Loans and reserve for credit losses (Reserve for Loan Losses and Recorded Investment in Loans) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Total	$ 20,471	$ 20,857
Total loans	1,394,928	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	7,788	8,900
Reserve for loan losses Total	7,960	9,565
Recorded investment in loans Individually evaluated for impairment	28,644	32,227
Recorded investment in loans, Collectively evaluated for impairment	723,539	519,785
Total loans	752,183	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	728	535
Reserve for loan losses Total	728	535
Recorded investment in loans Individually evaluated for impairment	963	1,987
Recorded investment in loans, Collectively evaluated for impairment	104,048	50,516
Total loans	105,011	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	2,067	2,319
Reserve for loan losses Total	2,067	2,381
Recorded investment in loans Individually evaluated for impairment	461	430
Recorded investment in loans, Collectively evaluated for impairment	198,418	101,127
Total loans	198,879	101,557
Commercial and Industrial
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Individually evaluated for impairment	29	56
Reserve for loan losses Collectively evaluated for impairment	6,587	6,205
Reserve for loan losses Total	6,616	6,261
Recorded investment in loans Individually evaluated for impairment	3,793	5,823
Recorded investment in loans, Collectively evaluated for impairment	296,940	248,347
Total loans	300,733	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	1,181	1,401
Reserve for loan losses Total	1,181	1,401
Recorded investment in loans Individually evaluated for impairment	0	0
Recorded investment in loans, Collectively evaluated for impairment	38,122	35,990
Total loans	38,122	35,990
Allocated Financing Receivables [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Individually evaluated for impairment	201	783
Reserve for loan losses Collectively evaluated for impairment	18,351	19,360
Reserve for loan losses Total	18,552	20,143
Recorded investment in loans Individually evaluated for impairment	33,861	40,467
Recorded investment in loans, Collectively evaluated for impairment	1,361,067	955,765
Total loans	1,394,928	996,232
Unallocated Financing Receivables
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Total	$ 1,919	$ 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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- Definition

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

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

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-Subparagraph (h)

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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

-Publisher FASB

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-Topic 310

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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 942

-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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