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
	Mar. 31, 2020	Mar. 31, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Outstanding common equivalent shares	26,348	25,101
Stock Options and ESPP
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Outstanding common equivalent shares	9,424	7,705
Restricted Stock Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Outstanding common equivalent shares	5,403	5,875
Shares Related to Convertible Senior Notes
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Outstanding common equivalent shares	11,521	11,521