Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Common Stock [Member] | IPO [Member]
Stock issuance cost		$ 2,620
Common Stock [Member] | Secondary Offering [Member]
Stock issuance cost	$ 866
Series C Convertible Preferred Stock [Member]
Stock, issuance price per share			$ 0.56
Stock issuance cost			$ 335
Convertible preferred stock, call option liability			$ 864
Series D Preferred Stock [Member]
Stock, issuance price per share			$ 0.56
Stock issuance cost			$ 209
Convertible preferred stock, call option liability			$ 126
Series D-2 Preferred [Member] | Issuance Date of February 2014 [Member]
Stock, issuance price per share		$ 0.76
Stock issuance cost		$ 23
Series E Preferred Stock [Member] | Issuance Date of February 2014 [Member]
Stock, issuance price per share		$ 1.13
Stock issuance cost		$ 184