Debt - Carrying Amount (Details) - Convertible Debt - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Principal	$ 875,351	$ 460,000
Unamortized debt discount	0	(73,355)
Unamortized debt issuance costs	(20,528)	(8,059)
Net carrying amount	854,823	378,586
2023 Notes
Debt Instrument [Line Items]
Principal	45,351	230,000
Unamortized debt discount	0	(30,425)
Unamortized debt issuance costs	(621)	(3,009)
Net carrying amount	44,730	196,566
2025 Notes
Debt Instrument [Line Items]
Principal	230,000	230,000
Unamortized debt discount	0	(42,930)
Unamortized debt issuance costs	(5,629)	(5,050)
Net carrying amount	224,371	$ 182,020
2027 Notes
Debt Instrument [Line Items]
Principal	600,000
Unamortized debt discount	0
Unamortized debt issuance costs	(14,278)
Net carrying amount	$ 585,722