Income Taxes - Components of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Reserves and accruals	$ 21,823	$ 20,622
Net operating loss carryforwards	39,733	33,811
Research and development credit carryforwards	38,179	36,914
Deferred stock-based compensation	1,202	1,675
Intangibles	7,838	8,224
Operating lease liabilities	7,822	8,892
Capitalized research and development expenses	10,805	10,897
Other	442	0
Gross deferred tax assets	127,844	121,035
Valuation allowance	(99,585)	(95,518)	$ (77,144)	$ (77,756)
Gross deferred tax assets after valuation allowance	28,259	25,517
Deferred tax liabilities:
Depreciation	(6,399)	(1,272)
Convertible notes	(4,708)	(6,275)
Operating lease right-of-use assets	(6,529)	(7,076)
Other	0	(319)
Gross deferred tax liabilities	(17,636)	(14,942)
Net deferred tax assets	$ 10,623	$ 10,575