Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($)
$ in Thousands
Total
IPO [Member]
Secondary Offering [Member]
Convertible preferred stock [Member]
Convertible preferred stock [Member]
IPO [Member]
Convertible preferred stock [Member]
Series D-2 Preferred [Member]
Convertible preferred stock [Member]
Series E Preferred Stock [Member]
Common Stock [Member]
Common Stock [Member]
IPO [Member]
Common Stock [Member]
Secondary Offering [Member]
Additional Paid-in Capital [Member]
Additional Paid-in Capital [Member]
IPO [Member]
Additional Paid-in Capital [Member]
Secondary Offering [Member]
Other Comprehensive Income (Loss) [Member]
Accumulated Deficit [Member]
Beginning Balances at Dec. 31, 2013 $ (47,292)                   $ 6,454       $ (53,746)
Beginning Balances at Dec. 31, 2013       $ 57,497                      
Beginning Balances, shares at Dec. 31, 2013               1,257,311              
Beginning Balances, shares at Dec. 31, 2013       120,648,174                      
Issuance of convertible preferred stock           $ 9,977 $ 54,816                
Issuance of convertible preferred stock, shares           13,168,291 48,758,857                
Reclassification of warrant liability upon closing of IPO   $ 2,752                   $ 2,752      
Reclassification of call option liability upon closing of IPO   9,581                   9,581      
Conversion of convertible securities   122,290     $ (122,290)       $ 2     122,288      
Conversion of convertible securities, shares         (182,575,322)       15,876,104            
Issuance of common stock upon exercise of warrants 572                   572        
Issuance of common stock upon exercise of warrants, shares               158,179              
Issuance of stock   $ 132,137                   $ 132,137      
Issuance of stock, shares                 6,900,000            
Issuance of common stock upon exercise of options $ 59                   59        
Issuance of common stock upon exercise of options, shares 44,822             44,822              
Issuance of common stock under employee benefit plans $ 142                   142        
Issuance of common stock under employee benefit plans, shares               9,021              
Beneficial conversion feature related to the issuance of Series E preferred stock 25,559     $ (25,559)             25,559        
Deemed dividend related to beneficial conversion feature of convertible preferred stock (25,559)     $ 25,559             (25,559)        
Stock-based compensation 4,641                   4,641        
Net loss (57,513)                           (57,513)
Ending Balances at Dec. 31, 2014 167,369             $ 2     278,626       (111,259)
Ending Balances, shares at Dec. 31, 2014               24,245,437              
Issuance of stock     $ 80,209             $ 1     $ 80,208    
Issuance of stock, shares                   4,999,999          
Issuance of common stock upon exercise of options $ 121                   121        
Issuance of common stock upon exercise of options, shares 90,851             90,851              
Issuance of common stock under employee benefit plans $ 279                   279        
Issuance of common stock under employee benefit plans, shares               83,960              
Stock-based compensation 10,699                   10,699        
Net loss (82,177)                           (82,177)
Ending Balances at Dec. 31, 2015 176,500             $ 3     369,933       (193,436)
Ending Balances, shares at Dec. 31, 2015               29,420,247              
Issuance of stock     $ 59,136                   $ 59,136    
Issuance of stock, shares                   5,176,545          
Issuance of common stock upon exercise of options $ 140                   140        
Issuance of common stock upon exercise of options, shares 85,646             85,646              
Issuance of common stock under employee benefit plans $ 535                   535        
Issuance of common stock under employee benefit plans, shares               161,447              
Stock-based compensation 10,923                   10,923        
Unrealized loss on cash flow hedge (350)                         $ (350)  
Net loss (95,817)                           (95,817)
Ending Balances at Dec. 31, 2016 $ 151,067             $ 3     $ 440,667     $ (350) $ (289,253)
Ending Balances, shares at Dec. 31, 2016               34,843,885