Business and Summary of Significant Accounting Policies Business and Summary of Significant accounting Policies New Accounting Pronouncements (Details) $ in Millions	12 Months Ended
Dec. 30, 2017 USD ($)
New Accounting Pronouncements [Abstract]
Excess tax benefits reducing income tax expense	$ 1.4
Excess Tax Benefits From Share-based Compensation	$ 2.3

Amount of cash outflow for realized tax benefit related to deductible compensation cost reported on the entity's tax return for equity instruments in excess of the compensation cost for those instruments recognized for financial reporting purposes.

No definition available.

Name:	snbr_ExcessTaxBenefitsFromSharebasedCompensation
Namespace Prefix:	snbr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration