Property, Plant and Equipment (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 28, 2019	Dec. 29, 2018	Dec. 30, 2017
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 329,204	$ 309,541
Property, plant and equipment, net	184,550	171,032
Depreciation	23,000	21,900	$ 21,700
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	214,608	192,982
Property, plant and equipment, net	114,975	98,062
Inventory, parts and components, net of reserves	5,600	4,900
Machinery and Equipment [Member] | Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	15,000	19,400
Machinery and Equipment [Member] | Finance Leases [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	24,400	10,100
Property, plant and equipment, net	$ 17,900	$ 3,400