Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Additional Information (Detail)

v3.20.1
Summary of Significant Accounting Policies - Additional Information (Detail)
12 Months Ended
Dec. 31, 2019
USD ($)
Segment
Dec. 31, 2018
USD ($)
Dec. 31, 2017
USD ($)
Jan. 01, 2019
USD ($)
Dec. 31, 2016
PerformanceObligation
Summary Of Significant Accounting Policies [Line Items]          
Realized gains and losses on investments $ 0 $ 0 $ 0    
Other-than-temporary declines in value of marketable securities 0 0 0    
Impairment losses recognized $ 50,000        
Collaboration and license agreement termination period Sep. 30, 2019        
Unrecognized tax benefits that would, if recognized, affect the Company's effective tax rate $ 0        
Recognized interest or penalties on income tax $ 0 $ 0 $ 0    
Risk-free interest rate basis The risk-free interest rate is based on the average yield of five- and seven-year U.S. Treasury Bills as of the valuation date.        
Number of operating segment | Segment 1        
ROU assets $ 221,000     $ 600,000  
Lease liabilities 338,000     $ 700,000  
Collaboration Agreement [Member]          
Summary Of Significant Accounting Policies [Line Items]          
Unrecognized royalty revenue $ 0        
Collaboration Agreement [Member] | Novartis [Member]          
Summary Of Significant Accounting Policies [Line Items]          
Number of significant performance obligations | PerformanceObligation         2
Collaboration and license agreement termination period Sep. 30, 2019        
Minimum [Member]          
Summary Of Significant Accounting Policies [Line Items]          
Estimated useful lives of the assets 3 years        
Maximum [Member]          
Summary Of Significant Accounting Policies [Line Items]          
Estimated useful lives of the assets 5 years