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 |