Business Acquisition [Axis] Business Acquisition [Axis] Schedule of Regulatory Assets [Table] Schedule of Regulatory Assets [Table] Recoveries of accounts written off SEC Schedule, 12-09, Valuation Allowances and Reserves, Addition, Recovery Rental income Operating Lease, Lease Income 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) 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 Deferred: Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract] Preferred stock, shares outstanding (in shares) Preferred Stock, Shares Outstanding Unrealized (loss) gain on investment, net of taxes of $(188) in 2022, $68 in 2021 and $(247) in 2020 Unrealized gain (loss) on investment, net of tax effect Other Comprehensive Income (Loss), Available-for-Sale Securities Adjustment, Net of Tax, Portion Attributable to Parent Total regulatory assets, net Net Regulatory Assets Debt Instrument [Axis] Debt Instrument [Axis] Dividends paid Payments of Ordinary Dividends, Common Stock Real estate investments and nonutility properties Total real estate investments and nonutility properties Real Estate Investment Property, at Cost Property, plant, and equipment, gross Property, Plant and Equipment, Gross Other comprehensive (income) loss, defined benefit plan, prior service cost Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), after Tax 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 CTWS Credit Agreement Maturing August 2027 CTWS Credit Agreement Maturing August 2027 [Member] CTWS Credit Agreement Maturing August 2027 Utility plant: Public Utilities, Property, Plant and Equipment, Net [Abstract] Financial Instruments and Investments Fair Value of Financial Instruments, Policy [Policy Text Block] Public Utility [Axis] Public Utility [Axis] Depreciation Depreciation Rate Debt Instrument, Interest Rate, Stated Percentage Forfeited (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Non-Option Equity Instruments, Forfeitures and Expirations Additional paid-in capital Additional Paid in Capital, Common Stock Other intangible assets, measurement period adjustments Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Intangibles State Current State and Local Tax Expense (Benefit) Total liabilities assumed, measurement period adjustments Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Liabilities Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Liabilities Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] SJWTX Credit Agreement Maturing August 2027 SJWTX Credit Agreement Maturing August 2027 [Member] SJWTX Credit Agreement Maturing August 2027 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 Equity securities Defined Benefit Plan, Equity Securities [Member] Regulatory assets and deferred charges, less current portion, measurement period adjustments Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Regulatory Assets and Deferred Charges, Net Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Regulatory Assets and Deferred Charges, Net Equity Component [Domain] Equity Component [Domain] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Increase related to tax positions taken during the current year Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions Increase (decrease) in taxes attributable to: Increase (Decrease) in Tax Expense [Abstract] Increase (Decrease) in Tax Expense [Abstract] Fair value of plan assets Fair value of assets at beginning of year Fair value of plan assets at end of year Defined Benefit Plan, Plan Assets, Amount Cash paid during the year for: Supplemental Cash Flow Information [Abstract] Plan Name [Domain] Plan Name [Domain] Amounts Outstanding Long-Term Line of Credit Entity Address, State or Province Entity Address, State or Province MWRAM Monterey WRAM [Member] Monterey WRAM Other comprehensive income: Other Comprehensive Income (Loss), Net of Tax [Abstract] Performance-based and market-based restricted stock awards vested (in shares) Restricted Stock Awards, Performance-based, Vested Balance Restricted Stock Awards, Performance-based, Vested Balance Award Type [Axis] Award Type [Axis] Actuarial (gain)/loss Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) 2027 Defined Benefit Plan, Expected Future Benefit Payment, Year Five SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items] SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items] Other items, net Effective Income Tax Rate Reconciliation, Other Reconciling Items, Amount 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] Executive Supplemental Retirement Plan Supplemental Employee Retirement Plan [Member] Debt securities Defined Benefit Plan, Debt Security [Member] Public Utilities, Regulatory Proceeding [Axis] Public Utilities, Regulatory Proceeding [Axis] Long-term debt, less current portion Total long-term debt, less current portion Long-Term Debt, Excluding Current Maturities Variable Interest Entity, Not Primary Beneficiary Variable Interest Entity, Not Primary Beneficiary [Member] Condensed Financial Statements, Captions [Line Items] Condensed Financial Statements, Captions [Line Items] Postretirement benefits Increase (Decrease) in Obligation, Pension and Other Postretirement Benefits Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items] At The Market Offering At The Market Offering [Member] At The Market Offering Goodwill, measurement period adjustments Goodwill, measurement period adjustments Goodwill, Purchase Accounting Adjustments Investing activities: Net Cash Provided by (Used in) Investing Activities [Abstract] Schedule of Expected Benefit Payments Schedule of Expected Benefit Payments [Table Text Block] Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Share-based compensation from investment in subsidiaries Share-Based Compensation From Investment in Subsidiaries Share-Based Compensation From Investment in Subsidiaries Revolving Credit Facility Revolving Credit Facility [Member] Current: Current Income Tax Expense (Benefit), Continuing Operations [Abstract] Document Type Document Type Long-Term Debt Long-Term Debt [Text Block] Restricted net assets, subsidiaries, percent of consolidated assets Restricted Net Assets, Subsidiaries, Percent Of Consolidated Assets Restricted Net Assets, Subsidiaries, Percent Of Consolidated Assets Total production expenses Water Production Costs Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Number of subsidiaries that are primary beneficiaries Variable Interest Entity, Primary Beneficiary, Number Of Subsidiaries Variable Interest Entity, Primary Beneficiary, Number Of Subsidiaries Nonvested, beginning balance (in dollars per share) Nonvested, ending balance (in dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Unamortized investment tax credit Deferred Tax Assets, Tax Credit Carryforwards, General Business Deferred income taxes Deferred Income Tax Expense (Benefit) Noncurrent assets Assets for Plan Benefits, Defined Benefit Plan Public Utility, Property, Plant and Equipment [Table] Public Utility, Property, Plant and Equipment [Table] CEMA CEMA [Member] CEMA Other long-term liabilities Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities Assumed equity Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net Performance-based and market-based restricted stock awards issued (in shares) Restricted Stock Awards, Performance-based, Issued, Intrinsic Value Restricted Stock Awards, Performance-based, Issued, Intrinsic Value Debt Disclosure [Abstract] Debt Disclosure [Abstract] Total investments made to fund SERP Employer contributions Defined Benefit Plan, Plan Assets, Contributions by Employer Long-term borrowings held as restricted cash Proceeds from Issuance of Long-Term Debt Held As Restricted Cash Proceeds from Issuance of Long-Term Debt Held As Restricted Cash Current portion of long-term debt Current portion Long-Term Debt, Current Maturities Net cash provided by financing activities Net Cash Provided by (Used in) Financing Activities Capacity Agreement Capacity Agreement [Member] Capacity Agreement [Member] Accounting Policies [Abstract] Accounting Policies [Abstract] Interest on long-term debt, mortgage and other interest expense Interest Expense, Debt Line of Credit Line of Credit [Member] Lower Colorado River Authority Lower Colorado River Authority [Member] Lower Colorado River Authority [Member] 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 Proceeds to subsidiaries for notes receivable Payments For Note Receivables From Subsidiary Payments For Note Receivables From Subsidiary State revolving fund loans State Revolving Fund Loans [Member] State Revolving Fund Loans [Member] Liabilities assumed: Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities [Abstract] Schedule of Components of Income Tax