Loans Receivable and Allowance for Credit Losses - Credit Quality Indicators (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Total Loans
Total	$ 7,821,548		$ 7,821,548		$ 7,839,754
Total gross charge-offs
Total	2,772	$ 2,396	8,697	$ 3,231
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	314,892		314,892		648,608
2023/2022	692,190		692,190		1,882,747
2022/2021	1,863,843		1,863,843		1,639,402
2021/2020	1,563,510		1,563,510		649,900
2020/2019	617,809		617,809		632,951
Prior	2,354,298		2,354,298		1,981,490
Revolving Loans	335,450		335,450		325,009
Revolving Loans to Term Loans	67,761		67,761		64,558
Total	7,809,753		7,809,753		7,824,665
Total gross charge-offs
2024/2023			0		0
2023/2022			62		269
2022/2021			482		280
2021/2020			3,087		34
2020/2019			0		2,342
Prior			5,066		569
Revolving Loans			0		0
Revolving Loans to Term Loans			0		0
Total			8,697		3,494
Commercial real estate | One-to-four family
Total Loans
Total	2,739,024		2,739,024		2,794,726
Total gross charge-offs
Total	0	218	2	352
Commercial real estate | One-to-four family | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	87,553		87,553		156,279
2023/2022	156,802		156,802		787,911
2022/2021	767,780		767,780		793,843
2021/2020	759,992		759,992		272,498
2020/2019	256,013		256,013		165,966
Prior	709,050		709,050		616,336
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	2,737,190		2,737,190		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
Commercial real estate | One-to-four family | Pass | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	87,553		87,553		156,279
2023/2022	156,055		156,055		786,735
2022/2021	765,664		765,664		793,074
2021/2020	758,498		758,498		272,215
2020/2019	255,413		255,413		165,337
Prior	705,269		705,269		614,351
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	2,728,452		2,728,452		2,787,991
Commercial real estate | 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
Commercial real estate | One-to-four family | Substandard | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	0		0		0
2023/2022	747		747		1,176
2022/2021	2,116		2,116		769
2021/2020	1,494		1,494		283
2020/2019	600		600		629
Prior	3,781		3,781		1,985
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	8,738		8,738		4,842
Commercial real estate | Multifamily
Total Loans
Total	1,399,000		1,399,000		1,409,187
Total gross charge-offs
Total	0	0	0	0
Commercial real estate | Multifamily | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	16,708		16,708		111,612
2023/2022	123,376		123,376		317,277
2022/2021	312,776		312,776		359,983
2021/2020	337,587		337,587		157,294
2020/2019	166,583		166,583		202,923
Prior	441,970		441,970		260,098
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	1,399,000		1,399,000		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
Commercial real estate | Multifamily | Pass | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	16,708		16,708		111,612
2023/2022	123,376		123,376		317,277
2022/2021	307,033		307,033		359,983
2021/2020	336,837		336,837		157,294
2020/2019	166,583		166,583		202,923
Prior	440,868		440,868		255,578
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	1,391,405		1,391,405		1,404,667
Commercial real estate | 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	750		750		0
2020/2019	0		0		0
Prior	0		0		4,520
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	750		750		4,520
Commercial real estate | 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	5,743		5,743		0
2021/2020	0		0		0
2020/2019	0		0		0
Prior	1,102		1,102		0
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	6,845		6,845		0
Commercial real estate | Commercial real estate
Total Loans
Total	2,322,262		2,322,262		2,389,766
Total gross charge-offs
Total	0	0	120	150
Commercial real estate | Commercial real estate | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	88,218		88,218		191,030
2023/2022	178,271		178,271		427,801
2022/2021	439,488		439,488		372,948
2021/2020	374,771		374,771		176,504
2020/2019	161,473		161,473		237,134
Prior	1,070,538		1,070,538		971,660
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	2,312,759		2,312,759		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
Commercial real estate | Commercial real estate | Pass | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	88,218		88,218		191,030
2023/2022	178,271		178,271		422,058
2022/2021	428,615		428,615		371,578
2021/2020	373,770		373,770		174,705
2020/2019	154,958		154,958		236,263
Prior	958,565		958,565		930,740
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	2,182,397		2,182,397		2,326,374
Commercial real estate | 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	1,035		1,035		465
2021/2020	1		1		0
2020/2019	2,798		2,798		871
Prior	43,947		43,947		24,405
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	47,781		47,781		25,741
