Weighted average price per share (usd per share) Sale of Stock, Weighted Average Price Per Share Sale of Stock, Weighted Average Price Per Share Consolidated Entities [Axis] Consolidated Entities [Axis] CAPITALIZATION: Capitalization, Long-Term Debt and Equity [Abstract] Purchased water Cost of Purchased Water Maintenance Utilities Operating Expense, Maintenance Senior Notes Senior Notes [Member] Water Revenue Adjustment (“WRA”) Water Revenue Adjustment [Member] WRA [Member] Statistical Measurement [Domain] Statistical Measurement [Domain] Total current assets Assets, Current Schedule of Regulatory Assets, Net Schedule of Regulatory Assets [Table Text Block] Changes in operating assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Schedule of Defined Benefit Plans Disclosures [Table] Schedule of Defined Benefit Plans Disclosures [Table] Total Defined Benefit Plan, Net Periodic Benefit Cost (Credit) 4.85% Senior Note, Series P 4.85% Senior Note, Series P [Member] 4.85% Senior Note, Series P Cash paid during the period for: Supplemental Cash Flow Information [Abstract] Award Type [Domain] Award Type [Domain] Total operating expense Operating expense Utilities Operating Expense Regulatory Assets [Line Items] Regulatory Asset [Line Items] Income tax temporary differences, net Deferred Income Tax Charge [Member] Other, net Other Nonoperating Income (Expense) Entity Filer Category Entity Filer Category Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Payments to retire utility plant, net of salvage Payments for (Proceeds from) Removal Costs Statement [Table] Statement [Table] Current Fiscal Year End Date Current Fiscal Year End Date Employer plan contributions Defined Contribution Plan, Employer Discretionary Contribution Amount Earnings per Share Earnings Per Share, Policy [Policy Text Block] Company-funded Payments to Acquire Water Systems Using Company Funds Payments to Acquire Water Systems Using Company Funds DEFERRED INCOME TAXES Deferred Income Tax Liabilities, Net Performance Shares Performance Shares [Member] Unrecognized tax benefits Unrecognized Tax Benefits Segment Reporting [Abstract] Segment Reporting [Abstract] Accounts payable Accounts Payable, Current Tax receivable and payable, and other accrued taxes Increase (Decrease) in Accrued Taxes Payable Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Property taxes and other non-income taxes Utilities Operating Expense, Taxes COMMITMENTS AND CONTINGENCIES Commitments and Contingencies Investments Investments 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 Supplemental Employee Retirement Plan Supplemental Employee Retirement Plan [Member] 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. Other Benefits Other Postretirement Benefits Plan [Member] Capitalization Equity [Text Block] NET CASH PROVIDED BY OPERATING ACTIVITIES Net Cash Provided by (Used in) Operating Activities Issuance of common stock, net of issuance costs Proceeds from Issuance of Common Stock Class of Stock [Axis] Class of Stock [Axis] Geographical [Axis] Geographical [Axis] Groundwater extraction charges Groundwater Extraction Charges Groundwater Extraction Charges Real estate investments and nonutility properties Subtotal Real Estate Investment Property, at Cost Income Taxes Income Tax Disclosure [Text Block] Stockholders’ equity: Stockholders' Equity, Number of Shares, Par Value and Other Disclosure [Abstract] Number of people served from acquisition Public Utilities, Acquisition, Number of People Served Public Utilities, Acquisition, Number of People Served Amortization of prior service cost Defined Benefit Plan, Amortization of Prior Service Cost (Credit) Lines of credit Line of Credit, Current Other changes, net Increase (Decrease) in Other Operating Assets and Liabilities, Net Depreciation and amortization Depreciation, Depletion and Amortization Revenue Revenue [Policy Text Block] Interest rate Debt Instrument, Interest Rate, Stated Percentage CURRENT LIABILITIES: Liabilities, Current [Abstract] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Market-based RSU Market-based RSU [Member] Market-based RSU [Member] Water Conservation Memorandum Account (“WCMA”) Water Conservation Memorandum Account (WCMA) [Member] Water Conservation Memorandum Account (WCMA) Business Combination and Asset Acquisition [Abstract] Total stockholders’ equity Beginning balance Ending