Common Stock (Tables)

12 Months Ended

Dec. 31, 2012

Common Stock

Schedule of shares reserved for future issuance

(in thousands)	December 31, 2011		December 31, 2012
Conversion of Series B, Series C, Series D, Series E, Series F and Series G convertible preferred stock		66,256		—
Convertible preferred stock warrants		302		—
Common stock warrants		2,640		2,842
Options to purchase common stock		17,617		18,066
		86,815		20,908