General form of registration statement for all companies including face-amount certificate companies

Summary of Significant Accounting Policies - Receivables and Assets (Details)

v3.8.0.1
Summary of Significant Accounting Policies - Receivables and Assets (Details) - USD ($)
$ in Thousands
 9 Months Ended 12 Months Ended
Sep. 28, 2017
Dec. 29, 2016
Dec. 31, 2015
Receivables      
Allowance for doubtful accounts $ 257 $ 188 $ 133
Inventory Valuation and Shrinkage      
Inventory valuation reserves $ 3,357 $ 2,449 $ 2,476
Vendor Relationships      
Goodwill and Other Indefinite-Lived Intangible Assets      
Useful Life 10 years 10 years  
Minimum | Furniture, fixtures and equipment      
Fixed Assets      
Useful life 2 years 2 years  
Minimum | Leasehold improvements      
Fixed Assets      
Useful life 10 years 10 years  
Minimum | Computer software and hardware      
Fixed Assets      
Useful life 3 years 3 years  
Maximum | Furniture, fixtures and equipment      
Fixed Assets      
Useful life 7 years 7 years  
Maximum | Leasehold improvements      
Fixed Assets      
Useful life 25 years 25 years  
Maximum | Computer software and hardware      
Fixed Assets      
Useful life 7 years 7 years