Related Party Transactions (Details) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended
Dec. 31, 2012 Silver Creek Convertible notes	Apr. 30, 2012 Sanofi	Dec. 31, 2012 Directors, officers, scientific advisory board members and related parties Convertible notes
Related Party Transactions
Shares of common stock purchased by related party in connection with initial public offering		5,217,391
Debt issued	$ 1.6		$ 0.3

Increase of additional borrowings on existing and new debt instruments.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(f))

-URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 08

-Paragraph f

-Article 4

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