Property And Equipment (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 398,023	$ 405,977
Less allowance for depreciation	(321,333)	(325,961)
Property and equipment, net	76,690	80,016
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	301,334	307,244
Land, buildings and improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	77,760	78,522
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	8,955	9,947
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 9,974	$ 10,264