Supplemental Balance Sheet Information Related to Leases (Details) - USD ($) $ in Thousands	Mar. 29, 2019	Dec. 31, 2018
Operating Leases
Operating lease, right-of-use asset	$ 28,327	$ 0
Operating Lease, Liability, Current	7,190
Operating lease liabilities	22,575	0
Finance Leases
Finance lease liabilities	18,502	15,221
Total principal payable on finance lease	19,720
Property, Plant and Equipment	908,481	898,251
Allowance for depreciation, depletion and amortization	(656,326)	(647,233)
Property, plant, and equipment-net	252,155	$ 251,018
Other liabilities and accrued items	1,218
Property, Plant and Equipment [Member]
Property, Plant and Equipment	26,185
Allowance for depreciation, depletion and amortization	(2,906)
Property, plant, and equipment-net	$ 23,279