Annual report pursuant to Section 13 and 15(d)

Accounting Policies - Additional Information (Detail)

v3.20.4
Accounting Policies - Additional Information (Detail)
$ in Thousands
 12 Months Ended
Dec. 31, 2020
USD ($)
segment
Dec. 31, 2019
USD ($)
Jan. 01, 2019
USD ($)
Accounting Policies [Line Items]      
Maturity period of liquid investments 3 months    
Number of operating segments | segment 1    
Right-of-use assets $ 146 $ 329  
ASU 2016-02 [Member]      
Accounting Policies [Line Items]      
Change in Accounting Principle, Accounting Standards Update, Adopted [true false] true    
Change in Accounting Principle, Accounting Standards Update, Adoption Date Jan. 01, 2019    
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false] true    
Right-of-use assets     $ 500
Operating lease liability     $ 500
ASU 2018-13 [Member]      
Accounting Policies [Line Items]      
Change in Accounting Principle, Accounting Standards Update, Adopted [true false] true    
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false] true    
Restricted Stock Unit Awards [Member]      
Accounting Policies [Line Items]      
Award vesting period 4 years