Loans Receivable and Allowance for Credit Losses - Allowance for Loan Losses by Portfolio Segment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 52,873	$ 47,162	$ 52,803	$ 62,689	$ 62,689
Initial allowance related to PCD loans		633		633
Provision for (reversal of) credit losses	1,078	2,683	1,253	3,488
Recoveries	60	233	236	401
Charge-offs	(555)	(128)	(836)	(185)
Balance at end of period	53,456	50,583	53,456	50,583	52,803
Effect of adopting ASU No. 2016-13 ("CECL")
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period				(16,443)	(16,443)
Real estate loans | One-to-four family
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	12,789	8,814	11,802	8,798	8,798
Initial allowance related to PCD loans		131		131
Provision for (reversal of) credit losses	(1,763)	1,785	(642)	3,970
Recoveries	0	199	0	338
Charge-offs	0	(93)	(134)	(93)
Balance at end of period	11,026	10,836	11,026	10,836	11,802
Real estate loans | One-to-four family | Effect of adopting ASU No. 2016-13 ("CECL")
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period				(2,308)	(2,308)
Real estate loans | Multifamily
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	8,145	11,203	7,877	7,741	7,741
Initial allowance related to PCD loans		0		0
Provision for (reversal of) credit losses	1,247	(271)	1,515	5,221
Recoveries	0	0	0	0
Charge-offs	0	0	0	0
Balance at end of period	9,392	10,932	9,392	10,932	7,877
Real estate loans | Multifamily | Effect of adopting ASU No. 2016-13 ("CECL")
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period				(2,030)	(2,030)
Real estate loans | Commercial real estate
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	16,257	13,513	18,111	16,114	16,114
Initial allowance related to PCD loans		474		474
Provision for (reversal of) credit losses	19	493	(1,749)	2,119
Recoveries	0	0	0	0
Charge-offs	(64)	0	(150)	0
Balance at end of period	16,212	14,480	16,212	14,480	18,111
Real estate loans | Commercial real estate | Effect of adopting ASU No. 2016-13 ("CECL")
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period				(4,227)	(4,227)
Real estate loans | Construction
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	6,739	4,974	6,425	8,943	8,943
Initial allowance related to PCD loans		3		3
Provision for (reversal of) credit losses	196	593	510	(1,030)
Recoveries	0	0	0	0
Charge-offs	0	0	0	0
Balance at end of period	6,935	5,570	6,935	5,570	6,425
Real estate loans | Construction | Effect of adopting ASU No. 2016-13 ("CECL")
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period				(2,346)	(2,346)
Commercial business loans
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	7,320	7,143	6,897	20,214	20,214
Initial allowance related to PCD loans		19		19
Provision for (reversal of) credit losses	764	127	1,037	(7,640)
Recoveries	56	30	206	55
Charge-offs	(450)	(35)	(450)	(62)
Balance at end of period	7,690	7,284	7,690	7,284	6,897
Commercial business loans | Effect of adopting ASU No. 2016-13 ("CECL")
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period				(5,302)	(5,302)
Consumer loans | Home equity loans and advances
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	1,614	1,507	1,681	873	873
Initial allowance related to PCD loans		6		6
Provision for (reversal of) credit losses	575	(46)	514	840
Recoveries	4	4	24	8
Charge-offs	0	0	(26)	(27)
Balance at end of period	2,193	1,471	2,193	1,471	1,681
Consumer loans | Home equity loans and advances | Effect of adopting ASU No. 2016-13 ("CECL")
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period				(229)	(229)
Consumer loans | Other consumer loans
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	9	8	10	6	6
Initial allowance related to PCD loans		0		0
Provision for (reversal of) credit losses	40	2	68	8
Recoveries	0	0	6	0
Charge-offs	(41)	0	(76)	(3)
Balance at end of period	$ 8	$ 10	$ 8	10	10
Consumer loans | Other consumer loans | Effect of adopting ASU No. 2016-13 ("CECL")
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period				$ (1)	$ (1)