9,958	9,855	11,461	11,375	11,653	10,237
Financing receivable, before allowance for credit loss, fee and loan in process	1,761,465		1,756,051
Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, before allowance for credit loss, fee and loan in process	52,558		46,789
Consumer \| Home equity loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, allowance for credit loss, excluding accrued interest	417	421	349	330	330	338
Financing receivable, before allowance for credit loss, fee and loan in process	49,699		44,104
Consumer \| Other consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, allowance for credit loss, excluding accrued interest	104	$ 102	76	$ 84	$ 70	$ 68
Financing receivable, before allowance for credit loss, fee and loan in process	2,859		2,685
Receivables Acquired with Deteriorated Credit Quality
Financing Receivable, Allowance for Credit Losses [Line Items]
Related Allowance	12		9
Loans acquired with deteriorated credit quality collectively evaluated	147		132
Loans individually analyzed	901		1,584
Loans collectively evaluated	12,407		14,105
Receivables Acquired with Deteriorated Credit Quality \| Commercial \| Multi-family mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Related Allowance	0		0
Loans acquired with deteriorated credit quality collectively evaluated	0		0
Loans individually analyzed	0		0
Loans collectively evaluated	0		0
Receivables Acquired with Deteriorated Credit Quality \| Commercial \| Nonresidential mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Related Allowance	0		0
Loans acquired with deteriorated credit quality collectively evaluated	23		31
Loans individually analyzed	250		284
Loans collectively evaluated	1,618		2,145
Receivables Acquired with Deteriorated Credit Quality \| Commercial \| Commercial business
Financing Receivable, Allowance for Credit Losses [Line Items]
Related Allowance	0		0
Loans acquired with deteriorated credit quality collectively evaluated	35		6
Loans individually analyzed	0		0
Loans collectively evaluated	1,459		2,794
Receivables Acquired with Deteriorated Credit Quality \| Commercial \| Construction
Financing Receivable, Allowance for Credit Losses [Line Items]
Related Allowance	0		0
Loans acquired with deteriorated credit quality collectively evaluated	1		0
Loans individually analyzed	0		0
Loans collectively evaluated	5,735		5,735
Receivables Acquired with Deteriorated Credit Quality \| Residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Related Allowance	12		9
Loans acquired with deteriorated credit quality collectively evaluated	88		95
Loans individually analyzed	629		1,276
Loans collectively evaluated	3,595		3,431
Receivables Acquired with Deteriorated Credit Quality \| Consumer \| Home equity loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Related Allowance	0		0
Loans acquired with deteriorated credit quality collectively evaluated	0		0
Loans individually analyzed	22		24
Loans collectively evaluated	0		0
Receivables Acquired with Deteriorated Credit Quality \| Consumer \| Other consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Related Allowance	0		0
Loans acquired with deteriorated credit quality collectively evaluated	0		0
Loans individually analyzed	0		0
Loans collectively evaluated	0		0
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Allowance for Credit Losses [Line Items]
Related Allowance	98		853
Loans acquired with deteriorated credit quality collectively evaluated	44,198		43,945
Loans individually analyzed	36,779		38,293
Loans collectively evaluated	5,800,362		5,694,768
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Commercial \| Multi-family mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Related Allowance	8		0
Loans acquired with deteriorated credit quality collectively evaluated	24,652		24,125
Loans individually analyzed	24,787		22,591
Loans collectively evaluated	2,708,619		2,623,260
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Commercial \| Nonresidential mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Related Allowance	0		517
Loans acquired with deteriorated credit quality collectively evaluated	6,653		5,577
Loans individually analyzed	5,543		9,539
Loans collectively evaluated	980,663		936,107
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Commercial \| Commercial business
Financing Receivable, Allowance for Credit Losses [Line Items]
Related Allowance	50		228
Loans acquired with deteriorated credit quality collectively evaluated	1,432		1,339
Loans individually analyzed	1,799		714
Loans collectively evaluated	136,966		139,239
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Commercial \| Construction
Financing Receivable, Allowance for Credit Losses [Line Items]
Related Allowance	0		0
Loans acquired with deteriorated credit quality collectively evaluated	1,122		1,230
Loans individually analyzed	0		0
Loans collectively evaluated	168,987		203,502
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Related Allowance	40		108
Loans acquired with deteriorated credit quality collectively evaluated	9,818		11,249
Loans individually analyzed	4,547		5,429
Loans collectively evaluated	1,752,694		1,745,915
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Consumer \| Home equity loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Related Allowance	0		0
Loans acquired with deteriorated credit quality collectively evaluated	417		349
Loans individually analyzed	103		20
Loans collectively evaluated	49,574		44,060
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Consumer \| Other consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Related Allowance	0		0
Loans acquired with deteriorated credit quality collectively evaluated	104		76
Loans individually analyzed	0		0
Loans collectively evaluated	$ 2,859		$ 2,685