Property, Plant And Equipment (Schedule of Property, Plant and Equipment) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Cost	$ 824,354	$ 798,825
Accumulated depreciation	(339,872)	(312,226)
Net book value	484,482	486,599
Land and Improvements [Member]
Property, Plant and Equipment [Line Items]
Cost	361,623	362,781
Accumulated depreciation	(77,015)	(72,547)
Net book value	284,608	290,234
Buildings [Member]
Property, Plant and Equipment [Line Items]
Cost	252,774	252,182
Accumulated depreciation	(115,423)	(106,959)
Net book value	137,351	145,223
Yard and Automotive Equipment [Member]
Property, Plant and Equipment [Line Items]
Cost	66,871	57,983
Accumulated depreciation	(40,686)	(36,640)
Net book value	26,185	21,343
Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Cost	80,756	70,623
Accumulated depreciation	(68,431)	(60,258)
Net book value	12,325	10,365
Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Cost	31,760	28,490
Accumulated depreciation	(21,776)	(19,582)
Net book value	9,984	8,908
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Cost	19,756	19,735
Accumulated depreciation	(16,541)	(16,240)
Net book value	3,215	3,495
Assets under Development [Member]
Property, Plant and Equipment [Line Items]
Cost	10,814	7,031
Net book value	$ 10,814	$ 7,031