Net Loss Per Share - Schedule of Outstanding Common Equivalent Shares Excluded from Computation of Diluted Net Loss Per Share (Details) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding common equivalent shares (in shares)	26,516	25,524	26,516	25,524
Stock options and ESPP
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding common equivalent shares (in shares)	9,226	8,770	9,226	8,770
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding common equivalent shares (in shares)	5,769	5,233	5,769	5,233
Shares related to convertible senior notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding common equivalent shares (in shares)	11,521	11,521	11,521	11,521