Carrying value as of the balance sheet date of long-term debt (with maturities initially due after one year or beyond the operating cycle if longer) identified as Convertible Notes Payable, excluding current portion. Convertible Notes Payable is a written promise to pay a note which can be exchanged for a specified amount of another, related security, at the option of the issuer and the holder.

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Debt - Senior Convertible Notes (Details) - USD ($)	6 Months Ended	12 Months Ended
Debt - Senior Convertible Notes (Details) - USD ($)	Jun. 30, 2021	Dec. 31, 2020	May 31, 2020	Nov. 30, 2018
Senior Convertible Notes
Carrying amount of liability component	$ 1,710,700,000	$ 1,667,200,000
Senior Notes
Senior Convertible Notes
Principal amount	2,057,500,000	2,057,500,000
Unamortized debt discount	(329,800,000)	(371,100,000)
Unamortized debt issuance costs	(17,000,000.0)	(19,200,000)
Carrying amount of liability component	1,710,700,000	1,667,200,000
Carrying amount of equity component	461,000,000.0	461,000,000.0
Senior Notes \| Senior Convertible Notes due 2023
Senior Convertible Notes
Principal amount	$ 850,000,000.0	$ 850,000,000.0		$ 850,000,000.0
Remaining amortization period of debt discount on the liability component:	2 years 4 months 24 days	2 years 10 months 24 days
Senior Notes \| Senior Convertible Notes due 2025
Senior Convertible Notes
Principal amount	$ 1,207,500,000	$ 1,207,500,000	$ 1,210,000,000
Remaining amortization period of debt discount on the liability component:	4 years 4 months 24 days	4 years 10 months 24 days