Loans and reserve for credit losses (Reserve for Loan Losses and Recorded Investment in Loans) (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Total	$ 25,238	$ 24,415
Total loans	2,061,508	1,687,929
Allocated financing receivables
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Individually evaluated for impairment	99	242
Reserve for loan losses collectively evaluated for impairment	23,301	21,697
Reserve for loan losses Total	23,400	21,939
Recorded investment in loans Individually evaluated for impairment	11,800	6,942
Recorded investment in loans, collectively evaluated for impairment	2,049,708	1,680,987
Total loans	2,061,508	1,687,929
Unallocated
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Total	1,838	2,476
Commercial real estate: \| Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Individually evaluated for impairment	74	78
Reserve for loan losses collectively evaluated for impairment	5,945	3,856
Reserve for loan losses Total	6,019	3,934
Recorded investment in loans Individually evaluated for impairment	4,329	3,835
Recorded investment in loans, collectively evaluated for impairment	960,451	831,058
Total loans	964,780	834,893
Construction \| 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	1,857	1,044
Reserve for loan losses Total	1,857	1,044
Recorded investment in loans Individually evaluated for impairment	0	365
Recorded investment in loans, collectively evaluated for impairment	182,981	129,987
Total loans	182,981	130,352
Residential real estate \| 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	3,763	2,075
Reserve for loan losses Total	3,763	2,075
Recorded investment in loans Individually evaluated for impairment	0	18
Recorded investment in loans, collectively evaluated for impairment	465,466	298,372
Total loans	465,466	298,390
Commercial and industrial \| Commercial and industrial
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Individually evaluated for impairment	25	164
Reserve for loan losses collectively evaluated for impairment	10,524	13,805
Reserve for loan losses Total	10,549	13,969
Recorded investment in loans Individually evaluated for impairment	7,471	2,724
Recorded investment in loans, collectively evaluated for impairment	397,798	381,720
Total loans	405,269	384,444
Consumer \| 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	1,212	917
Reserve for loan losses Total	1,212	917
Recorded investment in loans Individually evaluated for impairment	0	0
Recorded investment in loans, collectively evaluated for impairment	43,012	39,850
Total loans	$ 43,012	$ 39,850

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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