Other Nontrade Receivables, Current Dividends per share (in usd per share) Common Stock, Dividends, Per Share, Cash Paid General Significant Accounting Policies [Text Block] Expected required and discretionary employer cash contributions Defined Benefit Plan, Expected Future Employer Contributions, Current Fiscal Year Statistical Measurement [Domain] Statistical Measurement [Domain] Total capitalization Capitalization, Long-Term Debt and Equity Expected return on assets Defined Benefit Plan, Expected Return (Loss) on Plan Assets Award Timing Predetermined Award Timing Predetermined [Flag] Entity File Number Entity File Number Additional Paid-in Capital Additional Paid-in Capital [Member] Tabular List, Table Tabular List [Table Text Block] New Accounting Standards New Accounting Pronouncements, Policy [Policy Text Block] Depreciable plant and equipment Public Utilities, Property, Plant And Equipment, Depreciable Plant And Equipment Public Utilities, Property, Plant And Equipment, Depreciable Plant And Equipment Accounts payable and other current liabilities Increase (Decrease) in Accounts Payable Trading Arrangements, by Individual Trading Arrangements, by Individual [Table] Basic (in usd per share) Earnings Per Share, Basic Adjustment to Compensation: Adjustment to Compensation [Axis] Named Executive Officers, Footnote Named Executive Officers, Footnote [Text Block] CTWS Employees CTWS Employees [Member] CTWS Employees Subsidiary or Equity Method Investee, Sale of Stock, Type [Table] Subsidiary or Equity Method Investee, Sale of Stock, Type [Table] Other comprehensive loss, net Other Comprehensive Income (Loss), Net of Tax Schedule of Segment Reporting Information, by Segment Schedule of Segment Reporting Information, by Segment [Table Text Block] Employee stock purchase plan (in shares) Stock Issued During Period, Shares, Employee Stock Purchase Plans Other Other Assets, Miscellaneous, Noncurrent Adjustment to Compensation, Amount Adjustment to Compensation Amount Pension Benefits Pension Plan [Member] Catastrophic event memorandum accounts (“CEMA”) Catastrophic Event Memorandum Accounts (“CEMA”) [Member] Catastrophic Event Memorandum Accounts (“CEMA”) Stock-based compensation Share-Based Payment Arrangement, Noncash Expense Depreciation and amortization Depreciation and amortization Utilities Operating Expense, Depreciation and Amortization Employee benefit costs Employee Benefit Costs [Member] Employee Benefit Costs Employee Stock Option Share-Based Payment Arrangement, Option [Member] Award Timing MNPI Disclosure Award Timing MNPI Disclosure [Text Block] Total stockholders’ equity Beginning balance Ending balance Equity, Attributable to Parent Insider Trading Policies and Procedures [Line Items] Total compensation costs charged to income Share-Based Payment Arrangement, Expense Schedule of Nonutility Properties Property, Plant and Equipment [Table Text Block] Common stock, shares authorized (in shares) Common Stock, Shares Authorized Common stock issuance, net of costs (in shares) Stock Issued During Period, Shares, New Issues Current assets: Assets, Current [Abstract] Transaction period Sale Of Stock, Transaction Period Sale Of Stock, Transaction Period Total capitalization and liabilities Liabilities and Equity Additions to utility plant: Payments To Acquire Public Utilities, Property, Plan And Equipment [Abstract] Payments To Acquire Public Utilities, Property, Plan And Equipment Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Capitalization and liabilities Liabilities and Equity [Abstract] Other (expense) income: Other Nonoperating Income (Expense) [Abstract] Cover [Abstract] Maximum Maximum [Member] Stockholders’ equity: Stockholders' Equity, Number of Shares, Par Value and Other Disclosure [Abstract] Capital expenditures Segment, Expenditure, Addition to Long-Lived Assets Accounting Policies [Abstract] Accounting Policies [Abstract] Incentive Plan Incentive Plan [Member] Incentive Plan [Member] Non-PEO NEO Average Total Compensation Amount Non-PEO NEO Average Total Compensation Amount Debt Instrument [Line Items] Debt Instrument [Line Items] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-Based Compensation Arrangements by Share-Based Payment Award [Table] Pension non-service credit Net Periodic Defined Benefits Expense (Reversal of Expense), Excluding Service Cost Component Adjustment to Non-PEO NEO Compensation Footnote Adjustment to Non-PEO NEO Compensation Footnote [Text Block] Pay vs Performance Disclosure [Line Items] Retirement Benefits [Abstract] Retirement Benefits [Abstract] Land Public Utilities, Property, Plant