Annual report pursuant to Section 13 and 15(d)

Income Tax - Additional Information (Detail)

v3.8.0.1
Income Tax - Additional Information (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Income Taxes [Line Items]        
Future enacted income tax rate assumed for both Federal and state deferred tax calculations   34.00% 34.00% 34.00%
Net operating loss carryforwards   $ 9,900 $ 1,300  
Unclaimed tax deductions   $ 15,500    
Starting range of research and development tax credits expiration period   2018    
Ending range of research and development tax credits expiration period   2037    
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   34.00% 34.00% 34.00%
Scenario, Forecast        
Income Taxes [Line Items]        
Income tax rate assumed for both State and Foreign deferred tax calculations 21.00%      
Investment tax credits carryforwards [Member]        
Income Taxes [Line Items]        
Investment tax credits   $ 2,603    
Research [Member]        
Income Taxes [Line Items]        
Investment tax credits   19,000,000    
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   120,400 115,900  
UNITED KINGDOM        
Income Taxes [Line Items]        
Net operating loss carryforwards   $ 849 $ 200