Loans Receivable and Allowance for Credit Losses - Credit Quality Indicators (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 6,951,786	$ 6,335,722
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Credit Quality Indicator [Line Items]
2022	780,000	1,702,481
2021	1,742,055	771,407
2020	756,082	789,875
2019	721,744	533,879
2018	493,665	555,250
Prior	2,076,825	1,657,885
Revolving Loans	359,605	317,728
Revolving Loans to Term Loans	457	426
Total	6,930,433	6,328,931
Real estate loans | One-to-four family
Financing Receivable, Credit Quality Indicator [Line Items]
Total	2,515,059	2,092,748
Real estate loans | One-to-four family | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Credit Quality Indicator [Line Items]
2022	374,154	793,848
2021	853,071	298,815
2020	308,495	197,707
2019	186,588	139,635
2018	134,263	135,171
Prior	655,144	527,141
Revolving Loans	0	0
Revolving Loans to Term Loans	0	0
Total	2,511,715	2,092,317
Real estate loans | One-to-four family | Pass | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Credit Quality Indicator [Line Items]
2022	374,154	793,848
2021	852,583	298,815
2020	308,495	196,244
2019	185,900	138,215
2018	133,938	134,811
Prior	653,327	525,615
Revolving Loans	0	0
Revolving Loans to Term Loans	0	0
Total	2,508,397	2,087,548
Real estate loans | One-to-four family | Special mention | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0	0
2021	0	0
2020	0	0
2019	0	0
2018	0	0
Prior	195	203
Revolving Loans	0	0
Revolving Loans to Term Loans	0	0
Total	195	203
Real estate loans | One-to-four family | Substandard | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0	0
2021	488	0
2020	0	1,463
2019	688	1,420
2018	325	360
Prior	1,622	1,323
Revolving Loans	0	0
Revolving Loans to Term Loans	0	0
Total	3,123	4,566
Real estate loans | Multifamily
Financing Receivable, Credit Quality Indicator [Line Items]
Total	1,077,459	1,041,108
Real estate loans | Multifamily | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Credit Quality Indicator [Line Items]
2022	103,694	312,738
2021	307,293	181,285
2020	177,317	231,252
2019	209,352	47,024
2018	47,552	131,169
Prior	232,251	137,640
Revolving Loans	0	0
Revolving Loans to Term Loans	0	0
Total	1,077,459	1,041,108
Real estate loans | Multifamily | Pass | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Credit Quality Indicator [Line Items]
2022	103,694	312,738
2021	307,293	181,285
2020	177,317	231,252
2019	209,352	47,024
2018	47,552	131,169
Prior	227,705	137,640
Revolving Loans	0	0
Revolving Loans to Term Loans	0	0
Total	1,072,913	1,041,108
Real estate loans | Multifamily | Special mention | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0	0
2021	0	0
2020	0	0
2019	0	0
2018	0	0
Prior	4,546	0
Revolving Loans	0	0
Revolving Loans to Term Loans	0	0
Total	4,546	0
Real estate loans | Multifamily | Substandard | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0	0
2021	0	0
2020	0	0
2019	0	0
2018	0	0
Prior	0	0
Revolving Loans	0	0
Revolving Loans to Term Loans	0	0
Total	0	0
Real estate loans | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total	2,322,757	2,175,662
Real estate loans | Commercial real estate | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Credit Quality Indicator [Line Items]
2022	189,253	381,222
2021	393,998	161,522
2020	179,305	279,884
2019	265,458	259,300
2018	256,893	225,913
Prior	1,021,776	862,395
Revolving Loans	0	0
Revolving Loans to Term Loans	0	0
Total	2,306,683	2,170,236
Real estate loans | Commercial real estate | Pass | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Credit Quality Indicator [Line Items]
2022	189,253	381,222
2021	393,998	161,136
2020	178,019	278,581
2019	264,387	241,669
2018	241,040	222,752
Prior	964,935	803,945
Revolving Loans	0	0
Revolving Loans to Term Loans	0	0
Total	2,231,632	2,089,305
Real estate loans | Commercial real estate | Special mention | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0	0
2021	0	0
2020	0	1,303
2019	1,071	16,070
2018	15,853	1,885
Prior	29,644	34,788
Revolving Loans	0	0
Revolving Loans to Term Loans	0	0
Total	46,568	54,046
Real estate loans | Commercial real estate | Substandard | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0	0
2021	0	386
2020	1,286	0
2019	0	1,561
2018	0	1,276
Prior	27,197	23,662
Revolving Loans	0	0
Revolving Loans to Term Loans	0	0
Total	28,483	26,885
Real estate loans | Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Total	277,750	295,047
Real estate loans | Construction | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Credit Quality Indicator [Line Items]
2022	64,943	107,070
2021	117,908	77,549
