Loans - Risk Category of Mortgage and Non-mortgage Loans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
2023	$ 461,365		$ 461,365
2022	1,178,656		1,178,656
2021	737,028		737,028
2020	563,345		563,345
2019	738,572		738,572
Prior	2,857,484		2,857,484
Revolving Loans Amortized Cost Basis	358,050		358,050
Revolving Loans converted to term loans	12,213		12,213
Total Loans	6,906,713		6,906,713		$ 6,934,769
Gross charge-offs
2021			1,675
2019			14
Prior			94
Revolving Loans Amortized Cost Basis			9,267
Charge-offs	21	$ 324	11,050	$ 1,410
Basis adjustments	10,639		10,639
Portfolio Layer Hedges on Closed Portfolio of Loans [Member] | Designated as Hedging Instrument [Member]
Gross charge-offs
Basis adjustments	10,600		10,600
Pass
2023	436,388		436,388
2022	1,168,374		1,168,374
2021	725,559		725,559
2020	558,968		558,968
2019	697,771		697,771
Prior	2,689,947		2,689,947
Revolving Loans Amortized Cost Basis	345,899		345,899
Revolving Loans converted to term loans	10,252		10,252
Total Loans	6,633,158		6,633,158
Watch
2023	10,042		10,042
2022	7,828		7,828
2021	5,732		5,732
2020	4,377		4,377
2019	26,343		26,343
Prior	139,456		139,456
Revolving Loans Amortized Cost Basis	2,747		2,747
Revolving Loans converted to term loans	1,321		1,321
Total Loans	197,846		197,846
Special Mention
2021	5,419		5,419
2019	14,430		14,430
Prior	2,650		2,650
Revolving Loans Amortized Cost Basis	2,000		2,000
Revolving Loans converted to term loans	197		197
Total Loans	24,696		24,696
Substandard
2023	14,935		14,935
2022	2,454		2,454
2021	318		318
2019	28		28
Prior	25,431		25,431
Revolving Loans Amortized Cost Basis	3,475		3,475
Revolving Loans converted to term loans	443		443
Total Loans	47,084		47,084		25,700
Increase in amortized cost	21,400		21,400
Doubtful
Revolving Loans Amortized Cost Basis	3,929		3,929
Total Loans	3,929		3,929
One-To-Four Family - Residential Portfolio Segment [Member]
2023	5,108		5,108
2022	23,829		23,829
2021	8,780		8,780
2020	16,857		16,857
2019	38,893		38,893
Prior	110,972		110,972
Revolving Loans Amortized Cost Basis	7,475		7,475
Revolving Loans converted to term loans	12,213		12,213
Total Loans	224,127		224,127		242,480
Gross charge-offs
Prior			12
Charge-offs		$ 2	12	2
One-To-Four Family - Residential Portfolio Segment [Member] | Pass
2023	5,108		5,108
2022	23,319		23,319
2021	8,506		8,506
2020	16,857		16,857
2019	38,153		38,153
Prior	104,508		104,508
Revolving Loans Amortized Cost Basis	7,475		7,475
Revolving Loans converted to term loans	10,252		10,252
Total Loans	214,178		214,178
One-To-Four Family - Residential Portfolio Segment [Member] | Watch
2022	510		510
2021	274		274
2019	740		740
Prior	1,527		1,527
Revolving Loans converted to term loans	1,321		1,321
Total Loans	4,372		4,372
One-To-Four Family - Residential Portfolio Segment [Member] | Special Mention
Prior	204		204
Revolving Loans converted to term loans	197		197
Total Loans	401		401
One-To-Four Family - Residential Portfolio Segment [Member] | Substandard
Prior	4,733		4,733
Revolving Loans converted to term loans	443		443
Total Loans	5,176		5,176
One-To-Four Family - Mixed-Use Property Portfolio Segment [Member]
2023	18,557		18,557
2022	43,937		43,937
2021	41,987		41,987
2020	31,274		31,274
2019	61,994		61,994
Prior	342,770		342,770
Total Loans	540,519		540,519		557,295
One-To-Four Family - Mixed-Use Property Portfolio Segment [Member] | Pass
2023	18,557		18,557
2022	43,937		43,937
2021	41,987		41,987
2020	31,274		31,274
2019	61,270		61,270
Prior	335,314		335,314
Total Loans	532,339		532,339
One-To-Four Family - Mixed-Use Property Portfolio Segment [Member] | Watch
2019	724		724
Prior	5,564		5,564
Total Loans	6,288		6,288
One-To-Four Family - Mixed-Use Property Portfolio Segment [Member] | Special Mention
Prior	636		636
Total Loans	636		636
One-To-Four Family - Mixed-Use Property Portfolio Segment [Member] | Substandard
Prior	1,256		1,256
Total Loans	1,256		1,256
Commercial Real Estate [Member]
2023	134,977		134,977
2022	326,545		326,545
2021	179,303		179,303
2020	148,835		148,835
2019	228,028		228,028
Prior	936,774		936,774
Total Loans	1,954,462		1,954,462		1,914,898
Gross charge-offs
Prior			8
Charge-offs			8
Commercial Real Estate [Member] | Pass
2023	134,977		134,977
2022	326,545		326,545
2021	177,860		177,860
2020	148,835		148,835
2019	218,458		218,458
Prior	913,106		913,106
Total Loans	1,919,781		1,919,781
Commercial Real Estate [Member] | Watch
2021	1,443		1,443
2019	9,570		9,570
Prior	23,668		23,668
Total Loans	34,681		34,681
Construction Portfolio Segment
2023	5,520		5,520
