Income taxes (Details Textual) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014
Income Tax Disclosure [Line Items]
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	$ 2,501

Amount of increase (decrease) in the valuation allowance for a specified deferred tax asset.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 45

-Paragraph 20

-URI http://asc.fasb.org/extlink&oid=37586315&loc=d3e32123-109318

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration