Income Taxes - Significant Components of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Net operating loss carryforwards	$ 447,761	$ 423,776
Research and other credits	70,258	66,666
Deferred revenue	29,658	29,758
Stock-based compensation	22,832	21,948
Capitalized research expenses	12,440	14,795
Sale of future royalties	12,319	20,153
Reserves and accruals	8,309	8,288
Property, plant and equipment	6,451	8,264
Other	3,158	2,218
Deferred tax assets before valuation allowance	613,186	595,866
Valuation allowance for deferred tax assets	(612,996)	(595,690)
Total deferred tax assets	190	176
Total deferred tax liabilities	0	0
Net deferred tax assets	$ 190	$ 176