Lines of Credit - Schedule of Lines of Credit (Details) - Revolving Credit Facility - Line of Credit - USD ($)	Dec. 31, 2024	Dec. 31, 2023	Feb. 06, 2023	Oct. 31, 2022
Line of Credit Facility [Line Items]
Line Limit	$ 350,000,000
Amounts Outstanding	119,124,000	$ 171,500,000
Unused Portion	230,876,000
Syndicated Credit Agreement
Line of Credit Facility [Line Items]
Line Limit	300,000,000
Amounts Outstanding	77,000,000	121,500,000
Unused Portion	223,000,000
SJW Group Credit Agreement Maturing August 2028
Line of Credit Facility [Line Items]
Line Limit	50,000,000
Amounts Outstanding	3,000,000	10,000,000
Unused Portion	47,000,000
SJWC Credit Agreement Maturing August 2028
Line of Credit Facility [Line Items]
Line Limit	140,000,000
Amounts Outstanding	44,000,000	56,000,000
Unused Portion	96,000,000
CTWS Credit Agreement Maturing August 2028
Line of Credit Facility [Line Items]
Line Limit	90,000,000
Amounts Outstanding	30,000,000	53,000,000
Unused Portion	60,000,000
SJWTX Credit Agreement Maturing August 2028
Line of Credit Facility [Line Items]
Line Limit	20,000,000
Amounts Outstanding	0	2,500,000
Unused Portion	20,000,000
CTWS Credit Agreement Maturing August 2028
Line of Credit Facility [Line Items]
Line Limit	10,000,000			$ 10,000,000
Amounts Outstanding	2,124,000	10,000,000
Unused Portion	7,876,000
CTWS Credit Agreement Maturing May 2025
Line of Credit Facility [Line Items]
Line Limit	40,000,000		$ 40,000,000
Amounts Outstanding	40,000,000	$ 40,000,000
Unused Portion	$ 0