Segment and Non-Tariffed Businesses Reporting - Schedule of Segment Reporting Information, by Segment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Operating revenue	$ 670,363	$ 620,698	$ 573,686
Operating expense	520,928	489,720	462,527
Operating income (loss)	149,435	130,978	111,159
Net income (loss)	84,987	73,828	60,478
Depreciation and amortization	105,868	104,417	94,400
Senior note and other interest expense	66,144	58,062	54,339
Income tax expense (benefit) in net income	5,956	8,496	8,369
Assets	4,345,067	3,755,056
Water Utility Services
Segment Reporting Information [Line Items]
Assets	4,242,704	3,648,748
Water Utility Services | Regulated
Segment Reporting Information [Line Items]
Operating revenue	652,045	603,000	558,154
Operating expense	506,923	473,141	449,401
Operating income (loss)	145,122	129,859	108,753
Net income (loss)	94,343	86,500	67,530
Depreciation and amortization	104,329	99,412	91,896
Senior note and other interest expense	42,743	37,958	34,308
Income tax expense (benefit) in net income	11,293	12,756	10,327
Assets	4,199,172	3,643,916
Water Utility Services | Non- tariffed
Segment Reporting Information [Line Items]
Operating revenue	12,634	12,093	10,153
Operating expense	7,452	9,538	7,138
Operating income (loss)	5,182	2,555	3,015
Net income (loss)	4,452	1,060	3,309
Depreciation and amortization	340	2,906	443
Senior note and other interest expense	329	0	0
Income tax expense (benefit) in net income	1,458	708	369
Assets	43,532	4,832
Real Estate Services | Non- tariffed
Segment Reporting Information [Line Items]
Operating revenue	5,684	5,605	5,379
Operating expense	2,956	3,719	3,585
Operating income (loss)	2,728	1,886	1,794
Net income (loss)	2,059	1,442	1,950
Depreciation and amortization	306	1,206	1,168
Senior note and other interest expense	0	0	0
Income tax expense (benefit) in net income	755	453	619
Assets	44,222	42,801
All Other | Non- tariffed
Segment Reporting Information [Line Items]
Operating revenue	0	0	0
Operating expense	3,597	3,322	2,403
Operating income (loss)	(3,597)	(3,322)	(2,403)
Net income (loss)	(15,867)	(15,174)	(12,311)
Depreciation and amortization	893	893	893
Senior note and other interest expense	23,072	20,104	20,031
Income tax expense (benefit) in net income	(7,550)	(5,421)	(2,946)
Assets	58,141	63,507
SJW Corp. | Regulated
Segment Reporting Information [Line Items]
Operating revenue	652,045	603,000	558,154
Operating expense	506,923	473,141	449,401
Operating income (loss)	145,122	129,859	108,753
Net income (loss)	94,343	86,500	67,530
Depreciation and amortization	104,329	99,412	91,896
Senior note and other interest expense	42,743	37,958	34,308
Income tax expense (benefit) in net income	11,293	12,756	10,327
Assets	4,199,172	3,643,916
SJW Corp. | Non- tariffed
Segment Reporting Information [Line Items]
Operating revenue	18,318	17,698	15,532
Operating expense	14,005	16,579	13,126
Operating income (loss)	4,313	1,119	2,406
Net income (loss)	(9,356)	(12,672)	(7,052)
Depreciation and amortization	1,539	5,005	2,504
Senior note and other interest expense	23,401	20,104	20,031
Income tax expense (benefit) in net income	(5,337)	(4,260)	$ (1,958)
Assets	$ 145,895	$ 111,140