Annual report pursuant to Section 13 and 15(d)

Income Taxes - Summary of Reconciliation of Expected Statutory Federal Income Tax Provision to Actual Income Tax Provision (Detail)

v3.10.0.1
Income Taxes - Summary of Reconciliation of Expected Statutory Federal Income Tax Provision to Actual Income Tax Provision (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Income Tax Disclosure [Abstract]      
Income tax benefit at federal statutory tax rate $ (15,235) $ (9,369) $ (9,068)
Change in valuation allowance 29,501 (32,709) 9,775
Effect of change in enacted tax rates   38,194  
State income taxes, net of federal benefit (10,112) 5,094 (458)
Permanent items 563 4,027 196
Research credits (4,717) (5,237) (445)
Income tax (benefit) expense $ 0 $ 0 $ 0