Statement Of Stockholders' Equity (USD $) In Thousands, except Share data	Total	Common Stock	Additional Paid in Capital, Common Stock	Other Additional Capital	Accumulated Deficit during Development Stage
Beginning Balance at Dec. 31, 2011	$ 71,607	$ 69	$ 246,519	$ 12,611	$ (187,592)
Beginning Balance (in shares) at Dec. 31, 2011		69,206,044
Stock-based compensation	2,290		2,290
Exercise of employee stock options (in shares)	8,300	8,300
Exercise of employee stock options	30		30
Exercise of warrants to purchase common stock (in shares)		192,603
Exercise of warrants to purchase common stock	622		788	(166)
Issuance of restricted common stock		170,302
Forfeiture of unvested restricted common stock		(66,360)
Expired warrants			5,433	(5,433)
Issuance of common stock in a securities offering, net of commission and expenses of $3,426 (in shares)		10,114,401
Issuance of common stock in a securities offering, net of commission and expenses of $3,426	49,170	11	49,159
Net loss	(48,083)				(48,083)
Ending Balance at Jun. 30, 2012	$ 75,636	$ 80	$ 304,219	$ 7,012	$ (235,675)
Ending Balance (in shares) at Jun. 30, 2012		79,625,290