Annual report pursuant to Section 13 and 15(d)

Federal Income Tax Provision Compared With Statutory Rates (Detail)

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Federal Income Tax Provision Compared With Statutory Rates (Detail)
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Income Tax Disclosure [Abstract]      
Statutory regular federal income tax rate (21.00%) (34.00%) (34.00%)
Change in valuation allowance 28.60% (90.60%) 40.40%
State tax benefit (net of federal benefit) (3.10%) (3.20%) (3.00%)
Research credits (1.70%) (1.70%) (3.40%)
Foreign amounts with no tax benefit     0.20%
Non-deductible expenses 0.30% 1.00% 0.60%
Effect of change in rate from federal Tax Reform 0.50% 127.10% 0.50%
Other (3.30%) (2.00%) (0.20%)
Total 0.30% (3.40%) 1.10%