Loans - Risk Category of Mortgage and Non-mortgage Loans (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
2024/2023	$ 43,945		$ 668,603
2023/2022	711,351		1,164,733
2022/2021	1,134,880		706,194
2021/2020	696,582		556,884
2020/2019	534,020		727,117
Prior	3,390,097		2,753,051
Revolving Loans Amortized Cost Basis	306,282		319,483
Revolving Loans converted to term loans	11,120		11,834
Total loans, net of fees and costs excluding portfolio layer basis adjustments	6,828,277		6,907,899
Gross charge-offs
2024/2023			40
2022/2021			1,675
2020/2019			28
Prior	58		147
Revolving Loans Amortized Cost Basis			9,267
Total	58	$ 9,298	11,157
Basis adjustments	6,334		949
Portfolio Layer Hedges on Closed Portfolio of Loans [Member] | Designated as Hedging Instrument [Member]
Gross charge-offs
Basis adjustments	6,300		900
Pass
2024/2023	43,945		643,427
2023/2022	700,546		1,150,854
2022/2021	1,118,313		694,182
2021/2020	680,958		552,523
2020/2019	516,276		685,238
Prior	3,157,974		2,585,019
Revolving Loans Amortized Cost Basis	293,846		303,521
Revolving Loans converted to term loans	9,441		10,067
Total loans, net of fees and costs excluding portfolio layer basis adjustments	6,521,299		6,624,831
Watch
2024/2023			10,072
2023/2022	9,965		11,480
2022/2021	8,624		6,227
2021/2020	9,608		4,361
2020/2019	15,030		26,149
Prior	196,805		136,956
Revolving Loans Amortized Cost Basis	5,398		8,582
Revolving Loans converted to term loans	1,027		1,130
Total loans, net of fees and costs excluding portfolio layer basis adjustments	246,457		204,957
Special Mention
2022/2021	5,516
2020/2019	2,714		15,637
Prior	17,571		4,206
Revolving Loans Amortized Cost Basis			495
Revolving Loans converted to term loans	209		169
Total loans, net of fees and costs excluding portfolio layer basis adjustments	26,010		20,507
Substandard
2024/2023			14,642
2023/2022	378		2,399
2022/2021	2,427		5,785
2021/2020	6,016
2020/2019			93
Prior	17,747		26,870
Revolving Loans Amortized Cost Basis	3,380		2,982
Revolving Loans converted to term loans	443		468
Total loans, net of fees and costs excluding portfolio layer basis adjustments	30,391		53,239
Doubtful
2024/2023			462
2023/2022	462
Revolving Loans Amortized Cost Basis	3,658		3,903
Total loans, net of fees and costs excluding portfolio layer basis adjustments	4,120		4,365
Multi-family Residential Portfolio Segment [Member]
2024/2023	11,694		254,340
2023/2022	253,688		465,939
2022/2021	463,924		277,203
2021/2020	274,790		217,496
2020/2019	211,325		300,822
Prior	1,405,690		1,141,217
Revolving Loans Amortized Cost Basis	5,156		5,209
Total loans, net of fees and costs excluding portfolio layer basis adjustments	2,626,267		2,662,226
Multi-family Residential Portfolio Segment [Member] | Pass
2024/2023	11,694		254,340
2023/2022	253,688		465,069
2022/2021	458,919		276,483
2021/2020	274,074		215,561
2020/2019	206,697		300,822
Prior	1,364,119		1,099,271
Revolving Loans Amortized Cost Basis	4,711		5,209
Total loans, net of fees and costs excluding portfolio layer basis adjustments	2,573,902		2,616,755
Multi-family Residential Portfolio Segment [Member] | Watch
2023/2022			870
2022/2021			720
2021/2020	716		1,935
2020/2019	1,914
Prior	35,077		34,899
Revolving Loans Amortized Cost Basis	445
Total loans, net of fees and costs excluding portfolio layer basis adjustments	38,152		38,424
Multi-family Residential Portfolio Segment [Member] | Special Mention
2022/2021	5,005
2020/2019	2,714
Prior	644		1,193
Total loans, net of fees and costs excluding portfolio layer basis adjustments	8,363		1,193
Multi-family Residential Portfolio Segment [Member] | Substandard
Prior	5,850		5,854
Total loans, net of fees and costs excluding portfolio layer basis adjustments	5,850		5,854
Commercial Real Estate [Member]
2024/2023	10,059		199,420
2023/2022	198,620		322,446
2022/2021	321,015		176,460
2021/2020	175,431		147,871
2020/2019	137,224		226,203
Prior	1,084,200		887,224
Total loans, net of fees and costs excluding portfolio layer basis adjustments	1,926,549		1,959,624
Gross charge-offs
Prior			8
Total			8
Commercial Real Estate [Member] | Pass
2024/2023	10,059		199,420
2023/2022	198,620		322,446
2022/2021	320,578		175,045
2021/2020	174,072		147,871
2020/2019	130,344		216,964
Prior	1,006,197		862,641
Total loans, net of fees and costs excluding portfolio layer basis adjustments	1,839,870		1,924,387
Commercial Real Estate [Member] | Watch
2022/2021	437		1,415
2021/2020	1,359
2020/2019	6,880		9,239
Prior	77,855		23,484
Total loans, net of fees and costs excluding portfolio layer basis adjustments	86,531		34,138
Commercial Real Estate [Member] | Special Mention
Prior	148		1,099
Total loans, net of fees and costs excluding portfolio layer basis adjustments	148		1,099
One-To-Four Family - Mixed-Use Property Portfolio Segment [Member]
2024/2023	763		22,852
2023/2022	22,750		43,579
2022/2021	42,836		41,604
2021/2020	41,201		30,984
2020/2019	29,456		61,261
Prior	381,849		332,804
Total loans, net of fees and costs excluding portfolio layer basis adjustments	518,855		533,084
One-To-Four Family - Mixed-Use Property Portfolio Segment [Member] | Pass
2024/2023	763		22,852
2023/2022	22,750		43,579
2022/2021	42,836		41,604
2021/2020	41,201		30,984
2020/2019	29,456		60,308
Prior	374,421		326,246
Total loans, net of fees and costs excluding portfolio layer basis adjustments	511,427		525,573
One-To-Four Family - Mixed-Use Property Portfolio Segment [Member] | Watch
2020/2019			233
Prior	5,033		4,777
Total loans, net of fees and costs excluding portfolio layer basis adjustments	5,033		5,010
One-To-Four Family - Mixed-Use Property Portfolio Segment [Member] | Special Mention
2020/2019			720
Prior	1,248		564
Total loans, net of fees and costs excluding portfolio layer basis adjustments	1,248		1,284
One-To-Four Family - Mixed-Use Property Portfolio Segment [Member] | Substandard
Prior	1,147		1,217
Total loans, net of fees and costs excluding portfolio layer basis adjustments	1,147		1,217
One-To-Four Family - Residential Portfolio Segment [Member]
2024/2023			6,289
2023/2022	56,782		23,704
2022/2021	23,891		8,721
2021/2020	8,662		16,482
2020/2019	16,367		38,340
Prior	142,703		108,725
Revolving Loans Amortized Cost Basis	7,550		7,424
Revolving Loans converted to term loans	11,120		11,834
Total loans, net of fees and costs excluding portfolio layer basis adjustments	267,075		221,519
Gross charge-offs
Prior	14		23
Total	14	6	23
One-To-Four Family - Residential Portfolio Segment [Member] | Pass
2024/2023			6,289
2023/2022	56,782		23,197
2022/2021	23,380		8,451
2021/2020	8,396		16,482
2020/2019	16,367		36,779
Prior	135,207		102,293
Revolving Loans Amortized Cost Basis	7,550		7,424
Revolving Loans converted to term loans	9,441		10,067
Total loans, net of fees and costs excluding portfolio layer basis adjustments	257,123		210,982
One-To-Four Family - Residential Portfolio Segment [Member] | Watch
2023/2022			507
2022/2021			270
2021/2020	266
2020/2019			1,561
Prior	2,321		695
Revolving Loans converted to term loans	1,027		1,130
Total loans, net of fees and costs excluding portfolio layer basis adjustments	3,614		4,163
One-To-Four Family - Residential Portfolio Segment [Member] | Special Mention
2022/2021	511
Revolving Loans converted to term loans	209		169
Total loans, net of fees and costs excluding portfolio layer basis adjustments	720		169
One-To-Four Family - Residential Portfolio Segment [Member] | Substandard
Prior	5,175		5,737
Revolving Loans converted to term loans	443		468
Total loans, net of fees and costs excluding portfolio layer basis adjustments	5,618		6,205
Construction Portfolio Segment
2024/2023			5,809
2023/2022	6,083		3
2022/2021	3		5,793
2021/2020	5,793
Revolving Loans Amortized Cost Basis	48,262		46,656
Total loans, net of fees and costs excluding portfolio layer basis adjustments	60,141		58,261
Construction Portfolio Segment | Pass
2024/2023			5,809
2023/2022	6,083		3
2022/2021	3		5,793
Revolving Loans Amortized Cost Basis	48,262		46,656
Total loans, net of fees and costs excluding portfolio layer basis adjustments	54,348		58,261
Construction Portfolio Segment | Watch
2021/2020	5,793
Total loans, net of fees and costs excluding portfolio layer basis adjustments	5,793
Small Business Administration Portfolio Segment [Member]
2024/2023			1,984
2023/2022	1,966		3,283
2022/2021	3,265		4,510
2021/2020	3,026		3,443
2020/2019	2,031		653
Prior	6,154		6,472
Total loans, net of fees and costs excluding portfolio layer basis adjustments	16,442		20,345
Gross charge-offs
Prior			7
Total		$ 6	7
Small Business Administration Portfolio Segment [Member] | Pass
2024/2023			1,984
2023/2022	1,966		3,283
2022/2021	3,265		2,883
2021/2020	1,333		3,443
2020/2019	2,031		606
Prior	1,792		2,121
