Loans Receivable and Allowance for Credit Losses - Aging of Loans (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Financing Receivable, Past Due [Line Items]
Non-accrual	$ 28,000	$ 12,600
Total loans	7,821,548	7,839,754
Commercial real estate | One-to-four family
Financing Receivable, Past Due [Line Items]
Total loans	2,739,024	2,794,726
Commercial real estate | Multifamily
Financing Receivable, Past Due [Line Items]
Total loans	1,399,000	1,409,187
Commercial real estate | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total loans	2,322,262	2,389,766
Commercial real estate | Construction
Financing Receivable, Past Due [Line Items]
Total loans	510,439	443,094
Consumer loans | Home equity loans and advances
Financing Receivable, Past Due [Line Items]
Total loans	261,188	266,770
Consumer loans | Other consumer loans
Financing Receivable, Past Due [Line Items]
Total loans	2,877	2,801
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Past Due [Line Items]
Non-accrual	28,014	12,618
Total loans	7,809,753	7,824,665
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Commercial real estate | One-to-four family
Financing Receivable, Past Due [Line Items]
Non-accrual	7,368	3,139
Total loans	2,737,190	2,792,833
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Commercial real estate | Multifamily
Financing Receivable, Past Due [Line Items]
Non-accrual	0	0
Total loans	1,399,000	1,409,187
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Commercial real estate | Commercial real estate
Financing Receivable, Past Due [Line Items]
Non-accrual	9,413	2,740
Total loans	2,312,759	2,377,077
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Commercial real estate | Construction
Financing Receivable, Past Due [Line Items]
Non-accrual	0	0
Total loans	510,439	443,094
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Consumer loans | Home equity loans and advances
Financing Receivable, Past Due [Line Items]
Non-accrual	172	221
Total loans	261,041	266,632
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Consumer loans | Other consumer loans
Financing Receivable, Past Due [Line Items]
Non-accrual	0	0
Total loans	2,877	2,801
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Commercial business loans
Financing Receivable, Past Due [Line Items]
Non-accrual	11,061	6,518
Total loans	586,447	533,041
Financial Asset, Past Due | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Past Due [Line Items]
Total loans	47,885	37,940
Financial Asset, Past Due | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Commercial real estate | One-to-four family
Financing Receivable, Past Due [Line Items]
Total loans	24,886	16,891
Financial Asset, Past Due | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Commercial real estate | Multifamily
Financing Receivable, Past Due [Line Items]
Total loans	0	0
Financial Asset, Past Due | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Commercial real estate | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total loans	15,942	6,923
Financial Asset, Past Due | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Commercial real estate | Construction
Financing Receivable, Past Due [Line Items]
Total loans	0	0
Financial Asset, Past Due | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Consumer loans | Home equity loans and advances
Financing Receivable, Past Due [Line Items]
Total loans	712	963
Financial Asset, Past Due | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Consumer loans | Other consumer loans
Financing Receivable, Past Due [Line Items]
Total loans	2	1
Financial Asset, Past Due | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Commercial business loans
Financing Receivable, Past Due [Line Items]
Total loans	6,343	13,162
30-59 Days | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Past Due [Line Items]
Total loans	34,655	15,297
30-59 Days | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Commercial real estate | One-to-four family
Financing Receivable, Past Due [Line Items]
Total loans	14,915	11,079
30-59 Days | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Commercial real estate | Multifamily
Financing Receivable, Past Due [Line Items]
Total loans	0	0
30-59 Days | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Commercial real estate | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total loans	15,492	1,711
30-59 Days | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Commercial real estate | Construction
Financing Receivable, Past Due [Line Items]
Total loans	0	0
30-59 Days | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Consumer loans | Home equity loans and advances
Financing Receivable, Past Due [Line Items]
Total loans	560	779
30-59 Days | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Consumer loans | Other consumer loans
Financing Receivable, Past Due [Line Items]
Total loans	2	1
30-59 Days | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Commercial business loans
Financing Receivable, Past Due [Line Items]
Total loans	3,686	1,727
60-89 Days | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Past Due [Line Items]
Total loans	8,831	11,657
60-89 Days | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Commercial real estate | One-to-four family
Financing Receivable, Past Due [Line Items]
Total loans	6,989	4,254
60-89 Days | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Commercial real estate | Multifamily
Financing Receivable, Past Due [Line Items]
Total loans	0	0
60-89 Days | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Commercial real estate | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total loans	450	2,472
60-89 Days | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Commercial real estate | Construction
Financing Receivable, Past Due [Line Items]
Total loans	0	0
60-89 Days | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Consumer loans | Home equity loans and advances
Financing Receivable, Past Due [Line Items]
Total loans	139	14
60-89 Days | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Consumer loans | Other consumer loans
Financing Receivable, Past Due [Line Items]
Total loans	0	0
60-89 Days | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Commercial business loans
Financing Receivable, Past Due [Line Items]
Total loans	1,253	4,917
90 Days or More | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Past Due [Line Items]
Total loans	4,399	10,986
90 Days or More | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Commercial real estate | One-to-four family
Financing Receivable, Past Due [Line Items]
Total loans	2,982	1,558
90 Days or More | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Commercial real estate | Multifamily
Financing Receivable, Past Due [Line Items]
Total loans	0	0
90 Days or More | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Commercial real estate | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total loans	0	2,740
90 Days or More | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Commercial real estate | Construction
Financing Receivable, Past Due [Line Items]
Total loans	0	0
90 Days or More | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Consumer loans | Home equity loans and advances
Financing Receivable, Past Due [Line Items]
Total loans	13	170
90 Days or More | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Consumer loans | Other consumer loans
Financing Receivable, Past Due [Line Items]
Total loans	0	0
90 Days or More | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Commercial business loans
Financing Receivable, Past Due [Line Items]
Total loans	1,404	6,518
Current | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Past Due [Line Items]
Total loans	7,761,868	7,786,725
Current | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Commercial real estate | One-to-four family
Financing Receivable, Past Due [Line Items]
Total loans	2,712,304	2,775,942
Current | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Commercial real estate | Multifamily
Financing Receivable, Past Due [Line Items]
Total loans	1,399,000	1,409,187
Current | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Commercial real estate | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total loans	2,296,817	2,370,154
Current | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Commercial real estate | Construction
Financing Receivable, Past Due [Line Items]
Total loans	510,439	443,094
Current | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Consumer loans | Home equity loans and advances
Financing Receivable, Past Due [Line Items]
Total loans	260,329	265,669
Current | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Consumer loans | Other consumer loans
Financing Receivable, Past Due [Line Items]
Total loans	2,875	2,800
Current | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Commercial business loans
Financing Receivable, Past Due [Line Items]
Total loans	$ 580,104	$ 519,879