Loans - Risk category of our loan portfolio (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
2021	$ 766,866
2020	722,177
2019	928,177
2018	994,128
2017	742,487
Prior	2,218,381
Revolving Loans Amortized Cost Basis	240,200
Lines of credit converted to term loans	17,938
Total	6,630,354
One-To-Four Family - Residential Portfolio Segment [Member]
2021	53,687
2020	31,937
2019	36,149
2018	34,713
2017	24,349
Prior	79,417
Revolving Loans Amortized Cost Basis	11,053
Lines of credit converted to term loans	17,938
Total	289,243
One-To-Four Family - Residential Portfolio Segment [Member] \| Pass [Member]
2021	53,687
2020	31,937
2019	35,424
2018	32,594
2017	21,016
Prior	73,993
Revolving Loans Amortized Cost Basis	10,907
Lines of credit converted to term loans	15,953
Total	275,511
One-To-Four Family - Residential Portfolio Segment [Member] \| Watch [Member]
2019	725
2017	2,216
Prior	1,229
Revolving Loans Amortized Cost Basis	146
Lines of credit converted to term loans	847
Total	5,163
One-To-Four Family - Residential Portfolio Segment [Member] \| Special Mention [Member]
2018	278
Prior	350
Lines of credit converted to term loans	337
Total	965
One-To-Four Family - Residential Portfolio Segment [Member] \| Substandard [Member]
2018	1,841
2017	1,117
Prior	3,845
Lines of credit converted to term loans	801
Total	7,604
One-To-Four Family - Mixed-Use Property Portfolio Segment [Member]
2021	32,110
2020	35,677
2019	70,360
2018	76,576
2017	58,991
Prior	308,629
Total	582,343
One-To-Four Family - Mixed-Use Property Portfolio Segment [Member] \| Pass [Member]
2021	32,110
2020	35,677
2019	70,360
2018	73,236
2017	52,100
Prior	298,763
Total	562,246
One-To-Four Family - Mixed-Use Property Portfolio Segment [Member] \| Watch [Member]
2018	2,834
2017	6,131
Prior	7,088
Total	16,053
One-To-Four Family - Mixed-Use Property Portfolio Segment [Member] \| Special Mention [Member]
Prior	1,279
Total	1,279
One-To-Four Family - Mixed-Use Property Portfolio Segment [Member] \| Substandard [Member]
2018	506
2017	760
Prior	1,499
Total	2,765
Commercial Real Estate
2021	135,839
2020	168,266
2019	266,332
2018	259,933
2017	187,145
Prior	730,218
Total	1,747,733
Commercial Real Estate \| Pass [Member]
2021	131,648
2020	167,334
2019	254,288
2018	247,434
2017	184,502
Prior	660,127
Total	1,645,333
Commercial Real Estate \| Watch [Member]
2021	4,191
2020	932
2019	4,472
2018	12,499
2017	2,643
Prior	67,755
Total	92,492
Commercial Real Estate \| Special Mention [Member]
Prior	1,632
Total	1,632
Commercial Real Estate \| Substandard [Member]
2019	7,572
Prior	704
Total	8,276
Construction Portfolio Segment [Member]
2021	3,477
2020	25,417
2019	16,913
2018	12,848
2017	8,480
Revolving Loans Amortized Cost Basis	4,233
Total	71,368
Construction Portfolio Segment [Member] \| Pass [Member]
2021	3,477
2020	25,417
2019	14,798
2018	1,993
Revolving Loans Amortized Cost Basis	4,233
Total	49,918
Construction Portfolio Segment [Member] \| Watch [Member]
2019	2,115
2018	9,125
2017	5,880
Total	17,120
Construction Portfolio Segment [Member] \| Special Mention [Member]
2018	857
2017	2,600
Total	3,457
Construction Portfolio Segment [Member] \| Substandard [Member]
2018	873
Total	873
Multi-family Residential Portfolio Segment [Member]
2021	218,819
2020	241,458
2019	339,477
2018	446,594
2017	353,566
Prior	895,409
Revolving Loans Amortized Cost Basis	5,698
