Consolidated Statements of Changes in Stockholders' Equity (Deficit) - USD ($)
$ in Thousands
Common Stock.
Additional Paid-In Capital
Accumulated Deficit
Total
Balance at Dec. 31, 2012 $ 7 $ 5,483 $ (71,786) $ (66,296)
Balance (in shares) at Dec. 31, 2012 7,386,133      
Increase (Decrease) in Stockholders' Equity        
Exercise of stock options $ 1 324   325
Exercise of stock options (in shares) 290,604      
Accretion of issuance costs on redeemable convertible preferred stock   (347)   (347)
Stock-based compensation expense   2,426   2,426
Repurchase of common shares   (69) (110) (179)
Repurchase of common shares (in shares) (47,604)      
Net loss     (27,953) (27,953)
Balance at Dec. 31, 2013 $ 8 7,817 (99,849) (92,024)
Balance (in shares) at Dec. 31, 2013 7,629,133      
Increase (Decrease) in Stockholders' Equity        
Exercise of stock options $ 1 2,281   2,282
Exercise of stock options (in shares) 940,642      
Grant of common stock   55   55
Grant in common stock (in shares) 5,000      
Accretion of issuance costs on redeemable convertible preferred stock   (89)   (89)
Stock-based compensation expense   7,527   7,527
Conversion of redeemable convertible preferred stock to common stock $ 23 98,113   98,136
Conversion of redeemable convertible preferred stock to common stock (in shares) 23,501,208      
Conversion of Series D warrants to common stock warrants   821   821
Issuance of common stock, net of issuance costs $ 9 100,293   100,302
Issuance of common stock, net of issuance costs ( in shares) 8,626,377      
Exercise of warrants to purchase common stock (in shares) 32,709      
Net loss     (28,999) (28,999)
Balance at Dec. 31, 2014 $ 41 216,818 (128,848) $ 88,011
Balance (in shares) at Dec. 31, 2014 40,735,069     40,735,069
Increase (Decrease) in Stockholders' Equity        
Exercise of stock options $ 1 5,335   $ 5,336
Exercise of stock options (in shares) 1,141,731      
Stock-based compensation expense   11,749   11,749
Issuance of common stock in connection with settlement of restricted stock units, net of withholdings   (436)   (436)
Issuance of common stock in connection with settlement of restricted stock units, net of withholdings (in shares) 248,088      
Issuance of common stock, net of issuance costs $ 4 117,108   117,112
Issuance of common stock, net of issuance costs ( in shares) 3,625,000      
Issuance of common stock award   750   750
Issuance of common stock award (in shares) 26,567      
Net loss     (26,733) (26,733)
Balance at Dec. 31, 2015 $ 46 $ 351,324 $ (155,581) $ 195,789
Balance (in shares) at Dec. 31, 2015 45,776,455     45,776,455