Income Taxes (Schedule of Effective Income Tax Rate Reconciliation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Taxes [Abstract]
Income before income taxes	$ 152,512	$ 77,394	$ 130,494
Statutory federal and provincial tax rate in Canada	27.00%	26.00%	26.00%
Expected income tax expense	$ 41,178	$ 20,122	$ 33,928
Non-deductible expenses	4,810	5,668	3,891
Adjustments to prior years provision to statutory tax returns	1,323	(528)	(824)
Changes in the valuation of deferred tax assets	(771)	(1,089)	(259)
Different tax rates of subsidiaries operating in foreign jurisdictions	(17,145)	(12,269)	(3,786)
U.S. tax reform impacts	4,899	(9,734)
Impairment of Goodwill			6,129
Change in estimate of deductibility of stock options		(1,557)
Unrecognized tax benefits	(1,800)	3,291	799
Benefits of deductible stock options vested and exercised	(2,434)	(1,359)	(1,042)
Deductions for tax purposes in excess of accounting expenses	(383)	(380)	(490)
Other	1,329	(77)	(1,364)
Income tax expense	$ 31,006	$ 2,088	$ 36,982