Quarterly report pursuant to Section 13 or 15(d)

Stockholder's Equity - Summary of Common Stock Shares Activity (Detail)

v3.19.2
Stockholder's Equity - Summary of Common Stock Shares Activity (Detail) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2019
Jun. 30, 2018
Jun. 30, 2019
Jun. 30, 2018
Common Stock Outstanding Roll Forward [Roll Forward]        
Beginning balance $ 11,330 $ 36,844 $ 31,225 $ 21,410
Beginning balance (in shares)     47,971,989  
Net loss (8,403) (10,757) $ (31,311) (14,761)
Stock-based compensation expense 446 468 938 893
Common stock issued through employee stock purchase plan     21 20
Common stock issued, net of expenses 4,046   6,556 18,998
Common stock issued for April 2019 conversion of Notes 2,984   2,984  
Common stock issued for vested restricted stock units (1) (2) (11) (7)
Ending balance $ 10,402 26,553 $ 10,402 26,553
Ending balance (in shares) 54,520,131   54,520,131  
Common Stock        
Common Stock Outstanding Roll Forward [Roll Forward]        
Beginning balance $ 50 $ 47 $ 48 $ 29
Beginning balance (in shares) 50,232,429 46,843,441 47,971,989 28,971,651
Net loss $ 0 $ 0 $ 0 $ 0
Stock-based compensation expense 0 0 0 0
Common stock issued through employee stock purchase plan     $ 0 $ 0
Common stock issued through employee stock purchase plan (in shares)     19,259 13,591
Common stock issued, net of expenses $ 2   $ 6 $ 18
Common stock issued, net of expenses (in shares) 2,660,909   4,887,478 17,852,193
Common stock issued for April 2019 conversion of Notes $ 2   $ 2  
Common stock issued for April 2019 conversion of Notes (in shares) 1,626,000   1,626,000  
Common stock issued for vested restricted stock units $ 0 $ 0 $ (2) $ 0
Common stock issued for vested restricted stock units (in shares) 793 631 15,405 6,637
Ending balance $ 54 $ 47 $ 54 $ 47
Ending balance (in shares) 54,520,131 46,844,072 54,520,131 46,844,072
Additional Paid-in Capital        
Common Stock Outstanding Roll Forward [Roll Forward]        
Beginning balance $ 251,906 $ 246,049 $ 248,895 $ 226,631
Net loss 0 0 0 0
Stock-based compensation expense 446 468 938 893
Common stock issued through employee stock purchase plan     21 20
Common stock issued, net of expenses 4,044   6,550 18,980
Common stock issued for April 2019 conversion of Notes 2,982   2,982  
Common stock issued for vested restricted stock units (1) 0 (9) (7)
Ending balance 259,377 246,517 259,377 246,517
Accumulated Deficit        
Common Stock Outstanding Roll Forward [Roll Forward]        
Beginning balance (240,626) (209,252) (217,718) (205,250)
Net loss (8,403) (10,757) (31,311) (14,761)
Stock-based compensation expense 0 0 0 0
Common stock issued through employee stock purchase plan     0 0
Common stock issued, net of expenses 0   0 0
Common stock issued for April 2019 conversion of Notes 0   0  
Common stock issued for vested restricted stock units 0 (2) 0 0
Ending balance $ (249,029) $ (220,011) $ (249,029) $ (220,011)