balance Equity, Attributable to Parent Business Acquisition [Line Items] Business Acquisition [Line Items] Non-tariffed Unregulated Operation [Member] Regulated Regulated Operation [Member] Dividends paid Payments of Ordinary Dividends, Common Stock Impairment, long-lived asset Impairment, Long-Lived Asset, Held-for-Use Diluted (usd per share) Earnings Per Share, Diluted Schedule of Investments [Table] Schedule of Investments [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-Based Compensation Arrangements by Share-Based Payment Award [Table] Customers, net of allowances for uncollectible accounts of $6,414 and $5,753 on June 30, 2023 and December 31, 2022, respectively Accounts Receivable, after Allowance for Credit Loss, Current Land Land Land Public Utilities, Property, Plant and Equipment, Land Other regulatory mechanisms, net Regulatory Mechanisms, Other, Net Regulatory Mechanisms, Other, Net LESS RESTRICTED CASH, END OF PERIOD Restricted Cash and Cash Equivalents Income before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest 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 Current regulatory assets, net Less: current regulatory assets, net Regulatory Asset, Current Schedule of Net Benefit Costs Schedule of Net Benefit Costs [Table Text Block] Utility plant: Public Utilities, Property, Plant and Equipment, Net [Abstract] Aggregate gross sales price (up to) Sale of Stock, Aggregate Gross Sales Price Sale of Stock, Aggregate Gross Sales Price OTHER (EXPENSE) INCOME: Other Nonoperating Income (Expense) [Abstract] Fair Value Measurement Fair Value Measurement, Policy [Policy Text Block] Trading Symbol Trading Symbol Long-term debt, fair value Long-Term Debt, Fair Value Fair Value, Inputs, Level 2 Fair Value, Inputs, Level 2 [Member] NET INCOME Net income Net income (loss) Net Income (Loss) Total current liabilities Liabilities, Current Entity Emerging Growth Company Entity Emerging Growth Company Accrued interest Interest Payable, Current Assets held for sale Asset, Held-for-Sale, Not Part of Disposal Group CAPITALIZATION AND LIABILITIES Liabilities and Equity [Abstract] ESPP Employee Stock Purchase Plan [Member] Employee Stock Purchase Plan [Member] Schedule of Regulatory Assets [Table] Schedule of Regulatory Assets [Table] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Other Other Assets, Miscellaneous, Noncurrent Unrecognized tax benefits, period increase (decrease) Unrecognized Tax Benefits, Period Increase (Decrease) Accounts receivable and accrued unbilled utility revenue Increase (Decrease) in Receivables Document Fiscal Period Focus Document Fiscal Period Focus Service cost Defined Benefit Plan, Service Cost Accrued groundwater extraction charges, purchased water and power Accrued groundwater extraction charges, purchased water and power Accrued groundwater extraction charges, purchased water and power Service-based restricted stock vesting period Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period Stock-based compensation Share-Based Payment Arrangement, Noncash Expense Real Estate Services Reportable Segment Two [Member] Reportable Segment Two [Member] General Significant Accounting Policies [Text Block] Common Stock Common Stock [Member] Fair Value, Inputs, Level 1 Fair Value, Inputs, Level 1 [Member] At The Market Offering Member At The Market Offering Member [Member] At The Market Offering Member City Area Code City Area Code Entity Address, Postal Zip Code Entity Address, Postal Zip Code Other, net Other Regulatory Assets [Member] Other Regulatory Assets [Member] Goodwill Goodwill Equity Components [Axis] Equity Components [Axis] Remaining shares available for issuance (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant Document Fiscal Year Focus Document Fiscal Year Focus Geographical [Domain] Geographical [Domain] KT Water Resource L. P. KT Water Resource L. P. [Member] KT Water Resource L. P. Entity Small Business Entity Small Business Minimum Minimum [Member] Local Phone Number Local Phone Number Number of subsidiaries Number of Subsidiaries Number of Subsidiaries Forecast Forecast [Member] DIVIDENDS PER SHARE (usd per share) Dividends per share (usd per share) Common Stock, Dividends, Per Share, Cash Paid Other comprehensive income (loss), net Other Comprehensive Income (Loss), Net of Tax Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] ASSETS Assets [Abstract] 2022 General Rate Case Interim Memorandum Account 2022 General Rate Case Interim Memorandum Account [Member] 2022 General Rate Case Interim Memorandum Account Long-term borrowings Proceeds from Issuance of Long-Term Debt Retirement Plan Type [Domain] Retirement Plan Type [Domain] Restricted Stock Units (RSUs) Restricted Stock Units (RSUs) [Member] Postretirement pensions and other postretirement benefits Pension and Other Postretirement Plans Costs [Member] San Jose Water Company San Jose Water Company [Member] San Jose Water Company [Member] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] 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 Retirement Benefits [Abstract] Retirement Benefits [Abstract] Income taxes Income Taxes Paid, Net NET CASH PROVIDED BY FINANCING ACTIVITIES Net Cash Provided by (Used in) Financing Activities Retirement Plan Type [Axis] Retirement Plan Type [Axis] Additions to real estate investments Payments to Acquire Real Estate Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Other changes, net Payments for (Proceeds from) Other Investing Activities Retained Earnings Retained Earnings [Member] POSTRETIREMENT BENEFIT PLANS Liability, Defined Benefit Plan, Noncurrent Current portion of long-term debt Long-Term Debt, Current Maturities Utility property installed by developers Utility Property Installed by Developer Utility Property Installed by Developer Total capitalization and liabilities Liabilities and Equity Total other assets Other Assets, Noncurrent Schedule of Real Estate Investments and Nonutility Properties Schedule of Real Estate Investments [Table Text Block] Tabular disclosure of real estate investments. Basic (usd per share) Earnings Per Share, Basic Schedule of Long-term Debt Instruments [Table] Schedule of Long-Term Debt Instruments [Table] Employee stock purchase plan Stock Issued During Period, Value, Employee Stock Purchase Plan Accounting Policies [Abstract] Accounting Policies [Abstract] Construction in progress Public Utilities, Property, Plant and Equipment, Construction Work in Progress Depreciation and amortization Depreciation and amortization Utilities Operating Expense, Depreciation and Amortization Sale of Stock [Domain] Sale of Stock [Domain] WEIGHTED AVERAGE SHARES OUTSTANDING Weighted Average Number of Shares Outstanding Basic and Diluted [Abstract] Weighted Average Number of Shares Outstanding Basic and Diluted [Abstract] Shares issued in offering (shares) Sale of Stock, Number of Shares Issued in Transaction REVENUE Total revenues Operating revenue Revenues Fair value of plan assets Defined Benefit Plan, Plan Assets, Amount OTHER ASSETS: Other Assets, Noncurrent [Abstract] Southern Comal County, Texas Southern Comal County, Texas [Member] Southern Comal County, Texas Interest on long-term debt and other interest expense Interest Expense, Debt Entity Address, City or Town Entity Address, City or Town Capitalization, long-term debt and equity Capitalization, Long-Term Debt and Equity Schedule of Segment Reporting Information, by Segment Schedule of Segment Reporting Information, by Segment [Table Text Block] Unrealized gain (loss) on investment, net of taxes Other Comprehensive Income (Loss), Available-for-Sale Securities Adjustment, Net of Tax, Portion Attributable to Parent INVESTING ACTIVITIES: Net Cash Provided by (Used in) Investing Activities [Abstract] Monterey Water Revenue Adjustment Mechanism (“MWRAM”) Monterey Water Revenue Adjustment Mechanism (MWRAM) [Member] Monterey Water Revenue Adjustment Mechanism (MWRAM) Award Type [Axis] Award Type [Axis] 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 Number of equity instruments granted (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period Plan Name [Domain] Plan Name [Domain] Document Quarterly Report Document Quarterly Report Interest on long-term debt and other interest expense Interest Expense Accrued payables for additions to utility plant Capital Expenditures Incurred but Not yet Paid Fair Value, Measurements, Fair Value Hierarchy [Domain] Fair Value Hierarchy and NAV [Domain] Document Transition Report Document Transition Report Net real estate investments and nonutility properties Real Estate Investment Property, Net Total utility plant Property, Plant and Equipment, Gross Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [Table] Texas Water Texas Water [Member] Texas Water Accounts payable and other current liabilities Increase (Decrease) in Accounts Payable Common stock, shares authorized (shares) Common Stock, Shares Authorized Expected return on assets Defined Benefit Plan, Expected Return (Loss) on Plan Assets Repayments on line of credit Repayments of Lines of Credit Long-term Debt, Type [Domain] Long-Term Debt, Type [Domain] Entity File Number Entity File Number Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Prepaid expenses Prepaid Expense, Current Employee stock purchase plan (in shares) Stock Issued During Period, Shares, Employee Stock Purchase Plans Entity Shell Company Entity Shell Company Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [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] CTWS Employees CTWS Employees [Member] CTWS Employees Total equity distribution Sale of Stock, Total Equity Distribution Agreement Remaining Sale of Stock, Total Equity Distribution Agreement Remaining Title of Individual [Domain] Title of Individual [Domain] 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 Business combinations debt premium, net Business combinations debt premium [Member] Business combinations debt premium Gain on sale of nonutility property 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 Long-Lived Assets Held-for-sale by Asset Type [Axis] Long-Lived Assets Held-for-Sale by Asset Type [Axis] Common stock, shares issued (shares) Common Stock, Shares, Issued 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 Business combination, purchase price Business Combination, Consideration Transferred Security Exchange Name Security Exchange Name Deferred income taxes Deferred Income Tax Expense (Benefit) Long-term debt, book value Long-Term Debt Net proceeds from stock offering Sale of Stock, Consideration Received on Transaction Accumulated other comprehensive income Accumulated Other Comprehensive Income (Loss), Net of Tax Gain on sale of nonutility property Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property Target vesting percentage Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Rights, Percentage 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 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 Recognition period for unrecognized compensation cost Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition Other changes, net Proceeds from (Payments for) Other Financing Activities Maximum Maximum [Member] COMPREHENSIVE INCOME Comprehensive Income (Loss), Net of Tax, Attributable to Parent Unrecognized compensation costs Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount Document Type Document Type Gain on sale of real estate investments Gain (Loss) on Sale of Properties Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Issuance of restricted and deferred stock units (in shares) Shares Issued, Shares, Share-Based Payment Arrangement, after Forfeiture Entity Address, Address Line One Entity Address, Address Line One All Other Other Segments [Member] Entity Registrant Name Entity Registrant Name Refunds of advances for construction Repayments Of Advances For Construction, Financing Activities Repayments Of Advances For Construction, Financing Activities Less accumulated depreciation and amortization Public Utilities, Property, Plant and Equipment, Accumulated Depreciation Basis of Accounting Basis of Accounting, Policy [Policy Text Block] Document Period End Date Document Period End Date Borrowings on line of credit Proceeds from Lines of Credit Business Acquisition [Axis] Business Acquisition [Axis] Income tax payable Taxes Payable, Current Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Repayments of long-term borrowings Repayments of Long-Term Debt Allowance for uncollectible accounts Accounts Receivable, Allowance for Credit Loss, Current Entity Central Index Key Entity Central Index Key Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Compensation costs charged to income: Share-Based Payment Arrangement, Expense Other current liabilities Other Liabilities, Current Intangible assets Finite-Lived Intangible Assets, Gross Provision for income taxes Provision (benefit) for income taxes Income Tax Expense (Benefit) Allowance for equity funds used during construction Public Utilities, Allowance for Funds Used During Construction, Additions Income Statement [Abstract] Income Statement [Abstract] Schedule