Annual report pursuant to Section 13 and 15(d)

Stock-Based Compensation (Details Textual)

v3.10.0.1
Stock-Based Compensation (Details Textual)
12 Months Ended
Jun. 01, 2015
shares
Dec. 29, 2018
USD ($)
$ / shares
shares
Dec. 29, 2018
GBP (£)
shares
Dec. 30, 2017
USD ($)
$ / shares
shares
Dec. 31, 2016
USD ($)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Ratio for additional common stock shares issued, under ESPP   16.67% 16.67%    
2012 Director Equity Plan [Member]          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Aggregate number of shares authorized for grant   270,000      
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   24,250 24,250 26,000  
Share-based compensation expenses under Director's plan | $   $ 1,213,000   $ 1,240,000 $ 831,000
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% 85.00%    
Employee Stock Purchase Plan and U.K. Plan [Member]          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Aggregate number of shares authorized for grant   1,096,875      
Shares available for issuance   505,595      
Number of shares purchased by employees   40,714 40,714 31,983  
Weighted average price | $ / shares   $ 38.01   $ 36.20  
Share-based compensation expenses | $   $ 324,000   $ 429,000 312,000
Minimum [Member] | Employee Stock Purchase Plan and U.K. 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 and U.K. 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    
Allowable employees purchase rate of common stock based on annual salary   10.00% 10.00%    
Maximum [Member] | 2012 Director Equity 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      
Equity Incentive Plan (2011 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   361,298      
Restricted stock expense | $   $ 2,728,000   $ 2,376,000 $ 3,676,000
Total unrecognized compensation | $   $ 4,789,000      
Recognized weighted average period (in years)   1 year 9 months 7 days 1 year 9 months 7 days    
Nonemployee Director Equity and Deferred Compensation Plan [Member]          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Shares available for issuance   124,624