Allowance for Credit Losses - Allowance for Credit Losses and Balance of Loans Receivable (Detail) - USD ($) $ in Thousands	12 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2020
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans receivable allowance for credit loss	$ 47,058	$ 58,165
Allowance	58,165	37,327	$ 33,274
Loans Individually Analyzed	3,709	3,874
Loans collectively evaluated	43,012	50,332
Total allowance for credit losses	47,058	58,165
Loans individually analyzed	69,528	69,068
Loans collectively evaluated	5,347,702	4,748,747
Loans and Leases Receivable, Gross	5,436,576	4,880,310
Loans receivable, Unaccreted yield adjustments	18,731	28,916
Loans receivable	5,417,845	4,851,394
Allowance	47,058	58,165	37,327
Impact of adopting Topic 326		19,640
Total charge offs	4,737	1,612	189
Total recoveries	1,148	30	45
Initial allowance on PCD loans		3,901
(Reversal of) provision for credit losses	(7,518)	(1,121)	4,197
Non-Residential Mortgage [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans receivable allowance for credit loss	10,590	16,243
Allowance	16,243	8,763	9,672
Loans Individually Analyzed	2,696	2,025
Loans collectively evaluated	7,821	10,826
Total allowance for credit losses	10,590	16,243
Loans individually analyzed	31,517	30,668
Loans collectively evaluated	982,911	1,016,413
Loans and Leases Receivable, Gross	1,019,838	1,079,444
Allowance	10,590	16,243	8,763
Impact of adopting Topic 326		2,390
Total charge offs	2,646	80	0
Total recoveries	812	0	10
Initial allowance on PCD loans		1,720
(Reversal of) provision for credit losses	(3,819)	3,450	(919)
Commercial Business [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans receivable allowance for credit loss	1,792	2,086
Allowance	2,086	1,926	2,467
Loans Individually Analyzed	16	33
Loans collectively evaluated	1,767	2,038
Total allowance for credit losses	1,792	2,086
Loans individually analyzed	293	729
Loans collectively evaluated	175,247	165,506
Loans and Leases Receivable, Gross	176,807	168,951
Allowance	1,792	2,086	1,926
Impact of adopting Topic 326		(421)
Total charge offs	193	1,446	50
Total recoveries	160	17	2
Initial allowance on PCD loans		1,007
(Reversal of) provision for credit losses	(261)	1,003	(493)
Construction [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans receivable allowance for credit loss	1,486	1,170
Allowance	1,170	236	136
Loans Individually Analyzed	0	0
Loans collectively evaluated	1,486	1,121
Total allowance for credit losses	1,486	1,170
Loans individually analyzed	1,561	2,228
Loans collectively evaluated	132,835	78,606
Loans and Leases Receivable, Gross	140,131	93,804
Allowance	1,486	1,170	236
Impact of adopting Topic 326		80
Total charge offs	0	0	0
Total recoveries	0	0	0
Initial allowance on PCD loans		99
(Reversal of) provision for credit losses	316	755	100
One-to Four-Family Residential Mortgage [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans receivable allowance for credit loss	7,540	9,747
Allowance	9,747	4,860	3,377
Loans Individually Analyzed	148	447
Loans collectively evaluated	7,163	8,974
Total allowance for credit losses	7,540	9,747
Loans individually analyzed	8,402	15,553
Loans collectively evaluated	1,630,867	1,423,766
Loans and Leases Receivable, Gross	1,645,816	1,447,721
Allowance	7,540	9,747	4,860
Impact of adopting Topic 326		9,106
Total charge offs	0	13	0
Total recoveries	147	4	0
Initial allowance on PCD loans		720
(Reversal of) provision for credit losses	(2,354)	(4,930)	1,483
Other Consumer [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans receivable allowance for credit loss	84	36
Allowance	36	58	172
Loans Individually Analyzed	0	0
Loans collectively evaluated	84	36
Total allowance for credit losses	84	36
Loans individually analyzed	0	0
Loans collectively evaluated	2,866	3,259
Loans and Leases Receivable, Gross	2,866	3,259
Allowance	84	36	58
Impact of adopting Topic 326		(15)
Total charge offs	2	41	139
Total recoveries	2	9	33
Initial allowance on PCD loans		0
(Reversal of) provision for credit losses	48	25	(8)
Multi-Family Mortgage [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans receivable allowance for credit loss	25,321	28,450
Allowance	28,450	20,916	16,959
Loans Individually Analyzed	849	1,368
Loans collectively evaluated	24,472	26,927
Total allowance for credit losses	25,321	28,450
Loans individually analyzed	26,653	18,526
