Income Taxes (Schedule of Effective Income Tax Rate Reconciliation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Taxes [Abstract]
Income before income taxes	$ 176,436	$ 129,038	$ 134,755
Statutory federal and provincial tax rate in Canada	26.00%	26.00%	25.75%
Expected income tax expense	$ 45,873	$ 33,550	$ 34,699
Non-deductible expenses	2,579	2,392	2,396
Sale of capital property	(1,291)	(407)
Changes in valuation allowance	(5,828)	7,083	4,512
Different tax rates of subsidiaries operating in foreign jurisdictions	(3,426)	(4,773)	(2,798)
Other	(46)	(1,370)	1,501
Income tax expense	$ 37,861	$ 36,475	$ 40,310