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ALLOWANCE FOR CREDIT LOSSES - Allowance for Credit Losses and Balance of Loans Receivable (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Jun. 30, 2022
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, allowance for credit loss, excluding accrued interest	$ 44,930	$ 44,867	$ 48,734	$ 49,122	$ 48,877	$ 47,058
Loans individually analyzed	39,500
Financing receivable, before allowance for credit loss, fee and loan in process	5,775,090		5,850,476
Unaccreted yield adjustments	(16,754)		(21,055)
Loans receivable	5,758,336		5,829,421
Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, before allowance for credit loss, fee and loan in process	3,987,517		4,103,819
Commercial \| Multi-family mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, allowance for credit loss, excluding accrued interest	24,196	24,462	26,362	27,172	27,498	25,321
Financing receivable, before allowance for credit loss, fee and loan in process	2,645,195		2,761,775
Commercial \| Nonresidential mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, allowance for credit loss, excluding accrued interest	6,050	5,888	8,953	8,244	8,593	10,590
Financing receivable, before allowance for credit loss, fee and loan in process	965,539		968,574
Commercial \| Commercial business
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, allowance for credit loss, excluding accrued interest	1,545	1,293	1,440	1,729	1,819	1,792
Financing receivable, before allowance for credit loss, fee and loan in process	147,326		146,861
Commercial \| Construction
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, allowance for credit loss, excluding accrued interest	1,350	1,171	1,336	1,316	1,201	1,486
Financing receivable, before allowance for credit loss, fee and loan in process	229,457		226,609
Residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, allowance for credit loss, excluding accrued interest	11,375	11,653	10,237	10,265	9,355	7,540
Financing receivable, before allowance for credit loss, fee and loan in process	1,741,644		1,700,559
Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, before allowance for credit loss, fee and loan in process	45,929		46,098
Consumer \| Home equity loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, allowance for credit loss, excluding accrued interest	330	330	338	327	339	245
Financing receivable, before allowance for credit loss, fee and loan in process	42,731		43,549
Consumer \| Other consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, allowance for credit loss, excluding accrued interest	84	$ 70	68	$ 69	$ 72	$ 84
Financing receivable, before allowance for credit loss, fee and loan in process	3,198		2,549
Receivables Acquired with Deteriorated Credit Quality
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing receivable, allowance for credit losses, individually evaluated for impairment	12		3
Loans acquired with deteriorated credit quality collectively evaluated	157		211
Loans individually analyzed	1,277		928
Loans collectively evaluated	16,286		17,967
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	34		70
Loans individually analyzed	298		333
Loans collectively evaluated	2,207		3,562
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	22		9
Loans individually analyzed	0		0
Loans collectively evaluated	4,523		4,237
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	0		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	12		3
Loans acquired with deteriorated credit quality collectively evaluated	101		132
Loans individually analyzed	955		570
Loans collectively evaluated	3,821		4,433
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	24		25
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	215		3,417
Loans acquired with deteriorated credit quality collectively evaluated	44,546		45,103
Loans individually analyzed	38,269		41,699
Loans collectively evaluated	5,719,258		5,789,882
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	9		326
Loans acquired with deteriorated credit quality collectively evaluated	24,187		26,036
Loans individually analyzed	25,182		19,114
Loans collectively evaluated	2,620,013		2,742,661
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	8		3,001
Loans acquired with deteriorated credit quality collectively evaluated	6,008		5,882
Loans individually analyzed	4,190		16,207
Loans collectively evaluated	958,844		948,472
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	186		20
Loans acquired with deteriorated credit quality collectively evaluated	1,337		1,411
Loans individually analyzed	4,189		252
Loans collectively evaluated	138,614		142,372
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	1,350		1,336
Loans individually analyzed	0		0
Loans collectively evaluated	223,722		220,874
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	12		70
Loans acquired with deteriorated credit quality collectively evaluated	11,250		10,032
Loans individually analyzed	4,687		6,101
Loans collectively evaluated	1,732,181		1,689,455
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	330		338
Loans individually analyzed	21		25
Loans collectively evaluated	42,686		43,499
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	84		68
Loans individually analyzed	0		0
Loans collectively evaluated	$ 3,198		$ 2,549