Condensed Statements of Stockholders' Equity And Comprehensive Loss (Unaudited) (USD $) In Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)
Beginning balance at Dec. 31, 2010	$ 54,264	$ 5	$ 271,112	$ (216,852)	$ (1)
Beginning balance, shares at Dec. 31, 2010	45,004	45,004
Net loss	(31,987)			(31,987)
Unrealized gains in short-term investments	1				1
Comprehensive loss	(31,986)
Issuance of common stock, shares		2,185
Issuance of common stock	5,000		5,000
Issuance of common stock pursuant to vesting of restricted stock units, shares		8
Exercise of stock options, shares		1
Exercise of stock options	1		1
Share-based compensation expense	2,588		2,588
Ending balance at Jun. 30, 2011	$ 29,867	$ 5	$ 278,701	$ (248,839)	$ 0
Ending balance, shares at Jun. 30, 2011	47,198	47,198