Segmented Information (Geographic Information of Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 135,462	$ 109,318	$ 155,477	$ 115,618	$ 138,457	$ 102,217	$ 141,835	$ 98,588	$ 515,875	$ 481,097	$ 467,403
Assets	$ 1,120,115				$ 1,121,510				1,120,115	1,121,510
Operating Segments [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									515,875	481,097	467,403
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									257,824	223,770	224,214
Canada [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									166,528	154,392	135,545
Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									48,419	58,782	65,016
Other [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									$ 43,104	$ 44,153	$ 42,628