Loans Receivable and Allowance for Loan Losses (Allowance for Loan Losses) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended	12 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses: Beginning Balance	$ 25,534	$ 23,004	$ 23,734	$ 22,359	$ 22,359
Allowance for loan losses: Charge-offs			4	256	743
Allowance for loan losses: Recoveries		30	312	42	49
Allowance for loan losses: Provisions	3,300	755	4,800	1,644	2,069
Allowance for loan losses: Ending Balance	28,842	23,789	28,842	23,789	23,734
Allowance for loan losses: Ending balance: individually evaluated for impairment	3,401		3,401		3,264
Allowance for loan losses: Ending balance: collectively evaluated for impairment	25,441		25,441		20,470
Loans receivables: Ending balance: individually evaluated for impairment	26,838		26,838		26,912
Loans receivables: Ending balance: collectively evaluated for impairment	2,349,418		2,349,418		2,176,403
Loans receivables: Ending balance	2,376,256		2,376,256		2,203,315
Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses: Beginning Balance	3,131	2,907	2,722	2,748	2,748
Allowance for loan losses: Charge-offs			4		66
Allowance for loan losses: Recoveries		3		3	3
Allowance for loan losses: Provisions	(55)	547	358	706	37
Allowance for loan losses: Ending Balance	3,076	3,457	3,076	3,457	2,722
Allowance for loan losses: Ending balance: individually evaluated for impairment	398		398		380
Allowance for loan losses: Ending balance: collectively evaluated for impairment	2,678		2,678		2,342
Loans receivables: Ending balance: individually evaluated for impairment	8,233		8,233		8,455
Loans receivables: Ending balance: collectively evaluated for impairment	239,238		239,238		239,926
Loans receivables: Ending balance	247,471		247,471		248,381
Commercial and Multi-family [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses: Beginning Balance	14,949	15,221	15,372	14,168	14,168
Allowance for loan losses: Charge-offs				111	229
Allowance for loan losses: Recoveries				10	10
Allowance for loan losses: Provisions	1,993	(833)	1,570	321	1,423
Allowance for loan losses: Ending Balance	16,942	14,388	16,942	14,388	15,372
Allowance for loan losses: Ending balance: individually evaluated for impairment	318		318		342
Allowance for loan losses: Ending balance: collectively evaluated for impairment	16,624		16,624		15,030
Loans receivables: Ending balance: individually evaluated for impairment	9,725		9,725		13,231
Loans receivables: Ending balance: collectively evaluated for impairment	1,634,229		1,634,229		1,593,745
Loans receivables: Ending balance	1,643,954		1,643,954		1,606,976
Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses: Beginning Balance	1,105	1,209	1,244	1,003	1,003
Allowance for loan losses: Provisions	229	235	90	451	241
Allowance for loan losses: Ending Balance	1,334	1,454	1,334	1,454	1,244
Allowance for loan losses: Ending balance: collectively evaluated for impairment	1,334		1,334		1,244
Loans receivables: Ending balance: collectively evaluated for impairment	111,463		111,463		104,996
Loans receivables: Ending balance	111,463		111,463		104,996
Commercial Business [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses: Beginning Balance	3,957	3,367	3,790	3,933	3,933
Allowance for loan losses: Charge-offs				145	448
Allowance for loan losses: Recoveries		9	302	18	20
Allowance for loan losses: Provisions	354	686	219	256	285
Allowance for loan losses: Ending Balance	4,311	4,062	4,311	4,062	3,790
Allowance for loan losses: Ending balance: individually evaluated for impairment	2,665		2,665		2,518
Allowance for loan losses: Ending balance: collectively evaluated for impairment	1,646		1,646		1,272
Loans receivables: Ending balance: individually evaluated for impairment	7,255		7,255		3,938
Loans receivables: Ending balance: collectively evaluated for impairment	302,029		302,029		173,704
Loans receivables: Ending balance	309,284		309,284		177,642
Home Equity [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses: Beginning Balance	625	268	333	316	316
Allowance for loan losses: Recoveries		8	6	11	16
Allowance for loan losses: Provisions	55	1	345	(50)	1
Allowance for loan losses: Ending Balance	684	277	684	277	333
Allowance for loan losses: Ending balance: individually evaluated for impairment	20		20		24
