Lines of Credit and Long-Term Debt - Schedule of Components of Interest Expense (Details) - 3.5% Convertible Notes Due 2023 - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Debt Instrument [Line Items]
Cash interest expense	$ 1,750	$ 1,750	$ 5,250	$ 5,250
Non-cash interest expense	3,011	2,706	8,641	7,807
Total interest expense	$ 4,761	$ 4,456	$ 13,891	$ 13,057