Loans and reserve for credit losses (Reserve for Loan Losses and Recorded Investment in Loans) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Total	$ 24,415	$ 22,053
Total loans	1,687,929	1,492,540
Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Individually evaluated for impairment	78	60
Reserve for loan losses Collectively evaluated for impairment	3,856	5,554
Reserve for loan losses Total	3,934	5,614
Recorded investment in loans Individually evaluated for impairment	3,835	28,947
Recorded investment in loans, Collectively evaluated for impairment	831,058	727,705
Total loans	834,893	756,652
Construction
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Individually evaluated for impairment	0	0
Reserve for loan losses Collectively evaluated for impairment	1,044	1,133
Reserve for loan losses Total	1,044	1,133
Recorded investment in loans Individually evaluated for impairment	365	963
Recorded investment in loans, Collectively evaluated for impairment	129,987	124,465
Total loans	130,352	125,428
Residential real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Individually evaluated for impairment	0	0
Reserve for loan losses Collectively evaluated for impairment	2,075	2,121
Reserve for loan losses Total	2,075	2,121
Recorded investment in loans Individually evaluated for impairment	18	317
Recorded investment in loans, Collectively evaluated for impairment	298,372	204,370
Total loans	298,390	204,687
Commercial and industrial
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Individually evaluated for impairment	164	25
Reserve for loan losses Collectively evaluated for impairment	13,805	6,819
Reserve for loan losses Total	13,969	6,844
Recorded investment in loans Individually evaluated for impairment	2,724	3,495
Recorded investment in loans, Collectively evaluated for impairment	381,720	364,980
Total loans	384,444	368,475
Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Individually evaluated for impairment	0	0
Reserve for loan losses Collectively evaluated for impairment	917	1,047
Reserve for loan losses Total	917	1,047
Recorded investment in loans Individually evaluated for impairment	0	0
Recorded investment in loans, Collectively evaluated for impairment	39,850	37,298
Total loans	39,850	37,298
Allocated Financing Receivables
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Individually evaluated for impairment	242	85
Reserve for loan losses Collectively evaluated for impairment	21,697	16,674
Reserve for loan losses Total	21,939	16,759
Recorded investment in loans Individually evaluated for impairment	6,942	33,722
Recorded investment in loans, Collectively evaluated for impairment	1,680,987	1,458,818
Total loans	1,687,929	1,492,540
Unallocated
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Total	$ 2,476	$ 5,294

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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- 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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=35738203&loc=SL6953423-111524

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Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(d))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 7
-Subparagraph d
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Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 6
-Section L
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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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