Loans and Allowance for Loan Losses - Risk category of our loan portfolio (Details) $ in Thousands	Dec. 31, 2020 USD ($)
2020	$ 896,386
2019	991,017
2018	1,125,966
2017	808,364
2016	681,758
Prior	1,898,901
Revolving Loans Amortized Cost Basis	281,969
Lines of credit converted to term loans	20,313
Total	6,704,674
One-To-Four Family - Residential Portfolio Segment [Member]
2020	32,752
2019	37,869
2018	38,063
2017	24,595
2016	14,635
Prior	73,036
Revolving Loans Amortized Cost Basis	11,428
Lines of credit converted to term loans	20,313
Total	252,691
One-To-Four Family - Residential Portfolio Segment [Member] \| Pass [Member]
2020	32,266
2019	37,149
2018	38,063
2017	21,293
2016	13,229
Prior	65,916
Revolving Loans Amortized Cost Basis	10,793
Lines of credit converted to term loans	15,974
Total	234,683
One-To-Four Family - Residential Portfolio Segment [Member] \| Watch [Member]
2020	486
2019	720
2017	3,302
2016	446
Prior	2,599
Revolving Loans Amortized Cost Basis	635
Lines of credit converted to term loans	2,397
Total	10,585
One-To-Four Family - Residential Portfolio Segment [Member] \| Special Mention [Member]
Prior	1,338
Lines of credit converted to term loans	383
Total	1,721
One-To-Four Family - Residential Portfolio Segment [Member] \| Substandard [Member]
2016	960
Prior	3,183
Lines of credit converted to term loans	1,559
Total	5,702
One-To-Four Family - Mixed-Use Property Portfolio Segment [Member]
2020	37,307
2019	72,920
2018	81,923
2017	64,879
2016	55,122
Prior	294,734
Total	606,885
One-To-Four Family - Mixed-Use Property Portfolio Segment [Member] \| Pass [Member]
2020	36,491
2019	72,920
2018	77,037
2017	58,404
2016	53,518
Prior	282,169
Total	580,539
One-To-Four Family - Mixed-Use Property Portfolio Segment [Member] \| Watch [Member]
2020	816
2018	4,077
2017	6,107
2016	882
Prior	9,617
Total	21,499
One-To-Four Family - Mixed-Use Property Portfolio Segment [Member] \| Special Mention [Member]
2017	368
2016	722
Prior	1,433
Total	2,523
One-To-Four Family - Mixed-Use Property Portfolio Segment [Member] \| Substandard [Member]
2018	809
Prior	1,515
Total	2,324
Commercial Real Estate
2020	174,027
2019	273,802
2018	282,506
2017	209,766
2016	252,581
Prior	565,702
Total	1,758,384
Commercial Real Estate \| Pass [Member]
2020	173,089
2019	263,007
2018	266,949
2017	191,532
2016	220,560
Prior	499,186
Total	1,614,323
Commercial Real Estate \| Watch [Member]
2020	938
2019	1,359
2018	15,557
2017	15,687
2016	29,445
Prior	62,587
Total	125,573
Commercial Real Estate \| Special Mention [Member]
2017	2,547
2016	2,576
Prior	1,350
Total	6,473
Commercial Real Estate \| Substandard [Member]
2019	9,436
Prior	2,579
Total	12,015
Construction Portfolio Segment [Member]
2020	16,768
2019	17,908
2018	39,317
2017	8,578
Prior	590
Total	83,161
Construction Portfolio Segment [Member] \| Pass [Member]
2020	16,768
2019	16,793
2018	28,984
2017	5,253
Prior	590
Total	68,388
Construction Portfolio Segment [Member] \| Watch [Member]
2019	1,115
2018	9,572
2017	750
Total	11,437
Construction Portfolio Segment [Member] \| Special Mention [Member]
2018	761
2017	2,575
Total	3,336
Multi-family Residential Portfolio Segment [Member]
2020	246,677
2019	349,492
2018	482,623
2017	379,742
2016	286,106
Prior	785,766
Revolving Loans Amortized Cost Basis	5,571
Total	2,535,977
Multi-family Residential Portfolio Segment [Member] \| Pass [Member]
