Income Taxes (Summary of Income Tax Expense (Recovery)) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Taxes
Canadian, Current tax expense	$ 19,752	$ 13,209	$ 14,245
Canadian, Deferred tax expense (recovery)	3,346	3,958	(10,192)
Current tax expense before application of operating loss carryforwards	24,815	19,851	8,987
Tax benefit of operating loss carryforwards	(11,770)	(8,293)	(3,876)
Total foreign current tax expense	13,045	11,558	5,111
Deferred tax expense before adjustment to opening valuation allowance	5,727	2,386	(6,317)
Adjustment to opening valuation allowance	(247)	(105)	(759)
Total foreign deferred tax expense (recovery)	5,480	2,281	(7,076)
Income Tax Expense (Benefit), Total	$ 41,623	$ 31,006	$ 2,088