Receivable and Allowance for Credit Losses - Allowance for Loan Losses (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Allowance for credit losses:
Total	$ 55,096	$ 52,803	$ 62,689	$ 74,676
Total loans:
Total gross loans	7,839,754	7,641,593
Real estate loans | One-to-four family
Allowance for credit losses:
Total	13,017	11,802	8,798	13,586
Total loans:
Total gross loans	2,794,726	2,862,342
Real estate loans | Multifamily
Allowance for credit losses:
Total	8,742	7,877	7,741	8,799
Total loans:
Total gross loans	1,409,187	1,239,207
Real estate loans | Commercial real estate
Allowance for credit losses:
Total	15,757	18,111	16,114	21,882
Total loans:
Total gross loans	2,389,766	2,426,510
Real estate loans | Construction
Allowance for credit losses:
Total	7,758	6,425	8,943	11,271
Total loans:
Total gross loans	443,094	337,593
Commercial business loans
Allowance for credit losses:
Total	7,923	6,897	20,214	17,384
Total loans:
Total gross loans	533,410	497,965
Consumer loans | Home equity loans and advances
Allowance for credit losses:
Total	1,892	1,681	873	1,748
Total loans:
Total gross loans	266,770	274,551
Consumer loans | Other consumer loans
Allowance for credit losses:
Total	7	10	$ 6	$ 6
Total loans:
Total gross loans	2,801	3,425
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Allowance for credit losses:
Individually analyzed loans	614	339
Collectively analyzed loans	54,309	52,381
Total loans:
Individually analyzed loans	31,956	23,220
Collectively analyzed loans	7,792,709	7,601,314
Total gross loans	7,824,665	7,624,534
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Real estate loans | One-to-four family
Allowance for credit losses:
Individually analyzed loans	186	201
Collectively analyzed loans	12,827	11,591
Total loans:
Individually analyzed loans	4,063	4,164
Collectively analyzed loans	2,788,770	2,856,020
Total gross loans	2,792,833	2,860,184
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Real estate loans | Multifamily
Allowance for credit losses:
Individually analyzed loans	7	3
Collectively analyzed loans	8,735	7,874
Total loans:
Individually analyzed loans	382	457
Collectively analyzed loans	1,408,805	1,238,750
Total gross loans	1,409,187	1,239,207
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Real estate loans | Commercial real estate
Allowance for credit losses:
Individually analyzed loans	237	99
Collectively analyzed loans	15,378	17,961
Total loans:
Individually analyzed loans	15,360	16,729
Collectively analyzed loans	2,361,717	2,396,665
Total gross loans	2,377,077	2,413,394
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	7,758	6,415
Total loans:
Individually analyzed loans	0	0
Collectively analyzed loans	443,094	336,553
Total gross loans	443,094	336,553
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Commercial business loans
Allowance for credit losses:
Individually analyzed loans	154	10
Collectively analyzed loans	7,742	6,876
Total loans:
Individually analyzed loans	11,550	1,173
Collectively analyzed loans	521,491	496,296
Total gross loans	533,041	497,469
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Consumer loans | Home equity loans and advances
Allowance for credit losses:
Individually analyzed loans	30	26
Collectively analyzed loans	1,862	1,654
Total loans:
Individually analyzed loans	601	697
Collectively analyzed loans	266,031	273,605
Total gross loans	266,632	274,302
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	7	10
Total loans:
Individually analyzed loans	0	0
Collectively analyzed loans	2,801	3,425
Total gross loans	2,801	3,425
Financial Asset Acquired with Credit Deterioration
Allowance for credit losses:
Total	173	83
Total loans:
Total gross loans	15,089	17,059
Financial Asset Acquired with Credit Deterioration | Real estate loans | One-to-four family
Allowance for credit losses:
Total	4	10
Total loans:
Total gross loans	1,893	2,158
Financial Asset Acquired with Credit Deterioration | Real estate loans | Multifamily
Allowance for credit losses:
Total	0	0
Total loans:
Total gross loans	0	0
Financial Asset Acquired with Credit Deterioration | Real estate loans | Commercial real estate
Allowance for credit losses:
Total	142	51
Total loans:
Total gross loans	12,689	13,116
Financial Asset Acquired with Credit Deterioration | Real estate loans | Construction
Allowance for credit losses:
Total	0	10
Total loans:
Total gross loans	0	1,040
Financial Asset Acquired with Credit Deterioration | Commercial business loans
Allowance for credit losses:
Total	27	11
Total loans:
Total gross loans	369	496
Financial Asset Acquired with Credit Deterioration | Consumer loans | Home equity loans and advances
Allowance for credit losses:
Total	0	1
Total loans:
Total gross loans	138	249
Financial Asset Acquired with Credit Deterioration | Consumer loans | Other consumer loans
Allowance for credit losses:
Total	0	0
Total loans:
Total gross loans	$ 0	$ 0