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Income Taxes - Additional Information (Detail) - USD ($)
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Income Tax [Line Items]      
Operating loss carryforwards, latest expiration year   2037  
Operating loss carryforwards, expiration date   various years through 2037  
Operating loss carryforwards   $ 64,904,000 $ 62,655,000
Increase in operating loss carryforwards   2,249,000  
Net deferred tax asset recognized   $ 0  
Change period for unrecognized tax benefits   12 months  
Net decrease in deferred tax assets   $ 8,819,000  
Increase in deferred tax assets   724,000  
Tax cuts and jobs act of 2017, Change in tax rate in decrease in deferred tax assets   $ 9,543,000  
Statutory federal income tax rate   35.00% 35.00%
Scenario Plan [Member]      
Income Tax [Line Items]      
Statutory federal income tax rate 21.00%