Annual report pursuant to Section 13 and 15(d)

Income Taxes - Additional Information (Detail)

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Income Taxes - Additional Information (Detail) - USD ($)
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Income Taxes Disclosure [Line Items]        
U.S. corporate income tax rate   35.00%    
Valuation allowance recorded to offset income tax expense from revaluation of deferred tax assets and liabilities due to corporate tax rate change   $ 6,863,000 $ 0  
Income tax expense from revaluation of deferred tax assets and liabilities due to change corporate tax rate   $ 6,900,000    
Description of foreign operations   The Company currently has one foreign subsidiary that has not commenced operations.    
Increase in valuation allowance       $ 4,800,000
Unrecognized benefits   $ 1,143,000 0 $ 0
Accrued interest or penalties   0 $ 0  
Unrecognized tax benefits expected to be recognized in next twelve months   79,000    
Federal        
Income Taxes Disclosure [Line Items]        
Net operating loss carryforwards   $ 63,200,000    
Year net operating loss carryforwards begin to expire   2021    
Research and development credits   $ 1,100,000    
Year research and development credits begin to expire   2022    
State        
Income Taxes Disclosure [Line Items]        
Net operating loss carryforwards   $ 7,600,000    
Year net operating loss carryforwards begin to expire   2017    
Research and development credits   $ 4,900,000    
Scenario, Plan        
Income Taxes Disclosure [Line Items]        
U.S. corporate income tax rate 21.00%