Loans and reserve for credit losses (Reserve for Loan Loasses and Recorded Investment in Loans) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Total	$ 20,857	$ 27,261
Total loans	996,232	858,164
Commercial Real Estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Individually evaluated for impairment	665	1,088
Reserve for loan losses Collectively evaluated for impairment	8,900	10,508
Reserve for loan losses Total	9,565	11,596
Recorded investment in loans Individually evaluated for impairment	32,227	42,859
Recorded investment in loans, Collectively evaluated for impairment	519,785	482,442
Total loans	552,012	525,301
Construction
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Individually evaluated for impairment	0	440
Reserve for loan losses Collectively evaluated for impairment	535	1,143
Reserve for loan losses Total	535	1,583
Recorded investment in loans Individually evaluated for impairment	1,987	9,734
Recorded investment in loans, Collectively evaluated for impairment	50,516	35,916
Total loans	52,503	45,650
Residential real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Individually evaluated for impairment	62	1,141
Reserve for loan losses Collectively evaluated for impairment	2,319	2,410
Reserve for loan losses Total	2,381	3,551
Recorded investment in loans Individually evaluated for impairment	430	4,840
Recorded investment in loans, Collectively evaluated for impairment	101,127	80,654
Total loans	101,557	85,494
Commercial and Industrial
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Individually evaluated for impairment	56	829
Reserve for loan losses Collectively evaluated for impairment	6,205	6,438
Reserve for loan losses Total	6,261	7,267
Recorded investment in loans Individually evaluated for impairment	5,823	9,602
Recorded investment in loans, Collectively evaluated for impairment	248,347	152,611
Total loans	254,170	162,213
Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Individually evaluated for impairment	0	301
Reserve for loan losses Collectively evaluated for impairment	1,401	1,876
Reserve for loan losses Total	1,401	2,177
Recorded investment in loans Individually evaluated for impairment	0	1,636
Recorded investment in loans, Collectively evaluated for impairment	35,990	37,870
Total loans	35,990	39,506
Allocated Financing Receivables
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Individually evaluated for impairment	783	3,799
Reserve for loan losses Collectively evaluated for impairment	19,360	22,375
Reserve for loan losses Total	20,143	26,174
Recorded investment in loans Individually evaluated for impairment	40,467	68,671
Recorded investment in loans, Collectively evaluated for impairment	955,765	789,493
Total loans	996,232	858,164
Unallocated
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for loan losses Total	$ 714	$ 1,087