Quarterly report pursuant to Section 13 or 15(d)

Stock-Based Compensation (Details Textual)

v3.20.2
Stock-Based Compensation (Details Textual) - USD ($)
$ / shares in Units, $ in Thousands
6 Months Ended
Jun. 27, 2020
Jun. 29, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Recognized weighted average period (in years) 2 years 8 months 12 days  
Stock options granted to employees 18,121  
Exercise price of stock options granted to employees $ 39.75  
Contractual term of stock options 10 years  
Weighted average grant-date fair value of options vested $ 12.81  
Unrecognized compensation cost related to the stock options $ 127  
Award of shares granted (in shares) 145,000  
Stock-based compensation expense $ 2,447 $ 2,781
2012 Nonemployee Director Fees Plan [Member]    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Award of shares granted (in shares) 5,500 12,500
Stock-based compensation expense $ 235 $ 660
Employee Stock Purchase Plan [Member]    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Rate of common stock at market value 85.00%  
Employee Stock Purchase Plan and U.K. Plan [Member]    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Number of shares purchased by employees 23,364 25,481
Weighted average price $ 30.94 $ 33.09
Share-based compensation expenses $ 155 $ 329
Ratio for additional common stock shares issued, under ESPP 6  
Time Based [Member]    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Vesting period 3 years  
Performance Based [Member]    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Vesting period 3 years  
RSUs [Member] | Minimum [Member]    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Target amount percentage 0.00%  
RSUs [Member] | Maximum [Member]    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Target amount percentage 200.00%  
Restricted Stock and Restricted Stock Units [Member]    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Compensation expense $ 2,072 $ 1,859
Total unrecognized compensation $ 6,941  
Recognized weighted average period (in years) 2 years