Expense Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] Intangible assets, customer relationships Finite-Lived Customer Relationships, Gross Period for recognition of compensation cost Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition Schedule of Finite-Lived Intangible Assets Schedule of Finite-Lived Intangible Assets [Table Text Block] Minimum volume of water to be purchased (in million gallons) Long-term Purchase Commitment, Minimum Volume Required, Next Twelve Months Long-term Purchase Commitment, Minimum Volume Required, Next Twelve Months Schedule of Asset Retirement Obligations Schedule of Asset Retirement Obligations [Table Text Block] Payments for business/asset acquisitions Cash purchase price Payments to Acquire Businesses, Gross 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 2026 Defined Benefit Plan, Expected Future Benefit Payment, Year Four Subsequent Event Subsequent Events [Text Block] Proceeds from sale of real estate held-for-investment Proceeds from Sale of Real Estate Held-for-investment Benefits paid and settlements Defined Benefit Plan, Benefit Obligation, Benefits Paid Outstanding, beginning balance (in dollars per share) Outstanding, ending balance (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Weighted Average Grant Date Fair Value Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Weighted Average Grant Date Fair Value Benefit Plans Retirement Benefits [Text Block] Mutual funds Mutual Fund [Member] 2025 Advances for Construction, Estimated Refunds, Year Three Advances for Construction, Estimated Refunds, Year Three Other assets, measurement period adjustments Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Noncurrent Assets Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Noncurrent Assets Minimum Minimum [Member] Entity Emerging Growth Company Entity Emerging Growth Company Debt premium, net Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Unearned Premiums Reserve Common stock, par value (usd per share) Common Stock, Par or Stated Value Per Share Other intangible assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill Stock-based compensation Effective Income Tax Rate Reconciliation, Nondeductible Expense, Share-Based Payment Arrangement, Amount SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Table] SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Table] Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Trading Symbol Trading Symbol Entity File Number Entity File Number Utility Plant Intangible Assets Intangible Assets Disclosure [Text Block] Amortization period for taxes paid relating to advances and contributions Advances for Construction, Deferred Taxes, Amortization Period Advances for Construction, Deferred Taxes, Amortization Period 2026 Finite-Lived Intangible Asset, Expected Amortization, Year Four Accrued interest Interest Payable, Current Public Utilities, Regulatory Proceeding [Domain] Public Utilities, Regulatory Proceeding [Domain] Title of Individual [Axis] Title of Individual [Axis] Kennebec Water District Kennebec Water District [Member] Kennebec Water District [Member] Granted (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period Schedule of Line of Credit Facilities Schedule of Line of Credit Facilities [Table Text Block] Issued (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Non-Option Equity Instruments, Exercised Borrowings from lines of credit Proceeds from Lines of Credit Estimated required and discretionary employer cash contributions Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year Use of Estimates Use of Estimates, Policy [Policy Text Block] Postretirement Benefits, Type of Deferred Compensation [Axis] Other Postretirement Benefits, Individual Contracts, Type of Deferred Compensation [Axis] Business Combinations Business Combination Disclosure [Text Block] Other (expense) income: Other Nonoperating Income (Expense) [Abstract] Incentive Plan Incentive Plan [Member] Incentive Plan [Member] Union Member Union Member [Member] Union Member [Member] Accounts payable and other current liabilities Increase (Decrease) in Accounts Payable Income Taxes Income Tax Disclosure [Text Block] Regulated Regulated Operation [Member] Cash and equivalents Defined Benefit Plan, Cash and Cash Equivalents [Member] Credit Facility [Domain] Credit Facility [Domain] Depreciable plant and equipment Total depreciable plant and equipment Public Utilities, Property, Plant And Equipment, Depreciable Plant And Equipment Public Utilities, Property, Plant And Equipment, Depreciable Plant And Equipment —Basic (in dollars per share) Earnings Per Share, Basic 5.54% Senior Notes, Due May 2052 5.54% Senior Notes, Due May 2052 [Member] 5.54% Senior Notes, Due May 2052 Prepaid expenses Prepaid Expense, Current Deferred compensation arrangement with individual, by type of compensation, pension and other postretirement benefits Deferred Compensation Arrangement with Individual, by Type of Compensation, Pension and Other Postretirement Benefits [Member] Entity Interactive Data Current Entity Interactive Data Current 2027 Advances for Construction, Estimated Refunds, Year Five Advances for Construction, Estimated Refunds, Year Five 2023 Lessor, Operating Lease, Payment to be Received, Year One Changes in operating assets and liabilities, net of acquired assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Money market funds Money Market Funds [Member] Land and Building Land and Building [Member] Other comprehensive income (loss), net Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Maximum percent of base salary employees can designate for share purchase under the plan Share-Based Compensation Arrangement by Share-Based Payment Award, Maximum Employee Subscription Rate Issuance of restricted and deferred stock units Shares Issued, Value, Share-Based Payment Arrangement, after Forfeiture Class of Stock [Axis] Class of Stock [Axis] Thereafter Long-Term Debt, Maturity, after Year Five Income Taxes Income Tax, Policy [Policy Text Block] Lease renewal term Lessee, Operating Lease, Renewal Term Total assets acquired Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets Current assets: Assets, Current [Abstract] Cumulative reduction in unrecognized tax benefits, due to lapsing of statutes of limitations Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense Change in net deferred tax liabilities Deferred Tax Liabilities, Period Increase (Decrease) Deferred Tax Liabilities, Period Increase (Decrease) Collective bargaining agreement percent of wage increase for 2025 Collective Bargaining Agreement, Wage Increase, Percent, Year Three Collective Bargaining Agreement, Wage Increase, Percent, Year Three Retained earnings Retained Earnings (Accumulated Deficit) Schedule of Finite-Lived Intangible Assets [Table] Schedule of Finite-Lived Intangible Assets [Table] Public Utility, Property, Plant and Equipment [Line Items] Public Utility, Property, Plant and Equipment [Line Items] Number of service connections from acquisition Public Utilities, Acquisition, Service Connections Public Utilities, Acquisition, Service Connections Connecticut CONNECTICUT Document Fiscal Year Focus Document Fiscal Year Focus Defined Benefit Plan, Plan Assets, Category [Domain] Defined Benefit Plan, Plan Assets, Category [Domain] Operating activities: Net Cash Provided by (Used in) Operating Activities [Abstract] Buildings and improvements Investment Building and Building Improvements Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Transmission and distribution plant Public Utilities, Property, Plant and Equipment, Transmission and Distribution, Useful Life 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. Impairment of Long-Lived Assets and Goodwill Impairment or Disposal of Long-Lived Assets, Policy [Policy Text Block] Restricted stock and deferred restricted stock Restricted Stock and Deferred Restricted Stock [Member] Restricted Stock and Deferred Restricted Stock [Member] Deferred tax liabilities: Deferred Tax Liabilities, Gross [Abstract] Regulatory Asset [Axis] Regulatory Asset [Axis] Accounts receivable: Accounts Receivable, after Allowance for Credit Loss, Current [Abstract] Total assets acquired, measurement period adjustments Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Assets Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Assets Capitalization, long-term debt and equity Capitalization, Long-Term Debt and Equity Performance-based and market-based restricted stock awards outstanding (in shares) Restricted Stock Awards, Performance-based, Outstanding Balance Restricted Stock Awards, Performance-based, Outstanding Balance Schedule of Property, Plant and Equipment Public Utility Property, Plant, and Equipment [Table Text Block] Common stock, shares outstanding (in shares) Beginning balance (in shares) Ending balance (in shares) Common Stock, Shares, Outstanding Cost of capital memorandum accounts Cost of capital [Member] Cost of capital [Member] Goodwill Goodwill Long-Lived Tangible Asset [Axis] Long-Lived Tangible Asset [Axis] Actual return on plan assets Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss) Category of Item Purchased [Axis] Category of Item Purchased [Axis] Provision for income taxes Income tax expense Income tax expense (benefit) in net income Income Tax Expense (Benefit) Geographical [Domain] Geographical [Domain] Deferred income taxes Deferred Income Tax Liabilities, Net Entity Public Float Entity Public Float Estimated future retirement costs Asset Retirement Obligation Maximum number of shares per employee (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Maximum Number of Shares Per Employee Deferred income taxes, measurement period adjustments Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Deferred Income Taxes Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Deferred Income Taxes 2023 Defined Benefit Plan, Expected Future Benefit Payment, Year One Investments Investments Common stock, $0.001 par value; authorized 70,000,000 shares in 2022 and 2021; issued and outstanding 30,801,912 shares in 2022 and 30,181,348 shares in 2021 Common Stock, Value, Issued Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] Shares issuable under the plan upon exercise of outstanding 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] Deferred tax assets: Deferred Tax Assets, Gross [Abstract] Deferrals by executives and non-employee directors Deferred Compensation Arrangement With Individual, Deferral Amount Deferred Compensation Arrangement With Individual, Deferral Amount Current liabilities Liability, Defined Benefit Plan, Current Groundwater extraction charges Groundwater Extraction Charges Groundwater Extraction Charges Service area from acquisition Public Utilities, Acquisition, Service Area Public Utilities, Acquisition, Service Area Cash, cash equivalents and restricted cash, beginning of year Cash, cash equivalents and restricted cash, end of year Cash and cash equivalents Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents Current liabilities: Liabilities, Current [Abstract] Advances for Construction and Contributions in Aid of Construction Advances for Construction and Contributions in Aid of Construction, Policy [Policy Text Block] Disclosure of accounting policy for advances for construction and contributions in aid of construction. Public Utilities General Disclosures [Table] Public Utilities General Disclosures [Table] Cost of water to be purchased Purchase Obligation, to be Paid, Year One Lessor, Operating Lease, Payments, Fiscal Year Maturity [Abstract] Lessor, Operating Lease, Payments to be Received, Fiscal Year Maturity [Abstract] Retirement Plan Type [Domain] Retirement Plan Type [Domain] Other regulatory mechanisms, net Regulatory Mechanisms, Other, Net Regulatory Mechanisms, Other, Net Amendment Flag Amendment Flag Useful life of intangible assets Finite-Lived Intangible Asset, Useful Life Power Utilities Operating Expense, Purchased Power Long-term purchase commitment, minimum area required (in acre-feet of water) Long-term Purchase Commitment, Minimum Acre Feet Required Long-term Purchase Commitment, Minimum Acre Feet Required SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract] SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract] Kendall West Utility and Bandera East Utility Kendall West Utility and Bandera East Utility [Member] Kendall West Utility and Bandera East Utility Total liabilities assumed Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities Goodwill and Intangible Assets Disclosure [Abstract] Goodwill and Intangible Assets Disclosure [Abstract] Deferred income taxes Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities Tax receivable and accrued taxes Increase (Decrease) in Accrued Taxes Payable Total other assets Other Assets, Noncurrent Cost to retire utility plant, net of salvage Payments for (Proceeds from) Removal Costs Depreciation and amortization Depreciation, Depletion and Amortization Purchase price of common stock to employees under the plan, percent Share-Based Compensation Arrangement by Share-Based Payment Award, Purchase Price of Common Stock, Percent Thereafter Finite-Lived Intangible Asset, Expected Amortization, after Year Five Counterparty Name [Axis] Counterparty Name [Axis] Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Restricted and Deferred Restricted Stock Awards Activity Share-Based Compensation Arrangement by Share-Based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward] 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 Contributions in aid of construction and construction advances Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, CIAC and Advances Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, CIAC and Advances KT Water Resource L. P. KT Water Resource L. P. [Member] KT Water Resource L. P. Allowance for uncollectible accounts Accounts Receivable, Allowance for Credit Loss, Current Advice Letter No. 582 Advice Letter No. 582 [Member] Advice Letter No. 582 Total operating expense Operating expense Utilities Operating Expense Common stock, shares authorized (in shares) Common Stock, Shares Authorized Maximum Maximum [Member] Actuarial gain (loss), discount rate change Defined Benefit Plan Actuarial Gain (Loss), Discount Rate Change Defined Benefit Plan Actuarial Gain (Loss), Discount Rate Change Consolidation Policy Consolidation, Subsidiaries or Other Investments, Consolidated Entities, Policy [Policy Text Block] Real Estate Investments and Nonutility Properties Public Utilities, Real Estate, Policy [Policy Text Block] Disclosure of accounting policy for public utilities real estate. Financial Statement Schedule Condensed Financial Information of Parent Company Only Disclosure [Text Block] Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [Table] Cash and cash equivalents, end of year Cash and Cash Equivalents, at Carrying Value Office buildings and other structures Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment 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 Other long-term liabilities, measurement period adjustments Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Noncurrent Liabilities Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Noncurrent Liabilities Business Acquisition [Line Items] Business Acquisition [Line Items] Balancing and memorandum accounts, net Balancing and Memorandum Accounts [Member] Balancing and Memorandum Accounts [Member] Real estate selling expenses Real Estate Selling Expenses Real Estate Selling Expenses Current liabilities, including maturities of long-term debt, measurement period adjustments Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Current Liabilities Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Current Liabilities Capitalization Stockholders' Equity Note Disclosure [Text Block] Schedule of Net Benefit Costs Schedule of Net Benefit Costs [Table Text Block] Line of Credit Facility [Table] Line of Credit Facility [Table] Equipment Public Utilities, Property, Plant and Equipment, Equipment, Useful Life Actual plan asset allocations as a percent of total plan assets Defined Benefit Plan, Plan Assets, Actual Allocation, Percentage Income tax payable Income Tax Payable, Current Income Tax Payable, Current Useful Lives Estimated Useful Lives of Plant and Equipment [Abstract] Estimated Useful Lives of Plant and Equipment [Abstract] Title of 12(b) Security Title of 12(b) Security Southern Comal County, Texas Southern Comal County, Texas [Member] Southern Comal County, Texas Schedule of Defined Benefit Plans Disclosures [Table] Schedule of Defined Benefit Plans Disclosures [Table] Organization and Operations Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Fixed income Fixed Income Securities [Member] Condensed Financial Statements [Table] Condensed Financial Statements [Table] Schedule of Unrecognized Tax Benefits Roll Forward Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block] Subsequent Event [Line Items] Subsequent Event [Line Items] Repayments of lines of credit Repayments of lines of credit Repayments of Lines of Credit Schedule of Assumptions Used Defined Benefit Plan, Assumptions [Table Text Block] Income Tax Contingency [Line Items] Income Tax Contingency [Line Items] Segment and Non-Tariffed Businesses Reporting Segment Reporting Disclosure [Text Block] Property flow-through Effective Income Tax Rate Reconciliation, Nondeductible Expense, Depreciation, Amount Net deferred