of Investments [Line Items] Schedule of Investments [Line Items] Common stock issuance, net of costs (in shares) Stock Issued During Period, Shares, New Issues Accrued unbilled utility revenue Receivables, Long-Term Contracts or Programs OPERATING EXPENSE: Costs and Expenses [Abstract] Pension non-service cost Net Periodic Defined Benefits Expense (Reversal of Expense), Excluding Service Cost Component Title of 12(b) Security Title of 12(b) Security Regulatory assets, net not earning a return Remaining Amounts of Regulatory Assets for which No Return on Investment During Recovery Period is Provided Accrued payroll Employee-related Liabilities, Current Long-Lived Assets Held-for-sale, Name [Domain] Long-Lived Assets Held-for-Sale, Name [Domain] CONTRIBUTIONS IN AID OF CONSTRUCTION Contributions in Aid of Construction Total regulatory assets, net in Condensed Consolidated Balance Sheets Net Regulatory Assets Incentive Plan Incentive Plan [Member] Incentive Plan [Member] Unrecognized actuarial loss Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) Acquisitions Business Combination Disclosure [Text Block] Schedule of Major Streams of Revenue Disaggregation of Revenue [Table Text Block] Common stock issuance, net of costs Stock Issued During Period, Value, New Issues Equity [Abstract] Issuance of restricted and deferred stock units Shares Issued, Value, Share-Based Payment Arrangement, after Forfeiture Other current assets Other Assets, Current Revenue from contracts with customers Revenue from Contract with Customer, Excluding Assessed Tax Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Long-term Debt, Type [Axis] Long-Term Debt, Type [Axis] 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] Regulatory Matters Schedule of Regulatory Assets and Liabilities [Text Block] Amendment Flag Amendment Flag Depreciable plant and equipment Public Utilities, Property, Plant And Equipment, Depreciable Plant And Equipment Public Utilities, Property, Plant And Equipment, Depreciable Plant And Equipment Less accumulated depreciation and amortization Real Estate Investment Property, Accumulated Depreciation Share-based Payment Arrangement [Abstract] Share-Based Payment Arrangement [Abstract] Alternative revenue programs, net Alternative Revenue Programs, Net Alternative Revenue Programs, Net Entity Tax Identification Number Entity Tax Identification Number Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Interest Interest Paid, Excluding Capitalized Interest, Operating Activities Statistical Measurement [Axis] Statistical Measurement [Axis] Cost recovery balancing and memorandum accounts Cost Recovery Accounts [Member] Cost Recovery Accounts Entity Interactive Data Current Entity Interactive Data Current Bank Borrowings and Long-Term Liabilities Long-Term Debt [Text Block] Long-term debt, less current portion Long-Term Debt, Excluding Current Maturities Other production expenses Utilities Operating Expense, Other Warehouse Building Warehouse Building [Member] Warehouse Building Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Diluted (shares) Weighted Average Number of Shares Outstanding, Diluted Supplemental disclosure of non-cash activities: Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Segment [Domain] Segments [Domain] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Total production expenses Water Production Costs Retained earnings Retained Earnings (Accumulated Deficit) Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Water Utility Services Reportable Segment One [Member] Reportable Segment One [Member] Regulated Operations [Abstract] Regulated Operations [Abstract] Aggregate principal amount Debt Instrument, Face Amount Additional paid-in capital Additional Paid in Capital, Common Stock Production Expenses: Water Production Costs [Abstract] Water Production Costs [Abstract] Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Additional Paid-in Capital Additional Paid-in Capital [Member] CURRENT ASSETS: Assets, Current [Abstract] Total assets Assets Assets Entity Address, State or Province Entity Address, State or Province Cover [Abstract] OPERATING ACTIVITIES: Net Cash Provided by (Used in) Operating Activities [Abstract] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Stock-based compensation APIC, Share-Based Payment Arrangement, Increase for Cost Recognition 