Allowance for Loan Losses - Allowance for Loan Loss Activity by Class (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended	12 Months Ended
Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	$ 10,219	$ 10,196	$ 9,916	$ 10,344	$ 10,344
Charge offs	476	763	666	1,479	2,373
Recoveries	80	75	198	143	395
Provision for loan losses	375	400	750	900	1,550
Ending balance	10,198	9,908	10,198	9,908	9,916
Ending balance specifically evaluated for impairment	1,029	1,307	1,029	1,307	754
Ending balance collectively evaluated for impairment	9,169	8,601	9,169	8,601	9,162
Total	1,038,213	963,109	1,038,213	963,109	988,638
Ending balance specifically evaluated for impairment	28,193	32,748	28,193	32,748	29,531
Ending balance collectively evaluated for impairment	1,010,020	930,361	1,010,020	930,361	959,107
Commercial real estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	3,524	3,117	3,120	3,532	3,532
Charge offs	33	0	33	122	280
Recoveries	0	0	0	0	2
Provision for loan losses	464	(174)	868	(467)	(134)
Ending balance	3,955	2,943	3,955	2,943	3,120
Ending balance specifically evaluated for impairment	369	225	369	225	89
Ending balance collectively evaluated for impairment	3,586	2,718	3,586	2,718	3,031
Total	303,312	249,414	303,312	249,414	269,462
Ending balance specifically evaluated for impairment	10,685	12,566	10,685	12,566	10,717
Ending balance collectively evaluated for impairment	292,627	236,848	292,627	236,848	258,745
Commercial construction
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	345	807	580	823	823
Charge offs	0	9	58	9	9
Recoveries	0	0	0	0	1
Provision for loan losses	(27)	(93)	(204)	(109)	(235)
Ending balance	318	705	318	705	580
Ending balance specifically evaluated for impairment	97	275	97	275	302
Ending balance collectively evaluated for impairment	221	430	221	430	278
Total	18,439	39,504	18,439	39,504	24,881
Ending balance specifically evaluated for impairment	834	989	834	989	1,026
Ending balance collectively evaluated for impairment	17,605	38,515	17,605	38,515	23,855
Commercial other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	1,676	1,714	1,452	1,505	1,505
Charge offs	30	484	30	486	732
Recoveries	36	11	56	15	88
Provision for loan losses	96	430	300	637	591
Ending balance	1,778	1,671	1,778	1,671	1,452
Ending balance specifically evaluated for impairment	158	275	158	275	8
Ending balance collectively evaluated for impairment	1,620	1,396	1,620	1,396	1,444
Total	136,651	128,249	136,651	128,249	128,341
Ending balance specifically evaluated for impairment	1,479	2,106	1,479	2,106	1,234
Ending balance collectively evaluated for impairment	135,172	126,143	135,172	126,143	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	0	0	0	1	2
Ending balance	17	16	17	16	17
Ending balance specifically evaluated for impairment	0	0	0	0	0
Ending balance collectively evaluated for impairment	17	16	17	16	17
Total	25,531	22,821	25,531	22,821	19,751
Ending balance specifically evaluated for impairment	0	0	0	0	0
Ending balance collectively evaluated for impairment	25,531	22,821	25,531	22,821	19,751
Residential term
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	1,474	1,108	1,391	1,185	1,185
Charge offs	246	66	266	149	420
Recoveries	9	27	74	33	152
Provision for loan losses	128	115	166	115	474
Ending balance	1,365	1,184	1,365	1,184	1,391
Ending balance specifically evaluated for impairment	326	501	326	501	326
Ending balance collectively evaluated for impairment	1,039	683	1,039	683	1,065
Total	403,461	378,090	403,461	378,090	403,030
Ending balance specifically evaluated for impairment	14,105	15,420	14,105	15,420	15,088
Ending balance collectively evaluated for impairment	389,356	362,670	389,356	362,670	387,942
Residential construction
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	33	23	24	20	20
Charge offs	0	0	0	0	0
Recoveries	0	0	0	0	0
Provision for loan losses	1	4	10	7	4
Ending balance	34	27	34	27	24
Ending balance specifically evaluated for impairment	0	0	0	0	0
Ending balance collectively evaluated for impairment	34	27	34	27	24
Total	13,403	14,215	13,403	14,215	8,451
Ending balance specifically evaluated for impairment	0	0	0	0	0
Ending balance collectively evaluated for impairment	13,403	14,215	13,403	14,215	8,451
Home equity line of credit
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	905	1,044	893	1,060	1,060
Charge offs	73	61	122	508	582
Recoveries	1	8	2	30	31
Provision for loan losses	47	(73)	107	336	384
Ending balance	880	918	880	918	893
Ending balance specifically evaluated for impairment	28	31	28	31	29
Ending balance collectively evaluated for impairment	852	887	852	887	864
Total	112,536	108,788	112,536	108,788	110,202
Ending balance specifically evaluated for impairment	975	1,572	975	1,572	1,466
Ending balance collectively evaluated for impairment	111,561	107,216	111,561	107,216	108,736
Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	654	526	566	542	542
Charge offs	94	143	157	205	350
Recoveries	34	29	66	65	121
Provision for loan losses	41	168	160	178	253
Ending balance	635	580	635	580	566
Ending balance specifically evaluated for impairment	51	0	51	0	0
Ending balance collectively evaluated for impairment	584	580	584	580	566
Total	24,880	22,028	24,880	22,028	24,520
Ending balance specifically evaluated for impairment	115	95	115	95	0
Ending balance collectively evaluated for impairment	24,765	21,933	24,765	21,933	24,520
Unallocated
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	1,591	1,841	1,873	1,662	1,662
Charge offs	0	0	0	0	0
Recoveries	0	0	0	0	0
Provision for loan losses	(375)	23	(657)	202	211
Ending balance	1,216	1,864	1,216	1,864	1,873
Ending balance specifically evaluated for impairment	0	0	0	0	0
Ending balance collectively evaluated for impairment	1,216	1,864	1,216	1,864	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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