Property, Plant and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 1,350,768	$ 1,222,494
Accumulated depreciation and amortization	(896,466)	(799,930)
Property, plant and equipment, net	454,302	422,564	$ 357,470
Expenditures for maintenance and repairs	19,100	16,600	16,600
Depreciation expense	61,517	58,106	52,974
Software amortization	3,600	4,000	6,500
Capital expenditures and purchased software	87,637	73,492	50,595
Unamortized software cost	7,600	7,200
Asset held for sale real property			$ 4,988
Land and Land Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 14,853	13,339
Estimated useful life	25 years
Buildings [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 230,987	214,086
Buildings [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	25 years
Buildings [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	40 years
Building under capital lease [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 8,140	8,140
Estimated useful life	7 years
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 950,519	842,921
Machinery and Equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	5 years
Machinery and Equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	15 years
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 8,861	7,632
Estimated useful life	5 years
Computer and Other Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 15,610	15,264
Computer and Other Equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	3 years
Computer and Other Equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	10 years
Software [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 57,847	54,212
Software [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	5 years
Software [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	8 years
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 63,951	66,900
Capital lease [Member]
Property, Plant and Equipment [Line Items]
Accumulated depreciation and amortization	$ (2,400)	$ (900)