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Debt (Summary of Debt) (Details) - USD ($) $ in Thousands	3 Months Ended
Debt (Summary of Debt) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Dec. 21, 2016
Debt [Line Items]
Short-term debt	$ 25,933	$ 29,145
Total long-term debt	636,719	636,648
Total debt	662,652	665,793
Current portion	10,517	10,360
Non-current portion	626,202	626,288
Term Loan and Long-term Revolver Loan [Member]
Debt [Line Items]
Less: unamortized debt issue costs	(619)	(690)
Senior Unsecured Notes [Member]
Debt [Line Items]
Less: unamortized debt issue costs	(6,823)	(7,266)
Revolver Loan [Member]
Debt [Line Items]
Long-term Debt	$ 46,882	46,184
Weighted average interest rate	2.68%
2.72% Term Loan, Due October 2021 [Member] \| Term Loan and Long-term Revolver Loan [Member]
Debt [Line Items]
Long-term Debt	$ 97,279	98,420
Delayed Draw Term Loan, In Canadian Dollars, Available until October 2021 [Member] \| Term Loan and Long-term Revolver Loan [Member]
Debt [Line Items]
Weighted average interest rate	2.68%
5.375% Senior Unsecured Note, Due January 2025 [Member] \| Senior Unsecured Notes [Member]
Debt [Line Items]
Long-term Debt	$ 500,000	$ 500,000
Interest rate	5.375%		5.375%
Maturity date	Jan. 15, 2025