Loans Receivable - Credit-Rating Classification of Loans Receivable (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	$ 5,024,915	$ 4,880,310
Home Equity Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	41,501	47,871
Non-Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	1,085,988	1,079,444
Commercial Business [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	169,551	168,951
Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	121,137	93,804
Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	1,527,980	1,447,721
Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	2,755	3,259
Pass [Member] | Home Equity Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	39,296	45,532
Pass [Member] | Non-Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	1,016,754	1,000,585
Pass [Member] | Commercial Business [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	163,831	162,728
Pass [Member] | Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	119,347	91,557
Pass [Member] | Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	1,509,521	1,422,020
Pass [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	2,680	3,171
Special Mention | Home Equity Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	265	393
Special Mention | Non-Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	36,683	40,980
Special Mention | Commercial Business [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	3,538	3,722
Special Mention | Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	1,652	1,945
Substandard | Home Equity Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	1,940	1,946
Substandard | Non-Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	32,551	37,879
Substandard | Commercial Business [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	2,034	2,072
Substandard | Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	1,790	2,247
Substandard | Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	16,807	23,756
Substandard | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	0	1
Doubtful | Commercial Business [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	148	429
Doubtful | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	75	87
Revolving Credit Facility
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	89,258	103,307
Revolving Credit Facility | Home Equity Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	22,156	24,788
Revolving Credit Facility | Non-Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	6,087	6,150
Revolving Credit Facility | Commercial Business [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	54,790	66,127
Revolving Credit Facility | Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	5,735	5,735
Revolving Credit Facility | Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	375	375
Revolving Credit Facility | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	115	132
Revolving Credit Facility | Pass [Member] | Home Equity Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	22,156	24,788
Revolving Credit Facility | Pass [Member] | Non-Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	6,087	6,150
Revolving Credit Facility | Pass [Member] | Commercial Business [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	54,513	65,657
Revolving Credit Facility | Pass [Member] | Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	5,735	5,735
Revolving Credit Facility | Pass [Member] | Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	375	375
Revolving Credit Facility | Pass [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	40	44
Revolving Credit Facility | Special Mention | Commercial Business [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	216	461
Revolving Credit Facility | Substandard | Commercial Business [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	58
Revolving Credit Facility | Substandard | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	0	1
Revolving Credit Facility | Doubtful | Commercial Business [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	3	9
Revolving Credit Facility | Doubtful | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	75	87
Multi-Family Mortgage Member
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	2,076,003	2,039,260
Multi-Family Mortgage Member | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	2,009,865	1,973,826
Multi-Family Mortgage Member | Special Mention
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	26,123	37,941
Multi-Family Mortgage Member | Substandard
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	40,015	27,493
Term Loan Amortized Cost [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	1,080,925	1,028,561	$ 1,007,486	$ 500,255	$ 396,962	$ 574,903	$ 410,629	$ 531,566	$ 395,106	$ 774,870	$ 1,644,549	$ 1,366,848
Term Loan Amortized Cost [Member] | Home Equity Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	1,759	834	715	2,508	1,744	4,585	3,369	2,778	2,125	2,252	9,633	10,126
Term Loan Amortized Cost [Member] | Non-Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	201,205	100,345	86,936	77,146	64,161	79,955	62,003	73,696	55,954	284,343	609,642	457,809
Term Loan Amortized Cost [Member] | Commercial Business [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	36,918	44,555	39,520	19,064	12,736	4,861	4,150	16,432	12,742	4,399	8,695	13,513
Term Loan Amortized Cost [Member] | Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	7,868	40,332	85,564	17,404	9,492	11,203	3,058	13,860	6,513	1,641	2,907	3,629
Term Loan Amortized Cost [Member] | Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	312,625	560,543	531,111	125,646	92,280	71,821	54,558	75,265	56,834	120,706	480,197	493,365
Term Loan Amortized Cost [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	281	550	324	517	477	633	398	256	247	127	913	1,044
Term Loan Amortized Cost [Member] | Pass [Member] | Home Equity Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	1,759	834	715	2,508	1,744	4,585	3,245	2,778	2,125	2,241	7,552	7,798
Term Loan Amortized Cost [Member] | Pass [Member] | Non-Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	201,205	99,602	86,212	77,146	64,161	56,435	37,706	64,616	51,884	254,940	569,499	441,696
Term Loan Amortized Cost [Member] | Pass [Member] | Commercial Business [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	36,918	44,514	39,481	18,988	12,441	4,701	3,961	12,654	9,147	3,322	7,370	12,892
Term Loan Amortized Cost [Member] | Pass [Member] | Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	7,868	40,332	85,564	17,404	9,492	11,203	3,058	13,860	6,513	1,641	1,117	1,382
Term Loan Amortized Cost [Member] | Pass [Member] | Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	312,625	560,543	531,111	124,606	90,576	69,917	53,262	74,754	56,834	119,238	464,738	472,587
Term Loan Amortized Cost [Member] | Pass [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	281	550	324	517	477	633	398	256	247	127	913	1,044
Term Loan Amortized Cost [Member] | Special Mention | Home Equity Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross											265	393
Term Loan Amortized Cost [Member] | Special Mention | Non-Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross						23,520	23,364	4,146	4,070	8,801	9,249	4,513
Term Loan Amortized Cost [Member] | Special Mention | Commercial Business [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross					65		189	2,304	2,173	945	895	12
Term Loan Amortized Cost [Member] | Special Mention | Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross						1,233	1,213				439	712
Term Loan Amortized Cost [Member] | Substandard | Home Equity Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross							124			11	1,816	1,935
Term Loan Amortized Cost [Member] | Substandard | Non-Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross		743	724				933	4,934	0	20,602	30,894	11,600
Term Loan Amortized Cost [Member] | Substandard | Commercial Business [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross		41	39	76	230	160		1,474	1,422	132	285	189
Term Loan Amortized Cost [Member] | Substandard | Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross											1,790	2,247
Term Loan Amortized Cost [Member] | Substandard | Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross				1,040	1,704	671	83	511		1,468	15,020	20,066
Term Loan Amortized Cost [Member] | Doubtful | Commercial Business [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross											145	420
Term Loan Amortized Cost [Member] | Multi-Family Mortgage Member
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	520,269	281,402	263,316	257,970	216,072	401,845	283,093	349,279	260,691	361,402	532,562	387,362
Term Loan Amortized Cost [Member] | Multi-Family Mortgage Member | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross	$ 520,269	$ 281,402	$ 263,316	$ 257,970	$ 216,072	374,871	256,541	341,304	252,909	343,370	500,758	374,909
Term Loan Amortized Cost [Member] | Multi-Family Mortgage Member | Special Mention
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross						$ 26,974	16,370	5,079	4,994	4,834	4,759	1,054
Term Loan Amortized Cost [Member] | Multi-Family Mortgage Member | Substandard
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases receivable, Gross							$ 10,182	$ 2,896	$ 2,788	$ 13,198	$ 27,045	$ 11,399