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 9 Months Ended
Mar. 12, 2018
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Aug. 31, 2018
May 31, 2018
Dec. 31, 2017
Nov. 30, 2017
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%          
Employee Stock Purchase Plan to eligible employees, compensation expense recognized   $ 52,000 $ 52,000 $ 100,000 $ 100,000        
Proceeds from issuance of Common stock       7,700,000          
Share-based Compensation       13,658,000 12,048,000        
Adjustments To Additional Paid In Capital At Market Offering Costs       $ (240,000)          
Proceeds from Sale of Common Stock Gross Percent                 3.00%
Common Stock, Shares, Issued   56,183,480   56,183,480   147,741 86,289 50,991,285  
Common Stock, Value, Issued   $ 56,000   $ 56,000       $ 51,000  
Sale of Stock, Price Per Share   $ 4.33   $ 4.33          
Market Offering [Member]                  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                  
Shares Issued, Price Per Share   $ 2.61   $ 2.61          
Proceeds from issuance of Common stock       $ 7,000,000          
Issuance of Common Stock for At the Market Offering in shares       2,668,756          
Adjustments To Additional Paid In Capital At Market Offering Costs       $ 200,000          
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 $ 69,000,000                
Checkpoint Therapeutics, Inc [Member]                  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                  
Common Stock, Shares, Issued   1,841,774   1,841,774          
Common Stock, Value, Issued   $ 8,000,000   $ 8,000,000          
Maximum Authorized Amount of Shares to be Sold                 $ 100,000,000
Research and Development Expense [Member]                  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                  
Allocated Share-based Compensation Expense   1,800,000 1,600,000 4,900,000 4,800,000        
General and Administrative Expense [Member]                  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                  
Allocated Share-based Compensation Expense   $ 3,200,000 $ 2,700,000 $ 8,700,000 $ 7,200,000        
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       3 years 7 months 6 days          
Share-based Compensation       $ 9,800,000          
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        
Share-based Compensation         $ 1,700,000        
Employee Stock Option [Member]                  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                  
Common Stock issued in connection with the first ESPP offering       289,359          
Common Stock, Capital Shares Reserved for Future Issuance   710,641   710,641