Balancing and memorandum revenue account, refunds (collections) Balancing And Memorandum Revenue Account, Refunds (Collections) Balancing And Memorandum Revenue Account, Refunds (Collections) 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] Statistical Measurement [Domain] Statistical Measurement [Domain] Repayments of long-term borrowings Repayments of Long-Term Debt Capital expenditures Segment, Expenditure, Addition to Long-Lived Assets Cover [Abstract] Net change in cash and cash equivalents Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Other current liabilities Other Liabilities, Current Trading Symbol Trading Symbol Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] All Trading Arrangements All Trading Arrangements [Member] Compensation Actually Paid vs. Net Income Compensation Actually Paid vs. Net Income [Text Block] Non-NEOs Non-NEOs [Member] Service-based restricted stock vesting period Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period Company-funded Payments To Acquire Water Systems Using Company Funds Payments To Acquire Water Systems Using Company Funds Total capitalization Capitalization, Long-Term Debt and Equity Rule 10b5-1 Arrangement Adopted Rule 10b5-1 Arrangement Adopted [Flag] Awards Close in Time to MNPI Disclosures Awards Close in Time to MNPI Disclosures [Table] Income taxes Income Taxes Paid, Net Allowance for uncollectible accounts Accounts Receivable, Allowance for Credit Loss, Current Regulatory assets: Net Regulatory Assets [Abstract] 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] Pay vs Performance Disclosure [Line Items] Peer Group Total Shareholder Return Amount Peer Group Total Shareholder Return Amount Water supply costs Water Supply Costs [Member] Water Supply Costs Earnings per Share Earnings Per Share, Policy [Policy Text Block] Supplemental Employee Retirement Plan Supplemental Employee Retirement Plan [Member] Non-Rule 10b5-1 Arrangement Adopted Non-Rule 10b5-1 Arrangement Adopted [Flag] Award Timing Disclosures [Line Items] Other changes, net Increase (Decrease) in Other Operating Assets and Liabilities, Net Postretirement benefits Increase (Decrease) in Obligation, Pension and Other Postretirement Benefits Other Performance Measure, Amount Other Performance Measure, Amount Common stock, shares outstanding (in shares) Beginning balance (in shares) Ending balance (in shares) Common Stock, Shares, Outstanding Weighted-average interest rate on short-term Short-Term Debt, Weighted Average Interest Rate, at Point in Time Remaining shares available for issuance (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant Schedule of Regulatory Assets [Table] Regulated Operation, Regulatory Asset [Table] Plan Name [Domain] Plan Name [Domain] Service cost Defined Benefit Plan, Service Cost Total other assets Other Assets, Noncurrent Entity Tax Identification Number Entity Tax Identification Number Other Other Regulatory Liabilities [Member] Other Regulatory Liabilities Total regulatory assets Regulatory Asset Intangible assets Finite-Lived Intangible Assets, Gross Retirement Plan Type [Axis] Retirement Plan Type [Axis] Operating Segments Operating Segments [Member] Aggregate gross sales price (up to) Sale Of Stock, Aggregate Gross Sales Price Sale Of Stock, Aggregate Gross Sales Price Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities Net proceeds from stock offering Sale of Stock, Consideration Received on Transaction Operating activities: Net Cash Provided by (Used in) Operating Activities [Abstract] Unrecognized pensions and other postretirement benefits Pension and Other Postretirement Plans Costs [Member] Plan Name [Axis] Plan Name [Axis] Prepaid expenses Prepaid Expense, Current Equity Components [Axis] Equity Components [Axis] Land Public Utilities, Property, Plant and Equipment, Land Other current assets Other Assets, Current Award Timing Method Award Timing Method [Text Block] Total Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Trading Arrangements, by Individual Trading Arrangements, by Individual [Table] ESPP Employee Stock Purchase Plan Employee Stock Purchase Plan [Member] Employee Stock Purchase Plan [Member] Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Insider Trading Policies and Procedures [Line Items] Adjustment to Compensation, Amount