and Equipment, Land Forgone Recovery due to Disqualification of Tax Benefits, Amount Forgone Recovery due to Disqualification of Tax Benefits, Amount Acquisitions Business Combination [Text Block] Non-Rule 10b5-1 Arrangement Terminated Non-Rule 10b5-1 Arrangement Terminated [Flag] 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 Income before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Entity Shell Company Entity Shell Company Other noncurrent liabilities Other Liabilities, Noncurrent Schedule of Long-term Debt Instruments [Table] Schedule of Long-Term Debt Instruments [Table] Regulatory Assets [Line Items] Regulatory Asset [Line Items] Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Operating Segments Operating Segments [Member] Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Current portion of long-term debt Long-Term Debt, Current Maturities Company Selected Measure Amount Company Selected Measure Amount Award Timing MNPI Considered Award Timing MNPI Considered [Flag] Service-based restricted stock awards Service-Based Restricted Stock Awards [Member] Service-Based Restricted Stock Awards Comprehensive income Comprehensive Income (Loss), Net of Tax, Attributable to Parent 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 Name Measure Name Deferred income taxes Deferred Income Tax Liabilities, Net Document Fiscal Period Focus Document Fiscal Period Focus Rate of compensation increase Defined Benefit Plan, Rate Of Compensation Increase Defined Benefit Plan, Rate Of Compensation Increase Tax receivable and payable, and other accrued taxes Increase (Decrease) in Accrued Taxes Payable Award Timing Method Award Timing Method [Text Block] Litigation Case [Domain] Litigation Case [Domain] Award Type [Axis] Award Type [Axis] Advances for construction Contract with Customer, Liability, Noncurrent Total production expenses Production expenses Water Production Costs Total assets Assets Assets Income tax temporary differences Future income tax benefits due to customers Deferred Income Tax Charge [Member] Trading Symbol Trading Symbol Regulatory Liability [Axis] Regulatory Liability [Axis] Issuance of restricted and deferred stock units (in shares) Shares Issued, Shares, Share-Based Payment Arrangement, after Forfeiture Entity Address, City or Town Entity Address, City or Town Operating activities: Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract] Total utility plant Public Utilities, Property, Plant and Equipment, Plant in Service Other Segment Reporting, Other Segment Item, Amount Non-PEO NEO Average Compensation Actually Paid Amount Non-PEO NEO Average Compensation Actually Paid Amount Restricted Stock Units (RSUs) Restricted Stock Units (RSUs) [Member] Customer Assistance Program ("CAP") balancing account Customer Assistance Program Balancing Account [Member] Customer Assistance Program Balancing Account Compensation Actually Paid vs. Other Measure Compensation Actually Paid vs. Other Measure [Text Block] Entity Emerging Growth Company Entity Emerging Growth Company Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Postretirement benefits Increase (Decrease) in Obligation, Pension and Other Postretirement Benefits Repayments of lines of credit Repayments of Lines of Credit 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] Fair Value, Inputs, Level 2 Fair Value, Inputs, Level 2 [Member] Schedule of Regulatory Assets, Net Schedule of Regulatory Assets [Table Text Block] Insider Trading Policies and Procedures Not Adopted Insider Trading Policies and Procedures Not Adopted [Text Block] Common stock, shares outstanding (in shares) Beginning balance (in shares) Ending balance (in shares) Common Stock, Shares, Outstanding Regulatory Matters Schedule of Regulatory Assets and Liabilities [Text Block] Utility property installed by developers Utility Property Installed By Developer Utility Property Installed By Developer Plan Name [Axis] Plan Name [Axis] PEO PEO [Member] Schedule of Revenue Components Disaggregation of Revenue [Table Text Block] Purchase option period Sale Of Stock, Purchase Option Period Sale Of Stock, Purchase Option Period SJWC SJWC [Member] SJWC Postretirement benefit plans Assets for Plan Benefits, Defined Benefit Plan Changes in operating assets and liabilities, net of acquired assets and liabilities Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Increase (Decrease) in Operating Capital [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] Total operating expense Utilities Operating Expense Retained Earnings Retained Earnings [Member] Entity Address, Postal Zip Code Entity Address, Postal