Preferred Stock and Stockholders' Equity - Convertible Preferred Stock Warrants (Details)		0 Months Ended	1 Months Ended
	Jul. 27, 2012	Nov. 29, 2010 Common Stock [Member]	Jul. 31, 2010 Oxford [Member] Series B Preferred Stock [Member]	Jul. 31, 2010 Silicon Valley Bank [Member] Series B Preferred Stock [Member]	Jul. 31, 2010 Oxford/SVB [Member] Series B Preferred Stock [Member]	Nov. 29, 2010 Oxford/SVB [Member] Common Stock [Member]
Class of Stock [Line Items]
Conversion of convertible preferred stock to common stock at initial public offering, shares		14,240,000	1,145,455	445,455
Exercise price					1.10	11.00
Sale of warrants to purchase common stock	14,625,000					159,090