Loans Receivable and Allowance for Credit Losses - Credit Quality Indicators (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Total Loans
Total	$ 7,782,659		$ 7,782,659		$ 7,839,754
Total gross charge-offs
Total	803	$ 555	5,925	$ 836
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	198,168		198,168		648,608
2023/2022	666,614		666,614		1,882,747
2022/2021	1,875,907		1,875,907		1,639,402
2021/2020	1,579,286		1,579,286		649,900
2020/2019	627,266		627,266		632,951
Prior	2,429,478		2,429,478		1,981,490
Revolving Loans	326,953		326,953		325,009
Revolving Loans to Term Loans	66,837		66,837		64,558
Total	7,770,509		7,770,509		7,824,665
Total gross charge-offs
2024/2023			0		0
2023/2022			32		269
2022/2021			95		280
2021/2020			2,384		34
2020/2019			0		2,342
Prior			3,414		569
Revolving Loans			0		0
Revolving Loans to Term Loans			0		0
Total			5,925		3,494
Real estate loans | One-to-four family
Total Loans
Total	2,766,030		2,766,030		2,794,726
Total gross charge-offs
Total	0	0	2	134
Real estate loans | One-to-four family | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	57,856		57,856		156,279
2023/2022	157,089		157,089		787,911
2022/2021	782,087		782,087		793,843
2021/2020	772,144		772,144		272,498
2020/2019	261,321		261,321		165,966
Prior	733,680		733,680		616,336
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	2,764,177		2,764,177		2,792,833
Total gross charge-offs
2024/2023			0		0
2023/2022			0		208
2022/2021			0		197
2021/2020			0		0
2020/2019			0		29
Prior			2		151
Revolving Loans			0		0
Revolving Loans to Term Loans			0		0
Total			2		585
Real estate loans | One-to-four family | Pass | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	57,856		57,856		156,279
2023/2022	156,340		156,340		786,735
2022/2021	780,416		780,416		793,074
2021/2020	770,807		770,807		272,215
2020/2019	260,718		260,718		165,337
Prior	730,906		730,906		614,351
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	2,757,043		2,757,043		2,787,991
Real estate loans | One-to-four family | Special mention | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	0		0		0
2023/2022	0		0		0
2022/2021	0		0		0
2021/2020	0		0		0
2020/2019	0		0		0
Prior	0		0		0
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	0		0		0
Real estate loans | One-to-four family | Substandard | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	0		0		0
2023/2022	749		749		1,176
2022/2021	1,671		1,671		769
2021/2020	1,337		1,337		283
2020/2019	603		603		629
Prior	2,774		2,774		1,985
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	7,134		7,134		4,842
Real estate loans | Multifamily
Total Loans
Total	1,409,316		1,409,316		1,409,187
Total gross charge-offs
Total	0	0	0	0
Real estate loans | Multifamily | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	6,948		6,948		111,612
2023/2022	116,125		116,125		317,277
2022/2021	323,476		323,476		359,983
2021/2020	344,834		344,834		157,294
2020/2019	167,286		167,286		202,923
Prior	450,647		450,647		260,098
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	1,409,316		1,409,316		1,409,187
Total gross charge-offs
2024/2023			0		0
2023/2022			0		0
2022/2021			0		0
2021/2020			0		0
2020/2019			0		0
Prior			0		0
Revolving Loans			0		0
Revolving Loans to Term Loans			0		0
Total			0		0
Real estate loans | Multifamily | Pass | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	6,948		6,948		111,612
2023/2022	116,125		116,125		317,277
2022/2021	323,476		323,476		359,983
2021/2020	344,834		344,834		157,294
2020/2019	167,286		167,286		202,923
Prior	444,915		444,915		255,578
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	1,403,584		1,403,584		1,404,667
Real estate loans | Multifamily | Special mention | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	0		0		0
2023/2022	0		0		0
2022/2021	0		0		0
2021/2020	0		0		0
2020/2019	0		0		0
Prior	4,511		4,511		4,520
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	4,511		4,511		4,520
Real estate loans | Multifamily | Substandard | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	0		0		0
2023/2022	0		0		0
2022/2021	0		0		0
2021/2020	0		0		0
2020/2019	0		0		0
Prior	1,221		1,221		0
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	1,221		1,221		0
Real estate loans | Commercial real estate
Total Loans
Total	2,326,075		2,326,075		2,389,766
Total gross charge-offs
Total	120	64	120	150
Real estate loans | Commercial real estate | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	67,199		67,199		191,030
2023/2022	178,405		178,405		427,801
2022/2021	433,594		433,594		372,948
2021/2020	369,649		369,649		176,504
2020/2019	163,182		163,182		237,134
Prior	1,104,223		1,104,223		971,660
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	2,316,252		2,316,252		2,377,077
Total gross charge-offs
2024/2023			0		0
2023/2022			0		0
2022/2021			0		0
2021/2020			0		0
2020/2019			0		64
Prior			120		86
Revolving Loans			0		0
Revolving Loans to Term Loans			0		0
Total			120		150
Real estate loans | Commercial real estate | Pass | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	67,199		67,199		191,030
2023/2022	178,405		178,405		422,058
2022/2021	420,779		420,779		371,578
2021/2020	369,648		369,648		174,705
2020/2019	156,603		156,603		236,263
Prior	1,027,279		1,027,279		930,740
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	2,219,913		2,219,913		2,326,374
Real estate loans | Commercial real estate | Special mention | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	0		0		0
2023/2022	0		0		0
2022/2021	1,443		1,443		465
2021/2020	1		1		0
2020/2019	2,819		2,819		871
Prior	25,494		25,494		24,405
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	29,757		29,757		25,741
Real estate loans | Commercial real estate | Substandard | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	0		0		0
2023/2022	0		0		5,743
2022/2021	11,372		11,372		905
2021/2020	0		0		1,799
2020/2019	3,760		3,760		0
Prior	51,450		51,450		16,515
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	66,582		66,582		24,962
Real estate loans | Construction
Total Loans
Total	462,880		462,880		443,094
Total gross charge-offs
Total	0	0	0	0
Real estate loans | Construction | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	20,757		20,757		99,634
2023/2022	137,704		137,704		270,397
2022/2021	257,764		257,764		65,374
2021/2020	46,655		46,655		4,933
2020/2019	0		0		439
Prior	0		0		2,317
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	462,880		462,880		443,094
Total gross charge-offs
2024/2023			0		0
2023/2022			0		0
2022/2021			0		0
2021/2020			0		0
2020/2019			0		0
Prior			0		0
Revolving Loans			0		0
Revolving Loans to Term Loans			0		0
Total			0		0
Real estate loans | Construction | Pass | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	20,757		20,757		99,634
2023/2022	137,704		137,704		270,397
2022/2021	257,764		257,764		65,374
2021/2020	46,655		46,655		4,933
2020/2019	0		0		439
Prior	0		0		2,317
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	462,880		462,880		443,094
Real estate loans | Construction | Special mention | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	0		0		0
2023/2022	0		0		0
2022/2021	0		0		0
2021/2020	0		0		0
2020/2019	0		0		0
Prior	0		0		0
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	0		0		0
Real estate loans | Construction | Substandard | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	0		0		0
2023/2022	0		0		0
2022/2021	0		0		0
2021/2020	0		0		0
2020/2019	0		0		0
Prior	0		0		0
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	0		0		0
Commercial business loans | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	36,609		36,609		67,656
2023/2022	58,572		58,572		58,497
2022/2021	59,006		59,006		29,077
2021/2020	28,788		28,788		27,297
2020/2019	24,763		24,763		16,594
Prior	55,695		55,695		46,493
Revolving Loans	291,335		291,335		287,427
Revolving Loans to Term Loans	0		0		0
Total	554,768		554,768		533,041
Total gross charge-offs
2024/2023			0		0
2023/2022			0		0
2022/2021			0		31
2021/2020			2,352		34
2020/2019			0		2,249
Prior			3,291		304
Revolving Loans			0		0
Revolving Loans to Term Loans			0		0
Total			5,643		2,618
Commercial business loans | Pass | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	36,609		36,609		67,529
2023/2022	58,214		58,214		58,118
2022/2021	56,977		56,977		28,989
2021/2020	28,712		28,712		27,194
2020/2019	24,450		24,450		15,499
Prior	47,279		47,279		38,954
Revolving Loans	267,253		267,253		272,698
