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Convertible Notes (Schedule of Notes) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Nov. 17, 2017	Aug. 16, 2013
Debt instrument
Total long-term convertible notes	$ 156,031	$ 154,182	$ 152,359	$ 150,561	$ 148,788	$ 147,039
Convertible senior notes \| 1.375% convertible notes due 2023
Debt instrument
Face value	172,500				172,500		$ 172,500
Unamortized discount	(15,420)				(22,163)
Unamortized Debt Issuance Expense	(1,049)				(1,549)
Total convertible notes	156,031				148,788
Less current portion	0				0
Total long-term convertible notes	$ 156,031				$ 148,788
Convertible senior notes \| 1.125% Convertible Senior Notes due 2018
Debt instrument
Face value								$ 138,000