Adjustment to Compensation Amount Additional paid-in capital Additional Paid in Capital, Common Stock Compensation Amount Outstanding Recovery Compensation Amount Less: Segment Reconciliation [Abstract] Supplemental disclosure of non-cash activities: Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table [Member] Unrealized loss on investment, net of tax Other Comprehensive Income (Loss), Available-for-Sale Securities Adjustment, Net of Tax, Portion Attributable to Parent Entity Small Business Entity Small Business Less: accumulated depreciation and amortization Public Utilities, Property, Plant and Equipment, Accumulated Depreciation Company Selected Measure Amount Company Selected Measure Amount Tabular List, Table Tabular List [Table Text Block] Fair Value, Inputs, Level 3 Fair Value, Inputs, Level 3 [Member] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items] Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table [Member] Other Other Regulatory Assets [Member] Other Regulatory Assets [Member] Employee stock purchase plan (in shares) Stock Issued During Period, Shares, Employee Stock Purchase Plans 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 Accrued unbilled revenue Receivables, Long-Term Contracts or Programs Credit Facility [Domain] Credit Facility [Domain] Cash and cash equivalents, beginning of period Cash and cash equivalents, end of period Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents Contributions in aid of construction Contributions in Aid of Construction Income tax temporary differences Future income tax benefits due to customers Deferred Income Tax Charge [Member] Unrecognized compensation costs Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount At The Market Offering At The Market Offering [Member] At The Market Offering Current assets: Assets, Current [Abstract] Goodwill Goodwill Consolidation Items [Axis] Consolidation Items [Axis] Forgone Recovery due to Disqualification of Tax Benefits, Amount Forgone Recovery due to Disqualification of Tax Benefits, Amount Interest Interest Paid, Including Capitalized Interest, Operating and Investing Activities Employee Stock Option Share-Based Payment Arrangement, Option [Member] Other changes, net Proceeds from (Payments for) Other Financing Activities Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Antidilutive Security, Excluded EPS Calculation [Table] Comprehensive income Comprehensive Income (Loss), Net of Tax, Attributable to Parent Pension Benefits Pension Plan [Member] Repayments of lines of credit Repayments of Lines of Credit Security Exchange Name Security Exchange Name Award Type [Axis] Award Type [Axis] Net nonutility properties Property, Plant and Equipment, Net Dividends per share (in usd per share) Common Stock, Dividends, Per Share, Cash Paid Other Other Assets, Miscellaneous, Noncurrent Common stock, par value (in usd per share) Common Stock, Par or Stated Value Per Share Forgone Recovery, Explanation of Impracticability Forgone Recovery, Explanation of Impracticability [Text Block] Purchased water Cost of Purchased Water Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-Based Compensation Arrangements by Share-Based Payment Award [Table] Revolving Credit Facility Revolving Credit Facility [Member] Expiration Date Trading Arrangement Expiration Date CTWS Credit Agreement Maturing August 2025 CTWS Credit Agreement Maturing August 2025 [Member] CTWS Credit Agreement Maturing August 2025 Investing activities: Net Cash Provided by (Used in) Investing Activities [Abstract] Total Shareholder Return Amount Total Shareholder Return Amount Common stock, shares issued (in shares) Common Stock, Shares, Issued Equity Awards Adjustments, Footnote Equity Awards Adjustments, Footnote [Text Block] Line of credit facility, maximum borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Insider Trading Policies and Procedures Adopted Insider Trading Policies and Procedures Adopted [Flag] Less: accumulated depreciation Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Nonutility properties Subtotal Property, Plant and Equipment, Gross Debt Instrument [Line Items] Debt Instrument [Line Items] Named Executive Officers, Footnote Named Executive Officers, Footnote [Text Block] Common stock, shares authorized (in shares) Common