Components of Income Tax Provision (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Components Of Income Tax Expense Benefit [Line Items]
Current income tax provision (benefit)	$ 16,283	$ 16,387	$ 12,285
Deferred income tax provision (benefit)	(6,076)	(2,560)	(1,766)
Income Tax Provision (benefit)	10,207	13,827	10,519
CANADA
Components Of Income Tax Expense Benefit [Line Items]
Current income tax provision (benefit)	75	146	43
Deferred income tax provision (benefit)			0
UNITED STATES
Components Of Income Tax Expense Benefit [Line Items]
Current income tax provision (benefit)	8,095	9,434	9,678
Deferred income tax provision (benefit)	(2,272)	2,396	(2,378)
Other Countries
Components Of Income Tax Expense Benefit [Line Items]
Current income tax provision (benefit)	8,113	6,807	2,564
Deferred income tax provision (benefit)	$ (3,804)	$ (4,956)	$ 612