Schedule of Regulatory Assets [Table] Schedule of Regulatory Assets [Table] Rental income Operating Lease, Lease Income Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Regulated and Unregulated Operation [Domain] Regulated and Unregulated Operation [Domain] Refunds (Collections) Adjustments Balancing and Memorandum Revenue Account, Refunds (Collections) Balancing and Memorandum Revenue Account, Refunds (Collections) Entity Address, Postal Zip Code Entity Address, Postal Zip Code 4.85% Senior Note, Series P 4.85% Senior Note, Series P [Member] 4.85% Senior Note, Series P Purchased water Cost of Purchased Water Regulatory assets Net Regulatory Assets All Other Other Segments [Member] Debt Instrument [Axis] Debt Instrument [Axis] Dividends paid Payments of Ordinary Dividends, Common Stock Real estate investments and nonutility properties Subtotal Real Estate Investment Property, at Cost Property, plant, and equipment, gross Property, Plant and Equipment, Gross PRVMA PRVMA [Member] PRVMA Company-funded Payments to Acquire Water Systems Using Company Funds Payments to Acquire Water Systems Using Company Funds Other production expenses Utilities Operating Expense, Other Line of credit facility, maximum borrowing capacity Initial Sublimit Line of Credit Facility, Maximum Borrowing Capacity Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Utility plant: Public Utilities, Property, Plant and Equipment, Net [Abstract] Statistical Measurement [Domain] Statistical Measurement [Domain] Interest rate Debt Instrument, Interest Rate, Stated Percentage Share-based Payment Arrangement [Abstract] Share-Based Payment Arrangement [Abstract] Estimated employer contributions for the current fiscal year Defined Benefit Plan, Expected Future Employer Contributions, Current Fiscal Year Additional paid-in capital Additional Paid in Capital, Common Stock Total Defined Benefit Plan, Net Periodic Benefit Cost (Credit) NET INCOME Net income Net income (loss) Net Income (Loss) Attributable to Parent Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Anti-dilutive restricted common stock units excluded from computation of earnings per share (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Amortization of prior service cost Defined Benefit Plan, Amortization of Prior Service Cost (Credit) Subsequent Event Type [Axis] Subsequent Event Type [Axis] Equity Component [Domain] Equity Component [Domain] 2023 percent revenue increase Balancing and Memorandum Revenue Accounts, Percent Increase, Year One Balancing and Memorandum Revenue Accounts, Percent Increase, Year One Subsequent Event Type [Domain] Subsequent Event Type [Domain] Schedule of Regulatory Assets, Net Schedule of Regulatory Assets [Table Text Block] Aggregate gross sales price (up to) Sale of Stock, Aggregate Gross Sales Price Sale of Stock, Aggregate Gross Sales Price Target vesting percentage Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Rights, Percentage Property One Property One [Member] Property One Plan Name [Axis] Plan Name [Axis] 2024 percent revenue increase Balancing and Memorandum Revenue Accounts, Percent Increase, Year Two Balancing and Memorandum Revenue Accounts, Percent Increase, Year Two Fair value of plan assets Defined Benefit Plan, Plan Assets, Amount Cash paid during the period for: Supplemental Cash Flow Information [Abstract] ESPP Employee Stock Purchase Plan [Member] Employee Stock Purchase Plan [Member] Regulated Operations [Abstract] Regulated Operations [Abstract] Plan Name [Domain] Plan Name [Domain] Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Entity Address, State or Province Entity Address, State or Province MWRAM Monterey WRAM [Member] Monterey WRAM Fair Value, Inputs, Level 1 Fair Value, Inputs, Level 1 [Member] Public Utilities General Disclosures Public Utilities General Disclosures [Table Text Block] Accrued groundwater extraction charges, purchased water and power Accrued groundwater extraction charges, purchased water and power Accrued groundwater extraction charges, purchased water and power Award Type [Axis] Award Type [Axis] Unrecognized actuarial loss Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) NET CASH PROVIDED BY OPERATING ACTIVITIES Net Cash Provided by (Used in) Operating Activities At The Market Offering Member At The Market Offering Member [Member] At The Market Offering Member Other, net All others Other Regulatory Assets [Member] Other Regulatory Assets [Member] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] OPERATING