Loans (Narrative) (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($) loan	Dec. 31, 2016 USD ($) loan	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases receivable, allowance percentage		(0.09%)	(0.04%)
Total number of loans | loan		24	29
90 or greater days delinquent		$ 2,483	$ 7,705
Total non-accrual loans		4,693	8,374
Deferred loan fees and premiums include net deferred fees paid by customers		2,800	2,700
Offset by net deferred premiums paid to purchase loans		3,900	3,100
Loan portfolio		$ 1,150,044	$ 1,088,982
Percentage status of loan in portfolio		100.00%	100.00%
Allowance for loan loss		$ 10,515	$ 9,860
Charge-offs		482	1,169	$ 1,458
Loans, carrying amount		1,140,615	1,079,519
Non-accrual performing loans		2,210	669
Past Due		11,710	8,739
Loans receivable from related parties		$ 26,476	$ 26,464	28,105	$ 24,403
Number of TDR loans | loan		16	22
Number of accrual TDR loans | loan		15	16
Financing receivable post modification recorded investment		$ 10,790	$ 15,121
Accrual TDR loans		$ 10,021	$ 10,448
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total number of loans | loan		7	7
90 or greater days delinquent		$ 1,148	$ 2,371
Total non-accrual loans		1,987	2,371
Loan portfolio		$ 727,314	$ 667,105
Percentage status of loan in portfolio		63.25%	61.25%
Charge-offs		$ 217		78
Non-accrual performing loans		839
Past Due		$ 7,859	$ 2,855
Number of TDR loans | loan		9	8
Financing receivable post modification recorded investment		$ 9,273	$ 9,587
Commercial Construction Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage status of loan in portfolio		6.20%	9.30%
Residential First Mortgages Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total number of loans | loan		4	4
90 or greater days delinquent		$ 478	$ 623
Total non-accrual loans		985	623
Increase (decrease) in loans		25,500	64,200
Loan portfolio		$ 170,374	$ 171,004
Percentage status of loan in portfolio		14.81%	15.70%
Charge-offs				30
Non-accrual performing loans		$ 507
Past Due		$ 546	$ 623
Number of TDR loans | loan		2	2
Financing receivable post modification recorded investment		$ 527	$ 545
Residential Rentals Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total number of loans | loan		4	4
90 or greater days delinquent		$ 84	$ 577
Total non-accrual loans		825	577
Loan portfolio		$ 110,228	$ 101,897
Percentage status of loan in portfolio		9.58%	9.36%
Charge-offs		$ 42	$ 14
Non-accrual performing loans		741
Past Due		$ 291	$ 588
Number of TDR loans | loan		1	1
Financing receivable post modification recorded investment		$ 221	$ 227
Construction And Land Development Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total number of loans | loan			2
90 or greater days delinquent			$ 3,048
Total non-accrual loans			3,048
Loan portfolio		$ 27,871	$ 36,934
Percentage status of loan in portfolio		2.42%	3.39%
Charge-offs		$ 26	$ 526
Past Due			$ 3,048
Number of TDR loans | loan		2	4
Financing receivable post modification recorded investment		$ 729	$ 3,777
Home Equity And Second Mortgages Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total number of loans | loan		4	2
90 or greater days delinquent		$ 134	$ 61
Total non-accrual loans		257	61
Loan portfolio		$ 21,351	$ 21,399
Percentage status of loan in portfolio		1.86%	1.97%
Charge-offs		$ 14		100
Non-accrual performing loans		123
Past Due		$ 171	$ 224
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total number of loans | loan		2	5
90 or greater days delinquent		$ 172	$ 375
Total non-accrual loans		172	1,044
Loan portfolio		$ 56,417	$ 50,484
Percentage status of loan in portfolio		4.91%	4.64%
Charge-offs		$ 13	$ 594	432
Non-accrual performing loans			669
Past Due		$ 1,363	$ 706
Number of TDR loans | loan		1	5
Financing receivable post modification recorded investment		$ 4	$ 872
Consumer Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan portfolio		$ 573	$ 422
Percentage status of loan in portfolio		0.05%	0.04%
Charge-offs		$ 2	$ 1
Past Due		$ 1	$ 2
Commercial Equipment Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total number of loans | loan		3	5
90 or greater days delinquent		$ 467	$ 650
Total non-accrual loans		467	650
Loan portfolio		$ 35,916	$ 39,737
Percentage status of loan in portfolio		3.12%	3.65%
Charge-offs		$ 168	$ 34	$ 818
Past Due		$ 1,479	$ 693
Number of TDR loans | loan		1	2
Financing receivable post modification recorded investment		$ 36	$ 113
1-4 Family Units [Member] | Residential Rentals Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan portfolio		85,000	84,900
Apartment Buildings Rentals [Member] | Residential Rentals Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan portfolio		25,200	17,000
Adjustable Rate Residential First Mortgage [Member] | Residential First Mortgages Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan portfolio		$ 56,900	$ 45,600
Percentage status of loan in portfolio		5.00%	4.20%
Adjustable Rate Residential First Mortgage [Member] | Residential Rentals Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan portfolio		$ 93,400	$ 84,000
Percentage status of loan in portfolio		8.10%	7.70%
Foreclosure Of Stalled Residential Development Project [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount of loans removed from troubled debt restructuring		$ 3,000
Ten Loans And Five Customer Relationships [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total non-accrual loans		3,300
Financing Receivable Troubled Debt Restructuring [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in loans		$ (4,300)
Loans added to troubled debt restructuring | loan		0	1
Loans removed from troubled debt restructuring | loan			9
Amount of loans added to troubled debt restructuring			$ 196
Amount of loans removed from troubled debt restructuring			2,100
Interest income recognized on outstanding TDR loans		$ 327	357
TDR loan principal curtailment		$ 385	1,600
Seven Troubled Debt Restructuring Loans with Reserves [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans removed from troubled debt restructuring | loan		7
Amount of loans removed from troubled debt restructuring		$ 3,900
Specific reserves for TDR loans		$ 413
Number of TDR loans | loan		7
Financing receivable post modification recorded investment		$ 3,000
Nine Troubled Debt Restructuring Loans with Reserves [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Specific reserves for TDR loans			$ 844
Number of TDR loans | loan			9
Financing receivable post modification recorded investment			$ 5,700
Nonaccrual Loans With No Impairment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total non-accrual loans		3,800	7,800
Interest due to debt		85	947
Nonaccrual Loans With Impairment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total non-accrual loans		876	575
