Pension Liability, Other Postretirement Defined Benefit Plan, Noncurrent Supplemental information: Supplemental Cash Flow Information [Abstract] Recognized net actuarial loss Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) Debt issued Debt Instrument, Face Amount Vested (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Net income (loss) attributable to California Water Service Group Net Income (Loss) Attributable to Parent Consolidated Entities [Axis] Consolidated Entities [Axis] Net periodic benefit cost Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Other accrued benefits Other Accrued Benefits [Member] Represents the other accrued benefits not otherwise specified in the taxonomy. Short-term borrowings Proceeds from Short-term Debt Interest cost Defined Benefit Plan, Interest Cost Receivables: Receivables, Net, Current [Abstract] Statistical Measurement [Domain] Statistical Measurement [Domain] Receivable Type [Axis] Receivable Type [Axis] Retained earnings Retained Earnings (Accumulated Deficit) Schedule of Defined Benefit Plans Disclosures [Table] Schedule of Defined Benefit Plans Disclosures [Table] Performance period Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period RSUs Restricted Stock Units (RSUs) [Member] Maintenance Utilities Operating Expense, Maintenance Operating revenue Regulated Operating Revenue, Water Entity Filer Category Entity Filer Category Dividends paid on common stock Dividends, Common Stock, Cash Contributions in aid of construction Contributions in Aid of Construction Security Exchange Name Security Exchange Name Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Forfeited (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Residential Residential [Member] Residential [Member] Advances and contributions in aid of construction Proceeds From Contribution In Aid Of Construction, Financing Activities Proceeds From Contribution In Aid Of Construction, Financing Activities Income Statement [Abstract] Income Statement [Abstract] Additional paid-in capital Additional Paid in Capital, Common Stock Fair Value Estimate of Fair Value Measurement [Member] Entity Registrant Name Entity Registrant Name Allowance for borrowed funds used during construction Interest Costs Capitalized Adjustment Other assets Other Assets, Noncurrent Components of the pension plans and other postretirement benefits Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] Utility plant contribution by developers Noncash or Part Noncash Acquisition, Fixed Assets Acquired Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Expected return on plan assets Defined Benefit Plan, Expected Return (Loss) on Plan Assets Retirement Benefits [Abstract] Retirement Benefits [Abstract] Change in cash, cash equivalents, and restricted cash Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Entity File Number Entity File Number Retiree group health Postretirement Health Coverage [Member] Income tax (benefit) expense Income Tax Expense (Benefit) Total equity Balance at beginning of period Balance at end of period Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Customers, net Accounts Receivable, after Allowance for Credit Loss, Current Amendment Flag Amendment Flag Other regulatory liabilities Other Regulatory Assets (Liabilities) [Member] Series ZZZ Mortgage Bonds Series ZZZ Mortgage Bonds [Member] Series ZZZ Mortgage Bonds Equity Components [Axis] Equity Components [Axis] Entity Tax Identification Number Entity Tax Identification Number Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Document Fiscal Period Focus Document Fiscal Period Focus Total current assets Assets, Current Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Forfeited (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Other components of net periodic benefit cost Postretirement Benefit Costs [Member] Amortization of prior service cost Defined Benefit Plan, Amortization and Deferral of Gains (Losses) Defined Benefit Plan, Amortization and Deferral of Gains (Losses) Schedule of Stock by Class [Table] Schedule of Stock by Class [Table] Schedule of changes in total common stockholders' equity Schedule of Stockholders Equity [Table Text Block] Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Repurchase of common stock Stock Repurchased During Period, Value Fair Value of Financial Assets and Liabilities Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Current maturities of long-term debt, net Long-term Debt, Current Maturities Product and Service [Axis] Product and Service [Axis] CEBA Conservation Program Liability [Member] Discloses the amount of regulatory liability arising from the difference between conservation program liability, according to US GAAP, and the amount of conservation program liability considered for rate-making purposes, according the actions of the regulator. Accounts Receivable, Allowance for Credit Loss [Roll Forward] Accounts Receivable, Allowance for Credit Loss [Roll Forward] Schedule of Cash and Cash Equivalents Schedule of Cash and Cash Equivalents [Table Text Block] Other non-regulated revenue Other Non-Regulated Service [Member] Other Non-Regulated Service [Member] Unrecognized compensation cost Share-based Payment Arrangement, Nonvested Award, Excluding Option, Cost Not yet Recognized, Amount Public authorities Public Authorities [Member] Public Authorities [Member] Business Business [Member] Business [Member] 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 Equity Component [Domain] Equity Component [Domain] Title of Individual [Domain] Title of Individual [Domain] Repurchase of common stock (in shares) Stock Repurchased During Period, Shares Award Type [Domain] Award Type [Domain] Local Phone Number Local Phone Number Credit Facility [Domain] Credit Facility [Domain] ASSETS Assets [Abstract] Other current liabilities Increase (Decrease) in Other Current Liabilities Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Investment in business with noncontrolling interest Noncontrolling Interest, Increase From Investment In Business Noncontrolling Interest, Increase From Investment In Business Other components of net periodic benefit credit Defined Benefit Plan, Other Cost (Credit) Retirement Plan Type [Domain] Retirement Plan Type [Domain] Industrial Industrial [Member] Industrial [Member] Retained Earnings Retained Earnings [Member] Debt Instrument [Axis] Debt Instrument [Axis] March 31, 2022 Trade Accounts Receivable [Member] Debt Disclosure [Abstract] Debt Disclosure [Abstract] Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Level 2 Fair Value, Inputs, Level 2 [Member] Net utility plant Public Utilities, Property, Plant and Equipment, Net PCBA Pension Balancing Account [Member] Pension Balancing Account [Member] Secured Debt Secured Debt [Member] Income tax benefit Utilities Operating Expense (Income) Tax Expense (Benefit) The sum of the current income tax expense or benefit and the deferred income tax expense or benefit included in operating expense of a utility. Accrued payables for investments in utility plant Capital Expenditures Incurred but Not yet Paid Pension Plan and Other Postretirement Benefits Retirement Benefits [Text Block] Schedule basic and Diluted Earnings Per Share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Title of 12(b) Security Title of 12(b) Security Other current assets Increase (Decrease) in Other Current Assets Issuance of common stock Proceeds from Issuance of Common Stock TOTAL ASSETS Assets Director Director [Member] Repayment of short-term borrowings Repayments of Short-term Debt Income tax expense on other income and expenses Utilities Nonregulated Expense, Income Tax Expense (Benefit) The sum of the current income tax expense or benefit and the deferred income tax expense or benefit included in other income and expenses of a utility. Common stock, shares authorized (in shares) Common Stock, Shares Authorized General district balancing account receivable General District Balance Account Receivable [Member] General District Balance Account Receivable Basic (in dollars per share) Earnings (loss) per share of common stock - basic (in dollars per share) Earnings Per Share, Basic Cash paid for interest (net of amounts capitalized) Interest Paid, Excluding Capitalized Interest, Operating Activities Incremental expansion of borrowing capacity Line of Credit Facility, Incremental Expansion of Borrowing Capacity Line of Credit Facility, Incremental Expansion of Borrowing Capacity Title of Individual [Axis] Title of Individual [Axis] Unbilled revenue, net Receivables, Long-term Contracts or Programs Document Type Document Type Parent Company Parent Company [Member] Noncontrolling Interests Noncontrolling Interest [Member] Product and Service [Domain] Product and Service [Domain] Beginning balance (in shares) Ending balance (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Net loss attributable to noncontrolling interests Net Income (Loss) Attributable to Noncontrolling Interest Interest expense Interest Expense, Debt Disaggregation of Revenue Disaggregation of Revenue [Table Text Block] Stock-based Compensation Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Revolving