Loans and reserve for credit losses (Reserve for Loan Losses and Recorded Investment in Loans) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Total	$ 25,290	$ 24,415
Total loans	2,104,412	1,687,929
Commercial real estate portfolio
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Individually evaluated for impairment	0	78
Reserve for loan losses Collectively evaluated for impairment	6,321	3,856
Reserve for loan losses Total	6,321	3,934
Recorded investment in loans Individually evaluated for impairment	640	3,835
Recorded investment in loans, Collectively evaluated for impairment	1,002,968	831,058
Total loans	1,003,608	834,893
Construction portfolio
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	2,196	1,044
Reserve for loan losses Total	2,196	1,044
Recorded investment in loans Individually evaluated for impairment	0	365
Recorded investment in loans, Collectively evaluated for impairment	211,038	129,987
Total loans	211,038	130,352
Residential real estate portfolio
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	3,325	2,075
Reserve for loan losses Total	3,325	2,075
Recorded investment in loans Individually evaluated for impairment	0	18
Recorded investment in loans, Collectively evaluated for impairment	431,842	298,372
Total loans	431,842	298,390
Commercial and industrial portfolio
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Individually evaluated for impairment	2,000	164
Reserve for loan losses Collectively evaluated for impairment	8,657	13,805
Reserve for loan losses Total	10,657	13,969
Recorded investment in loans Individually evaluated for impairment	7,034	2,724
Recorded investment in loans, Collectively evaluated for impairment	407,402	381,720
Total loans	414,436	384,444
Consumer portfolio
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	1,203	917
Reserve for loan losses Total	1,203	917
Recorded investment in loans Individually evaluated for impairment	0	0
Recorded investment in loans, Collectively evaluated for impairment	43,488	39,850
Total loans	43,488	39,850
Allocated Financing Receivables
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Individually evaluated for impairment	2,000	242
Reserve for loan losses Collectively evaluated for impairment	21,702	21,697
Reserve for loan losses Total	23,702	21,939
Recorded investment in loans Individually evaluated for impairment	7,674	6,942
Recorded investment in loans, Collectively evaluated for impairment	2,096,738	1,680,987
Total loans	2,104,412	1,687,929
Unallocated
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Total	$ 1,588	$ 2,476

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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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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