Loans - Risk Category of Mortgage and Non-mortgage Loans (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
2024/2023	$ 332,370		$ 332,370		$ 668,603
2023/2022	680,182		680,182		1,164,733
2022/2021	1,091,546		1,091,546		706,194
2021/2020	685,651		685,651		556,884
2020/2019	517,844		517,844		727,117
Prior	3,207,386		3,207,386		2,753,051
Revolving Loans Amortized Cost Basis	290,684		290,684		319,483
Revolving Loans converted to term loans	10,481		10,481		11,834
Total loans, net of fees and costs excluding portfolio layer basis adjustments	6,816,144		6,816,144		6,907,899
Gross charge-offs
2024/2023					40
2022/2021					1,675
2020/2019					28
Prior			98		147
Revolving Loans Amortized Cost Basis			3,081		9,267
Total	3,110	$ 21	3,179	$ 11,050	11,157
Basis adjustments	(2,184)		(2,184)		949
Portfolio Layer Hedges on Closed Portfolio of Loans [Member] | Designated as Hedging Instrument [Member]
Gross charge-offs
Basis adjustments	2,200		2,200		900
Pass
2024/2023	322,936		322,936		643,427
2023/2022	669,260		669,260		1,150,854
2022/2021	1,070,929		1,070,929		694,182
2021/2020	671,146		671,146		552,523
2020/2019	498,322		498,322		685,238
Prior	3,054,630		3,054,630		2,585,019
Revolving Loans Amortized Cost Basis	283,622		283,622		303,521
Revolving Loans converted to term loans	8,350		8,350		10,067
Total loans, net of fees and costs excluding portfolio layer basis adjustments	6,579,195		6,579,195		6,624,831
Watch
2024/2023	8,704		8,704		10,072
2023/2022	4,610		4,610		11,480
2022/2021	18,188		18,188		6,227
2021/2020	7,428		7,428		4,361
2020/2019	16,750		16,750		26,149
Prior	107,573		107,573		136,956
Revolving Loans Amortized Cost Basis	2,183		2,183		8,582
Revolving Loans converted to term loans	1,534		1,534		1,130
Total loans, net of fees and costs excluding portfolio layer basis adjustments	166,970		166,970		204,957
Special Mention
2024/2023	730		730
2023/2022	5,383		5,383
2020/2019					15,637
Prior	22,344		22,344		4,206
Revolving Loans Amortized Cost Basis					495
Revolving Loans converted to term loans	157		157		169
Total loans, net of fees and costs excluding portfolio layer basis adjustments	28,614		28,614		20,507
Substandard
2024/2023					14,642
2023/2022	467		467		2,399
2022/2021	2,429		2,429		5,785
2021/2020	7,077		7,077
2020/2019	2,772		2,772		93
Prior	22,839		22,839		26,870
Revolving Loans Amortized Cost Basis	4,302		4,302		2,982
Revolving Loans converted to term loans	440		440		468
Total loans, net of fees and costs excluding portfolio layer basis adjustments	40,326		40,326		53,239
Doubtful
2024/2023					462
2023/2022	462		462
Revolving Loans Amortized Cost Basis	577		577		3,903
Total loans, net of fees and costs excluding portfolio layer basis adjustments	1,039		1,039		4,365
Multi-family Residential Portfolio Segment [Member]
2024/2023	90,888		90,888		254,340
2023/2022	248,775		248,775		465,939
2022/2021	450,935		450,935		277,203
2021/2020	285,635		285,635		217,496
2020/2019	204,856		204,856		300,822
Prior	1,356,138		1,356,138		1,141,217
Revolving Loans Amortized Cost Basis	5,614		5,614		5,209
Total loans, net of fees and costs excluding portfolio layer basis adjustments	2,642,841		2,642,841		2,662,226
Multi-family Residential Portfolio Segment [Member] | Pass
2024/2023	90,888		90,888		254,340
2023/2022	248,775		248,775		465,069
2022/2021	438,930		438,930		276,483
2021/2020	284,920		284,920		215,561
2020/2019	200,202		200,202		300,822
Prior	1,313,039		1,313,039		1,099,271
Revolving Loans Amortized Cost Basis	5,168		5,168		5,209
Total loans, net of fees and costs excluding portfolio layer basis adjustments	2,581,922		2,581,922		2,616,755
Multi-family Residential Portfolio Segment [Member] | Watch
2023/2022					870
2022/2021	12,000		12,000		720
2021/2020					1,935
2020/2019	1,882		1,882
Prior	31,112		31,112		34,899
Total loans, net of fees and costs excluding portfolio layer basis adjustments	44,994		44,994		38,424
Multi-family Residential Portfolio Segment [Member] | Special Mention
Prior	5,141		5,141		1,193
Total loans, net of fees and costs excluding portfolio layer basis adjustments	5,141		5,141		1,193
Multi-family Residential Portfolio Segment [Member] | Substandard
2022/2021	5		5
2021/2020	715		715
2020/2019	2,772		2,772
Prior	6,846		6,846		5,854
Revolving Loans Amortized Cost Basis	446		446
Total loans, net of fees and costs excluding portfolio layer basis adjustments	10,784		10,784		5,854
Commercial Real Estate [Member]
2024/2023	112,915		112,915		199,420
2023/2022	199,439		199,439		322,446
2022/2021	312,720		312,720		176,460
2021/2020	155,318		155,318		147,871
2020/2019	136,440		136,440		226,203
Prior	1,013,545		1,013,545		887,224
Total loans, net of fees and costs excluding portfolio layer basis adjustments	1,930,377		1,930,377		1,959,624
Gross charge-offs
Prior					8
Total				8	8
Commercial Real Estate [Member] | Pass
2024/2023	112,915		112,915		199,420
2023/2022	199,439		199,439		322,446
2022/2021	312,288		312,288		175,045
2021/2020	151,237		151,237		147,871
2020/2019	129,706		129,706		216,964
Prior	945,155		945,155		862,641
Total loans, net of fees and costs excluding portfolio layer basis adjustments	1,850,740		1,850,740		1,924,387
Commercial Real Estate [Member] | Watch
2022/2021	432		432		1,415
2021/2020	4,081		4,081
2020/2019	6,734		6,734		9,239
Prior	61,668		61,668		23,484
Total loans, net of fees and costs excluding portfolio layer basis adjustments	72,915		72,915		34,138
Commercial Real Estate [Member] | Special Mention
Prior	6,722		6,722		1,099
Total loans, net of fees and costs excluding portfolio layer basis adjustments	6,722		6,722		1,099
One-To-Four Family - Mixed-Use Property Portfolio Segment [Member]
2024/2023	10,516		10,516		22,852
2023/2022	23,692		23,692		43,579
2022/2021	45,880		45,880		41,604
2021/2020	40,935		40,935		30,984
2020/2019	28,193		28,193		61,261
Prior	369,088		369,088		332,804
Total loans, net of fees and costs excluding portfolio layer basis adjustments	518,304		518,304		533,084
One-To-Four Family - Mixed-Use Property Portfolio Segment [Member] | Pass
2024/2023	10,516		10,516		22,852
2023/2022	23,692		23,692		43,579
2022/2021	45,880		45,880		41,604
2021/2020	40,935		40,935		30,984
2020/2019	28,193		28,193		60,308
Prior	362,711		362,711		326,246
Total loans, net of fees and costs excluding portfolio layer basis adjustments	511,927		511,927		525,573
One-To-Four Family - Mixed-Use Property Portfolio Segment [Member] | Watch
2020/2019					233
Prior	5,355		5,355		4,777
Total loans, net of fees and costs excluding portfolio layer basis adjustments	5,355		5,355		5,010
One-To-Four Family - Mixed-Use Property Portfolio Segment [Member] | Special Mention
2020/2019					720
Prior	533		533		564
Total loans, net of fees and costs excluding portfolio layer basis adjustments	533		533		1,284
One-To-Four Family - Mixed-Use Property Portfolio Segment [Member] | Substandard
Prior	489		489		1,217
Total loans, net of fees and costs excluding portfolio layer basis adjustments	489		489		1,217
One-To-Four Family - Residential Portfolio Segment [Member]
2024/2023	2,141		2,141		6,289
2023/2022	54,837		54,837		23,704
2022/2021	23,602		23,602		8,721
2021/2020	7,780		7,780		16,482
2020/2019	16,142		16,142		38,340
Prior	130,848		130,848		108,725
Revolving Loans Amortized Cost Basis	6,575		6,575		7,424
Revolving Loans converted to term loans	10,481		10,481		11,834
Total loans, net of fees and costs excluding portfolio layer basis adjustments	252,406		252,406		221,519
Gross charge-offs
Prior			14		23
Total			14	12	23
One-To-Four Family - Residential Portfolio Segment [Member] | Pass
2024/2023	2,141		2,141		6,289
2023/2022	54,837		54,837		23,197
2022/2021	23,104		23,104		8,451
2021/2020	7,522		7,522		16,482
2020/2019	16,142		16,142		36,779
Prior	126,345		126,345		102,293
Revolving Loans Amortized Cost Basis	6,575		6,575		7,424
Revolving Loans converted to term loans	8,350		8,350		10,067
Total loans, net of fees and costs excluding portfolio layer basis adjustments	245,016		245,016		210,982
One-To-Four Family - Residential Portfolio Segment [Member] | Watch
2023/2022					507
2022/2021	498		498		270
2021/2020	258		258
2020/2019					1,561
Prior	2,580		2,580		695
Revolving Loans converted to term loans	1,534		1,534		1,130
Total loans, net of fees and costs excluding portfolio layer basis adjustments	4,870		4,870		4,163
One-To-Four Family - Residential Portfolio Segment [Member] | Special Mention
Prior	1,431		1,431
Revolving Loans converted to term loans	157		157		169
Total loans, net of fees and costs excluding portfolio layer basis adjustments	1,588		1,588		169
One-To-Four Family - Residential Portfolio Segment [Member] | Substandard
Prior	492		492		5,737
Revolving Loans converted to term loans	440		440		468
Total loans, net of fees and costs excluding portfolio layer basis adjustments	932		932		6,205
Construction Portfolio Segment
2024/2023					5,809
2023/2022	5,985		5,985		3
2022/2021	2		2		5,793
2021/2020	18,209		18,209
Revolving Loans Amortized Cost Basis	39,122		39,122		46,656
Total loans, net of fees and costs excluding portfolio layer basis adjustments	63,318		63,318		58,261
Construction Portfolio Segment | Pass
2024/2023					5,809
2023/2022	602		602		3
2022/2021	2		2		5,793
2021/2020	18,209		18,209
Revolving Loans Amortized Cost Basis	39,122		39,122		46,656
Total loans, net of fees and costs excluding portfolio layer basis adjustments	57,935		57,935		58,261
Construction Portfolio Segment | Special Mention
2023/2022	5,383		5,383
Total loans, net of fees and costs excluding portfolio layer basis adjustments	5,383		5,383
Small Business Administration Portfolio Segment [Member]
2024/2023	6,008		6,008		1,984
2023/2022	1,928		1,928		3,283
2022/2021	3,230		3,230		4,510
2021/2020	2,930		2,930		3,443
2020/2019	1,791		1,791		653
Prior	3,728		3,728		6,472
Total loans, net of fees and costs excluding portfolio layer basis adjustments	19,615		19,615		20,345
Gross charge-offs
Prior			7		7
Total	7		7	$ 7	7
Small Business Administration Portfolio Segment [Member] | Pass
2024/2023	6,008		6,008		1,984
2023/2022	1,928		1,928		3,283
2022/2021	3,230		3,230		2,883
2021/2020	1,238		1,238		3,443
2020/2019	1,791		1,791		606
Prior	1,507		1,507		2,121
Total loans, net of fees and costs excluding portfolio layer basis adjustments	15,702		15,702		14,320
Small Business Administration Portfolio Segment [Member] | Watch
2020/2019					47
Prior	840		840		2,847
Total loans, net of fees and costs excluding portfolio layer basis adjustments	840		840		2,894
Small Business Administration Portfolio Segment [Member] | Special Mention
Prior	335		335		348
Total loans, net of fees and costs excluding portfolio layer basis adjustments	335		335		348
Small Business Administration Portfolio Segment [Member] | Substandard
2022/2021					1,627
2021/2020	1,692		1,692
Prior	1,046		1,046		1,156
Total loans, net of fees and costs excluding portfolio layer basis adjustments	2,738		2,738		2,783
Commercial Business Portfolio Segment [Member]
2024/2023	58,955		58,955		131,186
2023/2022	99,338		99,338		128,643
2022/2021	82,751		82,751		61,295
2021/2020	48,062		48,062		34,063
2020/2019	25,913		25,913		45,514
Prior	106,992		106,992		84,690
Revolving Loans Amortized Cost Basis	239,068		239,068		260,105
Total loans, net of fees and costs excluding portfolio layer basis adjustments	661,079		661,079		745,496
Gross charge-offs
2024/2023					40
2022/2021					1,675
2020/2019					28
Prior			43		10
Revolving Loans Amortized Cost Basis			3,081		9,267
Total			3,124		11,020
Commercial Business Portfolio Segment [Member] | Pass
2024/2023	58,225		58,225		115,740
2023/2022	93,799		93,799		116,452
2022/2021	75,357		75,357		53,315
2021/2020	40,303		40,303		31,637
2020/2019	21,531		21,531		30,913
Prior	97,995		97,995		53,289
Revolving Loans Amortized Cost Basis	232,452		232,452		244,143
Total loans, net of fees and costs excluding portfolio layer basis adjustments	619,662		619,662		645,489
Commercial Business Portfolio Segment [Member] | Watch
2024/2023					342
2023/2022	4,610		4,610		9,792
2022/2021	4,970		4,970		3,822
2021/2020	3,089		3,089		2,426
2020/2019	4,382		4,382		14,483
Prior	5,619		5,619		18,495
Revolving Loans Amortized Cost Basis	2,183		2,183		8,582
Total loans, net of fees and costs excluding portfolio layer basis adjustments	24,853		24,853		57,942
Commercial Business Portfolio Segment [Member] | Special Mention
2024/2023	730		730
2020/2019					25
Prior	18		18
Revolving Loans Amortized Cost Basis					495
Total loans, net of fees and costs excluding portfolio layer basis adjustments	748		748		520
Commercial Business Portfolio Segment [Member] | Substandard
2024/2023					14,642
2023/2022	467		467		2,399
2022/2021	2,424		2,424		4,158
2021/2020	4,670		4,670
2020/2019					93
Prior	3,360		3,360		12,906
Revolving Loans Amortized Cost Basis	3,856		3,856		2,982
Total loans, net of fees and costs excluding portfolio layer basis adjustments	14,777		14,777		37,180
Commercial Business Portfolio Segment [Member] | Doubtful
2024/2023					462
2023/2022	462		462
Revolving Loans Amortized Cost Basis	577		577		3,903
Total loans, net of fees and costs excluding portfolio layer basis adjustments	1,039		1,039		4,365
Commercial Business Secured By Portfolio Segment [member]
2024/2023	50,947		50,947		46,723
2023/2022	46,188		46,188		177,136
2022/2021	172,426		172,426		130,608
2021/2020	126,782		126,782		106,545
2020/2019	104,509		104,509		54,324
Prior	226,969		226,969		191,786
Revolving Loans Amortized Cost Basis	189		189
Total loans, net of fees and costs excluding portfolio layer basis adjustments	728,010		728,010		707,122
Commercial Business Secured By Portfolio Segment [member] | Pass
2024/2023	42,243		42,243		36,993
2023/2022	46,188		46,188		176,825
2022/2021	172,138		172,138		130,608
2021/2020	126,782		126,782		106,545
2020/2019	100,757		100,757		38,846
Prior	207,800		207,800		139,025
Revolving Loans Amortized Cost Basis	189		189
Total loans, net of fees and costs excluding portfolio layer basis adjustments	696,097		696,097		628,842
Commercial Business Secured By Portfolio Segment [member] | Watch
2024/2023	8,704		8,704		9,730
2023/2022					311
2022/2021	288		288
2020/2019	3,752		3,752		586
Prior	399		399		51,759
Total loans, net of fees and costs excluding portfolio layer basis adjustments	13,143		13,143		62,386
Commercial Business Secured By Portfolio Segment [member] | Special Mention
2020/2019					14,892
Prior	14,886		14,886		1,002
Total loans, net of fees and costs excluding portfolio layer basis adjustments	14,886		14,886		15,894
Commercial Business Secured By Portfolio Segment [member] | Substandard
Prior	3,884		3,884
Total loans, net of fees and costs excluding portfolio layer basis adjustments	3,884		3,884
Other Portfolio Segment [Member]
Prior	78		78		133
Revolving Loans Amortized Cost Basis	116		116		89
Total loans, net of fees and costs excluding portfolio layer basis adjustments	194		194		222
Gross charge-offs
Prior			34		99
Total			34		99
Other Portfolio Segment [Member] | Pass
Prior	78		78		133
Revolving Loans Amortized Cost Basis	116		116		89
Total loans, net of fees and costs excluding portfolio layer basis adjustments	194		194		222
Consumer Portfolio Segment [Member]
Mortgage loans in process of foreclosure, amount	$ 1,800		$ 1,800		$ 4,800