Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended		395 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013
Income Statement [Abstract]
Revenues from license fees, grants and research contracts	$ 2,951	$ 11,207	$ 7,425	$ 22,419	$ 180,973
Operating expenses:
Research and development	12,984	13,849	26,746	28,654	412,414
General and administrative	7,054	2,915	13,181	6,196	132,268
Acquired in-process research and development					29,461
Operating loss	(17,087)	(5,557)	(32,502)	(12,431)	(393,170)
Other (loss) income:
Interest income and other, net	(19)	107	218	203	9,741
(Loss) income on change in warrant valuation	(1,945)	13,488	(28,851)	2,562	(95,819)
Realized gain on sale of short-term securities - available-for-sale					3,863
Write-down of short-term securities - available-for-sale					(17,001)
Other (expense) income, total	(1,964)	13,595	(28,633)	(2,765)	(99,216)
Net (loss) income	(19,051)	8,038	(61,135)	(9,666)	(492,386)
Other comprehensive (loss) income:
Write-down of short-term securities - available-for-sale					17,001
Realized gain on sale of short-term securities - available-for-sale					(3,863)
Unrealized loss on short-term securities - available-for-sale					(13,138)
Other comprehensive (loss) income, net of tax, total
Comprehensive (loss) income	$ (19,051)	$ 8,038	$ (61,135)	$ (9,666)	$ (492,386)
Net (loss) income per share - basic	$ (0.60)	$ 0.36	$ (1.92)	$ (0.43)
Net (loss) income per share - diluted	$ (0.60)	$ 0.35	$ (1.92)	$ (0.43)
Weighted average number of common shares outstanding for computing basic (loss) income per share	31,984	22,624	31,899	22,624
Weighted average number of common shares outstanding for computing diluted (loss) income per share	31,984	22,658	31,899	22,624