Total	2,501,021
Multi-family Residential Portfolio Segment [Member] \| Pass [Member]
2021	218,819
2020	237,600
2019	334,594
2018	430,396
2017	352,582
Prior	884,680
Revolving Loans Amortized Cost Basis	5,300
Total	2,463,971
Multi-family Residential Portfolio Segment [Member] \| Watch [Member]
2020	2,885
2019	3,707
2018	13,649
Prior	9,987
Revolving Loans Amortized Cost Basis	398
Total	30,626
Multi-family Residential Portfolio Segment [Member] \| Special Mention [Member]
2020	973
Total	973
Multi-family Residential Portfolio Segment [Member] \| Substandard [Member]
2019	1,176
2018	2,549
2017	984
Prior	742
Total	5,451
Commercial Business Secured By Portfolio Segment [member]
2021	131,864
2020	116,335
2019	90,400
2018	64,271
2017	39,991
Prior	146,956
Total	589,817
Commercial Business Secured By Portfolio Segment [member] \| Pass [Member]
2021	131,864
2020	92,989
2019	38,483
2018	45,725
2017	27,927
Prior	96,840
Total	433,828
Commercial Business Secured By Portfolio Segment [member] \| Watch [Member]
2020	23,346
2019	51,319
2018	18,546
2017	12,064
Prior	46,477
Total	151,752
Commercial Business Secured By Portfolio Segment [member] \| Special Mention [Member]
2019	598
Total	598
Commercial Business Secured By Portfolio Segment [member] \| Substandard [Member]
Prior	3,639
Total	3,639
Commercial Business Portfolio Segment [Member]
2021	86,513
2020	74,939
2019	107,214
2018	95,065
2017	66,258
Prior	53,938
Revolving Loans Amortized Cost Basis	219,137
Total	703,064
Commercial Business Portfolio Segment [Member] \| Pass [Member]
2021	86,496
2020	68,366
2019	84,638
2018	73,370
2017	28,721
Prior	52,443
Revolving Loans Amortized Cost Basis	190,737
Total	584,771
Commercial Business Portfolio Segment [Member] \| Watch [Member]
2021	17
2020	1,676
2019	22,545
2018	18,947
2017	32,250
Prior	37
Revolving Loans Amortized Cost Basis	12,697
Total	88,169
Commercial Business Portfolio Segment [Member] \| Special Mention [Member]
2018	2,433
2017	34
Revolving Loans Amortized Cost Basis	13,128
Total	15,595
Commercial Business Portfolio Segment [Member] \| Substandard [Member]
2020	4,897
2019	31
2018	315
2017	5,253
Prior	1,458
Revolving Loans Amortized Cost Basis	1,490
Total	13,444
Commercial Business Portfolio Segment [Member] \| Doubtful [Member]
Revolving Loans Amortized Cost Basis	1,085
Total	1,085
Small Business Administration Portfolio Segment [Member]
2021	104,557
2020	28,148
2019	1,332
2018	4,128
2017	3,707
Prior	3,762
Total	145,634
Small Business Administration Portfolio Segment [Member] \| Pass [Member]
2021	104,557
2020	28,148
2019	1,273
2018	1,545
2017	640
Prior	2,875
Total	139,038
Small Business Administration Portfolio Segment [Member] \| Watch [Member]
2019	59
2018	2,583
2017	2,076
Prior	833
Total	5,551
Small Business Administration Portfolio Segment [Member] \| Special Mention [Member]
Prior	48
Total	48
Small Business Administration Portfolio Segment [Member] \| Substandard [Member]
2017	991
Prior	6
Total	997
Other Portfolio Segment [Member]
Prior	52
Revolving Loans Amortized Cost Basis	79
Total	131
Other Portfolio Segment [Member] \| Pass [Member]
Prior	52
Revolving Loans Amortized Cost Basis	79
Total	131
Consumer Portfolio Segment [Member]
Mortgage Loans in Process of Foreclosure, Amount	$ 9,300	$ 5,900

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