Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Series C convertible preferred stock    
Sale price on common stock (in dollars per share) $ 0.95  
Series D convertible preferred stock    
Sale price on common stock (in dollars per share) 1.25 $ 1.25
Issuance costs   $ 67
Series E convertible preferred stock    
Sale price on common stock (in dollars per share) 1.53 $ 1.53
Issuance costs   $ 114
Series F convertible preferred stock    
Sale price on common stock (in dollars per share) $ 2.00  
Issuance costs $ 4,268