Statements Of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended			377 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011
Statements Of Operations [Abstract]
Revenues from license fees, grants and research contracts	$ 46,990	$ 29,420	$ 17,585	$ 136,219
Operating expenses:
Research and development	66,862	35,972	24,396	333,266
General and administrative	16,055	14,382	8,696	104,457
Acquired in-process research and development				29,461
Operating loss	(35,927)	(20,934)	(15,507)	(330,965)
Other non-operating (loss) income:
Interest (expense) income and other, net	587	259	(454)	9,169
Gain (loss) on change in warrant valuation	33,022	(11,502)	(9,198)	24,970
Realized gain on sale of short-term securities- available-for-sale				3,863
Write-down of short-term securities- available-for-sale				(17,001)
Total other non operating income	33,609	(11,243)	(9,652)	21,001
Net income (loss)	$ (2,318)	$ (32,177)	$ (25,159)	$ (309,964)
Net income (loss) per share-basic	$ (0.02)	$ (0.29)	$ (0.27)
Net income (loss) per share-diluted	$ (0.02)	$ (0.29)	$ (0.27)
Weighted average number of common shares outstanding for computing basic income (loss) per share (in thousands)	129,595	111,233	93,090
Weighted average number of common shares outstanding for computing diluted income (loss) per share (in thousands)	129,595	111,233	93,090