Document and Entity Information - shares	3 Months Ended
	Mar. 29, 2022	Apr. 29, 2022
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 29, 2022
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q1
Trading Symbol	BJRI
Entity Registrant Name	BJ’S RESTAURANTS, INC.
Entity Central Index Key	0001013488
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Current Reporting Status	Yes
Entity Common Stock, Shares Outstanding		23,438,991
Entity Interactive Data Current	Yes
Entity Shell Company	false
Entity File Number	0-21423
Entity Tax Identification Number	33-0485615
Entity Address, Address Line One	7755 Center Avenue
Entity Address, Address Line Two	Suite 300
Entity Address, City or Town	Huntington Beach
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	92647
City Area Code	714
Local Phone Number	500-2400
Title of 12(b) Security	Common Stock, No Par Value
Security Exchange Name	NASDAQ
Entity Incorporation, State or Country Code	CA
Document Quarterly Report	true
Document Transition Report	false