Statement Of Stockholders' Equity (USD $) In Thousands, except Share data	Total	Common Stock [Member]	Additional Paid in Capital, Common Stock [Member]	Other Additional Capital [Member]	Accumulated Deficit during Development Stage [Member]
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	3,482		3,482
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)		259,660
Exercise of warrants to purchase common stock	742		1,011	(269)
Issuance of restricted common stock		170,302
Forfeiture of unvested restricted common stock		123,370
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
Repurchase of shares of restricted common stock (in shares)		(15,740)
Repurchase of shares of restricted common stock	(96)		(96)
Net loss	(65,907)				(65,907)
Ending Balance at Sep. 30, 2012	$ 59,028	$ 80	$ 305,538	$ 6,909	$ (253,499)
Ending Balance (in shares) at Sep. 30, 2012		79,619,597