Stock, Shares Authorized Total equity distribution Sale Of Stock, Total Equity Distribution Agreement Remaining Sale Of Stock, Total Equity Distribution Agreement Remaining Basis of Accounting Basis of Accounting, Policy [Policy Text Block] Diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted MNPI Disclosure Timed for Compensation Value MNPI Disclosure Timed for Compensation Value [Flag] Long-term Debt, Type [Axis] Long-Term Debt, Type [Axis] Total stockholders’ equity Beginning balance Ending balance Equity, Attributable to Parent Business combinations debt premium Business Combinations Debt Premium [Member] Business Combinations Debt Premium 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 Power Utilities Operating Expense, Purchased Power Deferred income taxes Deferred Income Tax Expense (Benefit) Customers, net of allowances for credit losses of $1,149 and $1,172 on March 31, 2025 and December 31, 2024, respectively Accounts Receivable, after Allowance for Credit Loss, Current Sale of Stock [Domain] Sale of Stock [Domain] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Pension Adjustments Prior Service Cost Pension Adjustments Prior Service Cost [Member] Document Fiscal Period Focus Document Fiscal Period Focus Fair value of plan assets Defined Benefit Plan, Plan Assets, Amount All Executive Categories All Executive Categories [Member] Changed Peer Group, Footnote Changed Peer Group, Footnote [Text Block] Assets Assets [Abstract] Retirement Plan Type [Domain] Retirement Plan Type [Domain] Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Other comprehensive loss, net Other Comprehensive Income (Loss), Net of Tax Document Type Document Type Regulatory Matters Schedule of Regulatory Assets and Liabilities [Text Block] Amortization of actuarial (gain) loss Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) Pension Benefits Adjustments, Footnote Pension Benefits Adjustments, Footnote [Text Block] Schedule of Segment Reporting Information, by Segment Schedule of Segment Reporting Information, by Segment [Table Text Block] Total Shareholder Return Vs Peer Group Total Shareholder Return Vs Peer Group [Text Block] Refunds of advances for construction Repayments Of Advances For Construction, Financing Activities Repayments Of Advances For Construction, Financing Activities Schedule of Defined Benefit Plans Disclosures [Table] Defined Benefit Plan [Table] Regulatory Assets [Line Items] Regulatory Asset [Line Items] Maximum Maximum [Member] Equity Valuation Assumption Difference, Footnote Equity Valuation Assumption Difference, Footnote [Text Block] Accounts payable Accounts Payable, Current Accounting Policies [Abstract] Accounting Policies [Abstract] Fair Value Measurement Fair Value Measurement, Policy [Policy Text Block] Current Fiscal Year End Date Current Fiscal Year End Date Incentive Plan Incentive Plan [Member] Incentive Plan [Member] Revenue adjustment mechanisms Revenue Adjustment Mechanisms [Member] Revenue adjustment mechanisms Regulatory Asset [Domain] Regulatory Asset [Domain] Statistical Measurement [Axis] Statistical Measurement [Axis] Customer Assistance Program ("CAP") balancing account Customer Assistance Program Balancing Account [Member] Customer Assistance Program Balancing Account Weighted average shares outstanding Weighted Average Number of Shares Outstanding, Diluted, Adjustment [Abstract] PEO Name PEO Name Non-Rule 10b5-1 Arrangement Terminated Non-Rule 10b5-1 Arrangement Terminated [Flag] Income before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Non-PEO NEO Average Total Compensation Amount Non-PEO NEO Average Total Compensation Amount Award Type [Domain] Award Type [Domain] Name Outstanding Recovery, Individual Name Issuance of restricted and deferred stock units (in shares) Shares Issued, Shares, Share-Based Payment Arrangement, after Forfeiture Compensation Actually Paid vs. Company Selected Measure Compensation Actually Paid vs. Company Selected Measure [Text Block] Unrecognized pensions and other postretirement benefits Unrecognized Pensions and Other Postretirement Benefits [Member] Unrecognized Pensions and Other Postretirement Benefits Regulatory liabilities, less current portion Total regulatory liabilities, less current portion Regulatory Liability, Noncurrent Postretirement benefit plans Liability, Defined Benefit Plan, Noncurrent Non-PEO NEO Non-PEO NEO [Member] Title of Individual [Axis] Title and Position [Axis] Depreciable plant and equipment Public Utilities, Property, Plant And Equipment, Depreciable Plant And Equipment Public Utilities, Property, Plant And Equipment, Depreciable Plant And Equipment Maintenance Maintenance Utilities Operating Expense, Maintenance Additional Paid-in Capital Additional Paid-in Capital [Member] Cost of removal Cost of Removal [Member] Cost of Removal Award Timing Predetermined Award Timing Predetermined [Flag] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Dividends paid Payments of Ordinary Dividends, Common Stock Benefit Plans Retirement Benefits [Text Block] Regulatory Liability [Axis] Regulatory Liability [Axis] New Accounting Standards New Accounting Pronouncements, Policy [Policy Text Block] Amortization of prior service cost Defined Benefit Plan, Amortization of Prior Service Cost (Credit) Class of Stock [Axis] Class of Stock [Axis] Lines of Credit and Long-Term Liabilities Long-Term Debt [Text Block] Diluted (in usd per share) Earnings Per Share, Diluted Total production expenses Production expenses Water Production Costs Title of Individual [Domain] Title and Position [Domain] Name Measure Name Entity Interactive Data Current Entity Interactive Data Current Regulatory Liability [Domain] Regulatory Liability [Domain] Restatement does not require Recovery Restatement Does Not Require Recovery [Text Block] Target vesting percentage Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Rights, Percentage Other Nontrade Receivables, Current Retirement Benefits [Abstract] Retirement Benefits [Abstract] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Accounts receivable and accrued unbilled utility revenue Increase (Decrease) in Receivables Stock-based compensation Share-Based Payment Arrangement, Noncash Expense Provision for income taxes Income tax expense (benefit) Provision (benefit) for income taxes Income Tax Expense (Benefit) Interest cost Defined Benefit Plan, Interest Cost Unallocated Corporate Segment Reporting, Reconciling Item, Corporate Nonsegment [Member] Cash paid (refunded) during the period for: Supplemental Cash Flow Information [Abstract] Equity Plans Shareholders' Equity and Share-Based Payments [Text Block] Recognition period for unrecognized compensation cost Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition Revenue from contracts with customers Revenue from Contract with Customer, Excluding Assessed Tax Effective consolidated income tax rate Effective Income Tax Rate Reconciliation, Percent Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities Operating income Operating Income (Loss) Number of reportable segments Number of Reportable Segments Total capitalization and liabilities Liabilities and Equity Dividends paid Dividends Rule 10b5-1 Arrangement Terminated Rule 10b5-1 Arrangement Terminated [Flag] All Adjustments to Compensation All Adjustments to Compensation [Member] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Accrued payroll Employee-related Liabilities, Current Rate of compensation increase Defined Benefit Plan, Rate Of Compensation Increase Defined Benefit Plan, Rate Of Compensation Increase Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Regulated Operations [Abstract] Regulated Operations [Abstract] 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 Buildings and improvements Investment Building and Building Improvements Regulatory Asset [Axis] Regulatory Asset [Axis] Utility plant: Public Utilities, Property, Plant and Equipment, Net [Abstract] Underlying Security Market Price Change Underlying Security Market Price Change, Percent Expected return on assets Defined Benefit Plan, Expected Return (Loss) on Plan Assets Rental income Operating Lease, Lease Income Individual: Individual [Axis] Construction work in progress Public Utilities, Property, Plant and Equipment, Construction Work in Progress Accumulated Other Comprehensive Income AOCI Attributable to Parent [Member] Schedule of Regulatory Assets, Net Schedule of Regulatory Assets [Table Text Block] Restricted stock and deferred restricted stock Restricted Stock And Deferred Restricted Stock [Member] Restricted Stock and Deferred Restricted Stock [Member] Long-term Debt, Type [Domain] Long-Term Debt, Type [Domain] Entity Address, State or Province Entity Address, State or Province Statement [Line Items] Statement [Line Items] Pension non-service credit Net Periodic Defined Benefits Expense (Reversal of Expense), Excluding Service Cost Component Accounts receivable: Accounts Receivable, after Allowance for Credit Loss, Current [Abstract] Erroneous Compensation Analysis Erroneous Compensation Analysis [Text Block] Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] Schedule of Nonutility Properties Property, Plant and Equipment [Table Text Block] Compensation Actually Paid vs. Total Shareholder Return Compensation Actually Paid vs. Total Shareholder Return [Text Block] Capitalization and liabilities Liabilities and Equity [Abstract] Other assets: Other Assets, Noncurrent [Abstract] Schedule of Net Benefit Costs Schedule of Net Benefit Costs [Table Text Block] Other production expenses Utilities Operating Expense, Other Weighted average price per share (in usd per share) Sale Of Stock, Weighted Average Price Per Share Sale Of Stock, Weighted Average Price Per Share Minimum Minimum [Member] Restatement Determination Date Restatement Determination Date Stockholders’ equity: Stockholders' Equity, Number of Shares, Par Value and Other Disclosure [Abstract] Adoption Date Trading Arrangement Adoption Date Pay vs Performance Disclosure Pay vs Performance Disclosure [Table] Advances for construction Contract with Customer, Liability, Noncurrent Erroneously Awarded Compensation Recovery Erroneously Awarded Compensation Recovery [Table] Lines of credit Line of Credit, Current Total utility plant Public Utilities, Property, Plant and Equipment, Plant in Service Business Segments [Axis] Segments [Axis] Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year [Member] Exercise Price Award Exercise Price Cost to retire utility plant, net of salvage Payments for (Proceeds from) Removal Costs Arrangement Duration Trading Arrangement Duration Employee stock purchase plan Stock Issued During Period, Value, Employee Stock Purchase Plan Subsequent Event Subsequent Event [Member] Operating expense: Costs and Expenses [Abstract] Grant date fair value of equity instruments granted (in usd per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Investments Investments Shares issuable upon exercise of incentive plan awards (in shares) Share-Based Compensation Arrangement By Share-Based Payment Award, Shares Issuable Upon Exercise Number of shares reserved for issuance under equity instrument agreements awarded that validly exist and are outstanding, including vested instruments. Peer Group Issuers, Footnote Peer Group Issuers, Footnote [Text Block] Segment [Domain] Segments [Domain] Material Terms of Trading Arrangement Material Terms of Trading Arrangement [Text Block] Groundwater extraction charges Groundwater Extraction Charges Groundwater Extraction Charges All Individuals All Individuals [Member] Borrowings from lines of credit Proceeds from Lines of Credit PEO PEO [Member] Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Name Trading Arrangement, Individual Name Other, net Other Nonoperating Income (Expense) Other Benefits Other Postretirement Benefits Plan [Member] Market-based RSU Market-based RSU [Member] Market-based RSU [Member] Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] ESPP proceeds Proceeds, Issuance of Shares, Share-Based Payment Arrangement, Including Option Exercised 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 Awards Close in Time to MNPI Disclosures, Table Awards Close in Time to MNPI Disclosures [Table Text Block] Other (expense) income: Other Nonoperating Income (Expense) [Abstract] Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year [Member] Aggregate Erroneous Compensation Amount Aggregate Erroneous Compensation Amount Local Phone Number Local Phone Number Aggregate Erroneous Compensation Not Yet Determined Aggregate Erroneous Compensation Not Yet Determined [Text Block] Regulatory liabilities: Net Regulatory Liabilities [Abstract] Net Regulatory Liabilities Deferred income taxes Deferred Income Tax Liabilities, Net Changes in operating assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Total operating expense Utilities Operating Expense Unrealized loss on investment, tax expense (benefit) Other Comprehensive Income (Loss), Available-for-Sale Securities, Tax, Portion Attributable to Parent PEO Total Compensation Amount PEO Total Compensation Amount Accrued interest Interest Payable, Current Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Debt Disclosure [Abstract] Common Stock Common Stock [Member] Measure: Measure [Axis] Issuance of restricted and deferred stock units Shares Issued, Value, Share-Based Payment Arrangement, after Forfeiture Forgone Recovery due to Expense of Enforcement, Amount Forgone Recovery due to Expense of Enforcement, Amount Common stock issuance, net of costs (in shares) Stock Issued During Period, Shares, New Issues Line of Credit Line of Credit [Member] Entity Emerging Growth Company Entity Emerging Growth Company Segment Reporting [Abstract] Segment Reporting [Abstract] Entity Central Index Key Entity Central Index Key Water Utility Services Water Utility Services [Member] Water Utility Services Other Segment Reporting, Other Segment Item, Amount Non-GAAP Measure Description Non-GAAP Measure Description [Text Block] 2022 general rate case interim memorandum account 2022 General Rate Case Interim Memorandum Account [Member] 2022 General Rate Case Interim Memorandum Account Non-PEO NEO Average Compensation Actually Paid Amount Non-PEO NEO Average Compensation Actually Paid Amount Capitalization Equity [Text Block] Award Timing, How MNPI Considered Award Timing, How MNPI Considered [Text Block] Equity Component [Domain] Equity Component [Domain] Segment Reporting Segment Reporting Disclosure [Text Block] Current portion of long-term debt Long-Term Debt, Current Maturities Property taxes and other non-income taxes Property taxes and other non-income taxes Utilities Operating Expense, Taxes Additional 402(v) Disclosure Additional 402(v) Disclosure [Text Block] Stock-based compensation APIC, Share-Based Payment Arrangement, Increase for Cost Recognition Utility property installed by developers Utility Property Installed By Developer Utility Property Installed By Developer Entity Shell Company Entity Shell Company Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Title Trading Arrangement, Individual Title Statement [Table] Statement [Table] Interest on long-term debt and other interest expense Interest on long-term debt and other interest expense Interest Expense, Debt Employee benefit costs Employee Benefit Costs [Member] Employee Benefit Costs General Significant Accounting Policies [Text Block] Unrecognized tax benefits Unrecognized Tax Benefits Consolidation Items [Domain] Consolidation Items [Domain] City Area Code City Area Code Current liabilities: Liabilities, Current [Abstract] Net utility plant Public Utilities, Property, Plant and Equipment, Net Interest, net of amounts capitalized Interest Paid, Excluding Capitalized Interest, Operating Activities Revenue Revenue [Policy Text Block] Insider Trading Policies and Procedures Not Adopted Insider Trading Policies and Procedures Not Adopted [Text Block] Fair Value, Inputs, Level 1 Fair Value, Inputs, Level 1 [Member] Monterey Water Revenue Adjustment Mechanism Monterey Water Revenue Adjustment Mechanism (MWRAM) [Member] Monterey Water Revenue Adjustment Mechanism (MWRAM) Total current assets Assets, Current Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Capitalization: Capitalization, Long-Term Debt and Equity [Abstract] Tax receivable and payable, and other accrued taxes Increase (Decrease) in Accrued Taxes Payable Unused portion of line of credit Line of Credit Facility, Remaining Borrowing Capacity Schedule of Long-term Debt Instruments [Table] Schedule of Long-Term Debt Instruments [Table] Long-term debt, less current portion Long-Term Debt, Excluding Current Maturities Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Accrued groundwater extraction charges, purchased water and power Accrued Groundwater Extraction Charges, Purchased Water And Power Accrued Groundwater Extraction Charges, Purchased Water And Power Subsequent Event Type [Axis] Subsequent Event Type [Axis] Income Taxes Income Tax Disclosure [Text Block] Earnings per share Earnings Per Share [Abstract] Equity [Abstract] Retained earnings Retained Earnings (Accumulated Deficit) Class of Stock [Domain] Class of Stock [Domain] Administrative and general Administrative and general General and Administrative Expense Aggregate Available Trading Arrangement, Securities Aggregate Available Amount CTWS Employees CTWS Employees [Member] CTWS Employees Equity Awards Adjustments Equity Awards Adjustments [Member] Reduction in authorized return of equity Balancing Accounts, Increase (Decrease) In Authorized Return On Equity, Percentage Balancing Accounts, Increase (Decrease) In Authorized Return On Equity, Percentage Net cash provided by financing activities Net Cash Provided by (Used in) Financing Activities Underlying Securities Award Underlying Securities Amount Performance Shares Performance Shares [Member] Current regulatory assets Less: current regulatory assets Regulatory Asset, Current Credit Facility [Axis] Credit Facility [Axis] Amendment Flag Amendment Flag Long-term debt, fair value Long-Term Debt, Fair Value Entity Registrant Name Entity Registrant Name Adjustment to Non-PEO NEO Compensation Footnote Adjustment to Non-PEO NEO Compensation Footnote [Text Block] Stock Appreciation Rights (SARs) Stock Appreciation Rights (SARs) [Member] Depreciation and amortization Depreciation, Depletion and Amortization Fair Value as of Grant Date Award Grant Date Fair Value Postretirement benefit plans Assets for Plan Benefits, Defined Benefit Plan Shares issued in offering (in shares) Sale of Stock, Number of Shares Issued in Transaction Fair Value, Inputs, Level 2 Fair Value, Inputs, Level 2 [Member] Fair Value, Measurements, Fair Value Hierarchy [Domain] Fair Value Hierarchy and NAV [Domain] Recovery of Erroneously Awarded Compensation Disclosure [Line Items] Schedule of SJW Group's Revenue Components Disaggregation of Revenue [Table Text Block] Common stock issuance, net of costs Stock Issued During Period, Value, New Issues Entity Address, Postal Zip Code Entity Address, Postal Zip Code Restatement Determination Date: Restatement Determination Date [Axis] Title of 12(b) Security Title of 12(b) Security Common stock, $0.001 par value; authorized 70,000,000 shares; issued and outstanding shares 34,182,785 on March 31, 2025 and 33,629,169 on December 31, 2024 Common Stock, Value, Issued Land Land Share-based Payment Arrangement [Abstract] Share-Based Payment Arrangement [Abstract] Regulatory assets, less current portion Total regulatory assets, less current portion Regulatory Asset, Noncurrent Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Depreciation and amortization Depreciation and amortization Utilities Operating Expense, Depreciation and Amortization Other changes, net Payments for (Proceeds from) Other Investing Activities Current regulatory liabilities Less: current regulatory liabilities Regulatory Liability, Current Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested [Member] Financing activities: Net Cash Provided by (Used in) Financing Activities [Abstract] Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested [Member] Other balancing and memorandum accounts and regulatory mechanisms, net Regulatory Balancing And Memorandum Accounts And Regulatory Mechanisms, Net Regulatory Balancing And Memorandum Accounts And Regulatory Mechanisms, Net Total regulatory liabilities Regulatory Liability Basic (in usd per share) Earnings Per Share, Basic Accounts payable and other current liabilities Increase (Decrease) in Accounts Payable Issuance of common stock, net of issuance costs Proceeds from Issuance of Common Stock Adjustment To PEO Compensation, Footnote Adjustment To PEO Compensation, Footnote [Text Block] Award Timing MNPI Disclosure Award Timing MNPI Disclosure [Text Block] Accrued payables for additions to utility plant Capital Expenditures Incurred but Not yet Paid Aggregate Pension Adjustments Service Cost Aggregate Pension Adjustments Service Cost [Member] Compensation Actually Paid vs. Other Measure Compensation Actually Paid vs. Other Measure [Text Block] Total current liabilities Liabilities, Current Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year [Member] Total assets Assets Assets Number of equity instruments granted (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period Income tax Income Taxes Receivable, Current Other noncurrent liabilities Other Liabilities, Noncurrent Forgone Recovery due to