Zip Code Restatement Determination Date Restatement Determination Date Share-based Payment Arrangement [Abstract] Share-Based Payment Arrangement [Abstract] Cash and cash equivalents, beginning of period Cash and cash equivalents, end of period Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Income Statement [Abstract] Income Statement [Abstract] Provision for income taxes Income tax expense Provision (benefit) for income taxes Income Tax Expense (Benefit) 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. Sale of Stock [Domain] Sale of Stock [Domain] Balancing and memorandum revenue account, refunds (collections) Balancing And Memorandum Revenue Account, Refunds (Collections) Balancing And Memorandum Revenue Account, Refunds (Collections) Pension Adjustments Service Cost Pension Adjustments Service Cost [Member] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Nonutility properties Subtotal Property, Plant and Equipment, Gross Monterey Water Revenue Adjustment Mechanism (“MWRAM”) Monterey Water Revenue Adjustment Mechanism (MWRAM) [Member] Monterey Water Revenue Adjustment Mechanism (MWRAM) Restatement does not require Recovery Restatement Does Not Require Recovery [Text Block] Business Combination [Table] Business Combination [Table] Employer plan contributions Defined Contribution Plan, Employer Discretionary Contribution Amount Compensation Actually Paid vs. Company Selected Measure Compensation Actually Paid vs. Company Selected Measure [Text Block] City Area Code City Area Code Award Timing, How MNPI Considered Award Timing, How MNPI Considered [Text Block] All Trading Arrangements All Trading Arrangements [Member] Equity Awards Adjustments, Footnote Equity Awards Adjustments, Footnote [Text Block] Total Shareholder Return Vs Peer Group Total Shareholder Return Vs Peer Group [Text Block] Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Investing activities: Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract] Administrative and general Administrative and general General and Administrative Expense Pay vs Performance Disclosure Pay vs Performance Disclosure [Table] Underwritten Offering Underwritten Offering [Member] Underwritten Offering Net cash provided by operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation Market-based restricted stock awards Market-Based Restricted Stock Awards [Member] Market-Based Restricted Stock Awards Subsequent Event Subsequent Event [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 Goodwill Goodwill Equity Valuation Assumption Difference, Footnote Equity Valuation Assumption Difference, Footnote [Text Block] PEO Total Compensation Amount PEO Total Compensation Amount Long-term Debt, Type [Axis] Long-Term Debt, Type [Axis] Equity Components [Axis] Equity Components [Axis] Non-Rule 10b5-1 Arrangement Adopted Non-Rule 10b5-1 Arrangement Adopted [Flag] Water Utility Services Water Utility Services [Member] Water Utility Services Number of reportable segments Number of Reportable Segments Construction work in progress Public Utilities, Property, Plant and Equipment, Construction Work in Progress Cash paid (refunded) during the period for: Supplemental Cash Flow Information [Abstract] Other Performance Measure, Amount Other Performance Measure, Amount Regulatory liabilities, less current portion Total regulatory liabilities, less current portion Regulatory Liability, Noncurrent Entity Address, State or Province Entity Address, State or Province Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Antidilutive Security, Excluded EPS Calculation [Table] Fair Value Measurement Fair Value Measurement, Policy [Policy Text Block] Dividends paid Dividends Total current liabilities Liabilities, Current Over-Allotment Option Over-Allotment Option [Member] Total equity distribution Sale Of Stock, Total Equity Distribution Agreement Remaining Sale Of Stock, Total Equity Distribution Agreement Remaining Individual: Individual [Axis] Vesting [Axis] Vesting [Axis] Dividends paid Payments of Ordinary Dividends, Common Stock Other current assets Other Assets, Current Additional paid-in capital Additional Paid in Capital, Common Stock Net cash used in investing activities Cash Provided by (Used in) Investing Activity, Including Discontinued Operation 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] Interest, net of amounts capitalized Interest Paid, Excluding Capitalized Interest, Operating Activity Document Fiscal Year Focus Document Fiscal Year Focus Basis of Accounting Basis of Accounting, Policy [Policy Text Block] CWC CWC [Member] CWC Equity Plans Shareholders' Equity and Share-Based