Cover - shares	3 Months Ended
	Mar. 31, 2022	Apr. 25, 2022
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2022
Document Transition Report	false
Entity File Number	1-8966
Entity Registrant Name	SJW GROUP
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	77-0066628
Entity Address, Address Line One	110 West Taylor Street,
Entity Address, City or Town	San Jose,
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	95110
City Area Code	(408)
Local Phone Number	279-7800
Title of 12(b) Security	Common Stock, par value $0.001 per share
Trading Symbol	SJW
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		30,237,145
Entity Central Index Key	0000766829
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q1
Amendment Flag	false