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, 2024	Mar. 31, 2023	Dec. 31, 2023
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 55,096	$ 52,803	$ 52,803
Provision for (reversal of) credit losses	5,278	175
Recoveries	149	176
Charge-offs	(5,122)	(281)
Balance at end of period	55,401	52,873	55,096
Real estate loans | One-to-four family
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	13,017	11,802	11,802
Provision for (reversal of) credit losses	825	1,121
Recoveries	0	0
Charge-offs	(2)	(134)
Balance at end of period	13,840	12,789	13,017
Real estate loans | Multifamily
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	8,742	7,877	7,877
Provision for (reversal of) credit losses	(72)	268
Recoveries	0	0
Charge-offs	0	0
Balance at end of period	8,670	8,145	8,742
Real estate loans | Commercial real estate
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	15,757	18,111	18,111
Provision for (reversal of) credit losses	(525)	(1,768)
Recoveries	0	0
Charge-offs	0	(86)
Balance at end of period	15,232	16,257	15,757
Real estate loans | Construction
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	7,758	6,425	6,425
Provision for (reversal of) credit losses	309	314
Recoveries	1	0
Charge-offs	0	0
Balance at end of period	8,068	6,739	7,758
Commercial business loans
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	7,923	6,897	6,897
Provision for (reversal of) credit losses	4,665	272
Recoveries	143	151
Charge-offs	(5,020)	0
Balance at end of period	7,711	7,320	7,923
Consumer loans | Home equity loans and advances
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	1,892	1,681	1,681
Provision for (reversal of) credit losses	(24)	(61)
Recoveries	5	20
Charge-offs	0	(26)
Balance at end of period	1,873	1,614	1,892
Consumer loans | Other consumer loans
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	7	10	10
Provision for (reversal of) credit losses	100	29
Recoveries	0	5
Charge-offs	(100)	(35)
Balance at end of period	$ 7	$ 9	$ 7