Segmented Information (Geographic Information of Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 355,972	$ 245,346	$ 308,530	$ 260,178	$ 291,750	$ 227,401	$ 252,613	$ 199,427	$ 294,830	$ 300,976	$ 275,667	$ 255,504	$ 1,170,026	$ 971,191	$ 1,126,977
Operating Segments [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues													1,170,026	971,191	1,126,977
United States [Member] | Operating Segments [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues													548,695	452,599	555,837
Canada [Member] | Operating Segments [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues													284,989	245,106	293,956
Europe [Member] | Operating Segments [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues													180,817	127,706	109,024
Other [Member] | Operating Segments [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues													$ 155,525	$ 145,780	$ 168,160