Annual report pursuant to Section 13 and 15(d)

Employee Benefit Programs (Details)

v3.8.0.1
Employee Benefit Programs (Details) - USD ($)
$ / shares in Units, $ in Millions
 1 Months Ended 12 Months Ended
Jul. 31, 2017
Dec. 31, 2017
Dec. 25, 2016
Dec. 27, 2015
Employee Stock Purchase Plan        
Compensation expense   $ 4.8 $ 4.5 $ 4.7
Employee Defined Contribution Plan        
Minimum age of employees to be eligible to participate in defined contribution plan   21 years    
Percentage of matching contribution   50.00%   25.00%
Percentage of maximum compensation matched by employer   4.00%   4.00%
Matching contribution expense   $ 0.7 0.6 $ 0.3
Employee Deferred Compensation Plan | Deferred compensation, excluding share-based payments and retirement benefits        
Employee Deferred Compensation Plan        
Deferred payment, participant limit per calendar year as a percentage of base salary   75.00%    
Deferred payment, participant limit per calendar year as a percentage of variable compensation and commissions   100.00%    
Deferred payment, maximum employer match   50.00%   25.00%
Deferred payment, maximum matching contribution percentage   4.00%   4.00%
Deferred compensation expense   $ 1.0 0.6 $ 0.0
Employee Deferred Compensation Plan | Deferred compensation, excluding share-based payments and retirement benefits | Other assets, net        
Employee Deferred Compensation Plan        
Deferred compensation assets   9.3 9.2  
Employee Deferred Compensation Plan | Deferred compensation, excluding share-based payments and retirement benefits | Other non-current liability        
Employee Deferred Compensation Plan        
Liability for participant contributions and investment income   $ 9.3 $ 9.2  
Amended And Restated Employee Stock Purchase Plan        
Employee Stock Purchase Plan        
Number of shares outstanding 100,000      
Maximum percentage of base compensation that can be contributed by the eligible team members 15.00%      
Estimated subscription date fair value (as a percent) 85.00%      
Requisite employment period to be eligible to participate in the plan 1 year      
Requisite working hours per week to be eligible to participate in the plan 20 hours      
Operational period of the plan 6 months      
Number of shares issued under the plan   7,607    
Number of shares available for future issuance under the plan   92,393    
Risk-free interest rate (as a percent)   1.05% 0.55%  
Expected life   6 months 6 months  
Expected volatility (as a percent)   37.96% 37.64%  
Dividend yield (as a percent)   0.00% 0.00%  
Weighted average fair value per share at grant date (in dollars per share)   $ 11.16 $ 9.29  
Compensation expense   $ 0.2 $ 0.2 $ 0.2
Employee Stock Purchase Plan        
Employee Stock Purchase Plan        
Number of shares issued under the plan   17,294