Liabilities - Convertible Senior Notes - Carrying Amount (Details) - USD ($) $ in Thousands	Jun. 30, 2020	May 18, 2020	Dec. 31, 2019	Jan. 10, 2017
Debt
Principal amount	$ 381,695		$ 345,000
Unamortized debt discount	(59,589)		(40,820)
Unamortized transaction costs	(4,792)		(4,112)
Net carrying value	317,314		300,068
2023 Notes
Debt
Principal amount	256,695		345,000	$ 345,000
Unamortized debt discount	(25,816)		(40,820)
Unamortized transaction costs	(2,601)		(4,112)
Net carrying value	228,278		$ 300,068
2027 Notes
Debt
Principal amount	125,000	$ 125,000
Unamortized debt discount	(33,773)	$ (34,200)
Unamortized transaction costs	(2,191)
Net carrying value	$ 89,036