Loans Receivable and Allowance for Credit Losses - Credit Quality Indicators (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 7,292,296	$ 6,335,722
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Credit Quality Indicator [Line Items]
2022	1,282,703	1,702,481
2021	1,716,361	771,407
2020	745,373	789,875
2019	711,959	533,879
2018	470,646	555,250
Prior	1,959,395	1,657,885
Revolving Loans	385,646	317,728
Revolving Loans to Term Loans	442	426
Total	7,272,525	6,328,931
Real estate loans | One-to-four family
Financing Receivable, Credit Quality Indicator [Line Items]
Total	2,708,293	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	628,998	793,848
2021	845,423	298,815
2020	299,287	197,707
2019	182,393	139,635
2018	128,095	135,171
Prior	621,918	527,141
Revolving Loans	0	0
Revolving Loans to Term Loans	0	0
Total	2,706,114	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	628,998	793,848
2021	844,780	298,815
2020	299,287	196,244
2019	181,706	138,215
2018	127,773	134,811
Prior	620,689	525,615
Revolving Loans	0	0
Revolving Loans to Term Loans	0	0
Total	2,703,233	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	0	203
Revolving Loans	0	0
Revolving Loans to Term Loans	0	0
Total	0	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	643	0
2020	0	1,463
2019	687	1,420
2018	322	360
Prior	1,229	1,323
Revolving Loans	0	0
Revolving Loans to Term Loans	0	0
Total	2,881	4,566
Real estate loans | Multifamily
Financing Receivable, Credit Quality Indicator [Line Items]
Total	1,142,459	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	177,878	312,738
2021	306,208	181,285
2020	184,752	231,252
2019	208,321	47,024
2018	43,451	131,169
Prior	221,849	137,640
Revolving Loans	0	0
Revolving Loans to Term Loans	0	0
Total	1,142,459	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	177,878	312,738
2021	306,208	181,285
2020	184,752	231,252
2019	208,321	47,024
2018	43,451	131,169
Prior	217,307	137,640
Revolving Loans	0	0
Revolving Loans to Term Loans	0	0
Total	1,137,917	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	4,542	0
Revolving Loans	0	0
Revolving Loans to Term Loans	0	0
Total	4,542	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	2,370,524	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	303,030	381,222
2021	398,986	161,522
2020	180,909	279,884
2019	266,275	259,300
2018	249,661	225,913
Prior	955,925	862,395
Revolving Loans	0	0
Revolving Loans to Term Loans	0	0
Total	2,354,786	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	303,030	381,222
2021	398,505	161,136
2020	179,623	278,581
2019	263,603	241,669
2018	233,911	222,752
Prior	906,137	803,945
Revolving Loans	0	0
Revolving Loans to Term Loans	0	0
Total	2,284,809	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	1,065	16,070
2018	15,750	1,885
Prior	34,248	34,788
Revolving Loans	0	0
Revolving Loans to Term Loans	0	0
Total	51,063	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	481	386
2020	1,286	0
2019	1,607	1,561
2018	0	1,276
Prior	15,540	23,662
Revolving Loans	0	0
Revolving Loans to Term Loans	0	0
Total	18,914	26,885
Real estate loans | Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Total	290,690	295,047
Real estate loans | Construction | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Credit Quality Indicator [Line Items]
2022	103,263	107,070
2021	107,388	77,549
2020	31,126	37,605
2019	14,216	41,591
2018	6,313	28,814
Prior	27,344	2,418
Revolving Loans	0	0
Revolving Loans to Term Loans	0	0
Total	289,650	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	103,263	107,070
2021	107,388	77,549
2020	31,126	37,498
2019	14,216	41,591
2018	6,313	28,814
Prior	27,344	2,418
Revolving Loans	0	0
Revolving Loans to Term Loans	0	0
Total	289,650	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	498,140	453,166
Commercial business loans | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Credit Quality Indicator [Line Items]
2022	47,082	84,551
2021	35,660	36,201
2020	34,164	27,237
2019	26,964	33,123
2018	30,844	22,151
Prior	39,560	27,170
Revolving Loans	283,204	221,799
Revolving Loans to Term Loans	0	0
Total	497,478	452,232
Commercial business loans | Pass | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Credit Quality Indicator [Line Items]
2022	47,082	84,113
2021	35,305	36,115
2020	34,044	25,156
2019	25,527	30,670
2018	27,075	21,762
Prior	39,171	26,515
Revolving Loans	274,439	210,597
Revolving Loans to Term Loans	0	0
Total	482,643	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	0	15
2020	57	1,729
2019	1,230	1,369
2018	1,081	18
Prior	41	46
Revolving Loans	3,241	3,291
Revolving Loans to Term Loans	0	0
Total	5,650	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	355	71
2020	63	352
2019	207	1,084
2018	2,688	371
Prior	348	609
Revolving Loans	5,524	7,911
Revolving Loans to Term Loans	0	0
Total	9,185	10,590
Consumer loans | Home equity loans and advances
Financing Receivable, Credit Quality Indicator [Line Items]
Total	279,976	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	21,064	22,393
2021	22,599	15,977
2020	15,021	15,906
2019	13,668	13,146
2018	12,246	12,023
Prior	92,678	101,116
Revolving Loans	102,106	95,576
Revolving Loans to Term Loans	442	426
Total	279,824	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	21,064	22,393
2021	22,599	15,977
2020	15,021	15,906
2019	13,668	13,146
2018	12,226	12,023
Prior	92,482	100,870
Revolving Loans	102,070	95,484
Revolving Loans to Term Loans	442	426
Total	279,572	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	20	0
Prior	196	246
Revolving Loans	36	92
Revolving Loans to Term Loans	0	0
Total	252	338
Consumer loans | Other consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total	2,214	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	1,388	659
2021	97	58
2020	114	284
2019	122	60
2018	36	9
Prior	121	5
Revolving Loans	336	353
Revolving Loans to Term Loans	0	0
Total	2,214	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	1,388	659
2021	97	58
2020	114	284
2019	122	60
2018	36	9
Prior	121	5
Revolving Loans	336	353
Revolving Loans to Term Loans	0	0
Total	2,214	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