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Additional Paid-in Capital [Member] Cost of removal Cost of Removal [Member] Cost of Removal Award Timing Predetermined Award Timing Predetermined [Flag] Dividends paid Payments of Ordinary Dividends, Common Stock Benefit Plans Retirement Benefits [Text Block] Regulatory Liability [Axis] Regulatory Liability [Axis] New Accounting Standards New Accounting Pronouncements, Policy [Policy Text Block] Amortization of prior service cost Defined Benefit Plan, Amortization of Prior Service Cost (Credit) Forecast Forecast [Member] Class of Stock [Axis] Class of Stock [Axis] Lines of Credit and Long-Term Liabilities Long-Term Debt [Text Block] Diluted (in usd per share) Earnings Per Share, Diluted Total production expenses Water Production Costs Title of Individual [Domain] Title and Position [Domain] Name Measure Name Entity Interactive Data Current Entity Interactive Data Current Regulatory Liability [Domain] Regulatory Liability [Domain] Restatement does not require Recovery Restatement Does Not Require Recovery [Text Block] Target vesting percentage Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Rights, Percentage Other Nontrade Receivables, Current Retirement Benefits [Abstract] Retirement Benefits [Abstract] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Indefinite life water rights reclassified from nonutility property to utility plant Indefinite Life Water Rights Reclassified From Nonutility Property to Utility Plant Indefinite Life Water Rights Reclassified From Nonutility Property to Utility Plant Water Utility Services Reportable Segment One [Member] Reportable Segment One [Member] Accounts receivable and accrued unbilled utility revenue Increase (Decrease) in Receivables Stock-based compensation Share-Based Payment Arrangement, Noncash Expense Provision for income taxes Provision (benefit) for income taxes Income Tax Expense (Benefit) Interest cost Defined Benefit Plan, Interest Cost Interest rate Debt Instrument, Interest Rate, Stated Percentage Schedule of Investments [Line Items] Schedule of Investments [Line Items] Cash paid during the period for: Supplemental Cash Flow Information [Abstract] Equity Plans Shareholders' Equity and Share-Based Payments [Text Block] Recognition period for unrecognized compensation cost Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition Revenue from contracts with customers Revenue from Contract with Customer, Excluding Assessed Tax Effective consolidated income tax rate Effective Income Tax Rate Reconciliation, Percent Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities Operating income Operating income (loss) Operating Income (Loss) Business Acquisition [Line Items] Business Acquisition [Line Items] Total capitalization and liabilities Liabilities and Equity Dividends paid Dividends Rule 10b5-1 Arrangement Terminated Rule 10b5-1 Arrangement Terminated [Flag] All Adjustments to Compensation All Adjustments to Compensation [Member] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Accrued payroll Employee-related Liabilities, Current Rate of compensation increase Defined Benefit Plan, Rate Of Compensation Increase Defined Benefit Plan, Rate Of Compensation Increase Number of service connections from acquisition Public Utilities, Acquisition, Service Connections Public Utilities, Acquisition, Service Connections Other intangible asset Other Intangible Assets, Net Nonutility properties and real estate investments Nonutility properties and real estate investments Nonutility Properties And Real Estate Investments, At Cost Nonutility Properties And Real Estate Investments, At Cost Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Regulated Operations [Abstract] Regulated Operations [Abstract] Accrued groundwater extraction charges, purchased water and power 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Actually Paid vs. Total Shareholder Return Compensation Actually Paid vs. Total Shareholder Return [Text Block] Accounts, Notes, Loans and Financing Receivable [Line Items] Accounts, Notes, Loans and Financing Receivable [Line Items] Capitalization and liabilities Liabilities and Equity [Abstract] Other assets: Other Assets, Noncurrent [Abstract] Schedule of Net Benefit