Net Loss per Share (Details) - shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 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)	1,220,008	992,665
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
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
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
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
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
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)	5,298,510	5,850,211	5,883,885