Net Loss Per Share (Tables)

12 Months Ended

Dec. 31, 2014

Net Loss Per Share

Computation of basic and diluted net loss per share attributable to common stockholders

	Year Ended December 31,
	2014		2013		2012
Net loss	$	(48,429)	$	(25,056)	$	(74,495)
Weighted-average common shares outstanding		70,837		58,540		55,828
Net loss per share — basic and diluted	$	(0.68)	$	(0.43)	$	(1.33)

Anti-dilutive shares excluded from the calculation of diluted net loss per share

	December 31,
	2014	2013	2012
Options to purchase common stock	25,590	18,363	15,419
Common stock warrants	3,926	5,931	5,154
Conversion of convertible preferred stock	—	2,857	—
Unvested restricted stock awards	828	55	122
Contingently redeemable shares	—	—	126
Convertible promissory notes	—	—	3,444
Total shares excluded from net loss per share attributable to common stockholders	30,344	27,206	24,265