Properties And Equipment (Schedule Of Properties And Equipment) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Total properties and equipment	$ 445,903	$ 410,403
Less accumulated depreciation	(270,140)	(248,370)
Net properties and equipment	175,763	162,033
Land [Member]
Property, Plant and Equipment [Line Items]
Total properties and equipment	8,360	7,964
Buildings and Building Improvements [Member]
Property, Plant and Equipment [Line Items]
Total properties and equipment	109,404	96,361
Transportation Equipment [Member]
Property, Plant and Equipment [Line Items]
Total properties and equipment	41,897	51,559
Machinery And Equipment [Member]
Property, Plant and Equipment [Line Items]
Total properties and equipment	123,102	111,183
Computer Software [Member]
Property, Plant and Equipment [Line Items]
Total properties and equipment	57,508	49,928
Furniture And Fixtures [Member]
Property, Plant and Equipment [Line Items]
Total properties and equipment	79,792	72,898
Projects Under Development [Member]
Property, Plant and Equipment [Line Items]
Total properties and equipment	$ 25,840	$ 20,510