CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income	Accumulated Deficit
Balance at Dec. 31, 2010	$ 75,255	$ 32	$ 232,679	$ 2,751	$ (160,207)
Balance (in shares) at Dec. 31, 2010		32,055,382
Increase (Decrease) in Stockholders' Equity
Shares Issued under Stock Option and Employee Stock Purchase Plans	173		173
Shares Issued under Stock Option and Employee Stock Purchase Plans (in shares)		80,254
Shares Issued in Connection with Cantor Agreement	2,155	1	2,154
Shares Issued in Connection with Cantor Agreement (in shares)		575,000
Shares Issued in Underwritten Offering	33,695	11	33,684
Shares Issued in Underwritten Offering (in shares)	11,500,000	11,500,000
Share-Based Compensation	2,342		2,342
Foreign Currency Translation Adjustments	(9)			(9)
Unrealized Gains (Losses) on Marketable Securities	(90)			(90)
Net Loss	(44,799)				(44,799)
Balance at Dec. 31, 2011	68,722	44	271,032	2,652	(205,006)
Balance (in shares) at Dec. 31, 2011		44,210,636
Increase (Decrease) in Stockholders' Equity
Shares Issued under Stock Option and Employee Stock Purchase Plans	163		163
Shares Issued under Stock Option and Employee Stock Purchase Plans (in shares)		70,587
Shares Issued in Connection with Cantor Agreement	40,138	8	40,130
Shares Issued in Connection with Cantor Agreement (in shares)		8,003,290
Shares Issued in Underwritten Offering	43,483	12	43,471
Shares Issued in Underwritten Offering (in shares)	12,075,000	12,075,000
Share-Based Compensation	2,298		2,298
Foreign Currency Translation Adjustments	2			2
Unrealized Gains (Losses) on Marketable Securities	91			91
Net Loss	(59,123)				(59,123)
Balance at Dec. 31, 2012	95,774	64	357,094	2,745	(264,129)
Balance (in shares) at Dec. 31, 2012	64,359,513	64,359,513
Increase (Decrease) in Stockholders' Equity
Shares Issued under Stock Option and Employee Stock Purchase Plans	5,403	1	5,402
Shares Issued under Stock Option and Employee Stock Purchase Plans (in shares)		840,228
Shares Issued in Connection with Cantor Agreement	17,134	2	17,132
Shares Issued in Connection with Cantor Agreement (in shares)		2,433,608
Shares Issued in Underwritten Offering	278,563	22	278,541
Shares Issued in Underwritten Offering (in shares)	21,613,483	21,613,483
Share-Based Compensation	4,548		4,548
Foreign Currency Translation Adjustments	(3)			(3)
Unrealized Gains (Losses) on Marketable Securities	(74)			(74)
Net Loss	(81,550)				(81,550)
Balance at Dec. 31, 2013	$ 319,795	$ 89	$ 662,717	$ 2,668	$ (345,679)
Balance (in shares) at Dec. 31, 2013	89,246,832	89,246,832