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Convertible Notes and Credit Facility - Schedule of Debt (Details) - Convertible Debt - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Nov. 30, 2019	Mar. 31, 2018	Feb. 28, 2014
Debt Instrument [Line Items]
Long-term debt, total	$ 54,121	$ 53,821
2.75% 2014 Notes due 2034
Debt Instrument [Line Items]
Interest rate on notes				2.75%	2.75%
Principal amount	1,079	1,079	$ 1,100	$ 51,300
Unamortized debt discount	(17)	(18)
Unamortized debt issuance cost	(4)	(4)			$ (1,100)
Long-term debt, total	1,058	1,057
5.25% 2019 Notes due 2024
Debt Instrument [Line Items]
Interest rate on notes			5.25%
Principal amount	55,000	55,000
Unamortized debt issuance cost	(1,937)	(2,236)
Long-term debt, total	$ 53,063	$ 52,764