Annual report pursuant to Section 13 and 15(d)

Income Taxes - Additional Information (Detail)

v3.8.0.1
Income Taxes - Additional Information (Detail) - USD ($)
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Income Taxes [Line Items]      
Change in valuation allowance $ 5,638,000 $ 4,260,000 $ 1,765,000
Cumulative net operating loss $ 41,600,000 $ 24,700,000 $ 14,900,000
Net operating loss expiration beginning period 2032    
U.S. corporate tax rate 34.00% 34.00% 34.00%
Net reduction in net deferred tax assets $ 3,346,000    
Income tax expense (benefit) $ 0 $ 0 $ 0
Scenario, Plan [Member]      
Income Taxes [Line Items]      
U.S. corporate tax rate 21.00%    
Accounting Standards Update 2016-09 [Member]      
Income Taxes [Line Items]      
Income tax expense (benefit) $ (813,000)    
Net impact of adoption $ 0