Statements of Convertible Preferred Stock, Redeemable Convertible Preferred Stock and Stockholders' Deficit (USD $) In Thousands, except Share data, unless otherwise specified		Total USD ($)	Common Stock	Additional Paid-In Capital Amount USD ($)	Accumulated Other Comprehensive Income (Loss) USD ($)	Accumulated Deficit USD ($)	Comprehensive Income (Loss) USD ($)	Series A-1 Convertible Preferred Stock USD ($)	Series A-2 Convertible Preferred Stock USD ($)	Series A-3 Convertible Preferred Stock USD ($)	Series A-4 Convertible Preferred Stock USD ($)	Series A-5 Convertible Preferred Stock USD ($)	Series A Convertible Preferred Stock USD ($)	Series B Convertible Preferred Stock USD ($)	Series C Convertible Preferred Stock USD ($)
Balance at Dec. 31, 2009		$ (101,598)		$ 3	$ 15	$ (101,616)							$ 93	$ 35,470	$ 96,131
Balance (in shares) at Dec. 31, 2009			320,424										61,664	1,599,997	10,146,629
Increase (Decrease) in Stockholders' Equity
Net loss		(14,630)				(14,630)	(14,630)
Unrealized loss from available-for-sale securities		(18)			(18)		(18)
Issuance of common stock		2		2
Issuance of common stock (in shares)			2,383
Stock-based compensation expense		134		134
Accretion of preferred stock issuance costs		(173)		(136)		(37)									173
Accretion of preferred stock to redemption value		(10,651)				(10,651)								2,839	7,812
Accretion of preferred stock investor rights/obligations		(1,318)				(1,318)									1,318
Balance at Dec. 31, 2010		(128,252)		3	(3)	(128,252)							93	38,309	105,434
Balance (in shares) at Dec. 31, 2010			322,807										61,664	1,599,997	10,146,629
Increase (Decrease) in Stockholders' Equity
Net loss		(42,476)				(42,476)	(42,476)
Unrealized loss from available-for-sale securities		8			8		8
Forced conversion to common stock		554		554									(33)	(296)	(225)
Forced conversion to common stock (in shares)			102,767										(21,661)	(177,697)	(314,496)
Recapitalization	[1]	60,981		8,269		52,712			75,979	9,629	271		(60)	(39,183)	(108,425)
Recapitalization (in shares)	[1]								983,208	142,227	3,998		(40,003)	(1,422,300)	(9,832,133)
Issuance of preferred stock								62,297				525
Issuance of preferred stock (in shares)								922,286				6,443
Accretion of dividends on preferred stock		(10,933)		(6,590)		(4,343)		1,968	4,000	579				1,170	3,216
Stock-based compensation expense		304		304
Stock options exercised		204		204
Stock options exercised (in shares)			219,825
Milestone payment settled with stock								1,410
Milestone payment settled with stock (in shares)								17,326
Balance at Dec. 31, 2011		(119,610)		2,744	5	(122,359)		65,675	79,979	10,208	271	525
Balance (in shares) at Dec. 31, 2011			645,399					939,612	983,208	142,227	3,998	6,443
Increase (Decrease) in Stockholders' Equity
Net loss		(69,128)				(69,128)	(69,128)
Unrealized loss from available-for-sale securities		(5)			(5)		(5)
Accretion of dividends on preferred stock		(13,992)		(4,818)		(9,174)		6,282	6,735	974
Stock-based compensation expense		1,795		1,795
Stock options exercised		279		279
Stock options exercised (in shares)			221,805
Balance at Dec. 31, 2012		$ (200,661)				$ (200,661)		$ 71,957	$ 86,714	$ 11,182	$ 271	$ 525
Balance (in shares) at Dec. 31, 2012			867,204					939,612	983,208	142,227	3,998	6,443

[1] The recapitalization includes the exchange of Series A, Series B and Series C shares for Series A-4, Series A-3, and Series A-2 shares, respectively, in addition to the 1:10 exchange of Series A-2, Series A-3, and Series A-4 preferred stock, which occurred in conjunction with the Merger, and is more fully described in note 4.