Lines of Credit	12 Months Ended
Lines of Credit	Dec. 31, 2020
Debt Disclosure [Abstract]
Lines of Credit	Lines of CreditSJWC entered into a $125,000 credit agreement (the “Credit Agreement”) with JPMorgan Chase Bank, N.A., as the lender (the “Lender”) on June 1, 2016. The Credit Agreement provides an unsecured credit facility with a letter of credit sublimit of $10,000. Proceeds of borrowings under the Credit Agreement may be used to refinance existing debt, for working capital, and for general corporate purposes. The Credit Agreement has a maturity date of June 1, 2021. On May 11, 2020, SJWC amended its $125,000 unsecured line of credit to increase the lending commitment by $15,000 to $140,000. In addition, on May 11, 2020, SJWC entered into an additional unsecured line of credit allowing borrowings of up to $50,000 for a six month period which had a zero balance at its maturity on November 11, 2020. The Credit Agreement contains customary representations, warranties and events of default, as well as certain restrictive covenants customary for facilities of this type, including restrictions on indebtedness, liens, acquisitions and investments, restricted payments, asset sales, and fundamental changes. The Credit Agreement also includes certain financial covenants that require the Company to maintain a maximum funded debt to capitalization ratio and a minimum interest coverage ratio. SJW Group and SJW Land Company (collectively, the “Borrowers”), entered into a $15,000 credit agreement with the Lender (the “SJW Group Credit Agreement”) on June 1, 2016, which provides an unsecured credit facility to the Borrowers with a letter of credit sublimit of $5,000. The SJW Group Credit Agreement matures on June 1, 2021. Borrowings under the SJW Group Credit Agreement bear interest under the same terms and conditions as those in the Credit Agreement. On April 24, 2020, SJW Group terminated the joint unsecured bank line of credit held by SJW Group and SJW Land Company effective April 29, 2020. In addition, on June 1, 2016, SJW Group, as guarantor, and SJWTX, Inc. (the “Borrower”), entered into a $5,000 credit agreement with the Lender (the “SJWTX Credit Agreement”), which provides an unsecured credit facility to the Borrower with a letter of credit sublimit of $1,000. The SJWTX Credit Agreement matures on June 1, 2021. CTWS maintains a $15,000 line of credit agreement with CoBank, ACB, which was scheduled to expire on July 1, 2020. On May 29, 2020, CTWS entered into a Second Amendment to the CTWS’s existing $15,000 credit agreement, dated as of August 6, 2014, with CoBank, ACB (“CoBank”), as amended by the First Amendment, dated October 28, 2015. The Second Amendment amends the prior agreement to, among other things, increase the total commitment by $25,000, from $15,000 to $40,000. The $40,000 line of credit expires on May 15, 2025. CTWS maintains an additional credit agreement that was temporarily increased to $95,000 with RBS Citizens, N.A. On March 1, 2020, the amount available on the RBS Citizens, N.A. line of credit was reduced to the original amount of $75,000. The line of credit matures on December 14, 2023. As of December 31, 2020 and 2019, SJW Group had outstanding balances on the lines of credit of $175,094 and $117,209, respectively. Cost of borrowing on the lines of credit averaged 1.78% and 3.73% as of December 31, 2020 and 2019, respectively. The SJW Group and SJWTX, Inc. unsecured bank lines of credit have the following affirmative covenants calculated with the financial statements of SJW Group, on a consolidated basis: (1) the funded debt cannot exceed 66-2/3% of total capitalization, and (2) net income available for interest charges for the trailing 12-calendar-month period cannot be less than 175% of interest charges. As of December 31, 2020, SJW Group and SJWTX, Inc. were in compliance with all covenants. SJWC’s unsecured bank lines of credit have the following affirmative covenants: (1) the funded debt cannot exceed 66-2/3% of total capitalization, and (2) net income available for interest charges for the trailing 12-calendar-month period cannot be less than 175% of interest charges. As of December 31, 2020, SJWC was in compliance with all covenants. The CTWS unsecured bank lines of credit have the following affirmative covenants: (1) Connecticut Water’s earnings before interest and taxes to its interest expense shall be equal or greater to 3 to 1, (2) Maine Water’s debt to capitalization ratio shall not exceed 60%, (3) Connecticut Water’s debt to capitalization ratio shall not exceed 60%, and (4) CTWS’s debt to capitalization ratio shall not exceed 65%. As of December 31, 2020, CTWS was in compliance with all covenants.