Net Loss per Share (Details)	3 Months Ended
Net Loss per Share (Details)	Mar. 31, 2014	Mar. 31, 2013
Restricted stock units
Potential dilutive securities that would have been anti-dilutive
Potential dilutive securities that would have been anti-dilutive due to net loss (in shares)	986,841
Redeemable convertible preferred stock, Series A
Potential dilutive securities that would have been anti-dilutive
Potential dilutive securities that would have been anti-dilutive due to net loss (in shares)	10,033,976	10,033,976
Redeemable convertible preferred stock, Series B
Potential dilutive securities that would have been anti-dilutive
Potential dilutive securities that would have been anti-dilutive due to net loss (in shares)	5,057,901	5,057,901
Redeemable convertible preferred stock, Series C
Potential dilutive securities that would have been anti-dilutive
Potential dilutive securities that would have been anti-dilutive due to net loss (in shares)	4,429,601	4,429,601
Redeemable convertible preferred stock, Series D
Potential dilutive securities that would have been anti-dilutive
Potential dilutive securities that would have been anti-dilutive due to net loss (in shares)	3,979,730	3,979,730
Warrants to purchase Series D redeemable convertible preferred stock
Potential dilutive securities that would have been anti-dilutive
Potential dilutive securities that would have been anti-dilutive due to net loss (in shares)	83,818	12,797
Stock options
Potential dilutive securities that would have been anti-dilutive
Potential dilutive securities that would have been anti-dilutive due to net loss (in shares)	6,738,838	5,033,358

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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