Income Taxes - Significant Components of Deferred Tax Assets and Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Deferred tax assets:
Net operating loss carryforwards	$ 351,354	$ 342,128
Research and other credits	52,769	51,125
Sale of future royalties	39,750
Deferred revenue	39,521	48,732
Stock-based compensation	23,746	19,268
Capitalized research expenses	7,192	9,514
Property and equipment	8,482	8,081
Reserves and accruals	8,776	8,083
Other	2,773	3,895
Deferred tax assets before valuation allowance	534,363	490,826
Valuation allowance for deferred tax assets	(534,268)	(490,689)
Total deferred tax assets	95	137
Deferred tax liabilities:
Property and equipment		(75)
Total deferred tax liabilities		(75)
Net deferred tax assets	$ 95	$ 62