Exchangeable Senior Notes - Repurchase of Debt (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jun. 21, 2013
Debt Instrument [Line Items]
Total consideration paid for repurchase	$ 1,977,805	$ 1,109,854	$ 1,088,679
2013 Notes
Debt Instrument [Line Items]
Principal amount repurchased		49,259	13,911
Extinguishment of liability component		49,019	13,692
Reacquisition of equity component		31,251	6,350
Total consideration paid for repurchase		80,270	20,042
Extinguishment of liability component		(49,019)	(13,692)
Discount on exchangeable senior notes		(230)	(184)	$ (3,750)
Related debt issuance costs		(10)	(35)	$ (1,672)
Gain/(loss) on repurchase		$ 0	$ 0