Consolidated Income Statements - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues:
Total revenues	$ 1,170,026	$ 971,191	$ 1,126,977
Operating expenses:
Selling, general and administrative expenses	382,676	323,270	283,529
Acquisition-related costs	5,093	38,272	11,829
Depreciation and amortization expenses	66,614	52,694	40,861
Gain on disposition of property, plant and equipment	(2,731)	(1,656)	(1,282)
Impairment loss		8,911	28,243
Foreign exchange (gain) loss	(212)	2,559	1,431
Total operating expenses	984,837	863,737	991,255
Operating income	185,189	107,454	135,722
Interest expense	(44,527)	(38,291)	(5,564)
Debt extinguishment costs			(6,787)
Other income, net	11,850	8,231	7,123
Income before income taxes	152,512	77,394	130,494
Current income tax	24,767	19,356	40,341
Deferred income tax	6,239	(17,268)	(3,359)
Income tax expense (recovery)	31,006	2,088	36,982
Net income	121,506	75,306	93,512
Net income attributable to:
Stockholders	121,479	75,027	91,832
Non-controlling interests	27	279	1,680
Net income	$ 121,506	$ 75,306	$ 93,512
Earnings per share attributable to stockholders:
Basic	$ 1.12	$ 0.70	$ 0.86
Diluted	$ 1.11	$ 0.69	$ 0.85
Weighted average number of shares outstanding:
Basic	108,063,349	107,044,348	106,630,323
Diluted	109,388,236	108,113,151	107,457,794
Service Revenues [Member]
Revenues:
Total revenues	$ 749,515	$ 624,417	$ 555,843
Operating expenses:
Direct expenses	159,058	133,189	113,296
Revenue from Inventory Sales [Member]
Revenues:
Total revenues	420,511	346,774	571,134
Operating expenses:
Direct expenses	$ 374,339	$ 306,498	$ 513,348