Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Jun. 30, 2018	Dec. 30, 2017
Income Taxes [Abstract]
2017 TCJA Provisional Tax Benefit	$ 2.9	$ 1.7

Tax Cuts And Jobs Act Of 2017 Incomplete Accounting Provisional Income Tax Expense Benefit

No definition available.

Name:	snbr_TaxCutsAndJobsActOf2017IncompleteAccountingProvisionalIncomeTaxExpenseBenefit
Namespace Prefix:	snbr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration