Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (USD $) In Thousands, except Share data, unless otherwise specified	Series B-2 Shares	Series B Convertible Preferred Stock	Series A-1 Convertible Preferred Stock	Series A-2 Convertible Preferred Stock	Series A-3 Convertible Preferred Stock	Series A-4 Convertible Preferred Stock	Series A-5 Convertible Preferred Stock	Series A-6 Convertible Preferred Stock	Common Stock	Additional paid-in-capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Total
Balance at Dec. 31, 2013		$ 43,892	$ 78,737	$ 93,977	$ 12,232	$ 271	$ 525	$ 23,168				$ (277,301)	$ (277,301)
Balance (in shares) at Dec. 31, 2013		701,235	939,612	983,208	142,227	3,998	6,443	496,111	385,664
Increase (Decrease) in Stockholders' Equity
Net loss												(44,517)	(44,517)
Unrealized gain from marketable securities											(10)		(10)
Issuance of preferred stock	26,152											(4,458)
Issuance of preferred stock (in shares)	448,060
Accretion of dividends on preferred stock	685	1,515	3,084	3,246	470					(4,542)			(9,000)
Issuance of warrants										41			41
Exercise of warrants									20,435
Exercise of options										3
Exercise of options (in shares)									1,168				1,000
Stock-based compensation expense										2,560			2,560
Issuance of common stock, net									1	50,437			50,438
Issuance of common stock (in shares)									7,012,744
Conversion of convertible preferred stock into common stock	(26,837)	(45,407)	(81,821)	(97,223)	(12,702)	(271)	(525)	(33,277)	2	298,061			298,063
Conversion of convertible preferred stock into common stock (in shares)	(448,060)	(701,235)	(939,612)	(983,208)	(142,227)	(3,998)	(6,443)	(682,958)	22,327,786
Reclassification of warrant liability to additional paid-in-capital										3,117			3,117
Reclassification of warrant liability to additional paid-in-capital										41			41
Stock options exercised										3
Balance at Sep. 30, 2014									$ 3	$ 349,677	$ (10)	$ (326,276)	$ 23,394
Balance (in shares) at Sep. 30, 2014									29,747,797