Loans Receivable and Allowance for Credit Losses - Loans Receivable (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	$ 7,725,645	$ 7,641,593
Net deferred loan costs, fees and purchased premiums and discounts	34,791	35,971
Loans receivable	7,760,436	7,677,564
Real estate loans | One-to-four family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	2,791,201	2,862,342
Real estate loans | Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	1,376,999	1,239,207
Real estate loans | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	2,399,479	2,426,510
Real estate loans | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	380,028	337,593
Commercial business loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	505,933	497,965
Consumer loans | Home equity loans and advances
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	269,453	274,551
Consumer loans | Other consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	2,552	3,425
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	7,709,538	7,624,534
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Real estate loans | One-to-four family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	2,789,269	2,860,184
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Real estate loans | Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	1,376,999	1,239,207
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Real estate loans | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	2,386,896	2,413,394
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Real estate loans | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	378,988	336,553
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Commercial business loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	505,524	497,469
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Consumer loans | Home equity loans and advances
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	269,310	274,302
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Consumer loans | Other consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	2,552	3,425
Financial Asset Acquired with Credit Deterioration
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	16,107	17,059
Financial Asset Acquired with Credit Deterioration | Real estate loans | One-to-four family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	1,932	2,158
Financial Asset Acquired with Credit Deterioration | Real estate loans | Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	0	0
Financial Asset Acquired with Credit Deterioration | Real estate loans | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	12,583	13,116
Financial Asset Acquired with Credit Deterioration | Real estate loans | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	1,040	1,040
Financial Asset Acquired with Credit Deterioration | Commercial business loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	409	496
Financial Asset Acquired with Credit Deterioration | Consumer loans | Home equity loans and advances
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	143	249
Financial Asset Acquired with Credit Deterioration | Consumer loans | Other consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	$ 0	$ 0