Shareholders' Deficit - Schedule of Repurchase of Common Stock (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 28, 2019	Dec. 29, 2018	Dec. 30, 2017
Repurchases Of Common Stock [Abstract]
Amount repurchased under Board-approved share repurchase program	$ 145,900	$ 279,101	$ 150,000
Amount repurchased in connection with the vesting of employee restricted stock grants	9,673	3,344	5,245
Total amount repurchased (based on trade dates)	$ 155,573	$ 282,445	$ 155,245

Disclosure of the equity impact of the value of stock that has been repurchased during the period and has not been retired and is not held in treasury. Some state laws may mandate the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

No definition available.

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