Financial Statement Schedule - Condensed Statements of Comprehensive Income (Details) - USD ($) $ in Thousands		12 Months Ended
	Jun. 29, 2021	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Condensed Financial Statements, Captions [Line Items]
Operating revenue		$ 670,363	$ 620,698	$ 573,686
Operating expense:
Administrative and general		98,656	95,404	87,332
Property taxes and other non-income taxes		34,475	32,572	30,964
Total operating expense		520,928	489,720	462,527
Operating income		149,435	130,978	111,159
Other (expense) income:
Interest on long-term debt and other interest expense		(66,144)	(58,062)	(54,339)
Gain on sale of asset	$ 3,000
Other, net		8,882	4,385	10,697
Income before income taxes		90,943	82,324	68,847
Provision for income taxes		5,956	8,496	8,369
Net income		84,987	73,828	60,478
Other comprehensive income, net		314	1,640	901
Comprehensive income		85,301	75,468	61,379
SJW Group
Condensed Financial Statements, Captions [Line Items]
Operating revenue		0	0	0
Operating expense:
Administrative and general		2,239	1,977	2,050
Property taxes and other non-income taxes		80	93	(38)
Total operating expense		2,319	2,070	2,012
Operating income		(2,319)	(2,070)	(2,012)
Other (expense) income:
Interest on long-term debt and other interest expense		(17,692)	(17,795)	(18,673)
Gain on sale of asset		0	0	3,000
Interest income on intercompany notes receivable		3,862	81	313
Other, net		1,034	(421)	(473)
Income before income taxes		(15,115)	(20,205)	(17,845)
Provision for income taxes		(4,294)	(5,523)	(4,660)
Equity earnings from subsidiaries, net of taxes		95,808	88,510	73,663
Subsidiaries
Other (expense) income:
Equity earnings from subsidiaries, net of taxes		$ 95,808	$ 88,510	$ 73,663