Financial Statement Schedule - Condensed Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating activities:
Net income (loss)	$ 84,987	$ 73,828	$ 60,478
Adjustments to reconcile net income to net cash provided by operating activities:
Deferred income taxes	(8,510)	(3,244)	(2,851)
Stock-based compensation	4,647	4,791	4,246
Gain on sale of asset	0	(6,197)	(11,421)
Changes in operating assets and liabilities, net of acquired assets and liabilities:
Accounts payable and other current liabilities	492	(1,388)	4,843
Tax receivable and payable, and other accrued taxes	(22,415)	(11,954)	(6,416)
Other changes, net	218	(1,339)	(2,123)
Net cash provided by operating activities	190,831	166,199	130,040
Investing activities:
Proceeds from sale of assets	0	975	18,228
Net cash used in investing activities	(322,272)	(244,328)	(259,995)
Financing activities:
Borrowings from lines of credit	146,415	158,779	96,625
Repayments of long-term borrowings	(4,347)	(89,177)	(76,113)
Issuance of common stock, net of issuance costs	80,659	39,085	91,028
Dividends paid	(47,905)	(43,582)	(40,137)
Net cash provided by financing activities	128,820	78,354	132,805
Net change in cash, cash equivalents and restricted cash	(2,621)	225	2,850
Cash, cash equivalents and restricted cash, beginning of year	12,344	12,119	9,269
Cash, cash equivalents and restricted cash, end of year	9,723	12,344	12,119
Cash paid during the year for:
Interest	67,508	63,677	58,175
Income taxes	23,020	6,853	8,466
SJW Group
Adjustments to reconcile net income to net cash provided by operating activities:
Earnings from investment in subsidiaries	(95,808)	(88,510)	(73,663)
Deferred income taxes	718	(163)	(185)
Stock-based compensation	696	779	679
Gain on sale of asset	0	0	(3,000)
Changes in operating assets and liabilities, net of acquired assets and liabilities:
Accounts payable and other current liabilities	281	185	(226)
Intercompany receivables	(6,018)	(3,916)	(1,586)
Tax receivable and payable, and other accrued taxes	1,550	6,883	4,782
Accrued interest	47	(15)	28
Return on capital from investments in subsidiaries	50,550	55,950	45,900
Other changes, net	607	500	605
Net cash provided by operating activities	37,610	45,521	33,812
Investing activities:
Proceeds to subsidiaries for notes receivable	(148,392)	(27,713)	(75,986)
Repayments from subsidiaries for notes receivable	91,740	20,634	85,651
Investments in subsidiaries	(25,500)	(25,892)	(35,118)
Proceeds from sale of assets	0	0	3,000
Net cash used in investing activities	(82,152)	(32,971)	(22,453)
Financing activities:
Borrowings from subsidiaries for notes payable	700	15,355	34,317
Repayments to subsidiaries for notes payable	(3,140)	(20,901)	(44,145)
Borrowings from lines of credit	10,000	0	0
Repayments of long-term borrowings	0	0	(50,000)
Issuance of common stock, net of issuance costs	80,659	39,085	91,029
Debt issuance costs	(46)	(224)	0
Dividends paid	(47,905)	(43,582)	(40,137)
Net cash provided by financing activities	40,268	(10,267)	(8,936)
Net change in cash, cash equivalents and restricted cash	(4,274)	2,283	2,423
Cash, cash equivalents and restricted cash, beginning of year	5,142	2,859	436
Cash, cash equivalents and restricted cash, end of year	868	5,142	2,859
Cash paid during the year for:
Interest	17,465	17,512	18,518
Income taxes	(4,870)	(5,483)	(4,998)
Supplemental disclosure of non-cash activities:
Share-based compensation from investment in subsidiaries	$ 3,778	$ 4,656	$ 4,413