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] Common stock, shares outstanding (shares) Beginning balance (in shares) Ending balance (in shares) Common Stock, Shares, Outstanding Dividends paid Dividends OTHER NONCURRENT LIABILITIES Other Liabilities, Noncurrent Interest cost Defined Benefit Plan, Interest Cost KT Water Development Ltd KT Water Development Ltd [Member] KT Water Development Ltd Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] Benefit Plans Retirement Benefits [Text Block] Pension Benefits Pension Plan [Member] Subsidiary, Sale of Stock [Line Items] Subsidiary, Sale of Stock [Line Items] Segment and Non-Tariffed Business Reporting Segment Reporting Disclosure [Text Block] 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 FINANCING ACTIVITIES: Net Cash Provided by (Used in) Financing Activities [Abstract] Regulated and Unregulated Operation [Domain] Regulated and Unregulated Operation [Domain] Rate of compensation increase Defined Benefit Plan, Rate of Compensation Increase Defined Benefit Plan, Rate of Compensation Increase Common stock, par value (usd per share) Common Stock, Par or Stated Value Per Share Sale of Stock [Axis] Sale of Stock [Axis] Number of service connections from acquisition Public Utilities, Acquisition, Service Connections Public Utilities, Acquisition, Service Connections Equity Component [Domain] Equity Component [Domain] Class of Stock [Domain] Class of Stock [Domain] NET CASH USED IN INVESTING ACTIVITIES Net Cash Provided by (Used in) Investing Activities Regulation Status [Axis] Regulation Status [Axis] Estimated employer contributions for the remainder of fiscal year Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year Debt Instrument [Axis] Debt Instrument [Axis] Postretirement benefits Increase (Decrease) in Obligation, Pension and Other Postretirement Benefits Scenario [Axis] Scenario [Axis] Debt Instrument [Line Items] Debt Instrument [Line Items] Basic (shares) Weighted Average Number of Shares Outstanding, Basic Entity Current Reporting Status Entity Current Reporting Status Effective consolidated income tax rate Effective Income Tax Rate Reconciliation, Percent OPERATING INCOME Operating income (loss) Operating Income (Loss) Buildings and improvements Investment Building and Building Improvements Equity Plans Shareholders' Equity and Share-Based Payments [Text Block] Consolidated Entities [Domain] Consolidated Entities [Domain] 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. Accumulated Other Comprehensive Income (Loss) AOCI Attributable to Parent [Member] Restricted stock and deferred restricted stock Restricted Stock and Deferred Restricted Stock [Member] Restricted Stock and Deferred Restricted Stock [Member] 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 ADVANCES FOR CONSTRUCTION Contract with Customer, Liability, Noncurrent SJW Group Corporate Segment [Member] ESPP proceeds Proceeds, Issuance of Shares, Share-Based Payment Arrangement, Including Option Exercised Title of Individual [Axis] Title of Individual [Axis] Rental income Operating Lease, Lease Income Unrealized income (loss) on investment, tax expense (benefit) Other Comprehensive Income (Loss), Available-for-Sale Securities, Tax, Portion Attributable to Parent Net regulatory assets, less current portion Total regulatory assets, net, less current portion Regulatory Asset, Noncurrent Other Nontrade Receivables, Current Business Segments [Axis] Segments [Axis] Statement [Line Items] Statement [Line Items] Plan Name [Axis] Plan Name [Axis] Debt Disclosure [Abstract] Scenario [Domain] Scenario [Domain] Regulatory Asset [Axis] Regulatory Asset [Axis] EARNINGS PER SHARE Earnings Per Share [Abstract] All other balancing and memorandum accounts All Other Balancing and Memorandum Accounts [Member] All Other Balancing and Memorandum Accounts Plan expense Stock or Unit Option Plan Expense Regulatory Asset [Domain] Regulatory Asset [Domain] Common stock, $0.001 par value; authorized 70,000,000 shares; issued and outstanding shares 31,731,030 on June 30, 2023 and 30,801,912 on December 31, 2022 Common Stock, Value, Issued Net utility plant Public Utilities, Property, Plant and Equipment, Net Administrative and general General and Administrative Expense Power Utilities Operating Expense, Purchased Power Accounts receivable: Accounts Receivable, after Allowance for Credit Loss, Current [Abstract]