Payments [Text Block] Forgone Recovery, Explanation of Impracticability Forgone Recovery, Explanation of Impracticability [Text Block] Repayments of long-term borrowings Repayments of Long-Term Debt Effective consolidated income tax rate Effective Income Tax Rate Reconciliation, Percent Entity Interactive Data Current Entity Interactive Data Current Plan Name [Domain] Plan Name [Domain] Recognition period for unrecognized compensation cost Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition Equity [Abstract] Less: Segment Reconciliation [Abstract] Segment Reporting Segment Reporting Disclosure [Text Block] Fair value of plan assets Defined Benefit Plan, Plan Assets, Amount Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Schedule of Net Benefit Costs Schedule of Net Benefit Costs [Table Text Block] Compensation Actually Paid vs. Total Shareholder Return Compensation Actually Paid vs. Total Shareholder Return [Text Block] Depreciation and amortization Depreciation, Depletion and Amortization Total other assets Other Assets, Noncurrent Accrued interest Interest Payable, Current Entity Central Index Key Entity Central Index Key PEO Name PEO Name Operating revenue Operating revenue Operating revenue Revenues Net proceeds from stock offering Sale of Stock, Consideration Received on Transaction 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] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Outstanding Aggregate Erroneous Compensation Amount Outstanding Aggregate Erroneous Compensation Amount Revolving Credit Facility Revolving Credit Facility [Member] Schedule of Defined Benefit Plans Disclosures [Table] Defined Benefit Plan [Table] Arrangement Duration Trading Arrangement Duration Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Tranche One Share-Based Payment Arrangement, Tranche One [Member] Business Segments [Axis] Segments [Axis] Exercise Price Award Exercise Price Entity Filer Category Entity Filer Category Class of Stock [Domain] Class of Stock [Domain] Local Phone Number Local Phone Number Capitalization: Capitalization, Long-Term Debt and Equity [Abstract] Additional 402(v) Disclosure Additional 402(v) Disclosure [Text Block] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Purchased water Cost of Purchased Water Assets Assets [Abstract] Long-term debt, less current portion Long-Term Debt, Excluding Current Maturities Credit Facility [Axis] Credit Facility [Axis] Underlying Security Market Price Change Underlying Security Market Price Change, Percent Vesting [Domain] Vesting [Domain] Benefit Plans Retirement Benefits [Text Block] Business Combination [Line Items] Business Combination [Line Items] Credit Facility [Domain] Credit Facility [Domain] Buildings and improvements Investment Building and Building Improvements Intangible assets Finite-Lived Intangible Assets, Gross 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] Target vesting percentage Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Rights, Percentage Entity Address, Address Line One Entity Address, Address Line One Allowance for equity funds used during construction Public Utilities, Allowance for Funds Used During Construction, Additions Accumulated Other Comprehensive Income AOCI Attributable to Parent [Member] Allowance for uncollectible accounts Accounts Receivable, Allowance for Credit Loss, Current Business Combination, Asset Acquisition, Transaction between Entities under Common Control, and Joint Venture Formation [Abstract] Company-funded Payments To Acquire Water Systems Using Company Funds Payments To Acquire Water Systems Using Company Funds Amortization of prior service cost Defined Benefit Plan, Amortization of Prior Service Cost (Credit) Other production expenses Utilities Operating Expense, Other Land Land Fair Value as of Grant Date Award Grant Date Fair Value Entity Registrant Name Entity Registrant Name Stock Price or TSR Estimation Method Stock Price or TSR Estimation Method [Text Block] Total Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Number of equity instruments granted (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period Title of Individual [Domain] Title and Position [Domain] Unrecognized compensation costs Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount Regulated Operations [Abstract] Regulated Operations [Abstract] Aggregate gross sales price (up to) Sale Of Stock, Aggregate Gross Sales Price Sale Of Stock, Aggregate Gross Sales Price Document Quarterly Report Document Quarterly Report Stock issuance costs recognized as a reduction of additional paid-in capital Adjustments to Additional Paid in