Net Loss Per Share - Summary of Shares Excluded from Calculation of Diluted Loss Per Share with a Potential Dilutive Impact (Details) - shares shares in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Shares excluded from calculation of diluted loss per share with a potential dilutive impact	3,683	3,065
Options to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Shares excluded from calculation of diluted loss per share with a potential dilutive impact	866	1,378
Employee Stock Purchase Plan
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Shares excluded from calculation of diluted loss per share with a potential dilutive impact	70	76
Restricted Stock Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Shares excluded from calculation of diluted loss per share with a potential dilutive impact	2,747	1,611