2020	40,766	37,605
2019	18,216	41,591
2018	9,826	28,814
Prior	25,051	2,418
Revolving Loans	0	0
Revolving Loans to Term Loans	0	0
Total	276,710	295,047
Real estate loans | Construction | Pass | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Credit Quality Indicator [Line Items]
2022	64,943	107,070
2021	117,908	77,549
2020	40,766	37,498
2019	18,216	41,591
2018	9,826	28,814
Prior	25,051	2,418
Revolving Loans	0	0
Revolving Loans to Term Loans	0	0
Total	276,710	294,940
Real estate loans | Construction | Special mention | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0	0
2021	0	0
2020	0	107
2019	0	0
2018	0	0
Prior	0	0
Revolving Loans	0	0
Revolving Loans to Term Loans	0	0
Total	0	107
Real estate loans | Construction | Substandard | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0	0
2021	0	0
2020	0	0
2019	0	0
2018	0	0
Prior	0	0
Revolving Loans	0	0
Revolving Loans to Term Loans	0	0
Total	0	0
Commercial business loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total	474,844	453,166
Commercial business loans | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Credit Quality Indicator [Line Items]
2022	28,615	84,551
2021	46,075	36,201
2020	34,434	27,237
2019	27,901	33,123
2018	32,008	22,151
Prior	43,452	27,170
Revolving Loans	261,660	221,799
Revolving Loans to Term Loans	0	0
Total	474,145	452,232
Commercial business loans | Pass | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Credit Quality Indicator [Line Items]
2022	28,615	84,113
2021	45,700	36,115
2020	34,306	25,156
2019	26,367	30,670
2018	28,320	21,762
Prior	42,923	26,515
Revolving Loans	252,220	210,597
Revolving Loans to Term Loans	0	0
Total	458,451	434,928
Commercial business loans | Special mention | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0	246
2021	224	15
2020	62	1,729
2019	1,322	1,369
2018	1,132	18
Prior	43	46
Revolving Loans	3,661	3,291
Revolving Loans to Term Loans	0	0
Total	6,444	6,714
Commercial business loans | Substandard | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0	192
2021	151	71
2020	66	352
2019	212	1,084
2018	2,556	371
Prior	486	609
Revolving Loans	5,779	7,911
Revolving Loans to Term Loans	0	0
Total	9,250	10,590
Consumer loans | Home equity loans and advances
Financing Receivable, Credit Quality Indicator [Line Items]
Total	281,786	276,563
Consumer loans | Home equity loans and advances | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Credit Quality Indicator [Line Items]
2022	18,100	22,393
2021	23,603	15,977
2020	15,643	15,906
2019	14,070	13,146
2018	13,078	12,023
Prior	99,021	101,116
Revolving Loans	97,618	95,576
Revolving Loans to Term Loans	457	426
Total	281,590	276,563
Consumer loans | Home equity loans and advances | Pass | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Credit Quality Indicator [Line Items]
2022	18,100	22,393
2021	23,603	15,977
2020	15,643	15,906
2019	14,070	13,146
2018	13,078	12,023
Prior	98,835	100,870
Revolving Loans	97,582	95,484
Revolving Loans to Term Loans	457	426
Total	281,368	276,225
Consumer loans | Home equity loans and advances | Special mention | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0	0
2021	0	0
2020	0	0
2019	0	0
2018	0	0
Prior	0	0
Revolving Loans	0	0
Revolving Loans to Term Loans	0	0
Total	0	0
Consumer loans | Home equity loans and advances | Substandard | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0	0
2021	0	0
2020	0	0
2019	0	0
2018	0	0
Prior	186	246
Revolving Loans	36	92
Revolving Loans to Term Loans	0	0
Total	222	338
Consumer loans | Other consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total	2,131	1,428
Consumer loans | Other consumer loans | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Credit Quality Indicator [Line Items]
2022	1,241	659
2021	107	58
2020	122	284
2019	159	60
2018	45	9
Prior	130	5
Revolving Loans	327	353
Revolving Loans to Term Loans	0	0
Total	2,131	1,428
Consumer loans | Other consumer loans | Pass | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Credit Quality Indicator [Line Items]
2022	1,241	659
2021	107	58
2020	122	284
2019	159	60
2018	45	9
Prior	130	5
Revolving Loans	327	353
Revolving Loans to Term Loans	0	0
Total	2,131	1,428
Consumer loans | Other consumer loans | Special mention | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0	0
2021	0	0
2020	0	0
2019	0	0
2018	0	0
Prior	0	0
Revolving Loans	0	0
Revolving Loans to Term Loans	0	0
Total	0	0
Consumer loans | Other consumer loans | Substandard | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0	0
2021	0	0
2020	0	0
2019	0	0
2018	0	0
Prior	0	0
Revolving Loans	0	0
Revolving Loans to Term Loans	0	0
Total	$ 0	$ 0