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Debt (Summary of Debt) (Details) - USD ($) $ in Thousands		12 Months Ended
Debt (Summary of Debt) (Details) - USD ($) $ in Thousands	Dec. 21, 2016	Dec. 31, 2019	Dec. 31, 2018
Debt [Line Items]
Short-term debt		$ 4,705	$ 19,896
Total long-term debt		645,481	711,298
Total debt		650,186	731,194
Current portion		18,277	13,126
Non-current portion		627,204	698,172
Delayed Draw Term Loans [Member]
Debt [Line Items]
Less: unamortized debt issue costs		(807)	(2,419)
Senior Unsecured Notes [Member]
Debt [Line Items]
Less: unamortized debt issue costs		(9,067)	(10,864)
3.958% Term Loan, Due October 2021 [Member] \| Delayed Draw Term Loans [Member]
Debt [Line Items]
Long-term Debt		$ 155,355	161,891
3.715% Term Loan, Due December 2019 [Member] \| Delayed Draw Term Loans [Member]
Debt [Line Items]
Long-term Debt			62,690
Delayed Draw Term Loan, In Canadian Dollars, Available until October 2021 [Member] \| Delayed Draw Term Loans [Member]
Debt [Line Items]
Weighted average interest rate		3.958%
Maturity date		Oct. 01, 2021
Delayed Draw Term Loan, In US Dollars, Available until October 2021 [Member] \| Delayed Draw Term Loans [Member]
Debt [Line Items]
Weighted average interest rate		3.715%
Maturity date		Oct. 01, 2021
5.375% Senior Unsecured Note, Due January 2025 [Member]
Debt [Line Items]
Interest rate	5.375%
Maturity date	Jan. 15, 2025
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%
Maturity date		Jan. 01, 2025