Loans and reserve for credit losses (Reserve for Loan Losses and Recorded Investment in Loans) (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Total	$ 23,501	$ 22,053
Total loans	1,626,590	1,492,540
Commercial Real Estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Individually evaluated for impairment	82	60
Reserve for loan losses Collectively evaluated for impairment	4,950	5,554
Reserve for loan losses Total	5,032	5,614
Recorded investment in loans Individually evaluated for impairment	4,591	28,947
Recorded investment in loans, Collectively evaluated for impairment	817,520	727,705
Total loans	822,111	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	1,356	1,133
Reserve for loan losses Total	1,356	1,133
Recorded investment in loans Individually evaluated for impairment	521	963
Recorded investment in loans, Collectively evaluated for impairment	134,755	124,465
Total loans	135,276	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	2,463	2,121
Reserve for loan losses Total	2,463	2,121
Recorded investment in loans Individually evaluated for impairment	55	317
Recorded investment in loans, Collectively evaluated for impairment	255,006	204,370
Total loans	255,061	204,687
Commercial and Industrial
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Individually evaluated for impairment	125	25
Reserve for loan losses Collectively evaluated for impairment	11,230	6,819
Reserve for loan losses Total	11,355	6,844
Recorded investment in loans Individually evaluated for impairment	2,862	3,495
Recorded investment in loans, Collectively evaluated for impairment	372,345	364,980
Total loans	375,207	368,475
Consumer Loans
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	1,001	1,047
Reserve for loan losses Total	1,001	1,047
Recorded investment in loans Individually evaluated for impairment	0	0
Recorded investment in loans, Collectively evaluated for impairment	38,935	37,298
Total loans	38,935	37,298
Allocated Financing Receivables
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Individually evaluated for impairment	207	85
Reserve for loan losses Collectively evaluated for impairment	21,000	16,674
Reserve for loan losses Total	21,207	16,759
Recorded investment in loans Individually evaluated for impairment	8,029	33,722
Recorded investment in loans, Collectively evaluated for impairment	1,618,561	1,458,818
Total loans	1,626,590	1,492,540
Unallocated Financing Receivables
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Total	$ 2,294	$ 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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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 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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