Commercial real estate | 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	9,838		9,838		905
2021/2020	1,000		1,000		1,799
2020/2019	3,717		3,717		0
Prior	68,026		68,026		16,515
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	82,581		82,581		24,962
Commercial real estate | Construction
Total Loans
Total	510,439		510,439		443,094
Total gross charge-offs
Total	0	0	0	0
Commercial real estate | Construction | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	35,915		35,915		99,634
2023/2022	157,306		157,306		270,397
2022/2021	269,493		269,493		65,374
2021/2020	47,725		47,725		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	510,439		510,439		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
Commercial real estate | Construction | Pass | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	35,915		35,915		99,634
2023/2022	157,306		157,306		270,397
2022/2021	258,931		258,931		65,374
2021/2020	47,725		47,725		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	499,877		499,877		443,094
Commercial real estate | 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	5,554		5,554		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	5,554		5,554		0
Commercial real estate | 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	5,008		5,008		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	5,008		5,008		0
Commercial business loans | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	73,200		73,200		67,656
2023/2022	58,734		58,734		58,497
2022/2021	55,061		55,061		29,077
2021/2020	26,717		26,717		27,297
2020/2019	23,594		23,594		16,594
Prior	50,904		50,904		46,493
Revolving Loans	298,237		298,237		287,427
Revolving Loans to Term Loans	0		0		0
Total	586,447		586,447		533,041
Total gross charge-offs
2024/2023			0		0
2023/2022			0		0
2022/2021			364		31
2021/2020			3,033		34
2020/2019			0		2,249
Prior			4,942		304
Revolving Loans			0		0
Revolving Loans to Term Loans			0		0
Total			8,339		2,618
Commercial business loans | Pass | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	71,735		71,735		67,529
2023/2022	58,408		58,408		58,118
2022/2021	54,552		54,552		28,989
2021/2020	26,194		26,194		27,194
2020/2019	23,293		23,293		15,499
Prior	42,311		42,311		38,954
Revolving Loans	258,085		258,085		272,698
Revolving Loans to Term Loans	0		0		0
Total	534,578		534,578		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	236		236		0
2021/2020	0		0		97
2020/2019	66		66		14
Prior	767		767		1,389
Revolving Loans	8,891		8,891		4,587
Revolving Loans to Term Loans	0		0		0
Total	9,960		9,960		6,517
Commercial business loans | Substandard | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	1,465		1,465		0
2023/2022	326		326		76
2022/2021	273		273		88
2021/2020	523		523		6
2020/2019	235		235		1,081
Prior	7,428		7,428		6,150
Revolving Loans	31,261		31,261		10,142
Revolving Loans to Term Loans	0		0		0
Total	41,511		41,511		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	261,188		261,188		266,770
Total gross charge-offs
Total	0	0	0	25
Consumer loans | Home equity loans and advances | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	11,015		11,015		20,198
2023/2022	17,596		17,596		20,713
2022/2021	19,144		19,144		18,139
2021/2020	16,708		16,708		11,368
2020/2019	10,145		10,145		9,877
Prior	81,770		81,770		84,518
Revolving Loans	36,902		36,902		37,261
Revolving Loans to Term Loans	67,761		67,761		64,558
Total	261,041		261,041		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	11,015		11,015		20,198
2023/2022	17,596		17,596		20,713
2022/2021	19,144		19,144		18,139
2021/2020	16,708		16,708		11,368
2020/2019	10,145		10,145		9,877
Prior	81,599		81,599		84,261
Revolving Loans	36,902		36,902		37,261
Revolving Loans to Term Loans	67,761		67,761		64,558
Total	260,870		260,870		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	171		171		257
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	171		171		257
Consumer loans | Other consumer loans
Total Loans
Total	2,877		2,877		2,801
Total gross charge-offs
Total	76	$ 10	236	$ 86
Consumer loans | Other consumer loans | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	2,283		2,283		2,199
2023/2022	105		105		151
2022/2021	101		101		38
2021/2020	10		10		6
2020/2019	1		1		18
Prior	66		66		68
Revolving Loans	311		311		321
Revolving Loans to Term Loans	0		0		0
Total	2,877		2,877		2,801
Total gross charge-offs
2024/2023			0		0
2023/2022			62		61
2022/2021			118		52
2021/2020			54		0
2020/2019			0		0
Prior			2		2
Revolving Loans			0		0
Revolving Loans to Term Loans			0		0
Total			236		115
Consumer loans | Other consumer loans | Pass | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2024/2023	2,283		2,283		2,199
2023/2022	105		105		151
2022/2021	101		101		38
2021/2020	10		10		6
2020/2019	1		1		18
Prior	66		66		68
Revolving Loans	311		311		321
Revolving Loans to Term Loans	0		0		0
Total	2,877		2,877		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