Property, Plant And Equipment (Schedule of Property, Plant and Equipment) (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Cost	$ 803,356	$ 782,664
Accumulated depreciation	(267,492)	(254,073)
Net book value	535,864	528,591
Land and Improvements [Member]
Property, Plant and Equipment [Line Items]
Cost	366,245	356,905
Accumulated depreciation	(57,091)	(54,551)
Net book value	309,154	302,354
Buildings [Member]
Property, Plant and Equipment [Line Items]
Cost	260,840	254,760
Accumulated depreciation	(86,215)	(82,100)
Net book value	174,625	172,660
Yard and Automotive Equipment [Member]
Property, Plant and Equipment [Line Items]
Cost	60,222	59,957
Accumulated depreciation	(39,401)	(38,848)
Net book value	20,821	21,109
Computer Software and Equipment [Member]
Property, Plant and Equipment [Line Items]
Cost	64,900	60,586
Accumulated depreciation	(55,458)	(50,754)
Net book value	9,442	9,832
Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Cost	23,204	22,432
Accumulated depreciation	(16,457)	(15,660)
Net book value	6,747	6,772
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Cost	21,731	20,893
Accumulated depreciation	(12,870)	(12,160)
Net book value	8,861	8,733
Assets under Development [Member]
Property, Plant and Equipment [Line Items]
Cost	6,214	7,131
Net book value	$ 6,214	$ 7,131