General (Policies)	6 Months Ended
Jun. 30, 2023
Accounting Policies [Abstract]
Basis of Accounting	The unaudited interim financial information has been prepared in accordance with accounting principles generally accepted in the United States of America and in accordance with the instructions for Form 10-Q and Rule 10-01 of Regulation S-X promulgated by the Securities and Exchange Commission. The Notes to Consolidated Financial Statements in SJW Group’s 2022 Annual Report on Form 10-K should be read with the accompanying unaudited condensed consolidated financial statements.
Revenue	Revenue Water sales are seasonal in nature and influenced by weather conditions. The timing of precipitation and climatic conditions can cause seasonal water consumption by customers to vary significantly. Due to the seasonal nature of the water business, the operating results for interim periods are not indicative of the operating results for a 12-month period. Revenue is generally higher in the warm, dry summer months when water usage and sales are greater, and lower in the winter months when cooler temperatures and increased precipitation curtail water usage resulting in lower sales.
Fair Value Measurement	Fair Value MeasurementThe following instruments are not measured at fair value on SJW Group’s condensed consolidated balance sheets as of June 30, 2023, but require disclosure of their fair values: cash and cash equivalents, accounts receivable and accounts payable. The estimated fair value of such instruments as of June 30, 2023, approximates their carrying value as reported on the condensed consolidated balance sheets. There have been no changes in valuation techniques during the three and six months ended June 30, 2023. The fair value of these instruments would be categorized as Level 2 in the fair value hierarchy, with the exception of cash and cash equivalents, which would be categorized as Level 1.
Earnings per Share	Earnings per ShareBasic earnings per share is calculated using income available to common stockholders, divided by the weighted average number of shares outstanding during the period. Diluted earnings per share is calculated using income available to common stockholders divided by the weighted average number of shares of common stock including both shares outstanding and shares potentially issuable in connection with restricted common stock awards under SJW Group’s long-term incentive plans, shares potentially issuable under the performance stock plans assumed through the business combination with CTWS, and shares potentially issuable under SJW Group’s employee stock purchase plans.

General (Policies)

6 Months Ended

Jun. 30, 2023

The unaudited interim financial information has been prepared in accordance with accounting principles generally accepted in the United States of America and in accordance with the instructions for Form 10-Q and Rule 10-01 of Regulation S-X promulgated by the Securities and Exchange Commission. The Notes to Consolidated Financial Statements in SJW Group’s 2022 Annual Report on Form 10-K should be read with the accompanying unaudited condensed consolidated financial statements.

Revenue

Water sales are seasonal in nature and influenced by weather conditions. The timing of precipitation and climatic conditions can cause seasonal water consumption by customers to vary significantly. Due to the seasonal nature of the water business, the operating results for interim periods are not indicative of the operating results for a 12-month period. Revenue is generally higher in the warm, dry summer months when water usage and sales are greater, and lower in the winter months when cooler temperatures and increased precipitation curtail water usage resulting in lower sales.

Fair Value Measurement

Fair Value MeasurementThe following instruments are not measured at fair value on SJW Group’s condensed consolidated balance sheets as of June 30, 2023, but require disclosure of their fair values: cash and cash equivalents, accounts receivable and accounts payable. The estimated fair value of such instruments as of June 30, 2023, approximates their carrying value as reported on the condensed consolidated balance sheets. There have been no changes in valuation techniques during the three and six months ended June 30, 2023. The fair value of these instruments would be categorized as Level 2 in the fair value hierarchy, with the exception of cash and cash equivalents, which would be categorized as Level 1.

Earnings per Share

Earnings per ShareBasic earnings per share is calculated using income available to common stockholders, divided by the weighted average number of shares outstanding during the period. Diluted earnings per share is calculated using income available to common stockholders divided by the weighted average number of shares of common stock including both shares outstanding and shares potentially issuable in connection with restricted common stock awards under SJW Group’s long-term incentive plans, shares potentially issuable under the performance stock plans assumed through the business combination with CTWS, and shares potentially issuable under SJW Group’s employee stock purchase plans.