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Retirement Benefit Plans (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 30, 2017
Dec. 31, 2016
Dec. 26, 2015
Schedule Defined Contribution Benefit Plan      
Percentage match by company applicable to first 3 percent of employee's contribution 100.00%    
Percentage match by company applicable to next 3 percent of employee's contribution 50.00%    
Maximum percentage of employee's eligible compensation eligible for 100% match (in hundredths) 3.00%    
Minimum percentage of employee's compensation eligible for 50% match 3.00%    
Maximum percentage of employee's compensation eligible for 50% match 6.00%    
Company maximum match as a percentage of eligible compensation (in hundredths) 4.50%    
Defined contribution plan, cost recognized $ 7.4 $ 6.6 $ 5.9