Credit Facility Revolving Credit Facility [Member] Number of shares Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Fair Value Measurement [Domain] Fair Value Measurement [Domain] Summary of Significant Accounting Policies Significant Accounting Policies [Text Block] Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities Short-term borrowings Short-term Debt Fair Value, Recurring and Nonrecurring [Table] Fair Value, Recurring and Nonrecurring [Table] Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Shares authorized to be issued under the plan (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized Capitalization: Capitalization, Long-term Debt and Equity [Abstract] Recoveries Accounts Receivable, Allowance for Credit Loss, Recovery Accrued expenses and other liabilities Accrued Liabilities and Other Liabilities Regulatory balancing accounts Short-term portion of the regulatory assets Regulatory Assets, Current Basic (in shares) Weighted average common shares outstanding, basic (in shares) Weighted Average Number of Shares Outstanding, Basic Diluted (in dollars per share) Earnings (loss) per share of common stock - diluted (in dollars per share) Earnings Per Share, Diluted Regulatory Liability [Axis] Regulatory Liability [Axis] Service cost Defined Benefit Plan, Service Cost Provision for credit loss expense Accounts Receivable, Credit Loss Expense (Reversal) Return of investment Proceeds from Equity Method Investment, Distribution, Return of Capital Level 1 Fair Value, Inputs, Level 1 [Member] Investing activities: Net Cash Provided by (Used in) Investing Activities [Abstract] Performance-Based Restricted Stock Unit Awards (RSUs) Performance-Based Restricted Stock Unit Awards (RSUs) [Member] Performance-Based Restricted Stock Unit Awards (RSUs) [Member] Regulatory Liability [Domain] Regulatory Liability [Domain] Other regulatory assets Other Regulatory Assets [Member] Represents information pertaining to other regulatory assets. Net cash provided by financing activities Net Cash Provided by (Used in) Financing Activities Change in value of life insurance contracts Life Insurance, Corporate or Bank Owned, Change in Value Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Weighted average shares outstanding: Weighted Average Number of Shares Outstanding, Diluted [Abstract] Entity Small Business Entity Small Business HCBA Health Care Balancing Account [Member] Rate action of a regulator resulting in capitalization or accrual of costs for the health care balancing account. Deferred income taxes Deferred Income Tax Liabilities, Net Vesting period Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Tank coating Tank Coating [Member] Rate action of a regulator resulting in capitalization or accrual of costs for the tank coating. TOTAL CAPITALIZATION AND LIABILITIES Liabilities and Equity Asset acquisition Payments for Asset Acquisitions Payments for Asset Acquisitions Less accumulated depreciation and amortization Public Utilities, Property, Plant and Equipment, Accumulated Depreciation Share-based Payment Arrangement, Restricted Stock and Restricted Stock Unit, Activity Share-based Payment Arrangement, Restricted Stock and Restricted Stock Unit, Activity [Table Text Block] Fair Value of Financial Assets and Liabilities Fair Value Disclosures [Text Block] Regulatory liabilities and other Regulatory and Other Liabilities Aggregate carrying value as of the balance sheet date of regulatory current liability and other liabilities. Accounts payable Accounts Payable, Current Water Arrearages Payment Program Increase (Decrease) In Allowance For Credit Losses, Water Arrearages Payment Program Increase (Decrease) In Allowance For Credit Losses, Water Arrearages Payment Program Depreciation and amortization Depreciation, Depletion and Amortization Schedule of fair value of long-term debt, including current maturities and advances for construction Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] CAPITALIZATION AND LIABILITIES Liabilities and Equity [Abstract] Tax benefits that, if recognized, would affect the effective tax rate Unrecognized Tax Benefits that Would Impact Effective Tax Rate Accounts payable Increase (Decrease) in Accounts Payable Common stock, shares outstanding (in shares) Common Stock, Shares, Outstanding Earnings (Loss) Per Share of Common Stock Earnings Per Share [Text Block] Entity Interactive Data Current Entity Interactive Data Current Regulatory Asset [Domain] Regulatory Asset [Domain] Minimum Minimum [Member] Document Period End Date