Allowance for loan losses: Ending balance: collectively evaluated for impairment	664		664		309
Loans receivables: Ending balance: individually evaluated for impairment	1,625		1,625		1,288
Loans receivables: Ending balance: collectively evaluated for impairment	61,856		61,856		63,350
Loans receivables: Ending balance	63,481		63,481		64,638
Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses: Beginning Balance	5			2	2
Allowance for loan losses: Recoveries			4
Allowance for loan losses: Provisions	(3)	1	2	(1)	(2)
Allowance for loan losses: Ending Balance	6	1	6	1
Allowance for loan losses: Ending balance: collectively evaluated for impairment	6		6
Loans receivables: Ending balance: collectively evaluated for impairment	603		603		682
Loans receivables: Ending balance	603		603		682
Unallocated [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses: Beginning Balance	1,762	32	273	189	189
Allowance for loan losses: Provisions	727	118	2,216	(39)	84
Allowance for loan losses: Ending Balance	2,489	150	2,489	150	273
Allowance for loan losses: Ending balance: collectively evaluated for impairment	2,489		2,489		273
Originated loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses: Beginning Balance	24,151	22,382	22,449	21,750	21,750
Allowance for loan losses: Charge-offs				256	257
Allowance for loan losses: Recoveries	4	7	306	15	15
Allowance for loan losses: Provisions	2,858	316	4,258	1,196	941
Allowance for loan losses: Ending Balance	27,013	22,705	27,013	22,705	22,449
Loans receivables: Ending balance	2,199,464		2,199,464		2,010,489
Originated loans [Member] \| Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses: Beginning Balance	2,787	2,471	2,422	2,374	2,374
Allowance for loan losses: Charge-offs					1
Allowance for loan losses: Provisions	(138)	109	227	206	49
Allowance for loan losses: Ending Balance	2,649	2,580	2,649	2,580	2,422
Loans receivables: Ending balance	213,095		213,095		212,020
Originated loans [Member] \| Commercial and Multi-family [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses: Beginning Balance	14,867	15,077	15,235	14,000	14,000
Allowance for loan losses: Charge-offs				111	111
Allowance for loan losses: Provisions	1,830	(826)	1,462	362	1,346
Allowance for loan losses: Ending Balance	16,697	14,251	16,697	14,251	15,235
Loans receivables: Ending balance	1,532,902		1,532,902		1,485,286
Originated loans [Member] \| Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses: Beginning Balance	1,105	1,209	1,244	1,003	1,003
Allowance for loan losses: Provisions	229	245	90	451	241
Allowance for loan losses: Ending Balance	1,334	1,454	1,334	1,454	1,244
Loans receivables: Ending balance	111,463		111,463		104,996
Originated loans [Member] \| Commercial Business [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses: Beginning Balance	3,004	3,328	2,945	3,869	3,869
Allowance for loan losses: Charge-offs				145	145
Allowance for loan losses: Recoveries		7	302	15	15
Allowance for loan losses: Provisions	154	660	(89)	256	(794)
Allowance for loan losses: Ending Balance	3,158	3,995	3,158	3,995	2,945
Loans receivables: Ending balance	289,814		289,814		157,413
Originated loans [Member] \| Home Equity [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses: Beginning Balance	621	265	330	313	313
Allowance for loan losses: Provisions	59	9	350	(39)	17
Allowance for loan losses: Ending Balance	680	274	680	274	330
Loans receivables: Ending balance	51,590		51,590		50,100
Originated loans [Member] \| Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses: Beginning Balance	5			2	2
Allowance for loan losses: Recoveries	4		4
Allowance for loan losses: Provisions	(3)	1	2	(1)	(2)
Allowance for loan losses: Ending Balance	6	1	6	1
Loans receivables: Ending balance	600		600		674
Originated loans [Member] \| Unallocated [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses: Beginning Balance	1,762	32	273	189	189
Allowance for loan losses: Provisions	727	118	2,216	(39)	84
Allowance for loan losses: Ending Balance	2,489	150	2,489	150	273
Acquired loans recorded at fair value [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses: Beginning Balance	1,279	404	1,122	335	335
Allowance for loan losses: Charge-offs			4		486