2022	3		3
2021	5,793		5,793
Revolving Loans Amortized Cost Basis	48,459		48,459
Total Loans	59,775		59,775		70,824
Construction Portfolio Segment | Pass
2023	5,520		5,520
2022	3		3
2021	5,793		5,793
Revolving Loans Amortized Cost Basis	48,459		48,459
Total Loans	59,775		59,775
Multi-family Residential Portfolio Segment [Member]
2023	171,298		171,298
2022	469,760		469,760
2021	279,408		279,408
2020	219,445		219,445
2019	306,987		306,987
Prior	1,166,656		1,166,656
Revolving Loans Amortized Cost Basis	4,075		4,075
Total Loans	2,617,629		2,617,629		2,605,172
Multi-family Residential Portfolio Segment [Member] | Pass
2023	171,298		171,298
2022	468,879		468,879
2021	279,408		279,408
2020	217,501		217,501
2019	306,987		306,987
Prior	1,127,156		1,127,156
Revolving Loans Amortized Cost Basis	4,075		4,075
Total Loans	2,575,304		2,575,304
Multi-family Residential Portfolio Segment [Member] | Watch
2022	881		881
2020	1,944		1,944
Prior	32,691		32,691
Total Loans	35,516		35,516
Multi-family Residential Portfolio Segment [Member] | Special Mention
Prior	1,461		1,461
Total Loans	1,461		1,461
Multi-family Residential Portfolio Segment [Member] | Substandard
Prior	5,348		5,348
Total Loans	5,348		5,348
Commercial Business Secured By Portfolio Segment [member]
2023	45,361		45,361
2022	178,373		178,373
2021	131,700		131,700
2020	106,902		106,902
2019	55,114		55,114
Prior	196,701		196,701
Total Loans	714,151		714,151
Commercial Business Secured By Portfolio Segment [member] | Pass
2023	35,585		35,585
2022	178,373		178,373
2021	131,700		131,700
2020	106,902		106,902
2019	40,114		40,114
Prior	143,676		143,676
Total Loans	636,350		636,350
Commercial Business Secured By Portfolio Segment [member] | Watch
2023	9,776		9,776
2019	597		597
Prior	53,025		53,025
Total Loans	63,398		63,398
Commercial Business Secured By Portfolio Segment [member] | Special Mention
2019	14,403		14,403
Total Loans	14,403		14,403
Commercial Business Portfolio Segment [Member]
2023	79,738		79,738
2022	132,908		132,908
2021	85,079		85,079
2020	36,419		36,419
2019	46,806		46,806
Prior	95,043		95,043
Revolving Loans Amortized Cost Basis	297,916		297,916
Total Loans	773,909		773,909
Gross charge-offs
2021			1,675
2019			14
Prior			11
Revolving Loans Amortized Cost Basis			9,267
Charge-offs			10,967
Commercial Business Portfolio Segment [Member] | Pass
2023	64,537		64,537
2022	124,017		124,017
2021	77,139		77,139
2020	33,986		33,986
2019	32,087		32,087
Prior	62,001		62,001
Revolving Loans Amortized Cost Basis	285,765		285,765
Total Loans	679,532		679,532
Commercial Business Portfolio Segment [Member] | Watch
2023	266		266
2022	6,437		6,437
2021	4,015		4,015
2020	2,433		2,433
2019	14,664		14,664
Prior	20,105		20,105
Revolving Loans Amortized Cost Basis	2,747		2,747
Total Loans	50,667		50,667
Commercial Business Portfolio Segment [Member] | Special Mention
2021	3,925		3,925
2019	27		27
Revolving Loans Amortized Cost Basis	2,000		2,000
Total Loans	5,952		5,952
Commercial Business Portfolio Segment [Member] | Substandard
2023	14,935		14,935
2022	2,454		2,454
2019	28		28
Prior	12,937		12,937
Revolving Loans Amortized Cost Basis	3,475		3,475
Total Loans	33,829		33,829
Commercial Business Portfolio Segment [Member] | Doubtful
Revolving Loans Amortized Cost Basis	3,929		3,929
Total Loans	3,929		3,929
Small Business Administration Portfolio Segment [Member]
2023	806		806
2022	3,301		3,301
2021	4,978		4,978
2020	3,613		3,613
2019	750		750
Prior	8,388		8,388
Total Loans	21,836		21,836		23,193
Gross charge-offs
Prior			7
Charge-offs			7	$ 1,054
Small Business Administration Portfolio Segment [Member] | Pass
2023	806		806
2022	3,301		3,301
2021	3,166		3,166
2020	3,613		3,613
2019	702		702
Prior	4,006		4,006
Total Loans	15,594		15,594
Small Business Administration Portfolio Segment [Member] | Watch
2019	48		48
Prior	2,876		2,876
Total Loans	2,924		2,924
Small Business Administration Portfolio Segment [Member] | Special Mention
2021	1,494		1,494
Prior	349		349
Total Loans	1,843		1,843
Small Business Administration Portfolio Segment [Member] | Substandard
2021	318		318
Prior	1,157		1,157
Total Loans	1,475		1,475
Other Portfolio Segment [Member]
Prior	180		180
Revolving Loans Amortized Cost Basis	125		125
Total Loans	305		305
Gross charge-offs
Prior			56
Charge-offs			56
Other Portfolio Segment [Member] | Pass
Prior	180		180
Revolving Loans Amortized Cost Basis	125		125
Total Loans	305		305
Consumer Portfolio Segment [Member]
Mortgage loans in process of foreclosure, amount	$ 4,700		$ 4,700		$ 5,200