Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity - Additional Information (Detail)

v3.10.0.1
Stockholders' Equity - Additional Information (Detail) - USD ($)
 3 Months Ended 6 Months Ended
Mar. 12, 2018
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Employee Stock Purchase Plan to eligible employees, compensation expense recognized   $ 43,000 $ 40,000 $ 81,000 $ 75,000
Share-based Compensation       8,623,000 7,736,000
Adjustments To Additional Paid In Capital At Market Offering Costs       $ (141,000)  
Market Offering [Member]          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Shares Issued, Price Per Share   $ 3.60   $ 3.60  
Proceeds from issuance of Common stock       $ 4,100,000  
Issuance of Common Stock for At the Market Offering in shares       1,130,835  
Adjustments To Additional Paid In Capital At Market Offering Costs       $ 71,000  
Checkpoint [Member]          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Shares Issued, Price Per Share $ 4.35        
Proceeds from issuance of Common stock $ 20,800,000        
Stock Issued During Period, Shares, New Issues 5,290,000        
Stock Issued During Period, Value, New Issues $ 23,000,000        
Payments of Stock Issuance Costs 2,200,000        
Available-for-sale Securities $ 77,000,000        
Research and Development Expense [Member]          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Allocated Share-based Compensation Expense   $ 800,000 2,400,000 3,100,000 3,200,000
General and Administrative Expense [Member]          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Allocated Share-based Compensation Expense   $ 2,800,000 $ 2,400,000 $ 5,500,000 $ 4,300,000
Restricted Stock [Member]          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition       2 years 10 months 24 days  
Share-based Compensation       $ 12,400,000  
Restricted Stock Units (RSUs) [Member]          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition         2 years 3 months 18 days
Share-based Compensation         $ 2,700,000
Employee Stock Option [Member]          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Employee Stock Purchase Plan to eligible employees, Reckoning fair value percentage during offering period   85.00%   85.00%  
Common Stock issued in connection with the first ESPP offering       289,359  
Common Stock, Capital Shares Reserved for Future Issuance   110,641   110,641