Financial Instruments (Schedule of Long-Term Debt) (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Long-term debt	$ 350,000	$ 398,009
Less: current portion	0	(9)
Long-term debt, net of current portion	350,000	398,000
Long-term Debt
Debt Instrument [Line Items]
Long-term debt	0	$ 9
Interest rate, effective percentage		5.50%
Line of Credit
Debt Instrument [Line Items]
Long-term debt	$ 350,000	$ 398,000
Interest rate, effective percentage	3.74%	3.50%

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

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