Costs Schedule of Net Benefit Costs [Table Text Block] Other production expenses Utilities Operating Expense, Other Weighted average price per share (in usd per share) Sale Of Stock, Weighted Average Price Per Share Sale Of Stock, Weighted Average Price Per Share Minimum Minimum [Member] Net nonutility properties and real estate investments Nonutility Properties And Real Estate Investments, Net Nonutility Properties And Real Estate Investments, Net Restatement Determination Date Restatement Determination Date Stockholders’ equity: Stockholders' Equity, Number of Shares, Par Value and Other Disclosure [Abstract] Adoption Date Trading Arrangement Adoption Date Pay vs Performance Disclosure Pay vs Performance Disclosure [Table] Advances for construction Contract with Customer, Liability, Noncurrent Service agreement, renewal term Service Agreement, Renewal Term Service Agreement, Renewal Term Erroneously Awarded Compensation Recovery Erroneously Awarded Compensation Recovery [Table] Lines of credit Line of Credit, Current Business Segments [Axis] Segments [Axis] Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year [Member] Exercise Price Award Exercise Price Cost to retire utility plant, net of salvage Payments for (Proceeds from) Removal Costs Arrangement Duration Trading Arrangement Duration Employee stock purchase plan Stock Issued During Period, Value, Employee Stock Purchase Plan Operating expense: Costs and Expenses [Abstract] Grant date fair value of equity instruments granted (in usd per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Investments Investments Shares issuable upon exercise of incentive plan awards (in shares) Share-Based Compensation Arrangement By Share-Based Payment Award, Shares Issuable Upon Exercise Number of shares reserved for issuance under equity instrument agreements awarded that validly exist and are outstanding, including vested instruments. 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P. KT Water Resource L. P. [Member] KT Water Resource L. P. 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(loss) on disposition of assets Gain (Loss) on Disposition of Assets Total current assets Assets, Current Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Senior Notes Senior Notes [Member] Capitalization: Capitalization, Long-Term Debt and Equity [Abstract] Tax receivable and payable, and other accrued taxes Increase (Decrease) in Accrued Taxes Payable Unused portion of line of credit Line of Credit Facility, Remaining Borrowing Capacity Schedule of Long-term Debt Instruments [Table] Schedule of Long-Term Debt Instruments [Table] Long-term debt, less current portion Long-Term Debt, Excluding Current Maturities Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Series 2024 Notes 5.78% Senior Notes due 2054 [Member] 5.78% Senior Notes due 2054 Accrued groundwater extraction charges, purchased water and power Accrued Groundwater Extraction Charges, Purchased Water And Power Accrued Groundwater 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Long-term debt, fair value Long-Term Debt, Fair Value Entity Registrant Name Entity Registrant Name Payments for business acquisition Payments to Acquire Businesses, Gross Adjustment to Non-PEO NEO Compensation Footnote Adjustment to Non-PEO NEO Compensation Footnote [Text Block] Stock Appreciation Rights (SARs) Stock Appreciation Rights (SARs) [Member] Depreciation and amortization Depreciation, Depletion and Amortization Fair Value as of Grant Date Award Grant Date Fair Value Postretirement benefit plans Assets for Plan Benefits, Defined Benefit Plan Shares issued in offering (in shares) Sale of Stock, Number of Shares Issued in Transaction Fair Value, Inputs, Level 2 Fair Value, Inputs, Level 2 [Member] Fair Value, Measurements, Fair Value Hierarchy [Domain] Fair Value Hierarchy and NAV [Domain] Geographical [Domain] Geographical [Domain] Recovery of Erroneously Awarded Compensation Disclosure [Line Items] Aggregate principal amount Debt Instrument, Face Amount Schedule of SJW Group's Revenue Components Disaggregation of Revenue [Table Text Block] Common stock issuance, net of costs Stock Issued During Period, Value, New Issues Entity Address, Postal Zip Code Entity Address, Postal Zip Code Restatement Determination Date: Restatement Determination Date [Axis] Title of 12(b) Security Title of 12(b) Security Common stock, $0.001 par value; authorized 70,000,000 shares; issued and outstanding shares 33,226,735 on September 30, 2024 and 32,023,004 on December 31, 2023 Common Stock, Value, Issued Land Land Share-based Payment Arrangement [Abstract] Share-Based Payment Arrangement [Abstract] Regulatory assets, less current portion Total regulatory assets, less current portion Regulatory Asset, Noncurrent Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Schedule of Investments [Table] Schedule of Investments [Table] Depreciation and amortization Depreciation and amortization Utilities Operating Expense, Depreciation and Amortization Other changes, net Payments for (Proceeds from) Other Investing Activities Current regulatory liabilities Less: current regulatory liabilities Regulatory Liability, Current Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested [Member] Financing activities: Net Cash Provided by (Used in) Financing Activities [Abstract] Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested [Member] Other balancing and memorandum accounts and regulatory mechanisms, net Regulatory Balancing And Memorandum Accounts And Regulatory Mechanisms, Net Regulatory Balancing And Memorandum Accounts And Regulatory Mechanisms, Net Total regulatory liabilities Regulatory Liability Basic (in usd per share) Earnings Per Share, Basic Accounts payable and other current liabilities Increase (Decrease) in Accounts Payable Issuance of common stock, net of issuance costs Proceeds from Issuance of Common Stock Proceeds from sale of real estate investments Proceeds from Sale, Real Estate, Held-for-Investment Adjustment To PEO Compensation, Footnote Adjustment To PEO Compensation, Footnote [Text Block] Award Timing MNPI Disclosure Award Timing MNPI Disclosure [Text Block] Acquisitions Business Combination And Asset Acquisitions [Text Block] Business Combination And Asset Acquisitions Accrued payables for additions to utility plant Capital Expenditures Incurred but Not yet Paid Aggregate Pension Adjustments Service Cost Aggregate Pension Adjustments Service Cost [Member] Asset acquisition, other current liabilities Asset Acquisition, Current Liabilities, Other Asset Acquisition, Current Liabilities, Other Compensation Actually Paid vs. Other Measure Compensation Actually Paid vs. Other Measure [Text Block] Total current liabilities Liabilities, Current Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year [Member] Total assets Total assets Assets Number of equity instruments granted (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period Long-Lived Assets Held-for-sale, Name [Domain] Long-Lived Assets Held-for-Sale, Name [Domain] Income tax Income Taxes Receivable, Current Other noncurrent liabilities Other Liabilities, Noncurrent Forgone Recovery due to Violation of Home Country Law, Amount Forgone Recovery due to Violation of Home Country Law, Amount Commitments and contingencies Commitments and Contingencies Alternative revenue programs, net Alternative Revenue Programs, Net Alternative Revenue Programs, Net Termination Date Trading Arrangement Termination Date Asset acquisition, other intangible asset Asset Acquisition, Recognized Identifiable Assets Acquired And Liabilities Assumed, Other Intangible Asset Asset Acquisition, Recognized Identifiable Assets Acquired And Liabilities Assumed, Other Intangible Asset Upfront concession fee Service Agreement, Upfront Concession Fee Service Agreement, Upfront Concession Fee Operating revenue Operating revenue Operating revenue Revenues Regulated Regulated Operation [Member] Regulatory assets and liabilities excluding cost of removal, income tax temporary differences, and postretirement benefits Increase (Decrease) To Regulatory Asset And Liabilities Excluding Cost Of Removal, Income Tax Temporary Differences, Net And Postretirement Benefits Increase (Decrease) To Regulatory Asset And Liabilities Excluding Cost Of Removal, Income Tax Temporary Differences, Net And Postretirement Benefits Asset acquisition, consideration transferred Asset Acquisition, Consideration Transferred Entity Address, City or Town Entity Address, City or Town Long-term borrowings Proceeds from Issuance of Long-Term Debt Warehouse Building Warehouse Building [Member] Warehouse Building Debt Instrument [Axis] Debt Instrument [Axis] Compensation costs charged to income: Share-Based Payment Arrangement, Expense Net income Net income Net income (loss) Net Income (Loss) Attributable to Parent Trading Arrangement: Trading Arrangement [Axis] Regulated and Unregulated Operation [Domain] Regulated and Unregulated Operation [Domain] Other Commitments [Table] Other Commitments [Table] Pay vs Performance Disclosure, Table Pay vs Performance [Table Text Block] Regulation Status [Axis] Regulation Status [Axis] Employer plan contributions Defined Contribution Plan, Employer Discretionary Contribution Amount Allowance for equity funds used during construction Public Utilities, Allowance for Funds Used During Construction, Additions Business Acquisition [Axis] Business Acquisition [Axis] Equity Awards Adjustments, Excluding Value Reported in Compensation Table Equity Awards Adjustments, Excluding Value Reported in the Compensation Table [Member] Production Expenses: Water Production Costs [Abstract] Water Production Costs [Abstract] Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year [Member] Entity File Number Entity File Number Consolidated Entities [Domain] Consolidated Entities [Domain] Document Fiscal Year Focus Document Fiscal Year Focus Income Statement [Abstract] Income Statement [Abstract] Entity Address, Address Line One Entity Address, Address Line One Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Name Forgone Recovery, Individual Name Document Period End Date Document Period End Date Sale of Stock [Axis] Sale of Stock [Axis] Non-tariffed Unregulated Operation [Member] Award Timing MNPI Considered Award Timing MNPI Considered [Flag] KT Water Development Ltd KT Water Development Ltd [Member] KT Water Development Ltd Insider Trading Arrangements [Line Items] Outstanding Aggregate Erroneous Compensation Amount Outstanding Aggregate Erroneous Compensation Amount Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] PEO Actually Paid Compensation Amount PEO Actually Paid Compensation Amount Adjustment to Compensation: Adjustment to Compensation [Axis] Subsidiary or Equity Method Investee, Sale of Stock by Subsidiary or Equity Investee [Table] Subsidiary or Equity Method Investee, Sale of Stock, Type [Table] Authorized revenue, threshold percentage Regulatory Balancing And Memorandum Accounts Review, Authorized Revenue, Threshold Percentage Threshold balance of regulatory balancing or memorandum accounts as a percentage of authorized revenue to trigger an account review. Document Transition Report Document Transition Report Assets held for sale Asset, Held-for-Sale, Not Part of Disposal Group Document Quarterly Report Document Quarterly Report Reduction in allowance for credit loss, per diluted share (in dollars per share) Accounts Receivable, Allowance For Credit Loss, Period Increase (Decrease), Per Diluted Share Accounts Receivable, Allowance For Credit Loss, Period Increase (Decrease), Per Diluted Share Accumulated other comprehensive income Accumulated Other Comprehensive Income (Loss), Net of Tax Entity Current Reporting Status Entity Current Reporting Status Retained Earnings Retained Earnings [Member] Pension Adjustments Service Cost Pension Adjustments Service Cost [Member] Asset Acquisition [Domain] Asset Acquisition [Domain] Estimated service lives of assets Public Utilities, Property, Plant and Equipment, Common, Useful Life Basic (in shares) Weighted Average Number of Shares Outstanding, Basic Stock Price or TSR Estimation Method Stock Price or TSR Estimation Method [Text Block] Proceeds from sale of productive assets Proceeds from Sale of Productive Assets Subsidiary, Sale of Stock [Line Items] Subsidiary, Sale of Stock [Line Items] Restricted Stock Units (RSUs) Restricted Stock Units (RSUs) [Member] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Executive Category: Executive Category [Axis] Name Awards Close in Time to MNPI Disclosures, Individual Name Entity Filer Category Entity Filer Category Income Statement Location [Domain] Statement of Income Location, Balance [Domain] Company Selected Measure Name Company Selected Measure Name