Allowance for loan losses: Recoveries	4	23	6	27	34
Allowance for loan losses: Provisions	444	304	603	369	1,239
Allowance for loan losses: Ending Balance	1,727	731	1,727	731	1,122
Loans receivables: Ending balance	173,611		173,611		187,216
Acquired loans recorded at fair value [Member] \| Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses: Beginning Balance	306	404	261	335	335
Allowance for loan losses: Charge-offs			4		65
Allowance for loan losses: Recoveries		3		3	3
Allowance for loan losses: Provisions	85	324	134	393	(12)
Allowance for loan losses: Ending Balance	391	731	391	731	261
Loans receivables: Ending balance	33,047		33,047		35,010
Acquired loans recorded at fair value [Member] \| Commercial and Multi-family [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses: Beginning Balance	63		58
Allowance for loan losses: Charge-offs					118
Allowance for loan losses: Recoveries				10	10
Allowance for loan losses: Provisions	163		168	(10)	166
Allowance for loan losses: Ending Balance	226		226		58
Loans receivables: Ending balance	110,337		110,337		118,577
Acquired loans recorded at fair value [Member] \| Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses: Recoveries		10
Allowance for loan losses: Provisions		(10)
Acquired loans recorded at fair value [Member] \| Commercial Business [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses: Beginning Balance	910		803
Allowance for loan losses: Charge-offs					303
Allowance for loan losses: Recoveries		2		3	5
Allowance for loan losses: Provisions	200	(2)	307	(3)	1,101
Allowance for loan losses: Ending Balance	1,110		1,110		803
Loans receivables: Ending balance	18,566		18,566		19,319
Acquired loans recorded at fair value [Member] \| Home Equity [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses: Recoveries	4	8	6	11	16
Allowance for loan losses: Provisions	(4)	(8)	(6)	(11)	(16)
Loans receivables: Ending balance	11,658		11,658		14,302
Acquired loans recorded at fair value [Member] \| Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivables: Ending balance	3		3		8
Acquired loans with deteriorated credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses: Beginning Balance	104	218	163	274	274
Allowance for loan losses: Recoveries	8
Allowance for loan losses: Provisions	(2)	135	(61)	79	(111)
Allowance for loan losses: Ending Balance	102	353	102	353	163
Loans receivables: Ending balance	3,181		3,181		5,610
Acquired loans with deteriorated credit [Member] \| Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses: Beginning Balance	38	32	39	39	39
Allowance for loan losses: Provisions	(2)	114	(3)	107
Allowance for loan losses: Ending Balance	36	146	36	146	39
Loans receivables: Ending balance	1,329		1,329		1,351
Acquired loans with deteriorated credit [Member] \| Commercial and Multi-family [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses: Beginning Balance	19	144	79	168	168
Allowance for loan losses: Provisions		(7)	(60)	(31)	(89)
Allowance for loan losses: Ending Balance	19	137	19	137	79
Loans receivables: Ending balance	715		715		3,113
Acquired loans with deteriorated credit [Member] \| Commercial Business [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses: Beginning Balance	43	39	42	64	64
Allowance for loan losses: Provisions		28	1	3	(22)
Allowance for loan losses: Ending Balance	43	67	43	67	42
Loans receivables: Ending balance	904		904		910
Acquired loans with deteriorated credit [Member] \| Home Equity [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses: Beginning Balance	4	3	3	3	3
Allowance for loan losses: Recoveries	4
Allowance for loan losses: Provisions			1
Allowance for loan losses: Ending Balance	4	$ 3	4	$ 3	3
Loans receivables: Ending balance	233		$ 233		$ 236
Acquired loans with deteriorated credit [Member] \| Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses: Recoveries	$ 4

Loans Receivable and Allowance for Loan Losses (Allowance for Loan Losses) (Details) - USD ($)
$ in Thousands

3 Months Ended

6 Months Ended

12 Months Ended

Jun. 30, 2020

Jun. 30, 2019

Jun. 30, 2020

Jun. 30, 2019

Dec. 31, 2019

Accounts, Notes, Loans and Financing Receivable [Line Items]

Allowance for loan losses: Beginning Balance

$ 25,534