Quarterly report pursuant to Section 13 or 15(d)

Summary of Warrant Activity (Detail)

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Summary of Warrant Activity (Detail) - Warrants
shares in Thousands
 9 Months Ended
Sep. 30, 2017
$ / shares
shares
Shares  
Beginning Balance | shares 11,406
Granted | shares 3,926
Ending Balance | shares 15,332
Warrants exercisable at September 30, 2017 | shares 11,271
Weighted Average Exercise Price  
Beginning Balance | $ / shares $ 3.64
Granted or Issued | $ / shares 1.80
Ending Balance | $ / shares 3.17
Warrants exercisable at September 30, 2017 | $ / shares $ 3.64