Loans Receivable and Allowance for Credit Losses - Allowance for Loan Losses (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Allowance for credit losses:
Total	$ 52,803	$ 62,689	$ 74,676	$ 61,709
Total loans:
Total	7,641,593	6,335,722
Real estate loans | One-to-four family
Allowance for credit losses:
Total	11,802	8,798	13,586	13,780
Total loans:
Total	2,862,342	2,092,748
Real estate loans | Multifamily
Allowance for credit losses:
Total	7,877	7,741	8,799	6,434
Total loans:
Total	1,239,207	1,041,108
Real estate loans | Commercial real estate
Allowance for credit losses:
Total	18,111	16,114	21,882	16,546
Total loans:
Total	2,426,510	2,175,662
Real estate loans | Construction
Allowance for credit losses:
Total	6,425	8,943	11,271	7,435
Total loans:
Total	337,593	295,047
Commercial business loans
Allowance for credit losses:
Total	6,897	20,214	17,384	15,836
Total loans:
Total	497,965	453,166
Consumer loans | Home equity loans and advances
Allowance for credit losses:
Total	1,681	873	1,748	1,669
Total loans:
Total	274,551	276,563
Consumer loans | Other consumer loans
Allowance for credit losses:
Total	10	6	$ 6	$ 9
Total loans:
Total	3,425	1,428
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Allowance for credit losses:
Individually analyzed loans	339	378
Collectively analyzed loans	52,381	62,311
Total loans:
Individually analyzed loans	23,220	24,287
Collectively analyzed loans	7,601,314	6,304,644
Total	7,624,534	6,328,931
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Real estate loans | One-to-four family
Allowance for credit losses:
Individually analyzed loans	201	258
Collectively analyzed loans	11,591	8,540
Total loans:
Individually analyzed loans	4,164	5,184
Collectively analyzed loans	2,856,020	2,087,133
Total	2,860,184	2,092,317
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Real estate loans | Multifamily
Allowance for credit losses:
Individually analyzed loans	3	0
Collectively analyzed loans	7,874	7,741
Total loans:
Individually analyzed loans	457	762
Collectively analyzed loans	1,238,750	1,040,346
Total	1,239,207	1,041,108
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Real estate loans | Commercial real estate
Allowance for credit losses:
Individually analyzed loans	99	97
Collectively analyzed loans	17,961	16,017
Total loans:
Individually analyzed loans	16,729	15,830
Collectively analyzed loans	2,396,665	2,154,406
Total	2,413,394	2,170,236
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Real estate loans | Construction
Allowance for credit losses:
Individually analyzed loans	0	0
Collectively analyzed loans	6,415	8,943
Total loans:
Individually analyzed loans	0	0
Collectively analyzed loans	336,553	295,047
Total	336,553	295,047
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Commercial business loans
Allowance for credit losses:
Individually analyzed loans	10	16
Collectively analyzed loans	6,876	20,198
Total loans:
Individually analyzed loans	1,173	1,806
Collectively analyzed loans	496,296	450,426
Total	497,469	452,232
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Consumer loans | Home equity loans and advances
Allowance for credit losses:
Individually analyzed loans	26	7
Collectively analyzed loans	1,654	866
Total loans:
Individually analyzed loans	697	705
Collectively analyzed loans	273,605	275,858
Total	274,302	276,563
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Consumer loans | Other consumer loans
Allowance for credit losses:
Individually analyzed loans	0	0
Collectively analyzed loans	10	6
Total loans:
Individually analyzed loans	0	0
Collectively analyzed loans	3,425	1,428
Total	3,425	1,428
Financial Asset Acquired with Credit Deterioration
Allowance for credit losses:
Total	83	0
Total loans:
Total	17,059	6,791
Financial Asset Acquired with Credit Deterioration | Real estate loans | One-to-four family
Allowance for credit losses:
Total	10	0
Total loans:
Total	2,158	431
Financial Asset Acquired with Credit Deterioration | Real estate loans | Multifamily
Allowance for credit losses:
Total	0	0
Total loans:
Total	0	0
Financial Asset Acquired with Credit Deterioration | Real estate loans | Commercial real estate
Allowance for credit losses:
Total	51	0
Total loans:
Total	13,116	5,426
Financial Asset Acquired with Credit Deterioration | Real estate loans | Construction
Allowance for credit losses:
Total	10	0
Total loans:
Total	1,040	0
Financial Asset Acquired with Credit Deterioration | Commercial business loans
Allowance for credit losses:
Total	11	0
Total loans:
Total	496	934
Financial Asset Acquired with Credit Deterioration | Consumer loans | Home equity loans and advances
Allowance for credit losses:
Total	1	0
Total loans:
Total	249	0
Financial Asset Acquired with Credit Deterioration | Consumer loans | Other consumer loans
Allowance for credit losses:
Total	0	0
Total loans:
Total	$ 0	$ 0