Annual report pursuant to Section 13 and 15(d)

Property And Equipment (Schedule Of Property And Equipment) (Details)

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Property And Equipment (Schedule Of Property And Equipment) (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 28, 2019
Dec. 29, 2018
Dec. 30, 2017
Property, Plant and Equipment [Line Items]      
Property and equipment, gross $ 181,436 $ 178,087  
Less accumulated depreciation and amortization 104,516 95,561  
Property and equipment, net 76,920 82,526  
Property and equipment, net 95,233 92,025  
Depreciation $ 13,088 15,222 $ 14,480
Buildings [Member]      
Property, Plant and Equipment [Line Items]      
Useful life 39 years 6 months    
Property and equipment, gross $ 71,256 71,326  
Laboratory And Production Equipment [Member]      
Property, Plant and Equipment [Line Items]      
Property and equipment, gross 33,180 31,969  
Computer Equipment And Software [Member]      
Property, Plant and Equipment [Line Items]      
Property and equipment, gross 53,421 51,410  
Furniture And Fixtures [Member]      
Property, Plant and Equipment [Line Items]      
Property and equipment, gross 6,512 6,524  
Automobiles [Member]      
Property, Plant and Equipment [Line Items]      
Property and equipment, gross 573 682  
Leasehold Improvements [Member]      
Property, Plant and Equipment [Line Items]      
Property and equipment, gross $ 13,396 13,102  
Land Improvements [Member]      
Property, Plant and Equipment [Line Items]      
Useful life 15 years    
Property and equipment, gross $ 3,098 3,074  
Land [Member]      
Property, Plant and Equipment [Line Items]      
Property and equipment, net 6,824 7,052  
Deposits And Projects In Process [Member]      
Property, Plant and Equipment [Line Items]      
Property and equipment, net $ 11,489 $ 2,447  
Minimum [Member] | Laboratory And Production Equipment [Member]      
Property, Plant and Equipment [Line Items]      
Useful life 5 years    
Minimum [Member] | Computer Equipment And Software [Member]      
Property, Plant and Equipment [Line Items]      
Useful life 3 years    
Minimum [Member] | Furniture And Fixtures [Member]      
Property, Plant and Equipment [Line Items]      
Useful life 3 years    
Minimum [Member] | Automobiles [Member]      
Property, Plant and Equipment [Line Items]      
Useful life 3 years    
Minimum [Member] | Leasehold Improvements [Member]      
Property, Plant and Equipment [Line Items]      
Useful life 3 years    
Maximum [Member] | Laboratory And Production Equipment [Member]      
Property, Plant and Equipment [Line Items]      
Useful life 7 years    
Maximum [Member] | Computer Equipment And Software [Member]      
Property, Plant and Equipment [Line Items]      
Useful life 5 years    
Maximum [Member] | Furniture And Fixtures [Member]      
Property, Plant and Equipment [Line Items]      
Useful life 5 years    
Maximum [Member] | Automobiles [Member]      
Property, Plant and Equipment [Line Items]      
Useful life 5 years    
Maximum [Member] | Leasehold Improvements [Member]      
Property, Plant and Equipment [Line Items]      
Useful life 5 years