tax liabilities Deferred Tax Liabilities, Net Capitalization and Liabilities Liabilities and Equity [Abstract] Equity earnings from subsidiaries, net of taxes Earnings from investment in subsidiaries Equity Earnings From Subsidiaries, Net of Tax Equity Earnings From Subsidiaries, Net of Tax Contractual Rights Contractual Rights [Member] Gain on sale of nonutility properties Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property Accounts payable Accounts Payable, Current Less accumulated depreciation and amortization Public Utilities, Property, Plant and Equipment, Accumulated Depreciation Income Tax Authority [Axis] Income Tax Authority [Axis] Number of employees Entity Number of Employees CTWS Employees CTWS Employees [Member] CTWS Employees Issuance of common stock, net of issuance costs Proceeds from Issuance of Common Stock —Basic (shares) Weighted Average Number of Shares Outstanding, Basic Intercompany payables Intercompany Payable, Current Intercompany Payable, Current 2026 Advances for Construction, Estimated Refunds, Year Four Advances for Construction, Estimated Refunds, Year Four Expenses recorded under the plan Stock or Unit Option Plan Expense Change in plan assets Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] Allowance for equity funds used during construction Public Utilities, Allowance for Funds Used During Construction, Additions Accrued interest Increase (Decrease) in Interest Payable, Net Construction in progress Public Utilities, Property, Plant and Equipment, Construction Work in Progress Office buildings and other structures Public Utilities, Property, Plant and Equipment, Other Property Plant and Equipment, Useful Life Entity Well-known Seasoned Issuer Entity Well-known Seasoned Issuer Contract with customer, fair value of advances Contract With Customer, Refund Liability, Fair Value Disclosure Contract With Customer, Refund Liability, Fair Value Disclosure Schedule of Long-term Debt Instruments [Table] Schedule of Long-Term Debt Instruments [Table] Significant Unobservable Inputs (Level 3) Fair Value, Inputs, Level 3 [Member] Refunds (Collections) Adjustments Balancing and Memorandum Cost Recovery Account, Refunds (Collections) Balancing and Memorandum Cost Recovery Account, Refunds (Collections) Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs by Plan Share-Based Payment Arrangement, Cost by Plan [Table Text Block] 2024 Lessor, Operating Lease, Payment to be Received, Year Two SJWC Credit Agreement Maturing August 2027 SJWC Credit Agreement Maturing August 2027 [Member] SJWC Credit Agreement Maturing August 2027 Schedule of Deferred Tax Assets and Liabilities Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Current contract water rate (in USD per million of gallons) Long-term Purchase Commitment, Fixed Price Long-term Purchase Commitment, Fixed Price CTWS Credit Agreement Maturing May 2025 CTWS Credit Agreement Maturing May 2025 [Member] CTWS Credit Agreement Maturing May 2025 SEC Schedule, 12-09, Valuation Allowances and Reserves Type [Axis] SEC Schedule, 12-09, Valuation Allowances and Reserves Type [Axis] Organization, Consolidation and Presentation of Financial Statements [Abstract] Number of variable interest entities Variable Interest Entities, Number Of Entities Variable Interest Entities, Number Of Entities Significant Observable Inputs (Level 2) Fair Value, Inputs, Level 2 [Member] Regulatory Assets [Line Items] Regulatory Asset [Line Items] Thereafter Advances for Construction, Estimated Refunds, After Year Five Advances for Construction, Estimated Refunds, After Year Five Current Fiscal Year End Date Current Fiscal Year End Date Regulatory assets and deferred charges, less current portion Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Regulatory Asses and Deferred Charges, net Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Regulatory Asses and Deferred Charges, Net Utility plant, net, measurement period adjustments Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Utility Plant, Net Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Utility Plant, Net Current assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Other Finite-Lived Intangible Assets [Line Items] Finite-Lived Intangible Assets [Line Items] SJWTX SJWTX, Inc. [Member] SJWTX, Inc. [Member] Net under-collected accounts Regulatory Balancing and Memorandum Accounts, Net Under-Collected Regulatory Balancing and Memorandum Accounts,, Net Under-Collected Share-based compensation APIC, Share-Based Payment Arrangement, Increase for Cost Recognition Plan participants contributions Defined Benefit Plan, Benefit Obligation, Contributions by Plan Participant Total current liabilities Liabilities, Current Schedule of Restricted and Deferred Restricted Stock Awards Share-Based Payment Arrangement, Restricted Stock Unit, Activity [Table Text Block] Unrecognized tax benefits that would impact effective tax rate Unrecognized Tax Benefits that Would Impact Effective Tax Rate Amended and Restated Revolving Credit Facility Amended and Restated Revolving Credit Facility [Member] Amended and Restated Revolving Credit Facility Capitalized merger costs Effective Income Tax Rate Reconciliation, Other Adjustments, Merger Costs Effective Income Tax Rate Reconciliation, Other Adjustments, Merger Costs Bargaining agreements, term Bargaining Agreements, Term Bargaining Agreements, Term Income Tax Authority [Domain] Income Tax Authority [Domain] Other changes, net Proceeds from (Payments for) Other Financing Activities Other assets: Other Assets, Noncurrent [Abstract] Over-Allotment Option Over-Allotment Option [Member] Unused Portion Line of Credit Facility, Remaining Borrowing Capacity Subsidiary, Sale of Stock [Line Items] Subsidiary, Sale of Stock [Line Items] Postretirement benefit plans, measurement period adjustments Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Postretirement Benefit Plans Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Postretirement Benefit Plans Credit Facility [Axis] Credit Facility [Axis] Public utility, bonds Public Utility, Bonds [Member] Equity [Abstract] Equity [Abstract] Subsequent Event [Table] Subsequent Event [Table] Other noncurrent assets and noncurrent liabilities Increase (Decrease) in Other Noncurrent Assets and Liabilities The increase (decrease) during the reporting period in other noncurrent operating assets and liabilities not seperately disclosed in the statement of cash flows. Vested (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period Production Expenses: Water Production Costs [Abstract] Water Production Costs [Abstract] Entity Tax Identification Number Entity Tax Identification Number Intercompany notes receivable Intercompany Notes Receivable, Current Intercompany Notes Receivable, Current Number of shares reserved for issuance under the plan (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized Schedule of Investments [Table] Schedule of Investments [Table] Outstanding, beginning balance (in shares) Outstanding ending balance (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Non-Option Equity Instruments, Outstanding, Number 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 Beginning Balance Ending Balance 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Post-retirement Benefit Plans Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Post-retirement Benefit Plans Entity Central Index Key Entity Central Index Key Connecticut Innovations Revenue Bonds, variable rate Connecticut Innovations Revenue Bonds, Variable Rate [Member] Connecticut Innovations Revenue Bonds, Variable Rate [Member] Components of Real Estate Investments [Abstract] Real Estate [Abstract] Future Amortization of Intangible Assets Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract] Investments in subsidiaries Investments In Subsidiaries Investments In Subsidiaries Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [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] Business combination, purchase price Business Combination, Consideration Transferred Entity [Domain] Entity [Domain] California franchise tax Deferred Tax Assets, State Taxes City Area Code City Area Code Assets Assets acquired: Assets [Abstract] Number of properties sold Number Of Properties Sold Number Of Properties Sold Other changes, net Increase (Decrease) in Other Operating Assets and Liabilities, Net Notice period required for contract adjustment Notice Period Required for Contract Adjustment Notice Period Required for Contract Adjustment Proceeds from sale of land held-for-investment Proceeds from Sale of Land Held-for-investment Commitments Commitments Disclosure [Text Block] Bank term loans Notes Payable to Banks [Member] Sale of Stock [Axis] Sale of Stock [Axis] Lines of credit Line of Credit, Current Liabilities, net Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position Earnings Per Share Earnings Per Share, Policy [Policy Text Block] 2023 Long-Term Debt, Maturity, Year One Postretirement 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assets, net not earning a return Remaining Amounts of Regulatory Assets for which No Return on Investment During Recovery Period is Provided Estimated service lives of assets Public Utilities, Property, Plant and Equipment, Common, Useful Life CTWS Credit Agreement Maturing December 2023 CTWS Credit Agreement Maturing December 2023 [Member] CTWS Credit Agreement Maturing December 2023 Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Net periodic benefit cost, rate of compensation increase Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase Entity Address, Postal Zip Code Entity Address, Postal Zip Code Reconciliation of Unrecognized Tax Benefits [Roll Forward] Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward] 2024 Long-Term Debt, Maturity, Year Two Business Combinations Business Combinations Policy [Policy Text Block] All Other Other Segments [Member] Repayments from subsidiaries for notes receivable Proceeds From Note Receivables From Subsidiary Proceeds From Note Receivables From Subsidiary PRVMA PRVMA [Member] PRVMA Line Limit Line of credit facility, maximum borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Utility plant Deferred Tax Liabilities, Property, Plant and Equipment Accounts written off SEC Schedule, 12-09, Valuation Allowances and Reserves, Deduction Lines of Credit Short-Term Debt [Text Block] Statistical Measurement [Domain] Statistical Measurement [Domain] Vested (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Vested, Weighted Average Grant Date Fair Value Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Vested, Weighted Average Grant Date Fair Value 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Next Twelve Months Regulated Operations [Abstract] Repayments to subsidiaries for notes payable Payments For Subsidiary Notes Payable Payments For Subsidiary Notes Payable Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Contributions in aid of construction and construction advances, measurement period adjustments Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, CIAC and Advances Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, CIAC and Advances Shares issued pursuant to the plan (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued Pursuant To The Plan Cumulative number of shares issued pursuant to the Plan. Quoted Prices in Active Markets for Identical Assets (Level 1) Fair Value, Inputs, Level 1 [Member] Schedule of Public Utilities General Disclosures Public Utilities General Disclosures [Table Text Block] Option Indexed to Issuer's Equity [Line Items] Option Indexed to Issuer's Equity [Line Items] Expected Future Benefit Payments [Abstract] Defined Benefit Plan, Expected Future Benefit Payment [Abstract] Granted (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted, Weighted Average Grant Date Fair Value Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted, Weighted Average Grant Date Fair Value 2022 GRC interim memorandum account 2022 GRC Interim Memorandum Account [Member] 2022 GRC Interim Memorandum Account Accrued groundwater extraction charges, purchased water and power Accrued groundwater extraction charges, purchased water and power Accrued groundwater extraction charges, purchased water and power Gain on sale of real estate investments Gains (Losses) on Sales of Investment Real Estate Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities Nonutility plant, measurement period adjustments Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Nonutility Plant, Net Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Nonutility Plant, Net Type of Deferred Compensation, All Types [Domain] Other Postretirement Benefits, Individual Contracts, Type of Deferred Compensation [Domain] Other All others Other Regulatory Assets [Member] Other Regulatory Assets [Member] Pension non-service cost Net Periodic Defined Benefits Expense (Reversal of Expense), Excluding Service Cost Component Adjustment to pension benefit plans, taxes Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax, Attributable to Parent Document Annual Report Document Annual Report Legal Entity [Axis] Legal Entity [Axis] Number of subsidiaries Number of Subsidiaries Number of Subsidiaries Subsidiaries Subsidiaries [Member] Geographical [Axis] Geographical [Axis] Utility Plant [Domain] Utility Plant [Domain] Postretirement benefit plans Noncurrent liabilities Liability, Defined Benefit Plan, Noncurrent Common stock issuance, net of costs Stock Issued During Period, Value, New Issues Utility plant, net Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Utility Plant, Net Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Utility Plant, Net Agreement to purchase water (in gallons of water) Long-term Purchase Commitment, Water Purchased Long-term Purchase Commitment, Water Purchased Preferred stock, shares issued (in shares) Preferred Stock, Shares Issued Nonvested Restricted and Deferred Restricted Stock Awards Activity Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] 2025 Defined Benefit Plan, Expected Future Benefit Payment, Year Three Major components of depreciable plant and equipment [Abstract] Property, Plant and Equipment, Net, by Type [Abstract] Business Segments [Axis] Segments [Axis] Real estate investments, net Real Estate Investment Property, Net Schedule of Real Estate Investments Schedule of Real Estate Investments [Table Text Block] Tabular disclosure of real estate investments. 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 4.54% Note Due May 2042 4.54% Note Due May 2042 [Member] 4.54% Note Due May 2042 Reductions related to tax positions taken in a prior year Unrecognized Tax Benefits, Decrease Resulting from Prior Period Tax Positions Schedule of Allocation of Plan Assets Schedule of Allocation of Plan Assets [Table Text Block] Guadalupe-Blanco River Authority Guadalupe Blanco River Authority [Member] Guadalupe-Blanco River Authority [Member] 2025 Long-Term Debt, Maturity, Year Three SEC Schedule, 12-09, Valuation Allowances and Reserves [Domain] SEC Schedule, 12-09, Valuation Allowances and Reserves [Domain] Subsequent Event Subsequent Event [Member] Unrealized gain (loss) on investment, taxes Other Comprehensive Income (Loss), Available-for-Sale Securities, Tax, Portion Attributable to Parent Pension Pension 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Available for Lease [Abstract] Assets Leased or Available for Lease [Abstract] Accrued payroll Employee-related Liabilities, Current Income before income taxes Income before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Segment [Domain] Segments [Domain] Other Deferred Tax Liabilities, Other Annual maximum contribution limit under Dependent Care Spending Account plan Dependent Care Spending Account, Annual Maximum Employee Contribution Dependent Care Spending Account, Annual Maximum Employee Contribution Regulatory Asset [Domain] Regulatory Asset [Domain] Schedule of Investments [Line Items] Schedule of Investments [Line Items] Award Type [Domain] Award Type [Domain] Income Tax Contingency [Table] Income Tax Contingency [Table] Weighted- Average Grant- Date Fair Value Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Weighted Average Grant Date Fair Value [Roll Forward] [Roll Forward] Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Weighted Average Grant Date Fair Value [Roll Forward] [Roll Forward] Business combinations debt premium Business combinations debt premium [Member] Business combinations debt premium Income tax Income Taxes Receivable, Current Gain on sale of TWA, real estate investments and nonutility properties 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 Equity funds capitalized Equity Funds Capitalized Equity Funds Capitalized Common stock issuance, net of costs (in shares) Stock Issued During Period, Shares, New Issues Customer Relationships Purchase premium customer relationships Customer Relationships [Member] Entity Address, City or Town Entity Address, City or Town Schedule of Estimated Refunds of Advances for Construction and Contributions in Aid of Construction Schedule of Estimated Refunds of Advances for Construction and Contributions in Aid of Construction [Table Text Block] Tabular disclosure of estimated refunds of advances for construction and contributions in aid of construction Issued (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Exercised, Weighted Average Grant Date Fair Value Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Exercised, Weighted Average Grant Date Fair Value 2028 - 2032 Defined Benefit Plan, Expected Future Benefit Payment, after Year Five for Next Five Years Restricted cash Restricted Cash and Cash Equivalents, Current Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Accrued interest, expense net of the benefit of tax deductions Unrecognized Tax Benefits, Interest on Income Taxes Accrued 2026 Lessor, Operating Lease, Payment to be Received, Year Four Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Auditor Name Auditor Name Pension Benefits Pension Plan [Member] Refunds of advances for construction Repayments Of Advances For Construction, Financing Activities Repayments Of Advances For Construction, Financing Activities Properties selling expenses Properties Selling Expenses Properties Selling Expenses Operating loss carryforwards Operating Loss Carryforwards SJW Group Credit Agreement Maturing August 2027 SJW Group Credit Agreement Maturing August 2027 [Member] SJW Group Credit Agreement Maturing August 2027 Water purchased (in millions of gallons) Purchased Water, Gallons Purchased Water, Gallons Advances for construction Contract with Customer, Liability, Noncurrent 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Earnings [Member] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Water Utility Services Reportable Segment One [Member] Reportable Segment One [Member] 2025 Lessor, Operating Lease, Payment to be Received, Year Three State Revolving Fund Loans Series T State Revolving Fund Loans Series T [Member] State Revolving Fund Loans Series T Common Stock Common Stock [Member] Number of purchase intervals Number Purchase Intervals for Employee Stock Purchase Plan, Number Purchase Intervals for Employee Stock Purchase Plan, Number of reportable segments Number of Reportable Segments Number of shares available for issuance (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant Schedule of Nonvested Restricted Stock Units Activity Schedule of Nonvested Restricted Stock Units Activity [Table Text Block] Revenue Revenue [Policy Text Block] Regulated operating revenue, water surcharge Regulated Operating Revenue, Water Surcharge Regulated Operating Revenue, Water Surcharge Statement [Table] Statement [Table] Vested (in dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Credit Agreement Credit Agreement [Member] Credit Agreement Adjustment to pension benefit plans, net of taxes of $793 in 2022, $264 in 2021 and $(324) in 2020 Adjustment to pension benefit plans, net of taxes Adjustment to pension benefit plans, net of taxes Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax and Reclassification Adjustment, Attributable to Parent Statistical Measurement [Axis] Statistical Measurement [Axis] Other Nontrade Receivables, Current Land Public Utilities, Property, Plant and Equipment, Land Customers, net of allowances for uncollectible accounts of $5,753 and $4,600 in 2022 and 2021, respectively Accounts Receivable, after Allowance for Credit Loss, Current Statement, Equity Components [Axis] Equity Components [Axis] Schedule of Amounts Recognized in Balance Sheet Schedule of Amounts Recognized in Balance Sheet [Table Text Block] Depreciation and amortization Utilities Operating Expense, Depreciation and Amortization Rate of compensation increase to company sponsored savings plan Defined Benefit Plan, Rate of Compensation Increase Defined Benefit Plan, Rate of Compensation Increase Period for performance standards Defined Benefit Plan, Period for Performance Standards Defined Benefit Plan, Period for Performance Standards Long-term Purchase Commitment, Category of Item Purchased [Domain] Long-Term Purchase Commitment, Category of Item Purchased [Domain] Statement [Line Items] Statement [Line Items] Unrecognized tax benefits before impact of deductions for state taxes, excluding interest and penalties Unrecognized Tax Benefits, Gross Unrecognized Tax Benefits, Gross Nonvested, beginning balance (in shares) Nonvested, ending balance (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number California Pollution Control Financing Authority Revenue Bond California Pollution Control Financing Authority Revenue Bonds Total [Member] California Pollution Control Financing Authority Revenue Bonds Total [Member] Intangible assets Finite-Lived Intangible Assets, Gross Depreciation expense as percentage of beginning of year balance of depreciable plant Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service Total Balancing and Memorandum Account [Roll Forward] Balancing and Memorandum Account [Roll Forward] Accumulated Other Comprehensive Income (Loss) AOCI Attributable to Parent [Member] Contingencies Contingencies Disclosure [Text Block] Auditor Firm ID Auditor Firm ID Document Transition Report Document Transition Report 2024 Defined Benefit Plan, Expected Future Benefit Payment, Year Two Local Phone Number Local Phone Number Bank Owned Life Insurance Life Insurance, Corporate or Bank Owned, Amount Restricted net assets, subsidiaries Restricted Net Assets, Subsidiaries Restricted Net Assets, Subsidiaries Operating income Operating income (loss) Operating Income (Loss) Current assets, measurement period adjustments Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Current Assets Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Current Assets Weighted average shares outstanding Weighted Average Number of Shares Outstanding, Diluted, Adjustment [Abstract] Sale of Stock, Weighted Average Price Per Share Sale of Stock, Weighted Average Price Per Share Sale of Stock, Weighted Average Price Per Share Acquiree's common shares converted in cash (in dollars per share) Business Combination, Consideration Transferred, Acquiree's Common Shares Converted In Cash Per Share Business Combination, Consideration Transferred, Acquiree's Common Shares Converted In Cash Per Share Regulatory Asset Increase (Decrease) Balancing and Memorandum Cost Recovery Account, Increase (Decrease) Balancing and Memorandum Cost Recovery Account, Increase (Decrease) 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] 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] Depreciable Utility Plant and Equipment Property, Plant and Equipment, Policy [Policy Text Block] Preferred stock, par value (usd per share) Preferred Stock, Par or Stated Value Per Share Income Statement [Abstract] Income Statement [Abstract] Federal Deferred Federal Income Tax Expense (Benefit) Customer advances for construction, non-refundable Customer Advances for Construction, Non-Refundable Customer Advances for Construction, Non-Refundable Additional Paid-in Capital Additional Paid-in Capital [Member] Impairment of long-lived asset Impairment, Long-Lived Asset, Held-for-Use Document Fiscal Period Focus Document Fiscal Period Focus Regulation Status [Axis] Regulation Status [Axis] Other balancing and memorandum accounts, net Regulatory Balancing and Memorandum Accounts Revenue, Net Regulatory Balancing and Memorandum Accounts Revenue, Net —Diluted (shares) Weighted Average Number of Shares Outstanding, Diluted Intangible Assets Goodwill and Intangible Assets, Intangible Assets, Policy [Policy Text Block] MDC The Metropolitan District [Member] The Metropolitan District [Member] Net regulatory assets, less current portion Net regulatory assets, less current portion Regulatory Asset, Noncurrent Long-term debt Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Long-Term Debt WRA WRA [Member] WRA [Member] Building and Building Improvements Building and Building Improvements [Member] Common stock, dividends per share, paid (usd per share) Common Stock, Dividends, Per Share, Cash Paid ICFR Auditor Attestation Flag ICFR Auditor Attestation Flag Recognition of significant event Defined Benefit Plan, Actuarial Gain (Loss), Immediate Recognition as Component in Net Periodic Benefit (Cost) Credit Current liabilities, including maturities of long-term debt Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities Capitalization: Capitalization, Long-Term Debt and Equity [Abstract] Granted (in dollars 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 Employer contributions to deferral plan Deferred Compensation Arrangement with Individual, Contributions by Employer Discount rate Asset Retirement Obligation, Discount Rate Asset Retirement Obligation, Discount Rate Number of people served from acquisition Public Utilities, Acquisition, Number of People Served Public Utilities, Acquisition, Number of People Served Preferred stock, shares authorized (in shares) Preferred Stock, Shares Authorized Long-term debt, measurement period adjustments Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Long-term