Loans collectively evaluated	2,382,437	2,015,135
Loans and Leases Receivable, Gross	2,409,090	2,039,260
Allowance		28,450	20,916
Impact of adopting Topic 326		8,408
Total charge offs		0	0
Total recoveries		0	0
Initial allowance on PCD loans		250
(Reversal of) provision for credit losses		(1,124)	3,957
Multi-Family Mortgage [Member] | Non-Residential Mortgage [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance	28,450
Allowance	25,321	28,450
Total charge offs	1,896
Total recoveries	0
(Reversal of) provision for credit losses	(1,233)
Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans receivable allowance for credit loss	26	2,843
Loans collectively evaluated	311	1,116
Total allowance for credit losses	26	2,843
Loans acquired with deteriorated credit quality individually evaluated	793	10,699
Loans acquired with deteriorated credit quality collectively evaluated	18,553	51,796
Receivables Acquired with Deteriorated Credit Quality [Member] | Non-Residential Mortgage [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans receivable allowance for credit loss	0	2,700
Loans collectively evaluated	73	692
Total allowance for credit losses	0	2,700
Loans acquired with deteriorated credit quality individually evaluated	377	6,519
Loans acquired with deteriorated credit quality collectively evaluated	5,033	25,844
Receivables Acquired with Deteriorated Credit Quality [Member] | Commercial Business [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans receivable allowance for credit loss	0	0
Loans collectively evaluated	9	15
Total allowance for credit losses	0	0
Loans acquired with deteriorated credit quality individually evaluated	0	183
Loans acquired with deteriorated credit quality collectively evaluated	1,267	2,533
Receivables Acquired with Deteriorated Credit Quality [Member] | Construction [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans receivable allowance for credit loss	0	0
Loans collectively evaluated	0	49
Total allowance for credit losses	0	0
Loans acquired with deteriorated credit quality individually evaluated	0	0
Loans acquired with deteriorated credit quality collectively evaluated	5,735	12,970
Receivables Acquired with Deteriorated Credit Quality [Member] | One-to Four-Family Residential Mortgage [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans receivable allowance for credit loss	0	122
Loans collectively evaluated	229	204
Total allowance for credit losses	0	122
Loans acquired with deteriorated credit quality individually evaluated	87	3,617
Loans acquired with deteriorated credit quality collectively evaluated	6,460	4,785
Receivables Acquired with Deteriorated Credit Quality [Member] | Other Consumer [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans receivable allowance for credit loss	0	0
Loans collectively evaluated	0	0
Total allowance for credit losses	0	0
Loans acquired with deteriorated credit quality individually evaluated	0	0
Loans acquired with deteriorated credit quality collectively evaluated	0	0
Receivables Acquired with Deteriorated Credit Quality [Member] | Multi-Family Mortgage [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans receivable allowance for credit loss	0	0
Loans collectively evaluated	0	155
Total allowance for credit losses	0	0
Loans acquired with deteriorated credit quality individually evaluated	0	0
Loans acquired with deteriorated credit quality collectively evaluated	0	5,599
Home Equity Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans receivable allowance for credit loss	245	433
Allowance	433	568	491
Loans Individually Analyzed	0	1
Loans collectively evaluated	219	410
Total allowance for credit losses	245	433
Loans individually analyzed	1,102	1,364
Loans collectively evaluated	40,539	46,062
Loans and Leases Receivable, Gross	42,028	47,871
Allowance	245	433	568
Impact of adopting Topic 326		92
Total charge offs	0	32	0
Total recoveries	27	0	0
Initial allowance on PCD loans		105
(Reversal of) provision for credit losses	(215)	(300)	$ 77
Home Equity Loans [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans receivable allowance for credit loss	26	21
Loans collectively evaluated	0	1
Total allowance for credit losses	26	21
Loans acquired with deteriorated credit quality individually evaluated	329	380
Loans acquired with deteriorated credit quality collectively evaluated	$ 58	$ 65