Annual report pursuant to Section 13 and 15(d)

Income Tax - Additional Information (Detail)

v3.8.0.1
Income Tax - Additional Information (Detail) - USD ($)
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Income Tax Contingency [Line Items]      
Federal statutory income tax rate   34.00% 34.00%
Decrease in net deferred tax assets due to reduction in the U.S. corporate income tax rate   $ 19,432,000  
Decrease in valuation allowance due to reduction in the U.S. corporate income tax rate   $ 19,432,000  
Tax credit carry forward expiration period   2033  
Operating loss carryforwards, limitations on use   Stock ownership of one or more 5% shareholders (shareholders owning 5% or more of the Company's outstanding capital stock) has increased on a cumulative basis by more than 50 percentage points.  
Maximum [Member]      
Income Tax Contingency [Line Items]      
Federal statutory income tax rate   35.00%  
Scenario, Forecast [Member]      
Income Tax Contingency [Line Items]      
Federal statutory income tax rate 21.00%    
Domestic Tax Authority [Member]      
Income Tax Contingency [Line Items]      
Operating loss carryforwards   $ 84,418,000  
Deferred tax assets, tax credit carryforwards, research   $ 2,686,000  
Tax credit research and development expiration period   2032  
State and Local Jurisdiction [Member]      
Income Tax Contingency [Line Items]      
Operating loss carryforwards   $ 85,515,000  
Deferred tax assets, tax credit carryforwards, research   $ 2,088,000