Debt Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Long-term Debt Long-term purchase commitment, wholesale discount (in USD per hundred cubic feet) Long-term Purchase Commitment, Wholesale Discount Long-term Purchase Commitment, Wholesale Discount 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 (in shares) Common Stock, Shares, Issued Accrued payables for additions to utility plant Capital Expenditures Incurred but Not yet Paid Santa Clara Valley Water District Santa Clara Valley Water District [Member] Santa Clara Valley Water District [Member] Property taxes and other non-income taxes Utilities Operating Expense, Taxes Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities Aggregate principal amount Debt Instrument, Face Amount Retirement obligation, present value Asset Retirement Obligation, Legally Restricted Assets, Fair Value 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 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] Contract agreement, term Contract Agreement, Term Contract Agreement, Term Entity Current Reporting Status Entity Current Reporting Status Condensed Financial Information Disclosure [Abstract] Other current liabilities Other Liabilities, Current Refunds (Collections) Adjustments Balancing and Memorandum Account, Refunds (Collections) Balancing and Memorandum Account, Refunds (Collections) Annual maximum contribution limit under Health Care Spending Account plan Health Care Spending Account, Annual Maximum Employee Contribution Health Care Spending Account, Annual Maximum Employee Contribution Schedule of Net Funded Status Schedule of Net Funded Status [Table Text Block] Master contract, negotiated term for delivery schedules Master Contract, Negotiated Term for Delivery Schedules Master Contract, Negotiated Term for Delivery Schedules Connecticut Water Company Connecticut Water Connecticut Water Company [Member] Connecticut Water Company [Member] Contract with customer, refund period Contract With Customer, Refund Liability, Refund Period Contract With Customer, Refund Liability, Refund Period Charged to expense SEC Schedule, 12-09, Valuation Allowances and Reserves, Additions, Charge to Cost and Expense Employee stock purchase plan (in shares) Shares issued during the period under the plan Stock Issued During Period, Shares, Employee Stock Purchase Plans Schedule of Recognized Identified Assets Acquired and Liabilities Assumed Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block] Funded status of obligation Regulatory Assets, Funded Status of Obligation Regulatory Assets, Funded Status of Obligation International Union of Operating Engineers International Union of Operating Engineers [Member] International Union of Operating Engineers Gain on sale of Texas Water Alliance (“TWA”) Gain on sale of properties Gain (Loss) on Sale of Properties Real Estate Services Reportable Segment Two [Member] Reportable Segment Two [Member] Other comprehensive income (loss), defined benefit plan, net loss Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, after Tax Major Supplier [Domain] Major Supplier [Domain] [Domain] for Major Supplier [Axis] 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 Forfeited (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeited in Period Total debt Long-Term Debt Other, net Other Nonoperating Income (Expense) Advances and contributions Deferred Tax Assets, Advances and Contributions Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from advances and contributions. Offering price per share (usd per share) Sale of Stock, Price Per Share Regulatory asset increase (decrease) Regulatory Asset Increase (Decrease) Balancing and Memorandum Revenue Account, Increase (Decrease) Balancing and Memorandum Revenue Account, Increase (Decrease) Accumulated other comprehensive income (loss) Accumulated Other Comprehensive Income (Loss), Net of Tax Net periodic benefit cost, expected return on plan assets Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-Term Rate of Return on Plan Assets Cash and Cash Equivalents Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy [Policy Text Block] SJWC San Jose Water Company [Member] San Jose Water Company [Member] Total current assets Assets, Current Income tax payable Taxes Payable, Current Income taxes Income Taxes Paid, Net Entity Small Business Entity Small Business Net intangible assets Finite-Lived Intangible Assets, Net Utility property installed by developers Utility Property Installed by Developer Utility Property Installed by Developer Equity award assumed in acquisition Adjustments to Additional Paid in Capital, Share-based Compensation, Equity Award Assumed in Acquisition Adjustments to Additional Paid in Capital, Share-based Compensation, Equity Award Assumed in Acquisition Infrastructure Infrastructure [Member] Infrastructure [Member] Summary of Significant Accounting Policies Significant Accounting Policies [Text Block] Unrecognized compensation cost Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward] SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward] Section 481(a) adjustments Deferred Tax Liabilities, Change in Accounting Policy Deferred Tax Liabilities, Change in Accounting Policy Capitalization ratio Debt Instrument, Covenant, Capitalization Ratio Debt Instrument, Covenant, Capitalization Ratio Public Utilities, General Disclosures [Line Items] Public Utilities, General Disclosures [Line Items] Long-Lived Tangible Asset [Domain] Long-Lived Tangible Asset [Domain] Deferred gain and other-property Deferred Tax Liabilities, Deferred Gain and Other-Property Related Deferred Tax Liabilities, Deferred Gain and Other-Property Related Consolidated Entities [Axis] Consolidated Entities [Axis] South Central Texas South Central Texas [Member] South Central Texas Return on capital from investments in subsidiaries Proceeds From Return On Capital From Investments In Subsidiaries Proceeds From Return On Capital From Investments In Subsidiaries Debt Instrument [Line Items] Debt Instrument [Line Items] Business Combination and Asset Acquisition [Abstract] Issuance of restricted and deferred stock units (in shares) Shares Issued, Shares, Share-Based Payment Arrangement, after Forfeiture Debt issuance costs Payments of Debt Issuance Costs Stockholders’ equity: Stockholders' Equity, Number of Shares, Par Value and Other Disclosure [Abstract] Additions to real estate investment Payments to Acquire Real Estate Balance, beginning of period Balance, end of period SEC Schedule, 12-09, Valuation Allowances and Reserves, Amount Public Stock Offering Public Stock Offering [Member] Public Stock Offering Land Land Share-Based Compensation Share-Based Payment Arrangement [Policy Text Block] Fixed income Fixed Income Funds [Member] 2024 Finite-Lived Intangible Asset, Expected Amortization, Year Two Benefits paid and settlements Defined Benefit Plan, Plan Assets, Benefits Paid SJWTX Credit Agreement SJWTX Credit Agreement [Member] SJWTX Credit Agreement [Member] Net proceeds from stock offering Sale of Stock, Consideration Received on Transaction 2026 Long-Term Debt, Maturity, Year Four Pensions, postretirement benefits and stock-based compensation Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Pensions and Postretirement Benefits Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Pensions and Postretirement Benefits Auditor Location Auditor Location Entity Filer Category Entity Filer Category Federal Current Federal Tax Expense (Benefit) Transmission and distribution plant Public Utilities, Property, Plant and Equipment, Transmission and Distribution Water Plant Water Plant [Member] Compensation costs charged to income: Share-Based Payment Arrangement, Expense Commitments and contingencies Commitments and Contingencies Security Exchange Name Security Exchange Name Executives and Non-employee Directors Executives and Non-employee Directors [Member] Executives and Non-employee Directors [Member] Implicit rate subsidy Defined Benefit Plan, Implicit Rate Subsidy Defined Benefit Plan, Implicit Rate Subsidy Revenue from contracts with customers Revenue from Contract with Customer, Excluding Assessed Tax Service cost Defined Benefit Plan, Service Cost Proceeds from sale of TWA, real estate investments and 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 Capitalized interest costs Interest Costs Capitalized Entity Voluntary Filers Entity Voluntary Filers Goodwill, impairment loss Goodwill, Impairment Loss Deferred gains on sales 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 Cash received from acquisition Cash Acquired from Acquisition Segment Reporting [Abstract] Segment Reporting [Abstract] Assumed equity, measurement period adjustments Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Assets