Loans and reserve for credit losses (Reserve for Loan Losses and Recorded Investment in Loans) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Total	$ 21,351	$ 20,857
Total loans	1,466,710	996,232
Commercial Real Estate Portfolio Segment
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Individually evaluated for impairment	172	665
Reserve for loan losses Collectively evaluated for impairment	6,811	8,900
Reserve for loan losses Total	6,983	9,565
Recorded investment in loans Individually evaluated for impairment	28,547	32,227
Recorded investment in loans, Collectively evaluated for impairment	722,760	519,785
Total loans	751,307	552,012
Construction Portfolio Segment
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	1,000	535
Reserve for loan losses Total	1,000	535
Recorded investment in loans Individually evaluated for impairment	963	1,987
Recorded investment in loans, Collectively evaluated for impairment	114,157	50,516
Total loans	115,120	52,503
Residential Portfolio Segment
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Individually evaluated for impairment	0	62
Reserve for loan losses Collectively evaluated for impairment	1,884	2,319
Reserve for loan losses Total	1,884	2,381
Recorded investment in loans Individually evaluated for impairment	322	430
Recorded investment in loans, Collectively evaluated for impairment	189,901	101,127
Total loans	190,223	101,557
Commercial and Industrial
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Individually evaluated for impairment	25	56
Reserve for loan losses Collectively evaluated for impairment	7,327	6,205
Reserve for loan losses Total	7,352	6,261
Recorded investment in loans Individually evaluated for impairment	3,656	5,823
Recorded investment in loans, Collectively evaluated for impairment	368,858	248,347
Total loans	372,514	254,170
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	1,099	1,401
Reserve for loan losses Total	1,099	1,401
Recorded investment in loans Individually evaluated for impairment	0	0
Recorded investment in loans, Collectively evaluated for impairment	37,546	35,990
Total loans	37,546	35,990
Allocated Financing Receivables
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Individually evaluated for impairment	197	783
Reserve for loan losses Collectively evaluated for impairment	18,121	19,360
Reserve for loan losses Total	18,318	20,143
Recorded investment in loans Individually evaluated for impairment	33,488	40,467
Recorded investment in loans, Collectively evaluated for impairment	1,433,222	955,765
Total loans	1,466,710	996,232
Unallocated Financing Receivables
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Total	$ 3,033	$ 714

The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

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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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.

+ References

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

-Publisher FASB

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-Topic 310

-SubTopic 10

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

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

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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

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-SubTopic 210

-Section S99

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

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- Definition

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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