Annual report pursuant to Section 13 and 15(d)

Income Taxes - Reconciliation of Statutory Tax Rates and Effective Tax Rates (Detail)

v3.20.1
Income Taxes - Reconciliation of Statutory Tax Rates and Effective Tax Rates (Detail)
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Income Tax Disclosure [Abstract]      
Statutory rate 21.00% 21.00% 34.00%
Valuation allowance 6.10% (25.20%) 51.50%
Federal tax rate change 0.00% 0.00% (93.30%)
General business credits (2.90%) 6.20% 10.80%
Expiration of stock options (21.40%) 0.00% 0.00%
Other (2.80%) (2.00%) (3.00%)
Effective tax rate 0.00% 0.00% 0.00%