Capital, Stock Issued, Issuance Costs Long-term debt, fair value Long-Term Debt, Fair Value Changed Peer Group, Footnote Changed Peer Group, Footnote [Text Block] Adjustment To PEO Compensation, Footnote Adjustment To PEO Compensation, Footnote [Text Block] Other Services Segment Reporting, Reconciling Item, Excluding Corporate Nonsegment [Member] 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 Interest cost Defined Benefit Plan, Interest Cost Investments Investments Title Trading Arrangement, Individual Title Peer Group Total Shareholder Return Amount Peer Group Total Shareholder Return Amount Restatement Determination Date: Restatement Determination Date [Axis] 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 Issuance of restricted and deferred stock units Shares Issued, Value, Share-Based Payment Arrangement, after Forfeiture Production expenses: Water Production Costs [Abstract] Water Production Costs [Abstract] Non-PEO NEO Non-PEO NEO [Member] Employee stock purchase plan Stock Issued During Period, Value, Employee Stock Purchase Plan Other changes, net Proceeds from (Payment for) Other Financing Activity Interest on long-term debt and other interest expense Interest on long-term debt and other interest expense Interest Expense, Debt Sale of Stock [Axis] Sale of Stock [Axis] Groundwater extraction charges Groundwater Extraction Charges Groundwater Extraction Charges Regulatory Asset [Axis] Regulatory Asset [Axis] Name Trading Arrangement, Individual Name 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 Award Type [Domain] Award Type [Domain] Equity Awards Adjustments Equity Awards Adjustments [Member] Pension Benefits Adjustments, Footnote Pension Benefits Adjustments, Footnote [Text Block] Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] Compensation Amount Outstanding Recovery Compensation Amount Recovery of Erroneously Awarded Compensation Disclosure [Line Items] Retirement Plan Type [Domain] Retirement Plan Type [Domain] MNPI Disclosure Timed for Compensation Value MNPI Disclosure Timed for Compensation Value [Flag] Name Awards Close in Time to MNPI Disclosures, Individual Name Quadvest Wholesale Asset Purchase Agreement Quadvest Wholesale Asset Purchase Agreement [Member] Quadvest Wholesale Asset Purchase Agreement 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 Aggregate Erroneous Compensation Not Yet Determined Aggregate Erroneous Compensation Not Yet Determined [Text Block] Regulatory assets, less current portion Total regulatory assets, less current portion Regulatory Asset, Noncurrent Restricted stock and deferred restricted stock Restricted Stock And Deferred Restricted Stock [Member] Restricted Stock and Deferred Restricted Stock [Member] Stock-based compensation APIC, Share-Based Payment Arrangement, Increase for Cost Recognition Accumulated other comprehensive income Accumulated Other Comprehensive Income (Loss), Net of Tax Litigation Case [Axis] Litigation Case [Axis] Accrued unbilled revenue Receivables, Long-Term Contracts or Programs Segment [Domain] Segments [Domain] Performance-based restricted stock awards Performance Shares [Member] Unused portion of line of credit Line of Credit Facility, Remaining Borrowing Capacity Aggregate Pension Adjustments Service Cost Aggregate Pension Adjustments Service Cost [Member] Fair Value, Measurements, Fair Value Hierarchy [Domain] Fair Value Hierarchy and NAV [Domain] Cost of removal Cost of Removal [Member] Cost of Removal Lines of credit Line of Credit, Current At The Market Offering At The Market Offering [Member] At The Market Offering Schedule of Recently Issued Accounting Standards Accounting Standards Update and Change in Accounting Principle [Table Text Block] Minimum Minimum [Member] Earnings per Share Earnings Per Share, Policy [Policy Text Block] Less: accumulated depreciation and amortization Less: accumulated depreciation and amortization Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Shares issuable under the plan upon exercise of outstanding awards (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Shares Issuable Upon Vesting Share-based Compensation Arrangement by Share-based Payment Award, Shares Issuable Upon Vesting Company Selected Measure Name Company Selected Measure Name Quadvest, L.P. Asset Purchase Agreement Quadvest Retail Asset Purchase Agreement [Member] Quadvest Retail Asset Purchase Agreement Revenue Revenue [Policy Text Block] Lines of Credit and Long-Term Liabilities Debt Disclosure [Text Block] Aggregate Available Trading Arrangement, Securities Aggregate Available Amount Accounts payable Accounts Payable, Current