Long-term Debt - Summary of Long-term Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Jan. 12, 2018
Debt Instrument [Line Items]
Total debt	$ 189,146	$ 248,169
Less: Current portion	(25,620)	(25,617)
Long-term debt	163,526	222,552
Unamortized debt issuance costs	$ 1,300	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	$ 141,692	167,594
Convertible Debt | 1.5% Convertible Unsecured Senior Notes Due February 2023
Debt Instrument [Line Items]
Unamortized debt issuance costs	$ 2,010	3,112
Stated interest rate	1.50%
Long-term debt, gross	$ 157,369	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	4,772	5,041
Revolving Credit Facility Due January 2022
Debt Instrument [Line Items]
Total debt	$ 17,682	$ 50,534