Document Period End Date Organization and Operations and Basis of Presentation Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Entity Central Index Key Entity Central Index Key Recoverable property losses Recoverable Property Losses [Member] Recoverable Property Losses [Member] Outstanding borrowings Long-term Line of Credit Consolidated Entities [Domain] Consolidated Entities [Domain] Net WRAM and MCBA long-term accounts receivable Accounts Receivable Net W R A M And M C B A Accounts Receivable [Member] Represents the net accounts receivable under Water Revenue Adjustment Mechanism (WRAM) and the Modified Cost Balancing Account (MCBA). Other Service, Other [Member] Unrecognized tax benefits Unrecognized Tax Benefits Operating expenses: Utilities Operating Expense [Abstract] Debt instrument, term Debt Instrument, Term Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Supplemental disclosure of non-cash activities: Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Non-regulated revenue Total non-regulated revenue Unregulated Operating Revenue Entity Address, State or Province Entity Address, State or Province Revenue Recognition, Leases Revenue Recognition, Leases [Policy Text Block] Other assets: Other Assets, Noncurrent [Abstract] Refunds of advances for construction Repayments of Advances for Construction Current liabilities: Liabilities, Current [Abstract] Total capitalization Capitalization, Long-term Debt and Equity Issuance of common stock Stock Issued During Period, Value, New Issues Receivable [Domain] Receivable [Domain] Non-Regulated Revenue Revenue [Policy Text Block] Administrative and general General and Administrative Expense Debt Instrument [Line Items] Debt Instrument [Line Items] Short-term and Long-term Borrowings Debt Disclosure [Text Block] Repayment of long-term debt Repayments of Long-term Debt Other operations Utilities Operating Expense, Other Trading Symbol Trading Symbol Earnings (loss) per share of common stock: Earnings per share: Earnings Per Share [Abstract] Schedule of Components of Income Tax Expense (Benefit) Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] Total other assets Total Other Assets Total noncurrent portion of other assets. Stock-based Compensation Share-based Payment Arrangement [Text Block] Level 3 Fair Value, Inputs, Level 3 [Member] Dividends paid Payments of Ordinary Dividends, Common Stock Beginning balance Total ending allowance balance Accounts Receivable, Allowance for Credit Loss Noncontrolling Interest [Table] Noncontrolling Interest [Table] Accounting Policies [Abstract] Accounting Policies [Abstract] Issuance of common stock (in shares) Stock Issued During Period, Shares, New Issues Number of reportable segments Number of Reportable Segments Allowance for equity funds used during construction Allowance for equity funds used during construction Public Utilities, Allowance for Funds Used During Construction, Additions Purchase of life insurance contracts Payment to Acquire Life Insurance Policy, Investing Activities Contingency loss recognized liability Loss Contingency Accrual Document Transition Report Document Transition Report Common stock, $0.01 par value; 68,000 shares authorized, 53,773 and 53,716 outstanding in 2022 and 2021, respectively Common Stock, Value, Issued Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Period for recognition Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition Beginning balance (in dollars per share) 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 Long-term debt, net Long-term Debt, Excluding Current Maturities Regulatory Assets and Liabilities Regulatory Assets and Liabilities [Line Items] Other Benefits Other Postretirement Benefits Plan [Member] Commitments and contingencies (Note 10) Commitments and Contingencies Recorded compensation costs for the RSAs and RSUs Share-based Payment Arrangement, Expense Entity Emerging Growth Company Entity Emerging Growth Company Entity Current Reporting Status Entity Current Reporting Status Weighted average price at grant Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Noncontrolling interest Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners Effective tax rate estimate Effective Income Tax Rate Reconciliation, Percent RSAs Restricted Stock [Member] Net income (loss) Net income (loss) Net income (loss) Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Operating and maintenance revenue Operating And Maintenance [Member] Represents the revenue and expense associated with operating and maintenance services provided for water and