Annual report pursuant to Section 13 and 15(d)

Income Tax - Additional Information (Detail)

v3.19.1
Income Tax - Additional Information (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Income Taxes [Line Items]      
Future enacted income tax rate assumed for both Federal and state deferred tax calculations 21.00% 34.00% 34.00%
Net operating loss carryforwards $ 17,600 $ 9,900  
Unclaimed tax deductions 14,500    
Net deferred tax assets recognized 0    
Unrecognized tax benefits 700    
Accrued interest and penalties related to income taxes $ 0 $ 0  
Income tax rate assumed for both State and Foreign deferred tax calculations 21.00% 34.00% 34.00%
Investment tax credits carryforwards [Member]      
Income Taxes [Line Items]      
Investment tax credits $ 2,655    
Research [Member]      
Income Taxes [Line Items]      
Investment tax credits $ 100    
Research and development tax credits expiration period 2038    
Canada | Investment tax credits carryforwards [Member]      
Income Taxes [Line Items]      
Investment tax credits $ 2,600 $ 2,600  
Canada | Non Capital Loss Carryforwards [Member]      
Income Taxes [Line Items]      
Investment tax credits 123,300 120,400  
UK      
Income Taxes [Line Items]      
Net operating loss carryforwards $ 1,829 $ 800