Capitalization	12 Months Ended
Dec. 31, 2018
Equity [Abstract]
CAPITALIZATION	Capitalization SJW Group is authorized to issue 36,000,000 shares of common stock of $0.001 par value per share. At December 31, 2018 and 2017, 28,404,316 and 20,520,856, respectively, shares of common stock were issued and outstanding. At December 31, 2018 and 2017, 1,000,000 shares of preferred stock of $0.001 par value per share were authorized for SJW Group. At December 31, 2018 and 2017, no shares of preferred stock were issued or outstanding. On November 28, 2018, SJW Group entered into an underwriting agreement with J.P. Morgan Securities LLC, Barclays Capital Inc., RBC Capital Markets, LLC and UBS Securities LLC, as representatives of the several underwriters (the “Underwriters”), pursuant to which SJW Group sold to the Underwriters an aggregate of 6,750,000 shares of SJW Group’s common stock, par value $0.001 per share (the “Firm Shares”), in an underwritten public offering. Pursuant to the underwriting agreement, SJW Group granted the Underwriters a 30-day option to purchase up to an additional 1,012,500 shares of its common stock (the “Option Shares”), which was exercised in full on December 3, 2018. The offering of the Firm Shares closed on December 3, 2018 and the offering of the Option Shares on December 5, 2018. SJW Group received net proceeds of approximately $358,256 from the sale of the Firm Shares and received additional net proceeds of approximately $53,738 from the sale of the Option Shares, in each case after deducting the underwriting discounts and commissions and estimated offering expenses payable by SJW Group. SJW Group intends to use the net proceeds from the offering, together with the net offering proceeds from new debt financing in 2019, to finance the proposed merger of CTWS and to pay related fees and expenses. See Note 12 for a discussion on the proposed CTWS merger. Pending such use, the company has invested the net proceeds temporarily in a short-term money market fund. The offering is not conditioned on the consummation of the proposed merger. If for any reason the proposed merger of CTWS does not close, then SJW Group intends to use the proceeds from the offering for general corporate purposes, which may include acquisitions, share repurchases or debt repayment. SJW Group will not have any obligation to repurchase any or all of its shares of common stock sold in the offering.

Capitalization

SJW Group is authorized to issue 36,000,000 shares of common stock of $0.001 par value per share. At December 31, 2018 and 2017, 28,404,316 and 20,520,856, respectively, shares of common stock were issued and outstanding.

At December 31, 2018 and 2017, 1,000,000 shares of preferred stock of $0.001 par value per share were authorized for SJW Group. At December 31, 2018 and 2017, no shares of preferred stock were issued or outstanding.

On November 28, 2018, SJW Group entered into an underwriting agreement with J.P. Morgan Securities LLC, Barclays Capital Inc., RBC Capital Markets, LLC and UBS Securities LLC, as representatives of the several underwriters (the “Underwriters”), pursuant to which SJW Group sold to the Underwriters an aggregate of 6,750,000 shares of SJW Group’s common stock, par value $0.001 per share (the “Firm Shares”), in an underwritten public offering. Pursuant to the underwriting agreement, SJW Group granted the Underwriters a 30-day option to purchase up to an additional 1,012,500 shares of its common stock (the “Option Shares”), which was exercised in full on December 3, 2018. The offering of the Firm Shares closed on December 3, 2018 and the offering of the Option Shares on December 5, 2018.

SJW Group received net proceeds of approximately $358,256 from the sale of the Firm Shares and received additional net proceeds of approximately $53,738 from the sale of the Option Shares, in each case after deducting the underwriting discounts and commissions and estimated offering expenses payable by SJW Group. SJW Group intends to use the net proceeds from the offering, together with the net offering proceeds from new debt financing in 2019, to finance the proposed merger of CTWS and to pay related fees and expenses. See Note 12 for a discussion on the proposed CTWS merger. Pending such use, the company has invested the net proceeds temporarily in a short-term money market fund. The offering is not conditioned on the consummation of the proposed merger. If for any reason the proposed merger of CTWS does not close, then SJW Group intends to use the proceeds from the offering for general corporate purposes, which may include acquisitions, share repurchases or debt repayment. SJW Group will not have any obligation to repurchase any or all of its shares of common stock sold in the offering.