Acquired and Liabilities Assumed, Net Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Assets Acquired and Liabilities Assumed, Net Regulatory asset - income tax temporary differences, net Deferred Tax Liability, Regulatory Asset, Income Tax Temporary Differences Deferred Tax Liability, Regulatory Asset, Income Tax Temporary Differences Change in benefit obligation Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] Deferred revenue Deferred Tax Assets, Deferred Income Schedule of Regulatory Asset Recorded on the Projected Benefit Obligation of the Postretirement Benefit Plans Schedule of Regulatory Asset Recorded on the Projected Benefit Obligation of the Postretirement Benefit Plans [Table Text Block] Schedule of Regulatory Asset Recorded on the Projected Benefit Obligation of the Postretirement Benefit Plans [Table Text Block] SJW Corp. Corporate Segment [Member] Administrative expenses paid Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Other Change Intercompany notes payable Intercompany Notes Payable, Current Intercompany Notes Payable, Current Defined Benefit Plan, Plan Assets, Category [Axis] Defined Benefit Plan, Plan Assets, Category [Axis] Documents Incorporated by Reference Documents Incorporated by Reference [Text Block] Benefit obligations, discount rate Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate Market gains Defined Benefit Plan, Amortization of Gain (Loss) Uncertain tax positions Effective Income Tax Rate Reconciliation, Uncertain Tax Positions Effective Income Tax Rate Reconciliation, Uncertain Tax Positions Total equity and liabilities Liabilities and Equity Vested (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Vested, Number Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Vested, Number Reduction in delivery schedule, percent Reduction in Delivery Schedule, Percent Reduction in Delivery Schedule, Percent Long-term Debt, Type [Axis] Long-Term Debt, Type [Axis] Cash Cash Borrowings from subsidiaries for notes payable Proceed From Subsidiary Notes Payable Proceed From Subsidiary Notes Payable SJWC Credit Agreement SJWC Credit Agreement [Member] SJWC Credit Agreement Accounts receivable and accrued unbilled utility revenue Increase (Decrease) in Receivables Total deferred tax assets Deferred Tax Assets, Gross Non- tariffed Unregulated Operation [Member] Investments, measurement period adjustments Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Financial Assets Regulatory asset - business combinations debt premium, net Deferred Tax Liabilities, Regulatory Asset, Debt Premium Deferred Tax Liabilities, Regulatory Asset, Debt Premium —Diluted (in dollars per share) Earnings Per Share, Diluted Sale of Stock [Domain] Sale of Stock [Domain] Charged to regulatory asset SEC Schedule, 12-09, Valuation Allowances And Reserves Charged To Regulatory Assets SEC Schedule, 12-09, Valuation Allowances And Reserves Charged To Regulatory Assets Beginning Balance Ending Balance Balancing and Memorandum Account, Net Balancing and Memorandum Account, Net Increase in delivery schedule, percent Increase in Delivery Schedule, Percent Increase in Delivery Schedule, Percent Other current assets Other Assets, Current Purchase commitment period Long-Term Purchase Commitment, Period Balance at beginning of year Balance at end of year Unrecognized Tax Benefits Intangibles Deferred Tax Liabilities, Intangible Assets Thereafter Lessor, Operating Lease, Payment to be Received, after Year Five Schedule of Future Minimum Rental Payments to be Received Lessor, Operating Lease, Payment to be Received, Fiscal Year Maturity [Table Text Block] Alternative revenue programs, net Alternative Revenue Programs, Net Alternative Revenue Programs, Net Net periodic benefit cost, discount rate Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate Pension flow-through Effective Income Tax Rate Reconciliation, Nondeductible Expense, Pensions Effective Income Tax Rate Reconciliation, Nondeductible Expense, Pensions Maine Water Company Maine Water Maine Water Company [Member] Maine Water Company [Member] Collective bargaining agreement percent of wage increase for 2024 Collective Bargaining Agreement, Wage Increase, Percent, Year Two Collective Bargaining Agreement, Wage Increase, Percent, Year Two Entity Address, Address Line One Entity Address, Address Line One Long-term Purchase Commitment [Table] Long-Term Purchase Commitment [Table] Class of Stock [Domain] Class of Stock [Domain] Expected return on assets Defined Benefit Plan, Expected Return (Loss) on Plan Assets Senior note and other interest expense Interest Expense CLWSC Canyon Lake Water Service Company [Member] Canyon Lake Water Service Company Retirement Plan Type [Axis] Retirement Plan Type [Axis] Service Agreements Service Agreements [Member] Long-term Purchase Commitment [Line Items] Long-Term Purchase Commitment [Line Items] Schedule of Long-term Debt Instruments Schedule of Long-Term Debt Instruments [Table Text Block] Funded status at end of year Defined Benefit Plan, Funded (Unfunded) Status of Plan Unamortized debt issuance costs Unamortized Debt Issuance Expense Contributions in aid of construction Contributions in Aid of Construction Schedule of Disaggregation of Revenue Disaggregation of Revenue [Table Text Block] Total deferred tax liabilities Deferred Tax Liabilities, Gross Administrative expenses paid Defined Benefit Plan, Plan Assets, Administration Expense Option Indexed to Issuer's Equity, Equity [Table] Option Indexed to Issuer's Equity, Equity [Table] Ownership percentage in Acequia Water Supply Corporation Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage Plan participants contributions Defined Benefit Plan, Plan Assets, Contributions by Plan Participant CTWS Connecticut Water Service, Inc. [Member] Connecticut Water Service, Inc. [Member] Actuarial gain (loss), data and other changes Defined Benefit Plan Actuarial Gain (Loss), Data And Other Changes Defined Benefit Plan Actuarial Gain (Loss), Data And Other Changes Regulatory Asset Increase (Decrease) Balancing and Memorandum Account, Increase (Decrease) Balancing and Memorandum Account, Increase (Decrease) KT Water Development Ltd KT Water Development Ltd [Member] KT Water Development Ltd Deferred revenue Deferred Tax Liabilities, Tax Deferred Income Valuation and Qualifying Accounts and Reserves SEC Schedule, 12-09, Schedule of Valuation and Qualifying Accounts Disclosure [Text Block] Cash and cash equivalents: Cash, Cash Equivalents, and Short-Term Investments [Abstract] Fair value of restricted stock awards Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested, Grant Date Fair Value Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested, Grant Date Fair Value 2027 Finite-Lived Intangible Asset, Expected Amortization, Year Five Other assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Assets Allowance for doubtful accounts: SEC Schedule, 12-09, Allowance, Credit Loss [Member] Weighted-  Average Grant- Date Fair Value Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Administrative and general General and Administrative Expense 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] Assets leased or available for lease Property, Plant, and Equipment, Lessor Asset under Operating Lease, after Accumulated Depreciation Income tax at federal statutory rate Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount RWA South Central Connecticut Regional Water Authority [Member] South Central Connecticut Regional Water Authority [Member] Financing activities: Net Cash Provided by (Used in) Financing Activities [Abstract] Intercompany receivables Increase (Decrease) In Intercompany Receivables, Current Increase (Decrease) In Intercompany Receivables, Current Audit Information [Abstract] Audit Information Customer advances for construction, refunded on service connections Customer Advances for Construction, Refunded on Service Connections Customer Advances for Construction, Refunded on Service Connections 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 Reversal of excess deferred taxes recognized in regulatory liability Effective Income Tax Rate Reconciliation, Reversal Of Excess Deferred Taxes Recognized In Regulatory Liability, Amount Effective Income Tax Rate Reconciliation, Reversal Of Excess Deferred Taxes Recognized In Regulatory Liability, Amount Concession fees Concession Fees [Member] Concession Fees [Member] Syndicated Credit Agreement Syndicated Credit Agreement [Member] Syndicated Credit Agreement Estimated Refunds of Advances for Construction [Abstract] Estimated Refunds of Advances for Construction [Abstract] Estimated Refunds of Advances for Construction [Abstract] SJWTX, Inc. Subsidiary One [Member] Subsidiary One [Member]