Income Taxes - Significant Components of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Net operating loss carryforwards	$ 399,361	$ 300,693
Research and other credits	128,015	116,955
Operating lease liabilities	36,907	0
Stock-based compensation	30,875	21,518
Property, plant and equipment	5,021	2,124
Capitalized research expenses	3,705	8,072
Reserves and accruals	2,934	8,066
Deferred revenue	1,908	4,467
Deferred tax assets before valuation allowance	608,726	461,895
Valuation allowance for deferred tax assets	(575,087)	(460,455)
Total deferred tax assets	33,639	1,440
Operating lease right-of-use assets	(31,718)	0
Other	(1,725)	(1,270)
Total deferred tax liabilities	(33,443)	(1,270)
Net deferred tax assets	$ 196	$ 170