Annual report pursuant to Section 13 and 15(d)

Income Tax - Additional Information (Detail)

v3.20.4
Income Tax - Additional Information (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Income Taxes [Line Items]      
Future enacted income tax rate assumed for both Federal and state deferred tax calculations 21.00% 21.00% 21.00%
Net operating loss carryforwards $ 34,800 $ 25,300  
Unclaimed tax deductions 16,000    
Net deferred tax assets recognized 0    
Unrecognized tax benefits 800    
Accrued interest and penalties related to income taxes 0 0  
Investment tax credits carryforwards [Member]      
Income Taxes [Line Items]      
Investment tax credits 3,029    
Research [Member]      
Income Taxes [Line Items]      
Investment tax credits $ 300    
Research and development tax credits expiration period 2040    
Canada | Investment tax credits carryforwards [Member]      
Income Taxes [Line Items]      
Investment tax credits $ 2,800 2,900  
Canada | Non Capital Loss Carryforwards [Member]      
Income Taxes [Line Items]      
Investment tax credits 105,600 104,200  
UK      
Income Taxes [Line Items]      
Net operating loss carryforwards $ 3,236 $ 2,700