Properties And Equipment (Schedule Of Properties And Equipment) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Total properties and equipment	$ 481,200	$ 445,903
Less accumulated depreciation	(293,380)	(270,140)
Net properties and equipment	187,820	175,763
Land [Member]
Property, Plant and Equipment [Line Items]
Total properties and equipment	9,385	8,360
Buildings and Building Improvements [Member]
Property, Plant and Equipment [Line Items]
Total properties and equipment	117,419	109,404
Transportation Equipment [Member]
Property, Plant and Equipment [Line Items]
Total properties and equipment	68,379	41,897
Machinery And Equipment [Member]
Property, Plant and Equipment [Line Items]
Total properties and equipment	129,835	123,102
Computer Software [Member]
Property, Plant and Equipment [Line Items]
Total properties and equipment	62,138	57,508
Furniture And Fixtures [Member]
Property, Plant and Equipment [Line Items]
Total properties and equipment	78,507	79,792
Projects Under Development [Member]
Property, Plant and Equipment [Line Items]
Total properties and equipment	$ 15,537	$ 25,840