Income Taxes - Tax Effects of Temporary Differences and Carryforwards that Give Rise to Significant Portions of the Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Net operating loss carryforwards	$ 76,033	$ 62,405
Tax credits	39,625	11,794
Amortization of deferred stock compensation - non- qualified	5,172	6,569
Reserves and accruals	1,528	1,140
Deferred revenue	20,312	20,991
Depreciation and amortization	15	0
Lease liability	434	0
Gross deferred tax assets	143,119	102,899
Less: valuation allowance	(142,761)	(102,891)
Total deferred tax assets	358	8
Deferred tax liabilities:
Depreciation and amortization	0	(8)
Right of use asset	(358)	0
Total deferred tax liabilities	(358)	(8)
Net deferred tax assets	$ 0	$ 0