Allowance for Loan Losses - Allowance for Loan Loss Activity by Class (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	$ 10,198	$ 9,908	$ 9,916	$ 10,344	$ 10,344
Charge offs	340	517	1,006	1,996	2,373
Recoveries	65	86	263	229	395
Provision for loan losses	375	200	1,125	1,100	1,550
Ending balance	10,298	9,677	10,298	9,677	9,916
Ending balance specifically evaluated for impairment	949	826	949	826	754
Ending balance collectively evaluated for impairment	9,349	8,851	9,349	8,851	9,162
Total	1,028,992	963,151	1,028,992	963,151	988,638
Ending balance specifically evaluated for impairment	28,185	30,786	28,185	30,786	29,531
Ending balance collectively evaluated for impairment	1,000,807	932,365	1,000,807	932,365	959,107
Commercial \| Real estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	3,955	2,943	3,120	3,532	3,532
Charge offs	0	132	33	254	280
Recoveries	0	1	0	1	2
Provision for loan losses	84	339	952	(128)	(134)
Ending balance	4,039	3,151	4,039	3,151	3,120
Ending balance specifically evaluated for impairment	381	71	381	71	89
Ending balance collectively evaluated for impairment	3,658	3,080	3,658	3,080	3,031
Total	297,808	268,741	297,808	268,741	269,462
Ending balance specifically evaluated for impairment	10,442	11,228	10,442	11,228	10,717
Ending balance collectively evaluated for impairment	287,366	257,513	287,366	257,513	258,745
Commercial \| Construction
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	318	705	580	823	823
Charge offs	17	0	75	9	9
Recoveries	4	0	4	0	1
Provision for loan losses	22	(147)	(182)	(256)	(235)
Ending balance	327	558	327	558	580
Ending balance specifically evaluated for impairment	99	282	99	282	302
Ending balance collectively evaluated for impairment	228	276	228	276	278
Total	18,828	23,624	18,828	23,624	24,881
Ending balance specifically evaluated for impairment	788	996	788	996	1,026
Ending balance collectively evaluated for impairment	18,040	22,628	18,040	22,628	23,855
Commercial \| Other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	1,778	1,671	1,452	1,505	1,505
Charge offs	137	246	167	732	732
Recoveries	24	51	80	66	88
Provision for loan losses	23	(100)	323	537	591
Ending balance	1,688	1,376	1,688	1,376	1,452
Ending balance specifically evaluated for impairment	68	8	68	8	8
Ending balance collectively evaluated for impairment	1,620	1,368	1,620	1,368	1,444
Total	131,198	119,097	131,198	119,097	128,341
Ending balance specifically evaluated for impairment	1,254	1,736	1,254	1,736	1,234
Ending balance collectively evaluated for impairment	129,944	117,361	129,944	117,361	127,107
Municipal
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	17	16	17	15	15
Charge offs	0	0	0	0	0
Recoveries	0	0	0	0	0
Provision for loan losses	1	0	1	1	2
Ending balance	18	16	18	16	17
Ending balance specifically evaluated for impairment	0	0	0	0	0
Ending balance collectively evaluated for impairment	18	16	18	16	17
Total	26,153	21,377	26,153	21,377	19,751
Ending balance specifically evaluated for impairment	0	0	0	0	0
Ending balance collectively evaluated for impairment	26,153	21,377	26,153	21,377	19,751
Residential \| Construction
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	34	27	24	20	20
Charge offs	0	0	0	0	0
Recoveries	0	0	0	0	0
Provision for loan losses	3	(5)	13	2	4
Ending balance	37	22	37	22	24
Ending balance specifically evaluated for impairment	0	0	0	0	0
Ending balance collectively evaluated for impairment	37	22	37	22	24
Total	14,269	12,029	14,269	12,029	8,451
Ending balance specifically evaluated for impairment	0	0	0	0	0
Ending balance collectively evaluated for impairment	14,269	12,029	14,269	12,029	8,451
Residential \| Term
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	1,365	1,184	1,391	1,185	1,185
Charge offs	72	38	338	187	420
Recoveries	14	4	88	37	152
Provision for loan losses	52	15	218	130	474
Ending balance	1,359	1,165	1,359	1,165	1,391
Ending balance specifically evaluated for impairment	318	435	318	435	326
Ending balance collectively evaluated for impairment	1,041	730	1,041	730	1,065
Total	403,159	385,145	403,159	385,145	403,030
Ending balance specifically evaluated for impairment	14,131	15,276	14,131	15,276	15,088
Ending balance collectively evaluated for impairment	389,028	369,869	389,028	369,869	387,942
Home equity line of credit
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	880	918	893	1,060	1,060
Charge offs	25	24	147	532	582
Recoveries	1	1	3	31	31
Provision for loan losses	18	6	125	342	384
Ending balance	874	901	874	901	893
Ending balance specifically evaluated for impairment	32	30	32	30	29
Ending balance collectively evaluated for impairment	842	871	842	871	864
Total	111,994	109,390	111,994	109,390	110,202
Ending balance specifically evaluated for impairment	1,400	1,550	1,400	1,550	1,466
Ending balance collectively evaluated for impairment	110,594	107,840	110,594	107,840	108,736
Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	635	580	566	542	542
Charge offs	89	77	246	282	350
Recoveries	22	29	88	94	121
Provision for loan losses	50	30	210	208	253
Ending balance	618	562	618	562	566
Ending balance specifically evaluated for impairment	51	0	51	0	0
Ending balance collectively evaluated for impairment	567	562	567	562	566
Total	25,583	23,748	25,583	23,748	24,520
Ending balance specifically evaluated for impairment	170	0	170	0	0
Ending balance collectively evaluated for impairment	25,413	23,748	25,413	23,748	24,520
Unallocated
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	1,216	1,864	1,873	1,662	1,662
Charge offs	0	0	0	0	0
Recoveries	0	0	0	0	0
Provision for loan losses	122	62	(535)	264	211
Ending balance	1,338	1,926	1,338	1,926	1,873
Ending balance specifically evaluated for impairment	0	0	0	0	0
Ending balance collectively evaluated for impairment	1,338	1,926	1,338	1,926	1,873
Total	0	0	0	0	0
Ending balance specifically evaluated for impairment	0	0	0	0	0
Ending balance collectively evaluated for impairment	$ 0	$ 0	$ 0	$ 0	$ 0

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

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- Definition

The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

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Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

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The balance of financing receivables that were collectively evaluated for impairment.

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- Definition

Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

+ References

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Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

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- Definition

Amount of expense related to estimated loss from loan and lease transactions.

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