Property, Plant And Equipment (Schedule of Property, Plant and Equipment) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Cost	$ 798,825	$ 831,243
Accumulated depreciation	(312,226)	(304,662)
Net book value	486,599	526,581
Land and Improvements [Member]
Property, Plant and Equipment [Line Items]
Cost	362,781	379,546
Accumulated depreciation	(72,547)	(68,706)
Net book value	290,234	310,840
Buildings [Member]
Property, Plant and Equipment [Line Items]
Cost	252,182	267,334
Accumulated depreciation	(106,959)	(103,544)
Net book value	145,223	163,790
Yard and Automotive Equipment [Member]
Property, Plant and Equipment [Line Items]
Cost	57,983	58,209
Accumulated depreciation	(36,640)	(38,126)
Net book value	21,343	20,083
Computer Software and Equipment [Member]
Property, Plant and Equipment [Line Items]
Cost	70,623	69,718
Accumulated depreciation	(60,258)	(60,451)
Net book value	10,365	9,267
Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Cost	28,490	25,430
Accumulated depreciation	(19,582)	(18,745)
Net book value	8,908	6,685
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Cost	19,735	21,467
Accumulated depreciation	(16,240)	(15,090)
Net book value	3,495	6,377
Assets under Development [Member]
Property, Plant and Equipment [Line Items]
Cost	7,031	9,539
Net book value	$ 7,031	$ 9,539