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Income Taxes - Schedule of Temporary Differences That Give Rise to Significant Net Deferred Tax Assets (Detail) - USD ($)
$ in Thousands
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
Deferred tax assets      
Net operating losses $ 62,619 $ 61,905  
Capitalized research and development expenses 282 423  
Credit carryforwards 167,498 167,501  
Deferred compensation 1,993 1,890  
Election out of installment method 956 820  
Accrued expenses 44 124  
Other temporary differences 672 720  
Installment sale tax basis 15,869 15,869  
Total gross deferred tax assets 249,933 249,252  
Valuation allowance $ (249,933) $ (249,252) $ (247,468)