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Long-term Debt - Summary of Long-term Debt (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Jan. 30, 2018	Jan. 12, 2018
Debt Instrument [Line Items]
Total debt	$ 255,116	$ 248,169
Less: Current portion	(25,626)	(25,617)
Long-term debt	229,490	222,552
Unamortized debt issuance costs	$ 1,200	1,400
1.5% Convertible Unsecured Senior Notes Due February 2023
Debt Instrument [Line Items]
Stated interest rate	1.50%		1.50%
Convertible Debt
Debt Instrument [Line Items]
Total debt	$ 155,480	167,594
Convertible Debt \| 1.5% Convertible Unsecured Senior Notes Due February 2023
Debt Instrument [Line Items]
Unamortized debt issuance costs	2,433	3,112
Stated interest rate				1.50%
Long-term debt, gross	174,569	192,250
Unsecured Debt
Debt Instrument [Line Items]
Total debt	25,000	25,000
Stated interest rate					2.50%
Other debt and finance lease obligations
Debt Instrument [Line Items]
Total debt	4,877	5,041
Revolving Credit Facility Due January 2022
Debt Instrument [Line Items]
Total debt	$ 69,759	$ 50,534