Financial Instruments (Financial Instruments Assets (Liabilities) Measured At Fair Value) (Details) - USD ($) $ in Thousands		9 Months Ended	12 Months Ended
		Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019
Financial Instruments And Fair Value Measurements [Line Items]
Cash and cash equivalents, Carrying Amount		$ 64,495	$ 96,202	$ 43,541
Long-term debt, Carrying Amount		(807,539)	(807,565)
Cash and cash equivalents, Fair Value		64,495	96,202
Cross Currency Swaps [Member]
Financial Instruments And Fair Value Measurements [Line Items]
Cross currency swaps, Carrying Amount		6,962	22,111
Cross currency swaps, Fair Value		6,962	22,111
Interest Rate Swap [Member]
Financial Instruments And Fair Value Measurements [Line Items]
Interest rate swaps-liabilities, Carrying Amount		(26,380)	(14,698)
Interest rate swaps-liabilities, Fair Value		(26,380)	(14,698)
Foreign Currency Forward Contracts [Member]
Financial Instruments And Fair Value Measurements [Line Items]
Foreign currency forward contracts, net, Carrying amount		128	601
Foreign currency forward contracts, net, Fair Value		128	601
Revolving credit facility [Member]
Financial Instruments And Fair Value Measurements [Line Items]
Long-term debt, Carrying Amount		(5,740)
Long-term debt, Fair Value		(6,046)
Term Loan Facility - Amended Credit Facility [Member]
Financial Instruments And Fair Value Measurements [Line Items]
Long-term debt, Carrying Amount	[1]	(795,483)	(801,764)
Long-term debt, Fair Value	[1]	(781,721)	(799,750)
Unamortized debt issuance costs		4,000	3,900
Other Long-Term Notes Payable [Member]
Financial Instruments And Fair Value Measurements [Line Items]
Long-term debt, Carrying Amount		(3,706)	(3,496)
Long-term debt, Fair Value		(3,186)	(1,557)
Level 1 [Member]
Financial Instruments And Fair Value Measurements [Line Items]
Cash and cash equivalents, Fair Value		64,495	96,202
Level 2 [Member] | Cross Currency Swaps [Member]
Financial Instruments And Fair Value Measurements [Line Items]
Cross currency swaps, Fair Value		6,962	22,111
Level 2 [Member] | Interest Rate Swap [Member]
Financial Instruments And Fair Value Measurements [Line Items]
Interest rate swaps-liabilities, Fair Value		(26,380)	(14,698)
Level 2 [Member] | Foreign Currency Forward Contracts [Member]
Financial Instruments And Fair Value Measurements [Line Items]
Foreign currency forward contracts, net, Fair Value		128	601
Level 2 [Member] | Revolving credit facility [Member]
Financial Instruments And Fair Value Measurements [Line Items]
Long-term debt, Fair Value		(6,046)
Level 2 [Member] | Term Loan Facility - Amended Credit Facility [Member]
Financial Instruments And Fair Value Measurements [Line Items]
Long-term debt, Fair Value	[1]	(781,721)	(799,750)
Level 2 [Member] | Other Long-Term Notes Payable [Member]
Financial Instruments And Fair Value Measurements [Line Items]
Long-term debt, Fair Value		$ (3,186)	$ (1,557)

[1] The carrying value of the term loan facility is net of unamortized debt issuance costs of $4.0 million and $3.9 million for the period ended September 30, 2020, and December 31, 2019, respectively.