Property, Plant And Equipment (Schedule of Property, Plant and Equipment) (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Cost	$ 807,652	$ 782,664
Accumulated depreciation	(279,018)	(254,073)
Net book value	528,634	528,591
Land and Improvements [Member]
Property, Plant and Equipment [Line Items]
Cost	366,504	356,905
Accumulated depreciation	(60,194)	(54,551)
Net book value	306,310	302,354
Buildings [Member]
Property, Plant and Equipment [Line Items]
Cost	260,472	254,760
Accumulated depreciation	(90,582)	(82,100)
Net book value	169,890	172,660
Yard and Automotive Equipment [Member]
Property, Plant and Equipment [Line Items]
Cost	58,574	59,957
Accumulated depreciation	(39,941)	(38,848)
Net book value	18,633	21,109
Computer Software and Equipment [Member]
Property, Plant and Equipment [Line Items]
Cost	65,205	60,586
Accumulated depreciation	(57,682)	(50,754)
Net book value	7,523	9,832
Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Cost	23,249	22,432
Accumulated depreciation	(16,839)	(15,660)
Net book value	6,410	6,772
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Cost	22,000	20,893
Accumulated depreciation	(13,780)	(12,160)
Net book value	8,220	8,733
Assets under Development [Member]
Property, Plant and Equipment [Line Items]
Cost	11,648	7,131
Net book value	$ 11,648	$ 7,131