EXPENSE: Costs and Expenses [Abstract] Pension 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Regulatory Matters Schedule of Regulatory Assets and Liabilities [Text Block] Income tax temporary differences, net Deferred Income Tax Charge [Member] Entity Shell Company Entity Shell Company Deferred income taxes Deferred Income Tax Expense (Benefit) 4.54% Note Due May 2042 4.54% Note Due May 2042 [Member] 4.54% Note Due May 2042 CEMA CEMA [Member] CEMA Subsequent Event Subsequent Event [Member] Pension Pension Balancing Account [Member] Pension Balancing Account [Member] Document Period End Date Document Period End Date Sales agreement, holdback amount Sales Agreement, Holdback Amount Sales Agreement, Holdback Amount Common stock issuance costs Adjustments to Additional Paid in Capital, Stock Issued, Issuance Costs Total assets Assets Assets Debt Disclosure [Abstract] EARNINGS PER SHARE Earnings Per Share [Abstract] Unrealized gain (loss) on investment, tax expense (benefit) OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment, Tax Performance Shares Performance Shares [Member] Current portion of long-term debt Long-Term Debt, Current Maturities NET CASH PROVIDED BY FINANCING ACTIVITIES Net Cash Provided by (Used in) Financing Activities Long-term debt, fair value Long-Term Debt, Fair Value Accounting Policies [Abstract] Accounting Policies [Abstract] Interest on long-term debt and other interest expense Interest Expense, Debt Accrued payroll Employee-related Liabilities, Current Line of Credit Line of Credit [Member] Income before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Segment [Domain] Segments [Domain] Interest cost Defined Benefit Plan, Interest Cost Total equity distribution Sale of Stock, Total Equity Distribution Agreement Remaining Sale of Stock, Total Equity Distribution Agreement Remaining Regulatory Asset [Domain] Regulatory Asset [Domain] Schedule of Investments [Line Items] Schedule of Investments [Line Items] Award Type [Domain] Award Type [Domain] Recognition period for unrecognized compensation cost Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition Business combinations debt premium, net Business combinations debt premium [Member] Business combinations debt premium Income tax Income Taxes Receivable, Current Payments for business acquisitions Payments to Acquire Businesses, Gross Gain on sale of nonutility properties and Texas Water Alliance Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property, And On Sale Of Investment Real Estate Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property, And On Sale Of Investment Real Estate Accrued unbilled utility revenue Receivables, Long-Term Contracts or Programs Entity Registrant Name Entity Registrant Name Receipts of advances and contributions in aid of construction Receipts Of Advances And Contributions In Aid Of Construction Receipts Of Advances And Contributions In Aid Of Construction Common stock issuance, net of costs (in shares) Stock Issued During Period, Shares, New Issues Subsequent Event Subsequent Events [Text Block] Proceeds from sale of real estate held-for-investment Proceeds from Sale of Real Estate Held-for-investment Entity Address, City or Town Entity Address, City or Town Benefit Plans Retirement Benefits [Text Block] Minimum Minimum [Member] Restricted cash Restricted Cash and Cash Equivalents, Current Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Entity Emerging Growth Company Entity Emerging Growth Company Common stock, par value (usd per share) Common Stock, Par or Stated Value Per Share Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Properties selling expenses Properties Selling Expenses Properties Selling Expenses Trading Symbol Trading Symbol Entity File Number Entity File Number ADVANCES FOR CONSTRUCTION Contract with Customer, Liability, Noncurrent 2022 revenue increase Balancing and Memorandum Revenue Account, Increase (Decrease), Current Fiscal Year Balancing and Memorandum Revenue Account, Increase (Decrease), Current Fiscal Year Accrued interest Interest Payable, Current SJWC SJWC [Member] SJWC Refunds of advances for construction Repayments of Advances for Construction Maintenance Utilities Operating Expense, Maintenance Title of Individual [Axis] Title of Individual [Axis] LESS RESTRICTED CASH, END OF PERIOD Restricted Cash and Cash Equivalents Number of equity instruments granted (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period