Net Loss per Share (Details)	3 Months Ended		9 Months Ended
Net Loss per Share (Details)	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
RSUs
Potential dilutive securities that would have been anti-dilutive
Potential dilutive securities that would have been anti-dilutive due to net loss (in shares)	1,013,239		1,013,239
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
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
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
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)		12,797		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)	6,282,657	5,483,948	6,282,657	5,483,948

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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