Total loans, net of fees and costs excluding portfolio layer basis adjustments	10,387		14,320
Small Business Administration Portfolio Segment [Member] | Watch
2020/2019			47
Prior	2,864		2,847
Total loans, net of fees and costs excluding portfolio layer basis adjustments	2,864		2,894
Small Business Administration Portfolio Segment [Member] | Special Mention
Prior	343		348
Total loans, net of fees and costs excluding portfolio layer basis adjustments	343		348
Small Business Administration Portfolio Segment [Member] | Substandard
2022/2021			1,627
2021/2020	1,693
Prior	1,155		1,156
Total loans, net of fees and costs excluding portfolio layer basis adjustments	2,848		2,783
Commercial Business Portfolio Segment [Member]
2024/2023	15,773		131,186
2023/2022	124,903		128,643
2022/2021	104,051		61,295
2021/2020	58,167		34,063
2020/2019	32,048		45,514
Prior	126,453		84,690
Revolving Loans Amortized Cost Basis	245,199		260,105
Total loans, net of fees and costs excluding portfolio layer basis adjustments	706,594		745,496
Gross charge-offs
2024/2023			40
2022/2021			1,675
2020/2019			28
Prior	33		10
Revolving Loans Amortized Cost Basis			9,267
Total	33		11,020
Commercial Business Portfolio Segment [Member] | Pass
2024/2023	15,773		115,740
2023/2022	123,793		116,452
2022/2021	93,740		53,315
2021/2020	52,370		31,637
2020/2019	29,623		30,913
Prior	90,356		53,289
Revolving Loans Amortized Cost Basis	233,208		244,143
Total loans, net of fees and costs excluding portfolio layer basis adjustments	638,863		645,489
Commercial Business Portfolio Segment [Member] | Watch
2024/2023			342
2023/2022	270		9,792
2022/2021	7,884		3,822
2021/2020	1,474		2,426
2020/2019	2,425		14,483
Prior	32,656		18,495
Revolving Loans Amortized Cost Basis	4,953		8,582
Total loans, net of fees and costs excluding portfolio layer basis adjustments	49,662		57,942
Commercial Business Portfolio Segment [Member] | Special Mention
2020/2019			25
Prior	23
Revolving Loans Amortized Cost Basis			495
Total loans, net of fees and costs excluding portfolio layer basis adjustments	23		520
Commercial Business Portfolio Segment [Member] | Substandard
2024/2023			14,642
2023/2022	378		2,399
2022/2021	2,427		4,158
2021/2020	4,323
2020/2019			93
Prior	3,418		12,906
Revolving Loans Amortized Cost Basis	3,380		2,982
Total loans, net of fees and costs excluding portfolio layer basis adjustments	13,926		37,180
Commercial Business Portfolio Segment [Member] | Doubtful
2024/2023			462
2023/2022	462
Revolving Loans Amortized Cost Basis	3,658		3,903
Total loans, net of fees and costs excluding portfolio layer basis adjustments	4,120		4,365
Commercial Business Secured By Portfolio Segment [member]
2024/2023	5,656		46,723
2023/2022	46,559		177,136
2022/2021	175,895		130,608
2021/2020	129,512		106,545
2020/2019	105,569		54,324
Prior	242,947		191,786
Total loans, net of fees and costs excluding portfolio layer basis adjustments	706,138		707,122
Commercial Business Secured By Portfolio Segment [member] | Pass
2024/2023	5,656		36,993
2023/2022	36,864		176,825
2022/2021	175,592		130,608
2021/2020	129,512		106,545
2020/2019	101,758		38,846
Prior	185,781		139,025
Total loans, net of fees and costs excluding portfolio layer basis adjustments	635,163		628,842
Commercial Business Secured By Portfolio Segment [member] | Watch
2024/2023			9,730
2023/2022	9,695		311
2022/2021	303
2020/2019	3,811		586
Prior	40,999		51,759
Total loans, net of fees and costs excluding portfolio layer basis adjustments	54,808		62,386
Commercial Business Secured By Portfolio Segment [member] | Special Mention
2020/2019			14,892
Prior	15,165		1,002
Total loans, net of fees and costs excluding portfolio layer basis adjustments	15,165		15,894
Commercial Business Secured By Portfolio Segment [member] | Substandard
Prior	1,002
Total loans, net of fees and costs excluding portfolio layer basis adjustments	1,002
Other Portfolio Segment [Member]
Prior	101		133
Revolving Loans Amortized Cost Basis	115		89
Total loans, net of fees and costs excluding portfolio layer basis adjustments	216		222
Gross charge-offs
Prior	11		99
Total	11		99
Other Portfolio Segment [Member] | Pass
Prior	101		133
Revolving Loans Amortized Cost Basis	115		89
Total loans, net of fees and costs excluding portfolio layer basis adjustments	216		222
Consumer Portfolio Segment [Member]
Mortgage loans in process of foreclosure, amount	$ 4,600		$ 4,800