Stock Appreciation Rights (SARs) Stock Appreciation Rights (SARs) [Member] All Executive Categories All Executive Categories [Member] Common stock, $0.001 par value; authorized 70,000,000 shares; issued and outstanding shares 41,839,540 on March 31, 2026 and 36,118,242 on December 31, 2025 Common Stock, Value, Issued Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Tranche Two Share-Based Payment Arrangement, Tranche Two [Member] Title of Individual [Axis] Title and Position [Axis] Schedule of Regulatory Assets [Table] Regulated Operation, Regulatory Asset [Table] Other assets: Other Assets, Noncurrent [Abstract] Diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Weighted-average interest rate on short-term Short-Term Debt, Weighted Average Interest Rate, at Point in Time Commitments and contingencies Commitments and Contingencies Non-GAAP Measure Description Non-GAAP Measure Description [Text Block] Entity Small Business Entity Small Business Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Supplemental Employee Retirement Plan Supplemental Employee Retirement Plan [Member] Document Transition Report Document Transition Report PFAS Litigation Settlement PFAS Litigation Settlement [Member] PFAS Litigation Settlement Underlying Securities Award Underlying Securities Amount Equity Component [Domain] Equity Component [Domain] Document Period End Date Document Period End Date PEO Actually Paid Compensation Amount PEO Actually Paid Compensation Amount Income Taxes Income Tax Disclosure [Text Block] Borrowings from lines of credit Proceeds from Lines of Credit Awards Close in Time to MNPI Disclosures, Table Awards Close in Time to MNPI Disclosures [Table Text Block] Other Other Regulatory Liabilities [Member] Other Regulatory Liabilities Document Type Document Type Total number of outstanding (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Non-Option Equity Instruments, Outstanding, Number Fair Value, Inputs, Level 3 Fair Value, Inputs, Level 3 [Member] Name Outstanding Recovery, Individual Name Loss Contingencies [Table] Loss Contingencies [Table] Power Utilities Operating Expense, Purchased Power Asset Acquisition [Domain] Asset Acquisition [Domain] Issuance of common stock, net of issuance costs Proceeds from Issuance of Common Stock Revenue from contracts with customers Revenue from Contract with Customer, Excluding Assessed Tax Refunds of advances for construction Repayments Of Advances For Construction, Financing Activities Repayments Of Advances For Construction, Financing Activities All Individuals All Individuals [Member] Long-term Debt, Type [Domain] Long-Term Debt, Type [Domain] Less: accumulated depreciation and amortization Public Utilities, Property, Plant and Equipment, Accumulated Depreciation Accounts receivable and accrued unbilled utility revenue Increase (Decrease) in Receivables Asset acquisition, consideration transferred Asset Acquisition, Consideration Transferred Name Forgone Recovery, Individual Name Property taxes and other non-income taxes Property taxes and other non-income taxes Utilities Operating Expense, Taxes Total current assets Assets, Current Statistical Measurement [Axis] Statistical Measurement [Axis] 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] ESPP proceeds Proceeds, Issuance of Shares, Share-Based Payment Arrangement, Including Option Exercised Regulatory Asset [Domain] Regulatory Asset [Domain] Aggregate Erroneous Compensation Amount Aggregate Erroneous Compensation Amount Peer Group Issuers, Footnote Peer Group Issuers, Footnote [Text Block] Number of shares vested but not issued (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 Current regulatory assets Less: current regulatory assets Regulatory Asset, Current Erroneous Compensation Analysis Erroneous Compensation Analysis [Text Block] Current liabilities: Liabilities, Current [Abstract] Other changes, net Increase (Decrease) in Other Operating Assets and Liabilities, Net Rule 10b5-1 Arrangement Terminated Rule 10b5-1 Arrangement Terminated [Flag] Fair Value, Inputs, Level 1 Fair Value, Inputs, Level 1 [Member] Per- and Polyfluoroalkyl substances legal settlement proceeds Per- And Polyfluoroalkyl Substances Legal Settlement Proceeds [Member] Per- And Polyfluoroalkyl Substances Legal Settlement Proceeds Diluted (in usd per share) Earnings Per Share, Diluted Erroneously Awarded Compensation Recovery Erroneously Awarded Compensation Recovery [Table] Customers, net of allowances for credit losses of $748 and $722 on March 31, 2026 and December 31, 2025, respectively Accounts Receivable, after Allowance for Credit Loss, Current