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Debt (Long-term Debt) (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Oct. 07, 2020	Nov. 15, 2019	Jun. 10, 2014
Debt Instrument [Line Items]
Less: Unamortized discount	$ (96,429)	$ (112,798)
Deferred issuance costs	(9,818)	(11,505)
Total debt	1,678,753	1,579,021
Less: current portion	(568,054)	(396,801)
Total long-term debt, less current portion	1,110,699	1,182,220
Senior Notes \| 4.625% Senior Notes
Debt Instrument [Line Items]
Stated interest rate			4.625%
Total Notes	750,000	750,000
Convertible Debt
Debt Instrument [Line Items]
Total Notes	1,300,000	1,702,414
Convertible Debt \| 3.25% Convertible Notes
Debt Instrument [Line Items]
Stated interest rate					3.25%
Total Notes	0	402,414
Convertible Debt \| 1.75% Convertible Notes
Debt Instrument [Line Items]
Stated interest rate				1.75%
Total Notes	550,000	550,000
Deferred issuance costs				$ (2,800)
Loans Payable \| Paycheck Protection Program, CARES Act
Debt Instrument [Line Items]
Total Notes	0	910
Loans Payable \| Bridge Loan
Debt Instrument [Line Items]
Total Notes	$ 485,000	$ 0