Net Loss Per Share Attributable to Common Stockholders (Tables)

3 Months Ended

Mar. 31, 2014

Earnings Per Share [Abstract]

Shares Excluded from Computation of Diluted Net Loss Per Share Attributable to Common Stockholders

The following common stock equivalents were excluded from the computation of diluted net loss per share attributable to common stockholders because they had an anti-dilutive impact (in thousands):

	Three Months Ended March 31,
	2014		2013
Options to purchase common stock		2,957		4,147
Unvested restricted stock		1,044		778
Employee Stock Purchase Program		12		—