Annual report pursuant to Section 13 and 15(d)

Income Taxes - Schedule of Reconciliation of Income Taxes at Statutory Federal Income Tax Rate to Net Income Taxes (Detail)

v3.8.0.1
Income Taxes - Schedule of Reconciliation of Income Taxes at Statutory Federal Income Tax Rate to Net Income Taxes (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Income Tax Disclosure [Abstract]    
U.S. federal taxes (benefit) at statutory rate $ (7,867) $ (3,750)
State federal income tax benefit (21) 10
Permanent differences 87 105
Research and development credits (237) (339)
Change in valuation allowance due to operations 4,766 3,974
Acquisition-related permanent differences 2,281 0
Expiring state carryovers and other 991 0
Change in valuation allowance due to Tax Act (6,863) 0
U.S. Statutory Rate Change due to Tax Act 6,863 0
Total $ 0 $ 0