Interest due to debt		$ 100	156
Minimum [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Debt maturity period		3 years
Minimum [Member] | Residential First Mortgages Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Debt maturity period		10 years
Minimum [Member] | Residential Rentals Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Debt maturity period		3 years
Maximum [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Debt maturity period		20 years
Maximum [Member] | Residential First Mortgages Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Debt maturity period		30 years
Maximum [Member] | Residential Rentals Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Debt maturity period		20 years
Unrated [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan portfolio		$ 75,581	51,503
Unrated [Member] | Residential Rentals Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan portfolio		28,428	25,563
Unrated [Member] | Construction And Land Development Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan portfolio		1,775	1,632
Unrated [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan portfolio		14,356	11,266
Unrated [Member] | Commercial Equipment Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan portfolio		10,856	11,769
Pass [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan portfolio		619,604	594,768
Pass [Member] | Residential Rentals Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan portfolio		80,279	74,989
Pass [Member] | Construction And Land Development Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan portfolio		25,367	31,525
Pass [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan portfolio		39,118	36,221
Pass [Member] | Commercial Equipment Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan portfolio		23,581	27,290
Substandard [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan portfolio		32,129	20,834
Substandard [Member] | Residential Rentals Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan portfolio		1,521	1,345
Substandard [Member] | Construction And Land Development Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan portfolio		729	3,777
Substandard [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan portfolio		2,943	2,997
Substandard [Member] | Commercial Equipment Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan portfolio		1,479	541
Doubtful [Member] | Commercial Equipment Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan portfolio			137
31 - 60 Days [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due		1,923	503
31 - 60 Days [Member] | Home Equity And Second Mortgages Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due		19	130
31 - 60 Days [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due		892	331
31 - 60 Days [Member] | Commercial Equipment Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due		1,012	42
61 - 89 Days [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due		7,304	531
61 - 89 Days [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due		6,711	484
61 - 89 Days [Member] | Residential First Mortgages Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due		68
61 - 89 Days [Member] | Residential Rentals Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due		207	11
61 - 89 Days [Member] | Home Equity And Second Mortgages Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due		18	33
61 - 89 Days [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due		299
61 - 89 Days [Member] | Consumer Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due		1	2
61 - 89 Days [Member] | Commercial Equipment Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due			1
90 or Greater Days [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due		2,483	7,705
90 or Greater Days [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due		1,148	2,371
90 or Greater Days [Member] | Residential First Mortgages Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due		478	623
90 or Greater Days [Member] | Residential Rentals Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due		84	577
90 or Greater Days [Member] | Construction And Land Development Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due			3,048
90 or Greater Days [Member] | Home Equity And Second Mortgages Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due		134	61
90 or Greater Days [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due		172	375
90 or Greater Days [Member] | Commercial Equipment Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due		467	650
Performing Financing Receivable [Member] | Residential First Mortgages Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan portfolio		169,896	170,381
Performing Financing Receivable [Member] | Home Equity And Second Mortgages Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan portfolio		21,217	21,338
Performing Financing Receivable [Member] | Consumer Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan portfolio		573	$ 422
Nonperforming Financing Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in loans		$ (3,700)
Percentage status of loan in portfolio		0.41%	0.77%
Nonperforming Financing Receivable [Member] | Residential First Mortgages Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan portfolio		$ 478	$ 623
Nonperforming Financing Receivable [Member] | Home Equity And Second Mortgages Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan portfolio		134	61
Nonperforming Financing Receivable [Member] | Foreclosure Of Stalled Residential Development Project [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in loans		$ (3,000)
Nonperforming Financing Receivable [Member] | Foreclosure Of Commercial Office Building [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in loans	$ (607)
Nonperforming Financing Receivable [Member] | Ten Loans And Five Customer Relationships [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total number of loans | loan		10
Percentage status of loan in portfolio		71.00%
Nonperforming Financing Receivable [Member] | Fifteen Loans Representing Six Customer Relationships [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total non-accrual loans			$ 6,400
Percentage status of loan in portfolio			77.00%
Number of loans | loan			15
Nonperforming Financing Receivable [Member] | One Troubled Debt Restructuring Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total number of loans | loan		1
Financing Receivable, Modifications, Pre-Modification Recorded Investment		$ 769
Nonperforming Financing Receivable [Member] | Six Troubled Debt Restructuring Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total number of loans | loan			6
Financing Receivable, Modifications, Pre-Modification Recorded Investment			$ 4,700