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, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Total Loans
Total	$ 7,725,645		$ 7,725,645		$ 7,641,593
Total gross charge-offs
Total	555	$ 128	836	$ 185
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2023	361,007		361,007		1,836,787
2022	1,845,749		1,845,749		1,697,890
2021	1,672,850		1,672,850		710,769
2020	673,999		673,999		694,400
2019	654,228		654,228		451,367
Prior	2,111,522		2,111,522		1,831,970
Revolving Loans	389,757		389,757		400,894
Revolving Loans to Term Loans	426		426		457
Total	7,709,538		7,709,538		7,624,534
Total gross charge-offs
2023			0		10
2022			38		18
2021			69		50
2020			17		143
2019			314		151
Prior			398		266
Revolving Loans			0		0
Revolving Loans to Term Loans			0		0
Total			836		638
Real estate loans | One-to-four family
Total Loans
Total	2,791,201		2,791,201		2,862,342
Total gross charge-offs
Total	0	93	134	93
Real estate loans | One-to-four family | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2023	44,275		44,275		829,363
2022	797,747		797,747		836,996
2021	820,234		820,234		294,721
2020	286,132		286,132		177,795
2019	172,214		172,214		125,377
Prior	668,667		668,667		595,932
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	2,789,269		2,789,269		2,860,184
Total gross charge-offs
2023			0		0
2022			0		0
2021			0		50
2020			0		0
2019			0		122
Prior			134		210
Revolving Loans			0		0
Revolving Loans to Term Loans			0		0
Total			134		382
Real estate loans | One-to-four family | Pass | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2023	44,275		44,275		829,363
2022	797,301		797,301		836,355
2021	818,807		818,807		294,721
2020	285,977		285,977		177,114
2019	171,383		171,383		125,057
Prior	667,095		667,095		595,097
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	2,784,838		2,784,838		2,857,707
Real estate loans | One-to-four family | Special mention | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2023	0		0		0
2022	0		0		0
2021	0		0		0
2020	0		0		0
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
2023	0		0		0
2022	446		446		641
2021	1,427		1,427		0
2020	155		155		681
2019	831		831		320
Prior	1,572		1,572		835
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	4,431		4,431		2,477
Real estate loans | Multifamily
Total Loans
Total	1,376,999		1,376,999		1,239,207
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
2023	96,325		96,325		315,157
2022	324,248		324,248		309,611
2021	353,124		353,124		167,955
2020	161,470		161,470		205,608
2019	205,147		205,147		38,849
Prior	236,685		236,685		202,027
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	1,376,999		1,376,999		1,239,207
Total gross charge-offs
2023			0		0
2022			0		0
2021			0		0
2020			0		0
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
2023	96,325		96,325		315,157
2022	324,248		324,248		309,611
2021	353,124		353,124		167,955
2020	161,470		161,470		205,608
2019	205,147		205,147		38,849
Prior	232,156		232,156		197,489
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	1,372,470		1,372,470		1,234,669
Real estate loans | Multifamily | Special mention | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2023	0		0		0
2022	0		0		0
2021	0		0		0
2020	0		0		0
2019	0		0		0
Prior	4,529		4,529		4,538
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	4,529		4,529		4,538
Real estate loans | Multifamily | Substandard | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2023	0		0		0
2022	0		0		0
2021	0		0		0
2020	0		0		0
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 | Commercial real estate
Total Loans
Total	2,399,479		2,399,479		2,426,510
Total gross charge-offs
Total	64	0	150	0
Real estate loans | Commercial real estate | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2023	142,915		142,915		448,313
2022	417,584		417,584		393,167
2021	372,455		372,455		173,254
2020	179,530		179,530		262,767
2019	245,264		245,264		247,366
Prior	1,029,148		1,029,148		888,527
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	2,386,896		2,386,896		2,413,394
Total gross charge-offs
2023			0		0
2022			0		0
2021			0		0
2020			0		0
2019			64		0
Prior			86		0
Revolving Loans			0		0
Revolving Loans to Term Loans			0		0
Total			150		0
Real estate loans | Commercial real estate | Pass | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2023	142,915		142,915		448,313
2022	417,584		417,584		392,689
2021	371,983		371,983		170,125
2020	176,425		176,425		260,268
2019	242,775		242,775		231,868
Prior	976,884		976,884		852,104
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	2,328,566		2,328,566		2,355,367
Real estate loans | Commercial real estate | Special mention | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2023	0		0		0
2022	0		0		478
2021	472		472		1,843
2020	0		0		892
2019	882		882		15,498
Prior	45,379		45,379		20,939
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	46,733		46,733		39,650
Real estate loans | Commercial real estate | Substandard | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2023	0		0		0
2022	0		0		0
2021	0		0		1,286
2020	3,105		3,105		1,607
2019	1,607		1,607		0
Prior	6,885		6,885		15,484
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	11,597		11,597		18,377
Real estate loans | Construction
Total Loans
Total	380,028		380,028		337,593
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
2023	34,856		34,856		159,751
2022	231,792		231,792		104,339
2021	75,358		75,358		28,058
2020	4,933		4,933		14,216
2019	1,321		1,321		870
Prior	30,728		30,728		29,319
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	378,988		378,988		336,553
Total gross charge-offs
2023			0		0
2022			0		0
2021			0		0
2020			0		0
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
2023	34,856		34,856		159,751
2022	231,792		231,792		104,339
2021	75,358		75,358		28,058
2020	4,933		4,933		14,216
2019	1,321		1,321		870
Prior	30,728		30,728		29,319
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	378,988		378,988		336,553
Real estate loans | Construction | Special mention | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2023	0		0		0
2022	0		0		0
2021	0		0		0
2020	0		0		0
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
2023	0		0		0
2022	0		0		0
2021	0		0		0
2020	0		0		0
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
Total Loans
Total	505,933		505,933		497,965
Total gross charge-offs
Total	450	35	450	62
Commercial business loans | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2023	31,917		31,917		58,631
2022	52,202		52,202		33,214
2021	32,551		32,551		32,911
2020	29,675		29,675		21,842
2019	19,034		19,034		27,749
Prior	54,360		54,360		27,630
Revolving Loans	285,785		285,785		295,492
Revolving Loans to Term Loans	0		0		0
Total	505,524		505,524		497,469
Total gross charge-offs
2023			0		0
2022			0		0
2021			31		0
2020			17		143
2019			250		29
Prior			152		18
Revolving Loans			0		0
Revolving Loans to Term Loans			0		0
Total			450		190
Commercial business loans | Pass | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2023	31,917		31,917		58,631
2022	51,978		51,978		32,880
2021	32,165		32,165		32,788
2020	29,608		29,608		20,705
2019	17,981		17,981		24,634
Prior	47,252		47,252		27,277
Revolving Loans	271,516		271,516		280,857
Revolving Loans to Term Loans	0		0		0
Total	482,417		482,417		477,772
Commercial business loans | Special mention | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2023	0		0		0
2022	148		148		110
2021	70		70		63
2020	42		42		1,137
2019	551		551		1,030
Prior	959		959		38
Revolving Loans	6,700		6,700		10,761
Revolving Loans to Term Loans	0		0		0
Total	8,470		8,470		13,139
Commercial business loans | Substandard | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2023	0		0		0
2022	76		76		224
2021	316		316		60
2020	25		25		0
2019	502		502		2,085
Prior	6,149		6,149		315
Revolving Loans	7,569		7,569		3,874
Revolving Loans to Term Loans	0		0		0
Total	14,637		14,637		6,558
Consumer loans | Home equity loans and advances
Total Loans
Total	269,453		269,453		274,551
Total gross charge-offs
Total	0	0	26	27
Consumer loans | Home equity loans and advances | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2023	8,893		8,893		22,903
2022	21,990		21,990		20,476
2021	19,072		19,072		13,770
2020	12,245		12,245		12,070
2019	11,196		11,196		11,126
Prior	91,837		91,837		88,439
Revolving Loans	103,651		103,651		105,061
Revolving Loans to Term Loans	426		426		457
Total	269,310		269,310		274,302
Total gross charge-offs
2023			0		0
2022			0		0
2021			0		0
2020			0		0
2019			0		0
Prior			26		33
Revolving Loans			0		0
Revolving Loans to Term Loans			0		0
Total			26		33
Consumer loans | Home equity loans and advances | Pass | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2023	8,893		8,893		22,903
2022	21,990		21,990		20,476
2021	19,072		19,072		13,770
2020	12,245		12,245		12,070
2019	11,196		11,196		11,126
Prior	91,591		91,591		88,251
Revolving Loans	103,638		103,638		105,005
Revolving Loans to Term Loans	426		426		457
Total	269,051		269,051		274,058
Consumer loans | Home equity loans and advances | Special mention | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2023	0		0		0
2022	0		0		0
2021	0		0		0
2020	0		0		0
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
2023	0		0		0
2022	0		0		0
2021	0		0		0
2020	0		0		0
2019	0		0		0
Prior	246		246		188
Revolving Loans	13		13		56
Revolving Loans to Term Loans	0		0		0
Total	259		259		244
Consumer loans | Other consumer loans
Total Loans
Total	2,552		2,552		3,425
Total gross charge-offs
Total	41	$ 0	76	$ 3
Consumer loans | Other consumer loans | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2023	1,826		1,826		2,669
2022	186		186		87
2021	56		56		100
2020	14		14		102
2019	52		52		30
Prior	97		97		96
Revolving Loans	321		321		341
Revolving Loans to Term Loans	0		0		0
Total	2,552		2,552		3,425
Total gross charge-offs
2023			0		10
2022			38		18
2021			38		0
2020			0		0
2019			0		0
Prior			0		5
Revolving Loans			0		0
Revolving Loans to Term Loans			0		0
Total			76		33
Consumer loans | Other consumer loans | Pass | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2023	1,826		1,826		2,669
2022	186		186		87
2021	56		56		100
2020	14		14		102
2019	52		52		30
Prior	84		84		96
Revolving Loans	321		321		341
Revolving Loans to Term Loans	0		0		0
Total	2,539		2,539		3,425
Consumer loans | Other consumer loans | Special mention | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Total Loans
2023	0		0		0
2022	0		0		0
2021	0		0		0
2020	0		0		0
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
2023	0		0		0
2022	0		0		0
2021	0		0		0
2020	0		0		0
2019	0		0		0
Prior	13		13		0
Revolving Loans	0		0		0
Revolving Loans to Term Loans	0		0		0
Total	$ 13		$ 13		$ 0