Restricted Stock Units (RSUs) Restricted Stock Units (RSUs) [Member] Effective consolidated income tax rate Effective Income Tax Rate Reconciliation, Percent Schedule of Borrowing Credit Agreement Schedule of Line of Credit Facilities [Table Text Block] Borrowings on line of credit Proceeds from Lines of Credit OTHER (EXPENSE) INCOME: Other Nonoperating Income (Expense) [Abstract] Water supply costs Water Supply Balancing Accounts [Member] Water Supply Balancing Accounts [Member] Incentive Plan Incentive Plan [Member] Incentive Plan [Member] Accounts payable and other current liabilities Increase (Decrease) in Accounts Payable Subsequent Events [Abstract] REVENUE Total revenues Operating revenue Revenues Income Taxes Income Tax Disclosure [Text Block] Current regulatory assets, net Less: current regulatory assets, net Regulatory Asset, Current Regulated Regulated Operation [Member] Credit Facility [Domain] Credit Facility [Domain] Depreciable plant and equipment Public Utilities, Property, Plant And Equipment, Depreciable Plant And Equipment Public Utilities, Property, Plant And Equipment, Depreciable Plant And Equipment Interest Interest Paid, Excluding Capitalized Interest, Operating Activities Basic (usd per share) Earnings Per Share, Basic Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] CTWS CTWS [Member] CTWS Credit Agreement Total stockholders’ equity Beginning balance Ending balance Stockholders' Equity Attributable to Parent Prepaid expenses Prepaid Expense, Current Up-front service concession payment Increase (Decrease) In Up-Front Service Concession Payment Increase (Decrease) In Up-Front Service Concession Payment Line of Credit Facility [Line Items] Line of Credit Facility [Line Items] Entity Interactive Data Current Entity Interactive Data Current Shares issued in offering (shares) Sale of Stock, Number of Shares Issued in Transaction Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Equity Plans Shareholders' Equity and Share-Based Payments [Text Block] Changes in operating assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Other Other Assets, Miscellaneous, Noncurrent Retained Earnings Retained Earnings [Member] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Water Utility Services Reportable Segment One [Member] Reportable Segment One [Member] Common Stock Common Stock [Member] Issuance of restricted and deferred stock units Shares Issued, Value, Share-Based Payment Arrangement, after Forfeiture Remaining shares available for issuance under the Incentive Plan (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant Class of Stock [Axis] Class of Stock [Axis] Revenue Revenue [Policy Text Block] Statement [Table] Statement [Table] Document Quarterly Report Document Quarterly Report Credit Agreement Credit Agreement [Member] Credit Agreement CURRENT ASSETS: Assets, Current [Abstract] Statistical Measurement [Axis] Statistical Measurement [Axis] Other Nontrade Receivables, Current Land Public Utilities, Property, Plant and Equipment, Land Retained earnings Retained Earnings (Accumulated Deficit) Customers, net of allowances for uncollectible accounts of $5,665 and $4,600 on September 30, 2022 and December 31, 2021, respectively Accounts Receivable, after Allowance for Credit Loss, Current Equity Components [Axis] Equity Components [Axis] Depreciation and amortization Utilities Operating Expense, Depreciation and Amortization Rate of compensation increase Defined Benefit Plan, Rate of Compensation Increase Defined Benefit Plan, Rate of Compensation Increase Document Fiscal Year Focus Document Fiscal Year Focus OPERATING ACTIVITIES: Net Cash Provided by (Used in) Operating Activities [Abstract] Statement [Line Items] Statement [Line Items] Buildings and improvements Investment Building and Building Improvements Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Intangible assets Finite-Lived Intangible Assets, Gross Total Balancing and Memorandum Account [Roll Forward] Balancing and Memorandum Account [Roll Forward] Accumulated Other Comprehensive Income AOCI Attributable to Parent [Member] 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. Restricted stock and deferred restricted stock Restricted Stock and Deferred Restricted Stock [Member] Restricted Stock and Deferred Restricted Stock [Member] Regulatory Asset [Axis] Regulatory Asset [Axis] Document Transition Report Document Transition Report Local Phone Number Local Phone Number Accounts receivable: Accounts Receivable, after