Consolidated Statement Of Stockholders' (Deficit) Equity (USD $) In Thousands, except Share data, unless otherwise specified	Common Stock [Member]	Additional Paid-In Capital [Member]	Deferred Stock-Based Compensation [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Deficit [Member]	Total
Balance at Dec. 31, 2008	$ 18	$ 209,370	$ (2)	$ 32	$ (190,144)	$ 19,274
Balance, shares at Dec. 31, 2008	17,568,402
Issuance of common stock upon exercise of stock options for cash		288				288
Issuance of common stock upon exercise of stock options for cash, shares	104,262
Issuance of common stock at $3.00 - $3.75 per share upon vesting of early exercised stock options		2				2
Issuance of common stock at $3.00 - $3.75 per share upon vesting of early exercised stock options, shares	785
Issuance of common stock under the Employee Stock Purchase Plan		77				77
Issuance of common stock under the Employee Stock Purchase Plan, shares	52,510
Stock-based compensation		2,517				2,517
Amortization of deferred stock-based compensation			2			2
Comprehensive loss:
Change in unrealized gain/(loss) on investments				(40)		(40)
Net loss					(21,867)	(21,867)
Total comprehensive loss						(21,907)
Balance at Dec. 31, 2009	18	212,254		(8)	(212,011)	253
Balance, shares at Dec. 31, 2009	17,725,959
Issuance of common stock upon exercise of stock options for cash		258				258
Issuance of common stock upon exercise of stock options for cash, shares	79,869
Issuance of common stock under the Employee Stock Purchase Plan		354				354
Issuance of common stock under the Employee Stock Purchase Plan, shares	63,280
Stock-based compensation		2,354				2,354
Comprehensive loss:
Change in unrealized gain/(loss) on investments				6		6
Net loss					(44,516)	(44,516)
Total comprehensive loss						(44,510)
Balance at Dec. 31, 2010	18	215,220		(2)	(256,527)	(41,291)
Balance, shares at Dec. 31, 2010	17,869,108
Issuance of common stock upon exercise of stock options for cash		41				41
Issuance of common stock upon exercise of stock options for cash, shares	22,207
Issuance of common stock under the Employee Stock Purchase Plan		162				162
Issuance of common stock under the Employee Stock Purchase Plan, shares	97,319
Stock-based compensation		3,065				3,065
Issuance of common stock, net of offering costs	12	11,854				11,866
Issuance of common stock, net of offering costs, shares	11,749,552
Issuance of warrant to purchase stock to investors at $0.14 per share including fair value		6,699				6,699
Issuance of warrant to purchase stock to investor at fair value		1,140				1,140
Release of restricted stock units	159,000
Comprehensive loss:
Change in unrealized gain/(loss) on investments				3		3
Net loss					(49,545)	(49,545)
Total comprehensive loss						(49,542)
Balance at Dec. 31, 2011	$ 30	$ 238,181		$ 1	$ (306,072)	$ (67,860)
Balance, shares at Dec. 31, 2011	29,897,186