Common stock (Reserved shares for issuance of common stock) (Details)	Dec. 31, 2013
Class of Stock [Line Items]
Common stock (in shares)	373,010
Options to purchase common stock
Class of Stock [Line Items]
Common stock (in shares)	328,519
Stock warrants
Class of Stock [Line Items]
Common stock (in shares)	44,491

Aggregate number of common shares reserved for future issuance.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.29)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_CommonStockCapitalSharesReservedForFutureIssuance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant