Subsequent Events (Details) (USD $) In Millions, except Share data, unless otherwise specified			6 Months Ended		1 Months Ended			0 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2013 Series A Convertible Preferred Stock	Jun. 30, 2012 Stock options	Aug. 31, 2013 Subsequent Event Series A Convertible Preferred Stock	Aug. 31, 2013 Subsequent Event Common Stock	Jul. 31, 2013 Subsequent Event Public Offering and Controlled Equity Offering	Jul. 31, 2013 Subsequent Event Public Offering and Controlled Equity Offering Cantor Fitzgerald & Co	Jul. 18, 2013 Subsequent Event Stock options
Subsequent Events
Number of shares sold	15,729,524	15,478,177					2,142,857	488,475
Gross proceeds from sale of shares							$ 15.0	$ 4.2
Shares authorized under stock option plan				3,666,667					6,000,000
Number of shares of preferred stock converted to common stock			17,500		17,500
Number of shares of common stock issued upon conversion of preferred stock						18,229