Gift Cards Liability and Loyalty Program Included in Accrued Expenses on Consolidated Balance Sheets (Detail) - USD ($) $ in Thousands	Dec. 29, 2020	Dec. 31, 2019
Contract With Customer Asset And Liability [Abstract]
Gift card liability	$ 17,274	$ 19,106
Deferred loyalty revenue	$ 6,121	$ 8,320

Contract with customer liability for unredeeemed gift cards.

No definition available.

Name:	bjri_ContractWithCustomerLiabilityForUnredeeemedGiftCards
Namespace Prefix:	bjri_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant