Long-Term Debt - Additional Information Related to Senior and Convertible Notes (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Nov. 15, 2019	Jun. 10, 2014
Debt Instrument [Line Items]
Principal amount	$ 1,703,324
Less: Unamortized discount	(112,798)	$ (139,981)
Deferred issuance costs	(11,505)	(14,058)
Total long-term debt	1,579,021	1,448,461
Convertible Debt
Debt Instrument [Line Items]
Principal amount	1,702,414	1,602,500
6.0% Senior Notes | Senior Notes
Debt Instrument [Line Items]
Principal amount	0	650,000
Less: Unamortized discount		(8,425)
Deferred issuance costs		(1,466)
Total long-term debt		640,109
4.625% Senior Notes | Senior Notes
Debt Instrument [Line Items]
Principal amount	750,000	0
Less: Unamortized discount	(5,523)
Deferred issuance costs	(1,761)
Total long-term debt	742,716
3.25% Convertible Notes | Convertible Debt
Debt Instrument [Line Items]
Additional paid-in capital	37,688	37,700		$ 37,700
Principal amount	402,414	402,500
Less: Unamortized discount	(4,644)	(14,363)		$ (59,000)
Deferred issuance costs	(855)	(2,605)
Total long-term debt	396,915	385,532
1.75% Convertible Notes | Convertible Debt
Debt Instrument [Line Items]
Additional paid-in capital	88,138	88,138	$ 88,100
Principal amount	550,000	550,000
Less: Unamortized discount	(102,631)	(117,193)	(118,900)
Deferred issuance costs	(8,889)	(9,987)	$ (2,800)
Total long-term debt	$ 438,480	$ 422,820