Financial Statement Schedule - Condensed Statements of Comprehensive Income (Details) - USD ($) $ in Thousands		12 Months Ended
	Jun. 29, 2021	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Condensed Financial Statements, Captions [Line Items]
Operating revenue		$ 620,698	$ 573,686	$ 564,526
Operating expense:
Administrative and general		95,404	87,332	79,741
Property taxes and other non-income taxes		32,572	30,964	29,886
Total operating expense		489,720	462,527	446,856
Operating income		130,978	111,159	117,670
Other (expense) income:
Interest on long-term debt, mortgage and other interest expense		(58,062)	(54,339)	(54,255)
Gain on sale of Texas Water Alliance (“TWA”)	$ 3,000	0	3,000	0
Other, net		4,385	6,770	5,906
Income before income taxes		82,324	68,847	69,895
Provision for income taxes		8,496	8,369	8,380
Net income		73,828	60,478	61,515
Other comprehensive income (loss), net		1,640	901	(1,190)
Comprehensive income		75,468	61,379	60,325
SJW Group
Condensed Financial Statements, Captions [Line Items]
Operating revenue		0	0	0
Operating expense:
Administrative and general		1,977	2,050	3,110
Property taxes and other non-income taxes		93	(38)	250
Total operating expense		2,070	2,012	3,360
Operating income		(2,070)	(2,012)	(3,360)
Other (expense) income:
Interest on long-term debt, mortgage and other interest expense		(17,795)	(18,673)	(19,430)
Gain on sale of Texas Water Alliance (“TWA”)		0	3,000	0
Other, net		(340)	(160)	(250)
Income before income taxes		(20,205)	(17,845)	(23,040)
Provision for income taxes		(5,523)	(4,660)	(6,414)
Equity earnings from subsidiaries, net of taxes		88,510	73,663	78,141
Subsidiaries
Other (expense) income:
Equity earnings from subsidiaries, net of taxes		$ 88,510	$ 73,663	$ 78,141