Allowance for Credit Loss, Current [Abstract] Capitalization, long-term debt and equity Capitalization, Long-Term Debt and Equity OPERATING INCOME Operating income (loss) Operating Income (Loss) Common stock, shares outstanding (shares) Beginning balance (in shares) Ending balance (in shares) Common Stock, Shares, Outstanding Cost of capital memorandum account Cost of capital [Member] Cost of capital [Member] Goodwill Goodwill Weighted average price per share (usd per share) Sale of Stock, Weighted Average Price Per Share Sale of Stock, Weighted Average Price Per Share Regulatory Asset Increase (Decrease) Balancing and Memorandum Cost Recovery Account, Increase (Decrease) Balancing and Memorandum Cost Recovery Account, Increase (Decrease) Name of Property [Domain] Name of Property [Domain] Adjustments to reconcile net income to net cash provided by operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Provision for income taxes Provision (benefit) for income taxes Income Tax Expense (Benefit) Subsidiary or Equity Method Investee, Sale of Stock by Subsidiary or Equity Investee [Table] Subsidiary or Equity Method Investee, Sale of Stock by Subsidiary or Equity Investee [Table] DEFERRED INCOME TAXES Deferred Income Tax Liabilities, Net Income Statement [Abstract] Income Statement [Abstract] Additional Paid-in Capital Additional Paid-in Capital [Member] Document Fiscal Period Focus Document Fiscal Period Focus Regulatory authorization for capital budget Regulatory Authorization For Capital Budget Regulatory Authorization For Capital Budget Regulation Status [Axis] Regulation Status [Axis] Diluted (shares) Weighted Average Number of Shares Outstanding, Diluted 2022 percent revenue increase Balancing and Memorandum Revenue Accounts, Percent Increase, Current Fiscal Year Balancing and Memorandum Revenue Accounts, Percent Increase, Current Fiscal Year Net regulatory assets, less current portion Total regulatory assets, net, less current portion Regulatory Asset, Noncurrent Water Rate Adjustment WRA [Member] WRA [Member] DIVIDENDS PER SHARE (usd per share) Dividends per share (usd per share) Common Stock, Dividends, Per Share, Cash Paid Investments Investments Common stock, $0.001 par value; authorized 70,000,000 shares; issued and outstanding shares 30,315,265 on September 30, 2022 and 30,181,348 on December 31, 2021 Common Stock, Value, Issued CAPITALIZATION: Capitalization, Long-Term Debt and Equity [Abstract] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] 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. Senior Notes Senior Notes [Member] Grant date fair value of equity instruments granted (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 Groundwater extraction charges Groundwater Extraction Charges Groundwater Extraction Charges CASH, CASH EQUIVALENTS AND RESTRICTED CASH, BEGINNING OF PERIOD CASH, CASH EQUIVALENTS AND RESTRICTED CASH, END OF PERIOD Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] CURRENT LIABILITIES: Liabilities, Current [Abstract] Market-based RSU Market-based RSU [Member] Market-based RSU [Member] Long-term borrowings Proceeds from Issuance of Long-Term Debt Common stock, shares issued (shares) Common Stock, Shares, Issued Public Utilities General Disclosures [Table] Public Utilities General Disclosures [Table] Accrued payables for additions to utility plant Capital Expenditures Incurred but Not yet Paid SJWTX, Inc. SJWTX, Inc. [Member] SJWTX, Inc. Retirement Plan Type [Domain] Retirement Plan Type [Domain] Property taxes and other non-income taxes Utilities Operating Expense, Taxes Other regulatory mechanisms, net Regulatory Mechanisms, Other, Net Regulatory Mechanisms, Other, Net Amendment Flag Amendment Flag NET CASH USED IN INVESTING ACTIVITIES Net Cash Provided by (Used in) Investing Activities Power Utilities Operating Expense, Purchased Power Aggregate principal amount Debt Instrument, Face Amount Contributions in aid of construction Payments to Acquire Water Systems using Contributions In Aid of Construction Payments to Acquire Water Systems using Contributions In Aid of Construction Other comprehensive (loss) income, net Other Comprehensive Income (Loss), Net of Tax Employee stock purchase plan Stock Issued During Period, Value, Employee Stock Purchase Plan COMPREHENSIVE INCOME Comprehensive Income (Loss), Net of Tax, Attributable to Parent ESPP proceeds Proceeds, Issuance of Shares, Share-Based Payment Arrangement, Including Option Exercised Schedule