Annual report pursuant to Section 13 and 15(d)

Stock-Based Compensation (Details Textual)

v3.19.3.a.u2
Stock-Based Compensation (Details Textual)
12 Months Ended
Jun. 01, 2015
shares
Dec. 28, 2019
USD ($)
$ / shares
shares
Dec. 28, 2019
GBP (£)
shares
Dec. 29, 2018
USD ($)
$ / shares
shares
Dec. 30, 2017
USD ($)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Fair value of RSUs/restricted stock granted | $   $ 5,079,000   $ 5,947,000 $ 2,628,000
2012 Nonemployee Director Fees Plan [Member]          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Aggregate number of shares authorized for grant   270,000      
Shares available for issuance   99,424      
Common stock shares for each nonemployee director 250        
Fee for the chairs of each Board committee 150.00%        
Annual retainer of common stock received by non employee directors   2,000 2,000    
Stock option granted, shares   25,200 25,200 24,250  
Share-based compensation expenses under Director's plan | $   $ 1,162,000   $ 1,213,000 1,240,000
Employee Stock Purchase Plan [Member]          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Aggregate number of shares authorized for grant   1,096,875      
Rate of common stock at market value   85.00% 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   49,195 49,195 40,714  
Weighted average price | $ / shares   $ 33.55   $ 38.01  
Share-based compensation expenses | $   $ 551,000   $ 324,000 429,000
Minimum [Member] | Employee Stock Purchase Plan [Member]          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Allowable employees purchase rate of common stock based on annual salary   10.00% 10.00%    
Minimum [Member] | Employee Stock Purchase Plan [Member] | United States [Member]          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Shares allowed to be purchased by employees | $   $ 25,000      
Minimum [Member] | Employee Stock Purchase Plan [Member] | United Kingdom [Member]          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Shares allowed to be purchased by employees | £     £ 1,500    
Maximum [Member] | 2012 Nonemployee Director Fees Plan [Member]          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Maximum number of share issuable to non employee directors per year   35,000      
2019 Plan [Member]          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Aggregate number of shares authorized for grant   1,000,000      
Shares available for issuance   999,000      
Time Based [Member]          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Vesting period   3 years 3 years    
Performance Based [Member]          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Vesting period   3 years 3 years    
RSUs [Member] | Minimum [Member]          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Target amount percentage   0.00% 0.00%    
RSUs [Member] | Maximum [Member]          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Target amount percentage   150.00% 150.00%    
Restricted Stock and Restricted Stock Units [Member]          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Compensation expense | $   $ 3,465,000   $ 2,728,000 $ 2,376,000
Total unrecognized compensation | $   $ 4,526,000      
Recognized weighted average period (in years)   1 year 8 months 12 days 1 year 8 months 12 days