CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (USD $) In Thousands, except Share data	Total USD ($)	Committed Equity Financing Facility USD ($)	Common Stock USD ($)	Common Stock Committed Equity Financing Facility	Additional Paid-in Capital USD ($)	Additional Paid-in Capital Committed Equity Financing Facility USD ($)	Accumulated Deficit USD ($)	Accumulated Other Comprehensive (Loss) Income USD ($)
Beginning balance at Dec. 31, 2009	$ 12,114		$ 4		$ 350,872		$ (339,245)	$ 483
Beginning balance (in shares) at Dec. 31, 2009			38,332,119
Issuance of common stock from exercise of stock options (in shares)	10,820		10,820
Issuance of common stock from exercise of stock options	11				11
Issuance of common stock pursuant to employee stock purchase plan (in shares)	81,032		81,032
Issuance of common stock pursuant to employee stock purchase plan	65				65
Issuance of common stock, net of issuance costs (in shares)				926,590
Issuance of common stock, net of issuance costs		747				747
Net loss (income)	15,139						15,139
Stock-based compensation	1,583				1,583
Other comprehensive (loss) income	29							29
Ending balance at Dec. 31, 2010	29,688		4		353,278		(324,106)	512
Ending balance (in shares) at Dec. 31, 2010			39,350,561
Issuance of common stock and warrants, net of issuance costs (in shares)			12,565,446
Issuance of common stock and warrants, net of issuance costs	13,900		1		13,899
Issuance of common stock from exercise of stock options (in shares)	10,434		10,434
Issuance of common stock from exercise of stock options	13				13
Issuance of common stock pursuant to employee stock purchase plan (in shares)	189,879		189,879
Issuance of common stock pursuant to employee stock purchase plan	109				109
Issuance of common stock in connection with lease termination (in shares)			782,339
Issuance of common stock in connection with lease termination	1,322				1,322
Net loss (income)	(22,765)						(22,765)
Stock-based compensation	1,598				1,598
Other comprehensive (loss) income	(503)							(503)
Ending balance at Dec. 31, 2011	23,362		5		370,219		(346,871)	9
Ending balance (in shares) at Dec. 31, 2011			52,898,659
Issuance of common stock and warrants, net of issuance costs (in shares)			19,000,000
Issuance of common stock and warrants, net of issuance costs	80,538		2		80,536
Issuance of common stock from exercise of stock options (in shares)	293,595		293,595
Issuance of common stock from exercise of stock options	453				453
Issuance of common stock pursuant to employee stock purchase plan (in shares)	205,862		205,862
Issuance of common stock pursuant to employee stock purchase plan	123				123
Issuance of common stock from exercise of warrants on a net issuance basis			936,100
Issuance of common stock under ATM Agreement, net of issuance costs (in shares)			5,347,137
Issuance of common stock under ATM Agreement, net of issuance costs	17,090		1		17,089
Reclassification to redeemable common stock (in shares)			(5,347,137)
Reclassification to redeemable common stock	(17,658)		(1)		(17,657)
Net loss (income)	(20,849)						(20,849)
Stock-based compensation	1,930				1,930
Other comprehensive (loss) income	(5)							(5)
Ending balance at Dec. 31, 2012	$ 84,984		$ 7		$ 452,693		$ (367,720)	$ 4
Ending balance (in shares) at Dec. 31, 2012			73,334,216