Loans Loan Categories and Past Due Loans(Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing Receivable, Recorded Investment, Past Due	$ 8,298	$ 12,708	$ 9,220
Current Loans	1,984,739	1,938,062	1,801,585
Total Loans	1,993,037	1,950,770	1,810,805
Loans 90 or More Days Past Due and Still Accruing Interest	0	319	0
Nonaccrual Loans	4,470	5,526	4,273
Financing Receivables, 30 to 59 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing Receivable, Recorded Investment, Past Due	5,585	8,124	6,092
Financing Receivables, 60 to 89 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing Receivable, Recorded Investment, Past Due	1,292	1,743	1,838
Financing Receivables, Equal to Greater than 90 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing Receivable, Recorded Investment, Past Due	1,421	2,841	1,290
Commercial
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing Receivable, Recorded Investment, Past Due	146	257	318
Current Loans	127,528	128,992	118,524
Total Loans	127,674	129,249	118,842
Loans 90 or More Days Past Due and Still Accruing Interest	0	0	0
Nonaccrual Loans	652	588	144
Commercial | Financing Receivables, 30 to 59 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing Receivable, Recorded Investment, Past Due	45	139	189
Commercial | Financing Receivables, 60 to 89 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing Receivable, Recorded Investment, Past Due	60	19	9
Commercial | Financing Receivables, Equal to Greater than 90 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing Receivable, Recorded Investment, Past Due	41	99	120
Commercial Real Estate Portfolio Segment
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing Receivable, Recorded Investment, Past Due	963	807	0
Current Loans	454,095	443,441	435,316
Total Loans	455,058	444,248	435,316
Loans 90 or More Days Past Due and Still Accruing Interest	0	0	0
Nonaccrual Loans	807	1,530	870
Commercial Real Estate Portfolio Segment | Financing Receivables, 30 to 59 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing Receivable, Recorded Investment, Past Due	156	0	0
Commercial Real Estate Portfolio Segment | Financing Receivables, 60 to 89 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing Receivable, Recorded Investment, Past Due	0	0	0
Commercial Real Estate Portfolio Segment | Financing Receivables, Equal to Greater than 90 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing Receivable, Recorded Investment, Past Due	807	807	0
Consumer Loans Financing
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing Receivable, Recorded Investment, Past Due	4,676	7,619	5,362
Current Loans	621,964	595,208	546,601
Total Loans	626,640	602,827	551,963
Loans 90 or More Days Past Due and Still Accruing Interest	0	6	0
Nonaccrual Loans	441	653	656
Consumer Loans Financing | Financing Receivables, 30 to 59 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing Receivable, Recorded Investment, Past Due	3,673	5,891	3,882
Consumer Loans Financing | Financing Receivables, 60 to 89 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing Receivable, Recorded Investment, Past Due	751	1,215	1,145
Consumer Loans Financing | Financing Receivables, Equal to Greater than 90 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing Receivable, Recorded Investment, Past Due	252	513	335
Residential
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing Receivable, Recorded Investment, Past Due	2,513	4,025	3,540
Current Loans	781,152	770,421	701,144
Total Loans	783,665	774,446	704,684
Loans 90 or More Days Past Due and Still Accruing Interest	0	313	0
Nonaccrual Loans	2,570	2,755	2,603
Residential | Financing Receivables, 30 to 59 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing Receivable, Recorded Investment, Past Due	1,711	2,094	2,021
Residential | Financing Receivables, 60 to 89 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing Receivable, Recorded Investment, Past Due	481	509	684
Residential | Financing Receivables, Equal to Greater than 90 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing Receivable, Recorded Investment, Past Due	$ 321	$ 1,422	$ 835