Financial Statement Schedule - Condensed Balance Sheets (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Mar. 08, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 9,723	$ 12,344	$ 12,119		$ 9,269
Other current assets	6,146	6,095
Total current assets	198,389	158,386
Other assets:
Other	8,056	7,323
Total other assets	962,868	925,478
Total assets	4,345,067	3,755,056
Stockholders’ equity:
Common stock, $0.001 par value; authorized 70,000,000 shares in 2023 and 2022; issued and outstanding 32,023,004 shares in 2023 and 30,801,912 shares in 2022	32	31
Additional paid-in capital	736,191	651,004
Retained earnings	495,383	458,356
Accumulated other comprehensive income	1,791	1,477
Total stockholders’ equity	1,233,397	1,110,868	1,034,519		917,160
Long-term debt, less current portion	1,526,699	1,491,965
Total capitalization	2,760,096	2,602,833
Current liabilities:
Lines of credit	171,500	159,578
Accrued interest	15,816	13,907
Other current liabilities	20,795	22,913
Total current liabilities	342,974	268,322
Deferred income taxes	238,528	218,155
Other noncurrent liabilities	22,492	25,884
Total equity and liabilities	$ 4,345,067	$ 3,755,056
Common stock, par value (usd per share)	$ 0.001	$ 0.001		$ 0.001
Common stock, shares authorized (in shares)	70,000,000	70,000,000
Common stock, shares issued (in shares)	32,023,004	30,801,912
Common stock, shares outstanding (in shares)	32,023,004	30,801,912
SJW Group
Assets
Investments in subsidiaries	$ 1,753,250	$ 1,675,545
Current assets:
Cash and cash equivalents	868	5,142	$ 2,859		$ 436
Intercompany receivables	2,239	0
Intercompany notes receivable	69,746	13,094
Other current assets	243	193
Total current assets	73,096	18,429
Other assets:
Other	193	183
Total other assets	193	183
Total assets	1,826,539	1,694,157
Stockholders’ equity:
Common stock, $0.001 par value; authorized 70,000,000 shares in 2023 and 2022; issued and outstanding 32,023,004 shares in 2023 and 30,801,912 shares in 2022	32	31
Additional paid-in capital	736,191	651,004
Retained earnings	495,383	458,356
Accumulated other comprehensive income	1,791	1,477
Total stockholders’ equity	1,233,397	1,110,868
Long-term debt, less current portion	557,028	556,627
Total capitalization	1,790,425	1,667,495
Current liabilities:
Lines of credit	10,000	0
Intercompany payables	0	789
Intercompany notes payable	1,726	4,166
Accrued interest	3,255	3,208
Income tax payable	16,427	14,736
Other current liabilities	629	398
Total current liabilities	32,037	23,297
Deferred income taxes	3,099	2,373
Other noncurrent liabilities	978	992
Total equity and liabilities	$ 1,826,539	$ 1,694,157