Unsecured Convertible Senior Notes - Unsecured convertible senior notes outstanding (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Principal amount	$ 320,030	$ 320,030
Unamortized discount		(6,572)
Unamortized debt issuance costs	(5,672)
Total unsecured convertible senior notes, net	314,358	313,458
2023 Unsecured Convertible Senior Notes
Debt Instrument [Line Items]
Principal amount	95,000	95,000
Unamortized discount		(1,282)
Unamortized debt issuance costs	(956)
Total unsecured convertible senior notes, net	94,044	93,718
Fair value of outstanding unsecured convertible senior notes (1)	85,263	87,163
2026 Unsecured Convertible Senior Notes
Debt Instrument [Line Items]
Principal amount	225,030	225,030
Unamortized discount		(5,290)
Unamortized debt issuance costs	(4,716)
Total unsecured convertible senior notes, net	220,314	219,740
Fair value of outstanding unsecured convertible senior notes (1)	$ 132,064	$ 171,867