Segmented Information (Geographic Information of Long-lived Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment	$ 526,581	$ 515,030
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment	275,628	282,103
Canada [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment	116,833	108,693
Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment	82,795	74,491
Other [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment	$ 51,325	$ 49,743