Condensed Consolidated Income Statements - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Condensed Consolidated Income Statements [Abstract]
Revenues (note 6)	$ 131,945	$ 115,618
Costs of services, excluding depreciation and amortization (note 7)	15,313	11,609
Gross revenue, net of expenses	116,632	104,009
Selling, general and administrative expenses (note 7)	68,307	63,756
Depreciation and amortization expenses (note 7)	10,080	10,616
Gain on disposition of property, plant and equipment	(246)	(175)
Foreign exchange gain	(683)	(3,207)
Operating income	39,174	33,019
Interest income	498	847
Interest expense	(1,363)	(1,269)
Equity income (note 18)	519	233
Other, net	698	713
Other income (expense)	352	524
Income before income taxes	39,526	33,543
Income tax expense (recovery) (note 8):
Current	10,009	10,713
Deferred	(477)	(1,280)
Income tax expense	9,532	9,433
Net income	29,994	24,110
Net income attributable to:
Stockholders	29,406	23,777
Non-controlling interests	$ 588	$ 333
Earnings per share attributable to stockholders (note 10):
Basic	$ 0.28	$ 0.22
Diluted	$ 0.27	$ 0.22
Weighted average number of shares outstanding (note 10):
Basic	106,917,280	107,484,944
Diluted	107,159,010	107,807,948