of Segment Reporting Information, by Segment Schedule of Segment Reporting Information, by Segment [Table Text Block] Entity Current Reporting Status Entity Current Reporting Status Other current liabilities Other Liabilities, Current Tax receivable and payable, and other accrued taxes Increase (Decrease) in Accrued Taxes Payable Total other assets Other Assets, Noncurrent Refunds (Collections) Adjustments Balancing and Memorandum Account, Refunds (Collections) Balancing and Memorandum Account, Refunds (Collections) Payments to retire utility plant, net of salvage Payments for (Proceeds from) Removal Costs Depreciation and amortization Depreciation, Depletion and Amortization Connecticut Water Company Connecticut Water Company [Member] Connecticut Water Company [Member] Employee stock purchase plan (in shares) Stock Issued During Period, Shares, Employee Stock Purchase Plans Gain on sale of Texas Water Alliance Gain on sale of real estate investments Gain (Loss) on Sale of Properties Real Estate Services Reportable Segment Two [Member] Reportable Segment Two [Member] Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Basis of Accounting Basis of Accounting, Policy [Policy Text Block] Repayments of long-term borrowings Repayments of Long-Term Debt Beginning Balance Ending Balance Balancing and Memorandum Cost Recovery Account, Net Balancing and Memorandum Cost Recovery Account, Net Title of Individual [Domain] Title of Individual [Domain] Public utilities, property, plant and equipment, net Public Utilities, Property, Plant and Equipment, Net Dividends paid Dividends Allowance for uncollectible accounts Accounts Receivable, Allowance for Credit Loss, Current Long-term debt, book value Long-Term Debt Other, net Other Nonoperating Income (Expense) Total operating expense Operating expense Utilities Operating Expense Unrealized gain (loss) on investment, net of tax OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment and Tax Offering price per share (usd per share) Sale of Stock, Price Per Share Common stock, shares authorized (shares) Common Stock, Shares Authorized Maximum Maximum [Member] Regulatory Asset Increase (Decrease) Balancing and Memorandum Revenue Account, Increase (Decrease) Balancing and Memorandum Revenue Account, Increase (Decrease) Accumulated other comprehensive income Accumulated Other Comprehensive Income (Loss), Net of Tax CASH AND CASH EQUIVALENTS, END OF PERIOD Cash and Cash Equivalents, at Carrying Value San Jose Water Company San Jose Water Company [Member] San Jose Water Company [Member] Total current assets Assets, Current Accrued groundwater extraction charges, purchased water and power Increase (Decrease) in Accrued Groundwater Extraction Charges, Purchased Water and Power Increase (Decrease) in Accrued Groundwater Extraction Charges, Purchased Water and Power Income tax payable Taxes Payable, Current Income taxes Income Taxes Paid, Net Balancing and memorandum accounts, net Balancing and Memorandum Accounts [Member] Balancing and Memorandum Accounts [Member] Entity Small Business Entity Small Business Number of reporting units Number of Reporting Units Capitalization Stockholders' Equity Note Disclosure [Text Block] Schedule of Net Benefit Costs Schedule of Net Benefit Costs [Table Text Block] Utility property installed by developers Utility Property Installed by Developer Utility Property Installed by Developer Line of Credit Facility [Table] Line of Credit Facility [Table] General Significant Accounting Policies [Text Block] Unrecognized compensation costs Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount WEIGHTED AVERAGE SHARES OUTSTANDING Weighted Average Number of Shares Outstanding Basic and Diluted [Abstract] Weighted Average Number of Shares Outstanding Basic and Diluted [Abstract] Capitalization ratio Debt Instrument, Covenant, Capitalization Ratio Debt Instrument, Covenant, Capitalization Ratio Public Utilities, General Disclosures [Line Items] Public Utilities, General Disclosures [Line Items] Title of 12(b) Security Title of 12(b) Security Schedule of Defined Benefit Plans Disclosures [Table] Schedule of Defined Benefit Plans Disclosures [Table] Consolidated Entities [Axis] Consolidated Entities [Axis] Subsequent Event [Line Items] Subsequent Event [Line Items] Repayments on line of credit Repayments of lines of credit Repayments of Lines of Credit Debt Instrument [Line Items] Debt Instrument [Line Items] Issuance of restricted and deferred stock units (in