Net Loss per Share (Tables)

9 Months Ended

Sep. 30, 2012

Net Loss per Share [Abstract]

Antidilutive securities excluded from computation of diluted net loss per share of common stock

	For the three months and nine months ended September 30,
	2012		2011
Convertible preferred stock		—		10,761,524
Stock options to purchase common stock		2,213,529		2,944,899
Restricted stock units for common stock		380,393		—
Restricted shares of common stock subject to repurchase		579,708		1,011,878
Common stock warrants		8,333		—
Convertible preferred stock warrants		—		19,999