Annual report pursuant to Section 13 and 15(d)

Income Taxes - Summary of Reconciliation of Statutory U.S. Federal Rate to Company's Effective Tax Rate (Detail)

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Income Taxes - Summary of Reconciliation of Statutory U.S. Federal Rate to Company's Effective Tax Rate (Detail)
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Income Tax Disclosure [Abstract]      
Federal income tax benefit at statutory rate (21.00%) (21.00%) (34.00%)
State income tax, net of federal benefit (15.09%) (5.64%) (9.95%)
Permanent items including change in fair value of warrants (21.87%) 4.80% (22.03%)
Change in valuation allowance 62.56% 23.95% (50.33%)
R&D tax credits (4.72%) (2.11%) (3.02%)
Deferred re-measurement     118.03%
Other 0.12%   (1.30%)
Effective income tax (benefit) expense rate 0.00% 0.00% 0.00%