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, 2012	$ 48,445	$ 83	$ 325,177	$ 6,909	$ (283,724)
Beginning Balance (in shares) at Dec. 31, 2012		83,236,840
Stock-based compensation	2,482		2,482
Exercise of employee stock options (in shares)	570,168	570,168
Exercise of employee stock options	956	1	955
Exercise of warrants to purchase common stock (in shares)		98,359
Exercise of warrants to purchase common stock	201		343	(142)
Expired warrants			3,110	(3,110)
Cancelled restricted stock		(163,747)
Repurchase of shares of restricted common stock (in shares)		(60,041)
Repurchase of shares of restricted common stock	(250)		(250)
Net loss	(48,203)				(48,203)
Ending Balance at Sep. 30, 2013	$ 3,631	$ 84	$ 331,817	$ 3,657	$ (331,927)
Ending Balance (in shares) at Sep. 30, 2013		83,681,579