Income Taxes - Income Taxes Effect of Each Type of Temporary Difference Comprising Net Differed Tax Asset (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Net operating losses	$ 125,859	$ 118,220
Stock-based compensation	7,565	7,111
Tax credits	14,690	9,149
Lease Liability	2,219	2,715
Other reserves and accrued liabilities	14,702	5,580
Gross deferred tax assets	165,035	142,775
Less: valuation allowance	(160,841)	(137,976)	$ (140,117)
Total deferred tax assets	4,194	4,799
Deferred tax liabilities:
Depreciation and amortization	(2,399)	(2,544)
Lease Asset	(1,784)	(2,242)
Other liabilities	(11)	(13)
Total deferred tax liabilities	$ (4,194)	$ (4,799)