Selected Quarterly Financial Data - Quarterly Financial Data (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule Of Quarterly Financial Data [Line Items]
Product sales	$ 10,405	$ 8,355	$ 9,694	$ 6,945	$ 6,073	$ 7,677	$ 8,641	$ 2,474	$ 35,399	$ 24,864	$ 27,412
Total revenue	21,146	18,412	23,684	17,949	15,782	27,068	17,331	11,299	81,191	71,480	159,039
Cost of goods sold	7,290	7,228	7,203	8,707	5,450	5,038	8,140	3,263	30,428	21,891	25,667
Research and development expenses	46,373	34,016	33,201	35,085	33,302	31,018	32,270	30,176	148,675	126,766	108,065
Operating loss	(43,381)	(32,900)	(26,988)	(37,932)	(34,468)	(21,338)	(34,264)	(33,867)	(141,201)	(123,937)	(28,255)
Net loss	$ (52,926)	$ (43,547)	$ (34,285)	$ (41,097)	$ (37,495)	$ (24,068)	$ (36,381)	$ (36,034)	$ (171,855)	$ (133,978)	$ (37,938)
Basic and diluted net loss per share	$ (0.46)	$ (0.38)	$ (0.30)	$ (0.36)	$ (0.33)	$ (0.21)	$ (0.32)	$ (0.33)	$ (1.50)	$ (1.19)	$ (0.40)