Loans Receivable and Allowance for Credit Losses - Allowance for Credit Losses (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022	Dec. 31, 2021
Allowance for credit losses:
Total	$ 52,873	$ 52,803	$ 47,162	$ 62,689
Total loans:
Total	7,751,328	7,641,593
Real estate loans | One-to-four family
Allowance for credit losses:
Total	12,789	11,802	8,814	8,798
Total loans:
Total	2,862,917	2,862,342
Real estate loans | Multifamily
Allowance for credit losses:
Total	8,145	7,877	11,203	7,741
Total loans:
Total	1,315,143	1,239,207
Real estate loans | Commercial real estate
Allowance for credit losses:
Total	16,257	18,111	13,513	16,114
Total loans:
Total	2,406,590	2,426,510
Real estate loans | Construction
Allowance for credit losses:
Total	6,739	6,425	4,974	8,943
Total loans:
Total	375,474	337,593
Commercial business loans
Allowance for credit losses:
Total	7,320	6,897	7,143	20,214
Total loans:
Total	517,116	497,965
Consumer loans | Home equity loans and advances
Allowance for credit losses:
Total	1,614	1,681	1,507	873
Total loans:
Total	271,766	274,551
Consumer loans | Other consumer loans
Allowance for credit losses:
Total	9	10	$ 8	$ 6
Total loans:
Total	2,322	3,425
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Allowance for credit losses:
Individually analyzed loans	376	339
Collectively analyzed loans	52,417	52,381
Total loans:
Individually analyzed loans	24,278	23,220
Collectively analyzed loans	7,710,805	7,601,314
Total	7,735,083	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	203	201
Collectively analyzed loans	12,582	11,591
Total loans:
Individually analyzed loans	4,753	4,164
Collectively analyzed loans	2,856,211	2,856,020
Total	2,860,964	2,860,184
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Real estate loans | Multifamily
Allowance for credit losses:
Individually analyzed loans	3	3
Collectively analyzed loans	8,142	7,874
Total loans:
Individually analyzed loans	438	457
Collectively analyzed loans	1,314,705	1,238,750
Total	1,315,143	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	104	99
Collectively analyzed loans	16,104	17,961
Total loans:
Individually analyzed loans	15,774	16,729
Collectively analyzed loans	2,378,144	2,396,665
Total	2,393,918	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	6,730	6,415
Total loans:
Individually analyzed loans	0	0
Collectively analyzed loans	374,434	336,553
Total	374,434	336,553
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Commercial business loans
Allowance for credit losses:
Individually analyzed loans	39	10
Collectively analyzed loans	7,264	6,876
Total loans:
Individually analyzed loans	2,634	1,173
Collectively analyzed loans	514,048	496,296
Total	516,682	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	27	26
Collectively analyzed loans	1,586	1,654
Total loans:
Individually analyzed loans	679	697
Collectively analyzed loans	270,941	273,605
Total	271,620	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	9	10
Total loans:
Individually analyzed loans	0	0
Collectively analyzed loans	2,322	3,425
Total	2,322	3,425
Financial Asset Acquired with Credit Deterioration
Allowance for credit losses:
Total	80	83
Total loans:
Total	16,245	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	1,953	2,158
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	49	51
Total loans:
Total	12,672	13,116
Financial Asset Acquired with Credit Deterioration | Real estate loans | Construction
Allowance for credit losses:
Total	9	10
Total loans:
Total	1,040	1,040
Financial Asset Acquired with Credit Deterioration | Commercial business loans
Allowance for credit losses:
Total	17	11
Total loans:
Total	434	496
Financial Asset Acquired with Credit Deterioration | Consumer loans | Home equity loans and advances
Allowance for credit losses:
Total	1	1
Total loans:
Total	146	249
Financial Asset Acquired with Credit Deterioration | Consumer loans | Other consumer loans
Allowance for credit losses:
Total	0	0
Total loans:
Total	$ 0	$ 0