2020	245,551
2019	343,887
2018	479,644
2017	376,275
2016	282,185
Prior	769,712
Revolving Loans Amortized Cost Basis	4,572
Total	2,501,826
Multi-family Residential Portfolio Segment [Member] \| Watch [Member]
2020	1,126
2019	4,906
2018	982
2017	931
2016	3,457
Prior	14,806
Revolving Loans Amortized Cost Basis	798
Total	27,006
Multi-family Residential Portfolio Segment [Member] \| Special Mention [Member]
2019	699
2017	2,536
2016	464
Prior	668
Total	4,367
Multi-family Residential Portfolio Segment [Member] \| Substandard [Member]
2018	1,997
Prior	580
Revolving Loans Amortized Cost Basis	201
Total	2,778
Commercial Business Secured By Portfolio Segment [member]
2020	135,188
2019	95,988
2018	71,406
2017	37,330
2016	51,192
Prior	107,074
Total	498,178
Commercial Business Secured By Portfolio Segment [member] \| Pass [Member]
2020	110,649
2019	43,909
2018	54,016
2017	36,010
2016	50,230
Prior	86,662
Total	381,476
Commercial Business Secured By Portfolio Segment [member] \| Watch [Member]
2020	24,539
2019	51,466
2018	17,390
2017	1,320
2016	962
Prior	16,192
Total	111,869
Commercial Business Secured By Portfolio Segment [member] \| Special Mention [Member]
2019	613
Total	613
Commercial Business Secured By Portfolio Segment [member] \| Substandard [Member]
Prior	4,220
Total	4,220
Commercial Business Portfolio Segment [Member]
2020	102,218
2019	141,585
2018	125,934
2017	78,752
2016	19,664
Prior	68,071
Revolving Loans Amortized Cost Basis	264,877
Total	801,101
Commercial Business Portfolio Segment [Member] \| Pass [Member]
2020	97,071
2019	118,501
2018	104,304
2017	51,627
2016	17,340
Prior	66,398
Revolving Loans Amortized Cost Basis	250,633
Total	705,874
Commercial Business Portfolio Segment [Member] \| Watch [Member]
2020	250
2019	22,490
2018	19,202
2017	20,591
2016	39
Prior	26
Revolving Loans Amortized Cost Basis	11,564
Total	74,162
Commercial Business Portfolio Segment [Member] \| Special Mention [Member]
2018	2,411
2017	93
Revolving Loans Amortized Cost Basis	246
Total	2,750
Commercial Business Portfolio Segment [Member] \| Substandard [Member]
2020	4,897
2019	594
2018	17
2017	6,441
2016	2,285
Prior	1,647
Revolving Loans Amortized Cost Basis	1,161
Total	17,042
Commercial Business Portfolio Segment [Member] \| Doubtful [Member]
Revolving Loans Amortized Cost Basis	1,273
Total	1,273
Small Business Administration Portfolio Segment [Member]
2020	151,449
2019	1,453
2018	4,194
2017	4,443
2016	2,458
Prior	1,573
Total	165,570
Small Business Administration Portfolio Segment [Member] \| Pass [Member]
2020	151,449
2019	1,453
2018	4,194
2017	1,327
2016	1,882
Prior	1,523
Total	161,828
Small Business Administration Portfolio Segment [Member] \| Watch [Member]
2017	1,948
2016	570
Total	2,518
Small Business Administration Portfolio Segment [Member] \| Special Mention [Member]
Prior	50
Total	50
Small Business Administration Portfolio Segment [Member] \| Substandard [Member]
2017	1,168
2016	6
Total	1,174
Taxi Medallion Portfolio Segment [Member]
2017	279
Prior	2,318
Total	2,597
Taxi Medallion Portfolio Segment [Member] \| Substandard [Member]
2017	279
Prior	2,318
Total	2,597
Other Portfolio Segment [Member]
Prior	37
Revolving Loans Amortized Cost Basis	93
Total	130
Other Portfolio Segment [Member] \| Pass [Member]
Prior	37
Revolving Loans Amortized Cost Basis	93
Total	$ 130

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