Convertible Senior Notes - Schedule of the Liability and Equity Components of the Convertible Senior Notes (Details) - Convertible Senior Notes - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Convertible Senior Notes due 2024
Debt Instrument [Line Items]
Principal	$ 600,000	$ 600,000
Less: Notes discounts and issuance costs, net of amortization	(98,944)	(117,078)
Net carrying amount	501,056	482,922
Equity component, net of issuance costs	138,064	138,064
Series A Notes
Debt Instrument [Line Items]
Principal	23,436	119,828
Less: Notes discounts and issuance costs, net of amortization	0	(2,540)
Net carrying amount	23,436	117,288
Equity component, net of issuance costs	15,559	79,555
Series B Notes
Debt Instrument [Line Items]
Principal	460,000	460,000
Less: Notes discounts and issuance costs, net of amortization	(34,843)	(49,650)
Net carrying amount	425,157	410,350
Equity component, net of issuance costs	$ 117,834	$ 117,834