Consolidated Statements of Stockholders' Equity (Deficit) (USD $) In Thousands, except Share data	Total	Common Stock [Member]	Additional Paid in Capital [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Accumulated Deficit [Member]
Beginning Balance at Dec. 31, 2010	$ 12,290	$ 1	$ 278,391	$ 2	$ (266,104)
Beginning Balance, shares at Dec. 31, 2010		5,976,591
Issuance of common stock and common stock warrants for cash	15,941		15,941
Issuance of common stock and common stock warrants for cash, shares		1,192,703
Issuance of common stock for cash under the Company's Equity Incentive Plan	2		2
Issuance of common stock for cash under the Company's Equity Incentive Plan,Shares		98
Issuance of common stock for cash under the Company's Employee Stock Purchase Plan	202		202
Issuance of common stock for cash under the Company's Employee Stock Purchase Plan, shares		24,998
Issuance of common stock upon vesting of restricted stock units		19,202
Compensation expense related to consultant stock options	17		17
Compensation expense related to fair value of employee share based awards	2,389		2,389
Comprehensive income (loss)	(2)			(2)
Net loss	(40,531)				(40,531)
Ending Balance at Dec. 31, 2011	(9,692)	1	296,942		(306,635)
Ending Balance, shares at Dec. 31, 2011		7,213,592
Issuance of common stock and common stock warrants for cash	20,231	1	20,230
Issuance of common stock and common stock warrants for cash, shares		4,400,000
Issuance of common stock for cash under the Company's Equity Incentive Plan	14,929		14,929
Issuance of common stock for cash under the Company's Equity Incentive Plan,Shares		3,812,225
Issuance of common stock for cash under the Company's Employee Stock Purchase Plan	82		82
Issuance of common stock for cash under the Company's Employee Stock Purchase Plan, shares		18,409
Issuance of common stock upon vesting of restricted stock units		323,299
Compensation expense related to fair value of employee share based awards	5,001		5,001
Net loss	(27,978)				(27,978)
Ending Balance at Dec. 31, 2012	2,573	2	337,184		(334,613)
Ending Balance, shares at Dec. 31, 2012		15,767,525
Issuance of common stock and common stock warrants for cash	6,347		6,347
Issuance of common stock and common stock warrants for cash, shares		1,437,481
Issuance of common stock for cash under the Company's Equity Incentive Plan	36		36
Issuance of common stock for cash under the Company's Equity Incentive Plan,Shares	10,317	10,317
Issuance of common stock for cash under the Company's Employee Stock Purchase Plan	200		200
Issuance of common stock for cash under the Company's Employee Stock Purchase Plan, shares		54,494
Issuance of common stock upon vesting of restricted stock units		9,987
Compensation expense related to fair value of employee share based awards	3,371		3,371
Beneficial conversion feature of convertible debt	3,112		3,112
Comprehensive income (loss)	1			1
Net loss	(39,615)				(39,615)
Ending Balance at Dec. 31, 2013	$ (23,975)	$ 2	$ 350,250	$ 1	$ (374,228)
Ending Balance, shares at Dec. 31, 2013		17,279,804