shares) Shares Issued, Shares, Share-Based Payment Arrangement, after Forfeiture Stockholders’ equity: Stockholders' Equity, Number of Shares, Par Value and Other Disclosure [Abstract] Segment and Non-Tariffed Business Reporting Segment Reporting Disclosure [Text Block] Additions to real estate investments Payments to Acquire Real Estate Public Stock Offering Public Stock Offering [Member] Public Stock Offering Land Land CAPITALIZATION AND LIABILITIES Liabilities and Equity [Abstract] Gain on sale of nonutility properties Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property SJWTX Credit Agreement SJWTX Credit Agreement [Member] SJWTX Credit Agreement [Member] Net proceeds from stock offering Sale of Stock, Consideration Received on Transaction Accounts payable Accounts Payable, Current Less accumulated depreciation and amortization Public Utilities, Property, Plant and Equipment, Accumulated Depreciation CTWS Employees CTWS Employees [Member] CTWS Employees Entity Filer Category Entity Filer Category Issuance of common stock, net of issuance costs Proceeds from Issuance of Common Stock Basic (shares) Weighted Average Number of Shares Outstanding, Basic Compensation costs charged to income: Share-Based Payment Arrangement, Expense COMMITMENTS AND CONTINGENCIES Commitments and Contingencies Security Exchange Name Security Exchange Name Plan expense Stock or Unit Option Plan Expense Allowance for equity funds used during construction Public Utilities, Allowance for Funds Used During Construction, Additions Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Construction in progress Public Utilities, Property, Plant and Equipment, Construction Work in Progress Revenue from contracts with customers Revenue from Contract with Customer, Excluding Assessed Tax Service cost Defined Benefit Plan, Service Cost Other balancing and memorandum accounts, net Regulatory Balancing And Memorandum Accounts Revenue, Net Regulatory Balancing And Memorandum Accounts Revenue, Net Proceeds from sale of nonutility properties and Texas Water Alliance Proceeds From Sale Of Property Held-For-Sale And From Sale Of Real Estate Investments Proceeds From Sale Of Property Held-For-Sale And From Sale Of Real Estate Investments Cover [Abstract] Schedule of Long-term Debt Instruments [Table] Schedule of Long-Term Debt Instruments [Table] Refunds (Collections) Adjustments Balancing and Memorandum Cost Recovery Account, Refunds (Collections) Balancing and Memorandum Cost Recovery Account, Refunds (Collections) Deferred gain on sale of properties Deferred Gains (Losses) on Sales of Properties Deferred Gains (Losses) on Sales of Properties Less accumulated depreciation and amortization Real Estate Investment Property, Accumulated Depreciation Schedule of Compensation Costs Charged to Income and Proceeds from the Exercise of Any Restricted Stock and Similar Instruments that are Recorded to Additional Paid-In Capital and Common Stock, by Award Type Share-Based Payment Arrangement, Cost by Plan [Table Text Block] Segment Reporting [Abstract] Segment Reporting [Abstract] SJW Group Corporate Segment [Member] SJW Group SJW Group [Member] SJW Group Total capitalization and liabilities Liabilities and Equity Long-term Debt, Type [Axis] Long-Term Debt, Type [Axis] Cash Cash SJWC Credit Agreement SJWC Credit Agreement [Member] SJWC Credit Agreement Accounts receivable and accrued unbilled utility revenue Increase (Decrease) in Receivables Fair Value, Inputs, Level 2 Fair Value, Inputs, Level 2 [Member] Regulatory Assets [Line Items] Regulatory Asset [Line Items] Current Fiscal Year End Date Current Fiscal Year End Date Non-tariffed Unregulated Operation [Member] Diluted (usd per share) Earnings Per Share, Diluted Sale of Stock [Domain] Sale of Stock [Domain] Beginning Balance Ending Balance Balancing and Memorandum Account, Net Balancing and Memorandum Account, Net Service-based restricted stock vesting period Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period Stock-based compensation APIC, Share-Based Payment Arrangement, Increase for Cost Recognition Total current liabilities Liabilities, Current Other current assets Other Assets, Current Unrecognized tax benefits Unrecognized Tax Benefits Alternative revenue programs, net Alternative Revenue Programs, Net Alternative Revenue Programs, Net Amended and Restated Revolving Credit Facility Amended and Restated Revolving Credit Facility [Member] Amended and Restated Revolving Credit Facility