Loans Receivable and Allowance for Credit Losses - Allowance for Loan Losses by Portfolio Segment (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 52,803	$ 62,689	$ 62,689
Provision for (reversal of) credit losses	175	805
Recoveries	176	168
Charge-offs	(281)	(57)
Balance at end of period	52,873	47,162	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	11,802	8,798	8,798
Provision for (reversal of) credit losses	1,121	2,185
Recoveries	0	139
Charge-offs	(134)	0
Balance at end of period	12,789	8,814	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	7,877	7,741	7,741
Provision for (reversal of) credit losses	268	5,492
Recoveries	0	0
Charge-offs	0	0
Balance at end of period	8,145	11,203	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	18,111	16,114	16,114
Provision for (reversal of) credit losses	(1,768)	1,626
Recoveries	0	0
Charge-offs	(86)	0
Balance at end of period	16,257	13,513	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	6,425	8,943	8,943
Provision for (reversal of) credit losses	314	(1,623)
Recoveries	0	0
Charge-offs	0	0
Balance at end of period	6,739	4,974	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	6,897	20,214	20,214
Provision for (reversal of) credit losses	272	(7,767)
Recoveries	151	25
Charge-offs	0	(27)
Balance at end of period	7,320	7,143	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	1,681	873	873
Provision for (reversal of) credit losses	(61)	886
Recoveries	20	4
Charge-offs	(26)	(27)
Balance at end of period	1,614	1,507	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	10	6	6
Provision for (reversal of) credit losses	29	6
Recoveries	5	0
Charge-offs	(35)	(3)
Balance at end of period	$ 9	8	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)