Lines of Credit and Long-Term Debt - Components of Interest Expense (Details) - 3.5% Convertible Notes Due 2023 - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Cash interest expense	$ 7,000	$ 7,000	$ 7,000
Non-cash interest expense	11,735	10,587	9,459
Total interest expense	$ 18,735	$ 17,587	$ 16,459