Financial Instruments (Schedule of Long-Term Debt) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Long-term debt	$ 398,009	$ 424,029
Less: current portion	(9)	(20)
Long-term debt, net of current portion	$ 398,000	$ 424,009
Interest rate, stated percentage	5.50%	5.50%
Line of Credit
Debt Instrument [Line Items]
Long-term debt	$ 398,000	$ 424,000
Interest rate, effective percentage	3.50%	3.43%
Other Long-term Debt
Debt Instrument [Line Items]
Long-term debt	$ 9	$ 29

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

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Contractual interest rate for funds borrowed, under the debt agreement.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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