Violation of Home Country Law, Amount Forgone Recovery due to Violation of Home Country Law, Amount Commitments and contingencies Commitments and Contingencies Alternative revenue programs, net Alternative Revenue Programs, Net Alternative Revenue Programs, Net Termination Date Trading Arrangement Termination Date Operating revenue Operating revenue Operating revenue Revenues Regulatory assets and liabilities excluding cost of removal, income tax temporary differences and postretirement benefits Increase (Decrease) To Regulatory Asset And Liabilities Excluding Cost Of Removal, Income Tax Temporary Differences, Net And Postretirement Benefits Increase (Decrease) To Regulatory Asset And Liabilities Excluding Cost Of Removal, Income Tax Temporary Differences, Net And Postretirement Benefits Entity Address, City or Town Entity Address, City or Town Long-term borrowings Proceeds from Issuance of Long-Term Debt Debt Instrument [Axis] Debt Instrument [Axis] Compensation costs charged to income: Share-Based Payment Arrangement, Expense Net income Net income Net Income (Loss) Net Income (Loss) Attributable to Parent Trading Arrangement: Trading Arrangement [Axis] Pay vs Performance Disclosure, Table Pay vs Performance [Table Text Block] Employer plan contributions Defined Contribution Plan, Employer Discretionary Contribution Amount Allowance for equity funds used during construction Public Utilities, Allowance for Funds Used During Construction, Additions Equity Awards Adjustments, Excluding Value Reported in Compensation Table Equity Awards Adjustments, Excluding Value Reported in the Compensation Table [Member] Production Expenses: Water Production Costs [Abstract] Water Production Costs [Abstract] Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year [Member] Entity File Number Entity File Number Document Fiscal Year Focus Document Fiscal Year Focus Income Statement [Abstract] Income Statement [Abstract] Entity Address, Address Line One Entity Address, Address Line One Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Name Forgone Recovery, Individual Name Document Period End Date Document Period End Date Sale of Stock [Axis] Sale of Stock [Axis] Award Timing MNPI Considered Award Timing MNPI Considered [Flag] Insider Trading Arrangements [Line Items] Other Services Segment Reporting, Reconciling Item, Excluding Corporate Nonsegment [Member] Outstanding Aggregate Erroneous Compensation Amount Outstanding Aggregate Erroneous Compensation Amount Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] PEO Actually Paid Compensation Amount PEO Actually Paid Compensation Amount Adjustment to Compensation: Adjustment to Compensation [Axis] Subsidiary or Equity Method Investee, Sale of Stock by Subsidiary or Equity Investee [Table] Subsidiary or Equity Method Investee, Sale of Stock, Type [Table] Authorized revenue, threshold percentage Regulatory Balancing And Memorandum Accounts Review, Authorized Revenue, Threshold Percentage Threshold balance of regulatory balancing or memorandum accounts as a percentage of authorized revenue to trigger an account review. Document Transition Report Document Transition Report Document Quarterly Report Document Quarterly Report Accumulated other comprehensive income Accumulated Other Comprehensive Income (Loss), Net of Tax Entity Current Reporting Status Entity Current Reporting Status Retained Earnings Retained Earnings [Member] Pension Adjustments Service Cost Pension Adjustments Service Cost [Member] Estimated service lives of assets Public Utilities, Property, Plant and Equipment, Common, Useful Life Basic (in shares) Weighted Average Number of Shares Outstanding, Basic Stock Price or TSR Estimation Method Stock Price or TSR Estimation Method [Text Block] Expected required and discretionary employer cash contributions Defined Benefit Plan, Expected Future Employer Contributions, Current Fiscal Year Subsidiary, Sale of Stock [Line Items] Subsidiary, Sale of Stock [Line Items] Restricted Stock Units (RSUs) Restricted Stock Units (RSUs) [Member] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Executive Category: Executive Category [Axis] Name Awards Close in Time to MNPI Disclosures, Individual Name Entity Filer Category Entity Filer Category Company Selected Measure Name Company Selected Measure Name