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Business and Summary of Significant Accounting Policies Fiscal Year (Details) | 12 Months Ended
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Dec. 30, 2017 | Dec. 31, 2016 | Jan. 02, 2016
Fiscal Year [Abstract] |  |  |
Fiscal Years | 364 days | 364 days | 364 days

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- Definition Fiscal Year [Abstract] + References No definition available. + Details
Name: | snbr_FiscalYearAbstract
Namespace Prefix: | snbr_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Duration of a fiscal period, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Includes, but not limited to, weeks in a year or quarter. + References No definition available. + Details
Name: | us-gaap_FiscalPeriodDuration
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration