Common Shares Reserved for Issuance - Schedule of Reserved Shares of Common Stock for Issuance (Details) - shares shares in Thousands	Sep. 30, 2020	Dec. 31, 2019
Class of Stock [Line Items]
Shares reserved for future issuance (shares)	78,320	76,852
Convertible senior notes
Class of Stock [Line Items]
Shares reserved for future issuance (shares)	33,856	35,442
Reserved under stock award plans
Class of Stock [Line Items]
Shares reserved for future issuance (shares)	40,148	37,982
Employee Stock Purchase Plan (ESPP)
Class of Stock [Line Items]
Shares reserved for future issuance (shares)	4,316	3,428