Consolidated Statements of Shareholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid in Capital [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Accumulated Deficit [Member]
Beginning Balance at Dec. 31, 2012	$ 2,573	$ 2	$ 337,184		$ (334,613)
Beginning Balance, shares at Dec. 31, 2012		15,767,525
Issuance of common stock for cash	6,347		6,347
Issuance of common stock for cash, shares		1,437,481
Issuance of common stock under our Equity Incentive Plan	36		36
Issuance of common stock under our Equity Incentive Plan, shares		10,317
Issuance of common stock for cash under our Employee Stock Purchase Plan	200		200
Issuance of common stock for cash under our 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
Change in unrealized (loss) income on marketable securities	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
Issuance of common stock for cash	5,600		5,600
Issuance of common stock for cash, shares		2,000,000
Issuance of common stock under our Equity Incentive Plan	79		79
Issuance of common stock under our Equity Incentive Plan, shares		22,842
Issuance of common stock for cash under our Employee Stock Purchase Plan	199		199
Issuance of common stock for cash under our Employee Stock Purchase Plan, shares		70,226
Issuance of common stock upon vesting of restricted stock units		31,825
Compensation expense related to fair value of employee share based awards	427		427
Beneficial conversion feature of convertible debt	1,032		1,032
Change in unrealized (loss) income on marketable securities	(4)			(4)
Net loss	(36,732)				(36,732)
Ending Balance at Dec. 31, 2014	(51,653)	$ 2	359,308	(3)	(410,960)
Ending Balance, shares at Dec. 31, 2014		19,404,697
Issuance of common stock warrant	1,721		1,721
Issuance of common stock for cash	$ 144		144
Issuance of common stock for cash, shares		125,000
Issuance of common stock under our Equity Incentive Plan, shares	0
Issuance of common stock for cash under our Employee Stock Purchase Plan	$ 38		38
Issuance of common stock for cash under our Employee Stock Purchase Plan, shares		26,157
Issuance of common stock upon vesting of restricted stock units		21,875
Compensation expense related to fair value of employee share based awards	1,120		1,120
Change in unrealized (loss) income on marketable securities	3			$ 3
Net loss	(21,310)				(21,310)
Ending Balance at Dec. 31, 2015	$ (71,658)	$ 2	$ 360,610		$ (432,270)
Ending Balance, shares at Dec. 31, 2015		19,577,729