Composition of Allowance for Loan Losses and Related Recorded Investment in Loans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Financing Receivable Allowance For Credit Losses [Line Items]
Balance, beginning of period	$ 13,761	$ 12,518	$ 12,329	$ 12,659	$ 12,659
Provision charged to expense	620	14	2,037	163	258
Losses charged-off	(4)	(380)	(6)	(782)	(732)
Recoveries	4	8	21	120	144
Balance, end of period	14,381	12,160	14,381	12,160	12,329
Ending balance: individually evaluated for impairment	295	489	295	489	459
Ending balance: collectively evaluated for impairment	14,086	11,671	14,086	11,671	11,870
Ending balance: individually evaluated for impairment	17,309	19,088	17,309	19,088	19,232
Ending balance: collectively evaluated for impairment	1,105,242	939,832	1,105,242	939,832	946,864
Total	1,122,551	958,920	1,122,551	958,920	966,096
1-4 Family Investor Owned
Financing Receivable Allowance For Credit Losses [Line Items]
Balance, beginning of period	3,857	3,574	3,503	3,799	3,799
Provision charged to expense	(1)	(49)	353	(297)	(311)
Losses charged-off					(8)
Recoveries				23	23
Balance, end of period	3,856	3,525	3,856	3,525	3,503
Ending balance: individually evaluated for impairment	121	266	121	266	265
Ending balance: collectively evaluated for impairment	3,735	3,259	3,735	3,259	3,238
Ending balance: individually evaluated for impairment	6,412	7,011	6,412	7,011	6,973
Ending balance: collectively evaluated for impairment	314,026	302,054	314,026	302,054	298,299
Total	320,438	309,065	320,438	309,065	305,272
1-4 Family Owner-Occupied
Financing Receivable Allowance For Credit Losses [Line Items]
Balance, beginning of period	1,194	1,168	1,067	1,208	1,208
Provision charged to expense	7	(99)	134	(139)	(141)
Balance, end of period	1,201	1,069	1,201	1,069	1,067
Ending balance: individually evaluated for impairment	137	158	137	158	149
Ending balance: collectively evaluated for impairment	1,064	911	1,064	911	918
Ending balance: individually evaluated for impairment	5,442	5,636	5,442	5,636	5,572
Ending balance: collectively evaluated for impairment	87,898	85,207	87,898	85,207	86,371
Total	93,340	90,843	93,340	90,843	91,943
Multifamily
Financing Receivable Allowance For Credit Losses [Line Items]
Balance, beginning of period	4,741	3,713	3,865	3,829	3,829
Provision charged to expense	148	30	1,024	(86)	36
Balance, end of period	4,889	3,743	4,889	3,743	3,865
Ending balance: collectively evaluated for impairment	4,889	3,743	4,889	3,743	3,865
Ending balance: individually evaluated for impairment	210		210
Ending balance: collectively evaluated for impairment	284,565	244,644	284,565	244,644	250,239
Total	284,775	244,644	284,775	244,644	250,239
Nonresidential Properties
Financing Receivable Allowance For Credit Losses [Line Items]
Balance, beginning of period	2,085	1,928	1,849	1,925	1,925
Provision charged to expense	98	(220)	330	(222)	(85)
Recoveries		2	4	7	9
Balance, end of period	2,183	1,710	2,183	1,710	1,849
Ending balance: individually evaluated for impairment	37	32	37	32	31
Ending balance: collectively evaluated for impairment	2,146	1,678	2,146	1,678	1,818
Ending balance: individually evaluated for impairment	5,245	5,103	5,245	5,103	5,548
Ending balance: collectively evaluated for impairment	212,526	190,849	212,526	190,849	201,677
Total	217,771	195,952	217,771	195,952	207,225
Construction and Land
Financing Receivable Allowance For Credit Losses [Line Items]
Balance, beginning of period	1,670	1,533	1,782	1,631	1,631
Provision charged to expense	49	315	(63)	217	151
Balance, end of period	1,719	1,848	1,719	1,848	1,782
Ending balance: collectively evaluated for impairment	1,719	1,848	1,719	1,848	1,782
Ending balance: individually evaluated for impairment		1,303		1,303	1,125
Ending balance: collectively evaluated for impairment	99,721	104,821	99,721	104,821	98,184
Total	99,721	106,124	99,721	106,124	99,309
Unallocated
Financing Receivable Allowance For Credit Losses [Line Items]
Balance, beginning of period		58
Provision charged to expense		(58)		(58)
Recoveries				58
Business
Financing Receivable Allowance For Credit Losses [Line Items]
Balance, beginning of period	204	533	254	260	260
Provision charged to expense	245	98	182	749	608
Losses charged-off		(380)		(782)	(724)
Recoveries	4	6	17	30	110
Balance, end of period	453	257	453	257	254
Ending balance: individually evaluated for impairment		33		33	14
Ending balance: collectively evaluated for impairment	453	224	453	224	240
Ending balance: individually evaluated for impairment		35		35	14
Ending balance: collectively evaluated for impairment	96,700	11,005	96,700	11,005	10,863
Total	96,700	11,040	96,700	11,040	10,877
Consumer
Financing Receivable Allowance For Credit Losses [Line Items]
Balance, beginning of period	10	11	9	7	7
Provision charged to expense	74	(3)	77	(1)
Losses charged-off	(4)		(6)
Recoveries				2	2
Balance, end of period	80	8	80	8	9
Ending balance: collectively evaluated for impairment	80	8	80	8	9
Ending balance: collectively evaluated for impairment	9,806	1,252	9,806	1,252	1,231
Total	$ 9,806	$ 1,252	$ 9,806	$ 1,252	$ 1,231