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ALLOWANCE FOR CREDIT LOSSES - Allowance for Credit Losses and Balance of Loans Receivable (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Jun. 30, 2024	Sep. 30, 2023	Jun. 30, 2023
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, allowance for credit loss, excluding accrued interest	$ 44,923	$ 44,939	$ 46,872	$ 48,734
Loans individually analyzed	39,800
Financing receivable, before allowance for credit loss, fee and loan in process	5,786,205	5,748,750
Unaccreted yield adjustments	(1,959)	(15,963)
Loans receivable	5,784,246	5,732,787
Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, before allowance for credit loss, fee and loan in process	3,970,269	3,945,910
Commercial \| Multi-family mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, allowance for credit loss, excluding accrued interest	24,368	24,125	25,590	26,362
Financing receivable, before allowance for credit loss, fee and loan in process	2,646,187	2,645,851
Commercial \| Nonresidential mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, allowance for credit loss, excluding accrued interest	6,913	6,125	7,437	8,953
Financing receivable, before allowance for credit loss, fee and loan in process	950,771	948,075
Commercial \| Commercial business
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, allowance for credit loss, excluding accrued interest	1,705	1,573	1,413	1,440
Financing receivable, before allowance for credit loss, fee and loan in process	145,984	142,747
Commercial \| Construction
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, allowance for credit loss, excluding accrued interest	1,503	1,230	1,317	1,336
Financing receivable, before allowance for credit loss, fee and loan in process	227,327	209,237
Residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, allowance for credit loss, excluding accrued interest	9,985	11,461	10,703	10,237
Financing receivable, before allowance for credit loss, fee and loan in process	1,768,230	1,756,051
Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, before allowance for credit loss, fee and loan in process	47,706	46,789
Consumer \| Home equity loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, allowance for credit loss, excluding accrued interest	357	349	342	338
Financing receivable, before allowance for credit loss, fee and loan in process	44,741	44,104
Consumer \| Other consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, allowance for credit loss, excluding accrued interest	92	76	$ 70	$ 68
Financing receivable, before allowance for credit loss, fee and loan in process	2,965	2,685
Receivables Acquired with Deteriorated Credit Quality
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, allowance for credit losses, individually evaluated for impairment	57	9
Loans acquired with deteriorated credit quality collectively evaluated	121	132
Loans individually analyzed	2,155	1,584
Loans collectively evaluated	13,406	14,105
Receivables Acquired with Deteriorated Credit Quality \| Commercial \| Multi-family mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, allowance for credit losses, individually evaluated for impairment	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]
Financing receivable, allowance for credit losses, individually evaluated for impairment	0	0
Loans acquired with deteriorated credit quality collectively evaluated	28	31
Loans individually analyzed	613	284
Loans collectively evaluated	1,741	2,145
Receivables Acquired with Deteriorated Credit Quality \| Commercial \| Commercial business
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, allowance for credit losses, individually evaluated for impairment	0	0
Loans acquired with deteriorated credit quality collectively evaluated	7	6
Loans individually analyzed	0	0
Loans collectively evaluated	2,811	2,794
Receivables Acquired with Deteriorated Credit Quality \| Commercial \| Construction
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, allowance for credit losses, individually evaluated for impairment	0	0
Loans acquired with deteriorated credit quality collectively evaluated	13	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]
Financing receivable, allowance for credit losses, individually evaluated for impairment	57	9
Loans acquired with deteriorated credit quality collectively evaluated	73	95
Loans individually analyzed	1,519	1,276
Loans collectively evaluated	3,119	3,431
Receivables Acquired with Deteriorated Credit Quality \| Consumer \| Home equity loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, allowance for credit losses, individually evaluated for impairment	0	0
Loans acquired with deteriorated credit quality collectively evaluated	0	0
Loans individually analyzed	23	24
Loans collectively evaluated	0	0
Receivables Acquired with Deteriorated Credit Quality \| Consumer \| Other consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, allowance for credit losses, individually evaluated for impairment	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]
Financing receivable, allowance for credit losses, individually evaluated for impairment	698	853
Loans acquired with deteriorated credit quality collectively evaluated	44,047	43,945
Loans individually analyzed	37,694	38,293
Loans collectively evaluated	5,732,950	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]
Financing receivable, allowance for credit losses, individually evaluated for impairment	0	0
Loans acquired with deteriorated credit quality collectively evaluated	24,368	24,125
Loans individually analyzed	21,980	22,591
Loans collectively evaluated	2,624,207	2,623,260
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Commercial \| Nonresidential mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, allowance for credit losses, individually evaluated for impairment	493	517
Loans acquired with deteriorated credit quality collectively evaluated	6,392	5,577
Loans individually analyzed	8,545	9,539
Loans collectively evaluated	939,872	936,107
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Commercial \| Commercial business
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, allowance for credit losses, individually evaluated for impairment	124	228
Loans acquired with deteriorated credit quality collectively evaluated	1,574	1,339
Loans individually analyzed	579	714
Loans collectively evaluated	142,594	139,239
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Commercial \| Construction
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, allowance for credit losses, individually evaluated for impairment	0	0
Loans acquired with deteriorated credit quality collectively evaluated	1,490	1,230
Loans individually analyzed	0	0
Loans collectively evaluated	221,592	203,502
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, allowance for credit losses, individually evaluated for impairment	81	108
Loans acquired with deteriorated credit quality collectively evaluated	9,774	11,249
Loans individually analyzed	6,571	5,429
Loans collectively evaluated	1,757,021	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]
Financing receivable, allowance for credit losses, individually evaluated for impairment	0	0
Loans acquired with deteriorated credit quality collectively evaluated	357	349
Loans individually analyzed	19	20
Loans collectively evaluated	44,699	44,060
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Consumer \| Other consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, allowance for credit losses, individually evaluated for impairment	0	0
Loans acquired with deteriorated credit quality collectively evaluated	92	76
Loans individually analyzed	0	0
Loans collectively evaluated	$ 2,965	$ 2,685