Quarterly report pursuant to Section 13 or 15(d)

Stock Incentive Plan - Schedule of Stock Option Activity (Detail)

v3.10.0.1
Stock Incentive Plan - Schedule of Stock Option Activity (Detail) - USD ($)
$ / shares in Units, $ in Thousands
 9 Months Ended 12 Months Ended
Sep. 30, 2018
Dec. 31, 2017
Shares    
Ending Balance 1,989,472  
Employee Stock Option [Member]    
Shares    
Beginning Balance 1,428,462  
Granted 650,000  
Exercised (17,615)  
Forfeited or expired (71,375)  
Ending Balance 1,989,472 1,428,462
Exercisable at end of period 1,055,716  
Expected to Vest 886,601  
Weighted Average Exercise Price    
Beginning Balance $ 5.20  
Granted 3.30  
Exercised 2.49  
Forfeited or expired 4.42  
Ending Balance 4.63 $ 5.20
Exercisable at end of period 5.51  
Expected to Vest 4.65  
Weighted Average Grant Date Fair value    
Beginning Balance 2.96  
Granted 1.86  
Exercised 2.11  
Forfeited or expired 3.20  
Ending Balance 2.60 $ 2.96
Exercisable at end of period 3.38  
Expected to Vest $ 2.62  
Weighted Average Remaining Contractual Term    
Contractual term 4 years 3 months 18 days 3 years 8 months 12 days
Exercisable at end of period 2 years 6 months  
Expected to Vest 4 years 3 months 18 days  
Aggregate Intrinsic Value    
Beginning Balance $ 653  
Exercised 35  
Forfeited or expired 28  
Ending Balance 312 $ 653
Exercisable at end of period 179  
Expected to Vest $ 128