Net Loss Per Share (Tables)

12 Months Ended

Dec. 31, 2017

Earnings Per Share [Abstract]

Schedule of Outstanding Shares of Common Stock Equivalents Excluded from Calculation of Diluted Net Loss Per Share Attributable to Common Stockholders

The following outstanding shares of common stock equivalents were excluded from the calculation of diluted net loss per share attributable to common stockholders for the periods presented because including them would have been antidilutive:

	As of December 31,
	2017		2016		2015
Options to purchase common stock		7,470,601		6,543,654		3,522,813
Common stock subject to repurchase		—		—		23,554
Total potential dilutive shares		7,470,601		6,543,654		3,546,367