Net Loss per Share - Schedule of Outstanding Options and Unvested Shares Excluded from Computation of Diluted Net Loss per Common Share (Details) - shares shares in Thousands		9 Months Ended
	Jun. 03, 2020	Sep. 30, 2020	Sep. 30, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from net loss per share (in shares)	1,800
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from net loss per share (in shares)		2,999	4,795
Unvested restricted stock awards and units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from net loss per share (in shares)		21,633	23,227
Convertible senior notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from net loss per share (in shares)		33,856	35,442
ESPP shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from net loss per share (in shares)		744	691