Allowance for Loan Losses - Allowance for Loan Loss Activity by Class (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	$ 10,344	$ 11,514	$ 11,514
Charge offs	716	395	3,495
Recoveries	68	136	1,175
Provision for loan losses	500us-gaap_ProvisionForLoanAndLeaseLosses	400us-gaap_ProvisionForLoanAndLeaseLosses	1,150us-gaap_ProvisionForLoanAndLeaseLosses
Ending balance	10,196	11,655	10,344
Ending balance specifically evaluated for impairment	1,436	2,786	1,803
Ending balance collectively evaluated for impairment	8,760	8,869	8,541
Total	939,169	868,914	917,564
Ending balance specifically evaluated for impairment	34,833	40,587	35,862
Ending balance collectively evaluated for impairment	904,336	828,327	881,702
Commercial real estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	3,532	4,602	4,602
Charge offs	122	20	1,205
Recoveries	0	1	144
Provision for loan losses	(293)	(83)	(9)
Ending balance	3,117	4,500	3,532
Ending balance specifically evaluated for impairment	248	1,019	346
Ending balance collectively evaluated for impairment	2,869	3,481	3,186
Total	242,021	240,187	242,311
Ending balance specifically evaluated for impairment	12,705	15,260	13,304
Ending balance collectively evaluated for impairment	229,316	224,927	229,007
Commercial construction
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	823	575	575
Charge offs	0	0	0
Recoveries	0	0	0
Provision for loan losses	(16)	15	248
Ending balance	807	590	823
Ending balance specifically evaluated for impairment	396	276	413
Ending balance collectively evaluated for impairment	411	314	410
Total	34,683	21,686	30,932
Ending balance specifically evaluated for impairment	1,380	1,492	1,380
Ending balance collectively evaluated for impairment	33,303	20,194	29,552
Commercial other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	1,505	2,276	2,276
Charge offs	2	174	989
Recoveries	4	64	758
Provision for loan losses	207	75	(540)
Ending balance	1,714	2,241	1,505
Ending balance specifically evaluated for impairment	347	834	129
Ending balance collectively evaluated for impairment	1,367	1,407	1,376
Total	115,455	97,276	104,531
Ending balance specifically evaluated for impairment	2,721	5,258	2,942
Ending balance collectively evaluated for impairment	112,734	92,018	101,589
Municipal
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	15	15	15
Charge offs	0	0	0
Recoveries	0	0	0
Provision for loan losses	1	0	0
Ending balance	16	15	15
Ending balance specifically evaluated for impairment	0	0	0
Ending balance collectively evaluated for impairment	16	15	15
Total	26,277	17,790	20,424
Ending balance specifically evaluated for impairment	0	0	0
Ending balance collectively evaluated for impairment	26,277	17,790	20,424
Residential term
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	1,185	1,099	1,099
Charge offs	83	119	699
Recoveries	6	4	36
Provision for loan losses	0	248	749
Ending balance	1,108	1,232	1,185
Ending balance specifically evaluated for impairment	421	574	519
Ending balance collectively evaluated for impairment	687	658	666
Total	383,869	372,479	384,032
Ending balance specifically evaluated for impairment	16,348	16,924	16,123
Ending balance collectively evaluated for impairment	367,521	355,555	367,909
Residential construction
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	20	21	21
Charge offs	0	0	0
Recoveries	0	0	25
Provision for loan losses	3	1	(26)
Ending balance	23	22	20
Ending balance specifically evaluated for impairment	0	0	0
Ending balance collectively evaluated for impairment	23	22	20
Total	13,036	12,360	12,160
Ending balance specifically evaluated for impairment	0	0	0
Ending balance collectively evaluated for impairment	13,036	12,360	12,160
Home equity line of credit
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	1,060	675	675
Charge offs	447	12	153
Recoveries	22	1	16
Provision for loan losses	409	44	522
Ending balance	1,044	708	1,060
Ending balance specifically evaluated for impairment	24	83	396
Ending balance collectively evaluated for impairment	1,020	625	664
Total	104,100	92,202	103,521
Ending balance specifically evaluated for impairment	1,654	1,653	2,087
Ending balance collectively evaluated for impairment	102,446	90,549	101,434
Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	542	573	573
Charge offs	62	70	449
Recoveries	36	66	196
Provision for loan losses	10	(52)	222
Ending balance	526	517	542
Ending balance specifically evaluated for impairment	0	0	0
Ending balance collectively evaluated for impairment	526	517	542
Total	19,728	14,934	19,653
Ending balance specifically evaluated for impairment	25	0	26
Ending balance collectively evaluated for impairment	19,703	14,934	19,627
Unallocated
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	1,662	1,678	1,678
Charge offs	0	0	0
Recoveries	0	0	0
Provision for loan losses	179	152	(16)
Ending balance	1,841	1,830	1,662
Ending balance specifically evaluated for impairment	0	0	0
Ending balance collectively evaluated for impairment	1,841	1,830	1,662
Total	0	0	0
Ending balance specifically evaluated for impairment	0	0	0
Ending balance collectively evaluated for impairment	$ 0	$ 0	$ 0

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

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

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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.

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

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