Loan Quality and Allowance for Loan Losses - Impairment Status of Loans Receivable (Detail) - USD ($) $ in Thousands	3 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Jun. 30, 2019
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-impaired loans	$ 4,625,914		$ 4,706,368
Impaired loans with no allowance for impairment	26,966		24,222
Recorded investment	840		363
Allowance for impairment	(42)		(31)
Balance of impaired loans net of allowance for impairment	798		332
Total impaired loans, excluding allowance for impairment:	27,806		24,585
Loans and Leases Receivable, Gross	4,653,720		4,730,953
Unpaid principal balance of impaired loans	35,444		31,948
Average balance of impaired loans	24,893	$ 23,508
Interest earned on impaired loans	122	44
Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-impaired loans	1,308,549		1,331,415
Impaired loans with no allowance for impairment	10,382		12,266
Recorded investment	819		363
Allowance for impairment	(34)		(31)
Balance of impaired loans net of allowance for impairment	785		332
Total impaired loans, excluding allowance for impairment:	11,201		12,629
Loans and Leases Receivable, Gross	1,319,750		1,344,044
Unpaid principal balance of impaired loans	13,565		14,985
Average balance of impaired loans	11,770	12,224
Interest earned on impaired loans	35	32
Non-Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-impaired loans	1,222,213		1,249,969
Impaired loans with no allowance for impairment	8,750		8,900
Total impaired loans, excluding allowance for impairment:	8,750		8,900
Loans and Leases Receivable, Gross	1,230,963		1,258,869
Unpaid principal balance of impaired loans	10,146		10,200
Average balance of impaired loans	8,823	7,234
Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-impaired loans	14,637		13,907
Loans and Leases Receivable, Gross	14,637		13,907
Unpaid principal balance of impaired loans	73		73
Commercial Business [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-impaired loans	63,571		64,308
Impaired loans with no allowance for impairment	3,297		1,455
Recorded investment	21
Allowance for impairment	(8)
Balance of impaired loans net of allowance for impairment	13
Total impaired loans, excluding allowance for impairment:	3,318		1,455
Loans and Leases Receivable, Gross	66,889		65,763
Unpaid principal balance of impaired loans	6,270		3,987
Average balance of impaired loans	1,951	2,364
Interest earned on impaired loans	51	3
Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-impaired loans	5,209		5,814
Loans and Leases Receivable, Gross	5,209		5,814
Multi-Family Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-impaired loans	1,919,907		1,946,321
Impaired loans with no allowance for impairment	3,061		70
Total impaired loans, excluding allowance for impairment:	3,061		70
Loans and Leases Receivable, Gross	1,922,968		1,946,391
Unpaid principal balance of impaired loans	3,544		779
Average balance of impaired loans	800	108
Interest earned on impaired loans	28
Home Equity Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-impaired loans	91,828		94,634
Impaired loans with no allowance for impairment	1,476		1,531
Total impaired loans, excluding allowance for impairment:	1,476		1,531
Loans and Leases Receivable, Gross	93,304		96,165
Unpaid principal balance of impaired loans	1,846		$ 1,924
Average balance of impaired loans	1,549	1,578
Interest earned on impaired loans	$ 8	$ 9

Impaired (recovered) financing receivables with related allowance recorded investment.

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- Definition

The balance of financing receivables that were collectively evaluated for impairment.

+ References

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-Publisher FASB
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-Topic 310
-SubTopic 10
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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.

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Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

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Amount of interest income recognized that the financing receivables (with related allowance for credit losses and without a related allowance for credit losses) were impaired.

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Amount of allowance for credit losses related to recorded investment.

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Amount of unpaid principal balance of impaired financing receivables with related allowance for credit losses and without related allowance for credit losses.

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Amount of investment in impaired financing receivables for which there is no related allowance for credit losses.

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Amount of investment in impaired financing receivables for which there is a related allowance for credit losses.

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- Definition

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.

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