Title of 12(b) Security Title of 12(b) Security Supplemental disclosure of non-cash activities: Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Other Other Regulatory Assets [Member] Other Regulatory Assets [Member] Number of shares issued (in shares) Sale of Stock, Number of Shares Issued in Transaction Unrecognized pensions and other postretirement benefits Unrecognized Pensions and Other Postretirement Benefits [Member] Unrecognized Pensions and Other Postretirement Benefits Earnings per share Earnings Per Share [Abstract] Consolidation Items [Domain] Consolidation Items [Domain] Variable Interest Entity, Not Primary Beneficiary Variable Interest Entity, Not Primary Beneficiary [Member] Revenue adjustment mechanisms Revenue Adjustment Mechanisms [Member] Revenue adjustment mechanisms Public Utilities General Disclosures [Table] Public Utilities General Disclosures [Table] Amortization of actuarial gain Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) Regulatory Liability [Domain] Regulatory Liability [Domain] Utility plant: Public Utilities, Property, Plant and Equipment, Net [Abstract] Employee Stock Purchase Plan Employee Stock Purchase Plan [Member] Employee Stock Purchase Plan [Member] Weighted average shares outstanding Weighted Average Number of Shares Outstanding, Diluted, Adjustment [Abstract] Income taxes Income Taxes Paid, Net Award Timing Disclosures [Line Items] Service cost Defined Benefit Plan, Service Cost Accrued payroll Employee-related Liabilities, Current Capitalization Equity [Text Block] MWC MWC [Member] MWC Net income (loss) Net income Net Income (Loss) Attributable to Parent Subsequent Event [Table] Subsequent Event [Table] Expiration Date Trading Arrangement Expiration Date Net utility plant Public Utilities, Property, Plant and Equipment, Net Variable interest entity, ownership percentage Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage Service-based restricted stock vesting period Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period Forward Purchase Agreements Forward Purchase Agreements [Member] Forward Purchase Agreements Net nonutility properties Property, Plant and Equipment, Net Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Adoption Date Trading Arrangement Adoption Date Compensation Actually Paid vs. Net Income Compensation Actually Paid vs. Net Income [Text Block] Entity Current Reporting Status Entity Current Reporting Status Awards Close in Time to MNPI Disclosures Awards Close in Time to MNPI Disclosures [Table] Operating income Operating Income (Loss) Line of Credit Line of Credit [Member] Consolidated Entities [Domain] Consolidated Entities [Domain] Retained earnings Retained Earnings (Accumulated Deficit) Schedule of Compensation Costs Charged to Income and Proceeds from the ESPP, by Award Type Share-Based Payment Arrangement, Cost by Plan [Table Text Block] Statement of Financial Position [Abstract] Statement of Financial Position [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] Executive Category: Executive Category [Axis] Class of Stock [Axis] Class of Stock [Axis] Long-term borrowings Proceeds from Issuance of Long-Term Debt Current Fiscal Year End Date Current Fiscal Year End Date Business combinations debt premium Business Combinations Debt Premium [Member] Business Combinations Debt Premium Subsequent Event Type [Domain] Subsequent Event Type [Domain] 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] Retirement Plan Type [Axis] Retirement Plan Type [Axis] Remaining shares available for issuance (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant Statement [Table] Statement [Table] Other, net Other Nonoperating Income (Expense) Deferred income taxes Deferred Income Tax Expense (Benefit) Adjustments to reconcile net income to net cash provided by operating activities: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity [Abstract] Regulatory assets: Net Regulatory Assets [Abstract] Financing activities: Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract] Equity Awards Adjustments, Excluding Value Reported in Compensation Table Equity Awards Adjustments, Excluding Value Reported in the Compensation Table [Member] Water supply costs Water Supply Costs [Member] Water Supply Costs Unrecognized tax benefits Unrecognized Tax Benefits 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 All Adjustments to Compensation All Adjustments to Compensation [Member] Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Amendment Flag Amendment Flag Sale of stock (in usd per share) Sale of Stock, Price Per Share Other Benefits Other Postretirement Benefits