Loans and Allowance for Credit Losses (Allowance for Credit Losses on Financing Receivables) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Allowance for credit losses:
Beginning balance	$ 9,132	$ 8,358	$ 8,726	$ 8,316
Charge-offs	(287)	(568)	(1,450)	(1,578)
Recoveries	105	219	273	446
Net charge-offs	(182)	(349)	(1,177)	(1,132)
Provision	345	605	1,746	1,430
Ending balance	9,295	8,614	9,295	8,614
Commercial and Residential Real Estate Portfolio Segment [Member] | Construction Loans [Member]
Allowance for credit losses:
Beginning balance	2,349	1,744	2,787	1,646
Charge-offs		(9)	(54)	(263)
Recoveries	11	8	27	24
Net charge-offs	11	(1)	(27)	(239)
Provision	(119)	275	(519)	611
Ending balance	2,241	2,018	2,241	2,018
Residential Portfolio Segment [Member]
Allowance for credit losses:
Beginning balance	2,096	2,035	1,953	2,181
Charge-offs	(70)	(407)	(393)	(525)
Recoveries	11	121	32	188
Net charge-offs	(59)	(286)	(361)	(337)
Provision	6	331	451	236
Ending balance	2,043	2,080	2,043	2,080
Commercial Real Estate Portfolio Segment [Member]
Allowance for credit losses:
Beginning balance	2,802	2,871	2,610	2,999
Charge-offs	(100)		(100)	(503)
Recoveries	8	10	27	20
Net charge-offs	(92)	10	(73)	(483)
Provision	174	306	347	671
Ending balance	2,884	3,187	2,884	3,187
Commercial Portfolio Segment [Member]
Allowance for credit losses:
Beginning balance	1,652	677	1,145	558
Charge-offs	(99)	(139)	(870)	(264)
Recoveries	67	79	167	201
Net charge-offs	(32)	(60)	(703)	(63)
Provision	184	300	1,362	422
Ending balance	1,804	917	1,804	917
Consumer Portfolio Segment [Member]
Allowance for credit losses:
Beginning balance	233	206	231	156
Charge-offs	(18)	(13)	(33)	(23)
Recoveries	8	1	20	13
Net charge-offs	(10)	(12)	(13)	(10)
Provision	100	(40)	105	8
Ending balance	$ 323	154	$ 323	154
Unallocated Financing Receivables [Member]
Allowance for credit losses:
Beginning balance		825		776
Provision		(567)		(518)
Ending balance		$ 258		$ 258