Revolving Loans to Term Loans	0		0		0
Total	519,494		519,494		508,981
Commercial business loans | Special mention | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	0		0		127
2023/2022	0		0		303
2022/2021	1,447		1,447		0
2021/2020	0		0		97
2020/2019	273		273		14
Prior	835		835		1,389
Revolving Loans	8,022		8,022		4,587
Revolving Loans to Term Loans	0		0		0
Total	10,577		10,577		6,517
Commercial business loans | Substandard | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	0		0		0
2023/2022	358		358		76
2022/2021	582		582		88
2021/2020	76		76		6
2020/2019	40		40		1,081
Prior	7,183		7,183		6,150
Revolving Loans	16,060		16,060		10,142
Revolving Loans to Term Loans	0		0		0
Total	24,299		24,299		17,543
Commercial business loans | Doubtful | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	0		0
2023/2022	0		0
2022/2021	0		0
2021/2020	0		0
2020/2019	0		0
Prior	398		398
Revolving Loans	0		0
Revolving Loans to Term Loans	0		0
Total	398		398
Consumer loans | Home equity loans and advances
Total Loans
Total	260,574		260,574		266,770
Total gross charge-offs
Total	0	0	0	26
Consumer loans | Home equity loans and advances | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	6,756		6,756		20,198
2023/2022	18,596		18,596		20,713
2022/2021	19,862		19,862		18,139
2021/2020	17,202		17,202		11,368
2020/2019	10,712		10,712		9,877
Prior	85,166		85,166		84,518
Revolving Loans	35,296		35,296		37,261
Revolving Loans to Term Loans	66,837		66,837		64,558
Total	260,427		260,427		266,632
Total gross charge-offs
2024/2023			0		0
2023/2022			0		0
2022/2021			0		0
2021/2020			0		0
2020/2019			0		0
Prior			0		26
Revolving Loans			0		0
Revolving Loans to Term Loans			0		0
Total			0		26
Consumer loans | Home equity loans and advances | Pass | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	6,756		6,756		20,198
2023/2022	18,596		18,596		20,713
2022/2021	19,862		19,862		18,139
2021/2020	17,202		17,202		11,368
2020/2019	10,712		10,712		9,877
Prior	84,990		84,990		84,261
Revolving Loans	35,296		35,296		37,261
Revolving Loans to Term Loans	66,837		66,837		64,558
Total	260,251		260,251		266,375
Consumer loans | Home equity loans and advances | Special mention | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	0		0		0
2023/2022	0		0		0
2022/2021	0		0		0
2021/2020	0		0		0
2020/2019	0		0		0
Prior	0		0		0
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	0		0		0
Consumer loans | Home equity loans and advances | Substandard | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	0		0		0
2023/2022	0		0		0
2022/2021	0		0		0
2021/2020	0		0		0
2020/2019	0		0		0
Prior	176		176		257
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	176		176		257
Consumer loans | Other consumer loans
Total Loans
Total	2,689		2,689		2,801
Total gross charge-offs
Total	60	$ 41	160	$ 76
Consumer loans | Other consumer loans | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	2,043		2,043		2,199
2023/2022	123		123		151
2022/2021	118		118		38
2021/2020	14		14		6
2020/2019	2		2		18
Prior	67		67		68
Revolving Loans	322		322		321
Revolving Loans to Term Loans	0		0		0
Total	2,689		2,689		2,801
Total gross charge-offs
2024/2023			0		0
2023/2022			32		61
2022/2021			95		52
2021/2020			32		0
2020/2019			0		0
Prior			1		2
Revolving Loans			0		0
Revolving Loans to Term Loans			0		0
Total			160		115
Consumer loans | Other consumer loans | Pass | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	2,043		2,043		2,199
2023/2022	123		123		151
2022/2021	118		118		38
2021/2020	14		14		6
2020/2019	2		2		18
Prior	67		67		68
Revolving Loans	322		322		321
Revolving Loans to Term Loans	0		0		0
Total	2,689		2,689		2,801
Consumer loans | Other consumer loans | Special mention | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	0		0		0
2023/2022	0		0		0
2022/2021	0		0		0
2021/2020	0		0		0
2020/2019	0		0		0
Prior	0		0		0
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	0		0		0
Consumer loans | Other consumer loans | Substandard | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	0		0		0
2023/2022	0		0		0
2022/2021	0		0		0
2021/2020	0		0		0
2020/2019	0		0		0
Prior	0		0		0
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	$ 0		$ 0		$ 0