Plan [Member] Termination Date Trading Arrangement Termination Date Net cash provided by financing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation Maintenance Maintenance Utilities Operating Expense, Maintenance Insider Trading Policies and Procedures Adopted Insider Trading Policies and Procedures Adopted [Flag] Measure: Measure [Axis] Other noncurrent assets and noncurrent liabilities Increase (Decrease) in Other Noncurrent Assets and Liabilities Increase (Decrease) in Other Noncurrent Assets and Liabilities Estimated service lives of assets Public Utilities, Property, Plant and Equipment, Common, Useful Life Tranche Three Share-Based Payment Arrangement, Tranche Three [Member] Receivable period for noncurrent cash proceeds receivable form legal settlement Loss Contingency, Receivable, Noncurrent Period Loss Contingency, Receivable, Noncurrent Period Regulatory liabilities: Net Regulatory Liabilities [Abstract] Net Regulatory Liabilities Basic (in shares) Weighted Average Number of Shares Outstanding, Basic Asset acquisition, number of appraisers Asset Acquisition, Number Of Appraisers Asset Acquisition, Number Of Appraisers Subsequent Events [Abstract] Segment Reporting [Abstract] Segment Reporting [Abstract] Pay vs Performance Disclosure, Table Pay vs Performance [Table Text Block] Debt Disclosure [Abstract] Forgone Recovery due to Violation of Home Country Law, Amount Forgone Recovery due to Violation of Home Country Law, Amount Public Utilities, General Disclosures [Line Items] Public Utilities, General Disclosures [Line Items] Entity Tax Identification Number Entity Tax Identification Number Operating expense: Costs and Expenses [Abstract] Asset Acquisition [Axis] Asset Acquisition [Axis] Interest Interest Paid, Including Capitalized Interest, Operating and Investing Activities Forgone Recovery due to Expense of Enforcement, Amount Forgone Recovery due to Expense of Enforcement, Amount Accrued groundwater extraction charges, purchased water and power Accrued Groundwater Extraction Charges, Purchased Water And Power Accrued Groundwater Extraction Charges, Purchased Water And Power Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items] Consolidated Entities [Axis] Consolidated Entities [Axis] Common stock, par value (in usd per share) Common Stock, Par or Stated Value Per Share Common stock, shares issued (in shares) Common Stock, Shares, Issued Income tax Income Taxes Receivable, Current Total regulatory liabilities Regulatory Liability Cost to retire utility plant, net of salvage Payments for (Proceeds from) Removal Costs Proceeds from legal settlements Proceeds from Legal Settlements Total regulatory assets Regulatory Asset Trading Arrangement: Trading Arrangement [Axis] Total Shareholder Return Amount Total Shareholder Return Amount Rental income Operating Lease, Lease Income Loss Contingencies [Line Items] Loss Contingencies [Line Items] Subsequent Events Subsequent Events [Text Block] Insider Trading Arrangements [Line Items] Unallocated Corporate Segment Reporting, Reconciling Item, Corporate Nonsegment [Member] Security Exchange Name Security Exchange Name Accounts receivable: Accounts Receivable, after Allowance for Credit Loss, Current [Abstract] Settlement payable to contract operators Settlement Liabilities, Current Accrued payables for additions to utility plant Capital Expenditures Incurred but Not yet Paid Contributions in aid of construction Contributions in Aid of Construction Pension Adjustments Prior Service Cost Pension Adjustments Prior Service Cost [Member] Prepaid expenses Prepaid Expense, Current Material Terms of Trading Arrangement Material Terms of Trading Arrangement [Text Block] Other current liabilities Other Liabilities, Current Postretirement benefit plans Liability, Defined Benefit Plan, Noncurrent 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 Common stock issuance, net of costs Stock Issued During Period, Value, New Issues Statement [Line Items] Statement [Line Items] Consolidation Items [Axis] Consolidation Items [Axis] Rule 10b5-1 Arrangement Adopted Rule 10b5-1 Arrangement Adopted [Flag] Cash and cash equivalents Cash and Cash Equivalent Subsequent Event [Line Items] Subsequent Event [Line Items] Common Stock Common Stock [Member] Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Non-NEOs Non-NEOs [Member] Subsidiary, Sale of Stock [Line Items] Subsidiary, Sale of Stock [Line Items] Net change in cash and cash equivalents Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation Alternative revenue programs, net Alternative Revenue Programs, Net Alternative Revenue Programs, Net