Segmented information (Geographic Information of Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 273,255	$ 303,429
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	190,530	183,573
Canada [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	35,643	31,531
Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	26,338	54,785
Other [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 20,744	$ 33,540