Commitments and contingencies (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014 ClinicalMilestone	Dec. 31, 2013
Commitments and contingencies [Abstract]
Potential future payments		$ 7.5
Number of clinical milestones	2
Payments made on achievement of clinical milestones	1.0
Potential future milestone payments on each additional final marketing approval	$ 2.0

The fair value, as of the date of each statement of financial position presented, of other assets which are owned but transferred to serve as collateral for the payment of the related debt obligation, and that are reclassified and separately reported in the statement of financial position because the transferee has the right by contract or custom to sell or re-pledge them.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 30

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6467456&loc=d3e113888-111728

Name:	us-gaap_PledgedAssetsSeparatelyReportedOtherAssetsPledgedAsCollateralAtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant