Consolidated Statements of Comprehensive Loss (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Consolidated Statements of Comprehensive Loss
Other revenue			$ 11,500
Operating expenses:
Research and development	12,095	5,706	34,654	18,190
General and administrative	4,747	3,647	16,267	8,410
Total operating expenses	16,842	9,353	50,921	26,600
Operating loss	(16,842)	(9,353)	(39,421)	(26,600)
Investment income	40	193	141	901
Interest expense	(525)	(222)	(1,802)	(225)
Gain on sale of assets, net			2	5
Loss before income taxes	(17,327)	(9,382)	(41,080)	(25,919)
Provision (benefit) for income taxes	0	0	(1,221)	4
Net loss	(17,327)	(9,382)	(39,859)	(25,923)
Basic and diluted net loss per share (in dollars per share)	$ (0.46)	$ (0.38)	$ (1.19)	$ (1.04)
Weighted average basic and diluted common shares outstanding (in shares)	37,389	25,013	33,577	24,916
Net loss	(17,327)	(9,382)	(39,859)	(25,923)
Comprehensive loss:
Unrealized (loss) gain on short-term investments, net of taxes		199		385
Comprehensive loss	$ (17,327)	$ (9,183)	$ (39,859)	$ (25,538)