Loan Quality and Allowance for Loan Losses - Performance Status of Loans Receivable (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Jun. 30, 2018
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and Leases Receivable, Gross	$ 4,715,516	$ 4,567,915
Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and Leases Receivable, Gross	1,325,105	1,297,453
Non-Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and Leases Receivable, Gross	1,249,215	1,302,961
Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and Leases Receivable, Gross	14,377	23,271
Commercial Business [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and Leases Receivable, Gross	66,476	85,825
Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and Leases Receivable, Gross	5,984	9,060
Multi-Family Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and Leases Receivable, Gross	1,956,571	1,758,584
Home Equity Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and Leases Receivable, Gross	97,788	90,761
Performing Financing Receivable [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and Leases Receivable, Gross	4,694,195	4,551,056
Performing Financing Receivable [Member] \| Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and Leases Receivable, Gross	1,314,295	1,288,261
Performing Financing Receivable [Member] \| Non-Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and Leases Receivable, Gross	1,240,545	1,297,621
Performing Financing Receivable [Member] \| Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and Leases Receivable, Gross	14,377	23,271
Performing Financing Receivable [Member] \| Commercial Business [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and Leases Receivable, Gross	65,586	84,587
Performing Financing Receivable [Member] \| Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and Leases Receivable, Gross	5,960	9,000
Performing Financing Receivable [Member] \| Multi-Family Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and Leases Receivable, Gross	1,956,490	1,758,468
Performing Financing Receivable [Member] \| Home Equity Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and Leases Receivable, Gross	96,942	89,848
Nonperforming Financing Receivable [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
90+ days past due accruing	24	60
Nonaccrual	21,297	16,799
Total nonperforming	21,321	16,859
Nonperforming Financing Receivable [Member] \| Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	10,810	9,192
Total nonperforming	10,810	9,192
Nonperforming Financing Receivable [Member] \| Non-Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	8,670	5,340
Total nonperforming	8,670	5,340
Nonperforming Financing Receivable [Member] \| Commercial Business [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	890	1,238
Total nonperforming	890	1,238
Nonperforming Financing Receivable [Member] \| Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
90+ days past due accruing	24	60
Total nonperforming	24	60
Nonperforming Financing Receivable [Member] \| Multi-Family Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	81	116
Total nonperforming	81	116
Nonperforming Financing Receivable [Member] \| Home Equity Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	846	913
Total nonperforming	$ 846	$ 913

Recorded investment in financing receivables that are 90 days or more past due and still accruing.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5111-111524

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- Definition

Recorded investment in financing receivables that are on nonaccrual status as of the balance sheet date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5111-111524

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82891408&loc=d3e4428-111522

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- Definition

Reflects the carrying amount of loans deemed to be questionable as to collection on which no interest is continuing to be recognized.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5111-111524

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