Shareholders' Deficit - Schedule of Repurchase of Common Stock (Details) - USD ($) $ in Thousands	12 Months Ended
Jan. 03, 2026	Dec. 28, 2024	Dec. 30, 2023
Share-Based Payment Arrangement [Abstract]
Amount repurchased under Board-approved share repurchase program	$ 0	$ 0	$ 0
Amount repurchased in connection with the vesting of employee restricted stock grants	1,213	768	3,747
Total amount repurchased (based on trade dates)	$ 1,213	$ 768	$ 3,747

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.

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