Maine Water Company Maine Water Company [Member] Maine Water Company [Member] Entity Address, Address Line One Entity Address, Address Line One Other changes, net Proceeds from (Payments for) Other Financing Activities OTHER ASSETS: Other Assets, Noncurrent [Abstract] Over-Allotment Option Over-Allotment Option [Member] Class of Stock [Domain] Class of Stock [Domain] Expected return on assets Defined Benefit Plan, Expected Return (Loss) on Plan Assets Interest on long-term debt and other interest expense Interest Expense Subsidiary, Sale of Stock [Line Items] Subsidiary, Sale of Stock [Line Items] Credit Facility [Axis] Credit Facility [Axis] Retirement Plan Type [Axis] Retirement Plan Type [Axis] Employer plan contributions Defined Contribution Plan, Employer Discretionary Contribution Amount Equity [Abstract] Subsequent Event [Table] Subsequent Event [Table] Production Expenses: Water Production Costs [Abstract] Water Production Costs [Abstract] Entity Tax Identification Number Entity Tax Identification Number Schedule of Investments [Table] Schedule of Investments [Table] CONTRIBUTIONS IN AID OF CONSTRUCTION Contributions in Aid of Construction 4.71% Senior Note, Series 2022, Due 2052 4.71% Senior Note, Series 2022, Due 2052 [Member] 4.71% Senior Note, Series 2022, Due 2052 Major Streams of Revenue Disaggregation of Revenue [Table Text Block] 2024 revenue increase Balancing and Memorandum Revenue Account, Increase (Decrease), Year Two Balancing and Memorandum Revenue Account, Increase (Decrease), Year Two Beginning Balance Ending Balance Balancing and Memorandum Revenue Account, Net Balancing and Memorandum Revenue Accounting, Net Consolidated Entities [Domain] Consolidated Entities [Domain] NET CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Regulatory Asset Increase (Decrease) Balancing and Memorandum Account, Increase (Decrease) Balancing and Memorandum Account, Increase (Decrease) Cash and cash equivalents: Cash, Cash Equivalents, and Short-Term Investments [Abstract] WCMA 2014-2017 WCMA [Member] 2014-2017 WCMA [Member] Entity Central Index Key Entity Central Index Key Name of Property [Axis] Name of Property [Axis] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-Based Compensation Arrangements by Share-Based Payment Award [Table] 2023 revenue increase Balancing and Memorandum Revenue Account, Increase (Decrease), Year One Balancing and Memorandum Revenue Account, Increase (Decrease), Year One Property Two Property Two [Member] Property Two Entity [Domain] Entity [Domain] City Area Code City Area Code ASSETS Assets [Abstract] Administrative and general General and Administrative Expense Number of properties sold Number Of Properties Sold Number Of Properties Sold Other changes, net Increase (Decrease) in Other Operating Assets and Liabilities, Net Long-term Debt, Type [Domain] Long-Term Debt, Type [Domain] Retirement Benefits [Abstract] Retirement Benefits [Abstract] Revenue accounts: Balancing and Memorandum Revenue Account [Roll Forward] Balancing and Memorandum Revenue Account [Roll Forward] Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Notes Payable to Banks Notes Payable to Banks [Member] Sale of Stock [Axis] Sale of Stock [Axis] Line of credit Line of Credit, Current FINANCING ACTIVITIES: Net Cash Provided by (Used in) Financing Activities [Abstract] Earnings per Share Earnings Per Share, Policy [Policy Text Block] Postretirement pensions and other postretirement benefits Postretirement Pensions and Other Medical Benefits [Member] Postretirement Pensions and Other Medical Benefits [Member] Supplemental disclosure of non-cash activities: Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Stock-based compensation Share-Based Payment Arrangement, Noncash Expense Regulatory assets and liabilities excluding income tax temporary differences, net and postretirement benefits Increase (Decrease) To Regulatory Asset And Liabilities Excluding Income Tax Temporary Differences, Net And Postretirement Benefits Increase (Decrease) To Regulatory Asset And Liabilities Excluding Income Tax Temporary Differences, Net And Postretirement Benefits OTHER NONCURRENT LIABILITIES Other Liabilities, Noncurrent Cost-recovery accounts: Balancing and Memorandum Cost Recovery Account [Roll Forward] Balancing and Memorandum Cost Recovery Account [Roll Forward] Regulatory assets, net not earning a return Remaining Amounts of Regulatory Assets for which No Return on Investment During Recovery Period is Provided