wastewater systems owned by private companies and municipalities. Restricted cash (included in "taxes, prepaid expenses and other assets") Restricted Cash, Current Ownership [Axis] Ownership [Axis] Regulatory assets Total Regulatory Assets Regulatory Assets, Noncurrent Other, net Nontrade Receivables, Current Legal Entity [Axis] Legal Entity [Axis] Cover [Abstract] Cover [Abstract] Cash, cash equivalents, and restricted cash at beginning of period Cash, cash equivalents, and restricted cash at end of period Total cash, cash equivalents, and restricted cash shown in the statements of cash flows Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Balance at the beginning of the period (in shares) Balance at the ending of the period (in shares) Shares, Issued Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Property and other taxes Utilities Operating Expense, Taxes Pension Plan and Other Postretirement Benefits Defined Benefit Plan Disclosure [Line Items] Taxes, prepaid expenses, and other assets Taxes, Prepaid Expenses and Other Assets, Current This element represents Taxes, prepaid expenses and other assets. Long-term debt, including current maturities, net Debt, Long-term and Short-term, Combined Amount Current assets: Assets, Current [Abstract] Net interest expense Interest Costs Incurred Cal Water Cal Water [Member] Represents California Water Company (Cal Water), a wholly-owned subsidiary of the Company. Entity Address, Postal Zip Code Entity Address, Postal Zip Code Risk premium (as a percent) Fair Value Inputs Risk Premium Represents the risk premium rate as an input to measure fair value. Noncontrolling Interest [Line Items] Noncontrolling Interest [Line Items] Diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Entity [Domain] Entity [Domain] Estimated cash contributions in the current fiscal year Defined Benefit Plan, Expected Future Employer Contributions, Current Fiscal Year Revenue from contracts with customers Revenue from Contract with Customer, Excluding Assessed Tax Interest expense: Interest Costs Incurred [Abstract] Income Taxes Income Tax Disclosure [Text Block] Accrued interest Interest Payable, Current Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Life insurance proceeds Proceeds from Life Insurance Policy Interest rate Debt Instrument, Basis Spread on Variable Rate Regulatory Assets and Liabilities Public Utilities Disclosure [Text Block] Equity Stockholders' Equity Note Disclosure [Text Block] Write-offs Accounts Receivable, Allowance for Credit Loss, Writeoff Schedule of components of net periodic benefit costs for the pension plans and other postretirement benefits Schedule of Net Benefit Costs [Table Text Block] Measurement Basis [Axis] Measurement Basis [Axis] Interim rates memorandum account (IRMA) long-term accounts receivable Interim Rates Long Term Accounts Receivable [Member] Represents the interim rates long term accounts receivable. Options vested on anniversary date Share Based Compensation Arrangement by Share-based Payment Award, Award Vesting Rate The rate of vesting of awards when they are no longer contingent on satisfaction of either a service condition, market condition or a performance condition, thereby giving the employee the legal right to convert the award to shares, to sell the shares, and be entitled to the cash proceeds of such sale. For example, vesting may be expressed as being 25 percent of the shares under option on each anniversary of the grant date. Other changes in noncurrent assets and liabilities Increase (Decrease) in Other Noncurrent Assets and Liabilities, Net Performance criteria adjustment (in shares) Share-based Compensation Arrangement By Share-based Payment Award, Equity Instruments Other Than Options, Performance Criteria Adjustment Share-based Compensation Arrangement By Share-based Payment Award, Equity Instruments Other Than Options, Performance Criteria Adjustment Regulatory balancing account revenue Revenue Not from Contract with Customer Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Cost Reported Value Measurement [Member] Equity [Abstract] Equity [Abstract] Document Quarterly Report Document Quarterly Report Officer Officer [Member] Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Materials and supplies at weighted average cost Public Utilities, Inventory Schedule of regulatory assets and liabilities Schedule of Regulatory Assets and Liabilities [Table Text Block] Tabular disclosure of detailed information about regulatory assets and liabilities. Schedule of Regulatory Assets and Liabilities [Table] Schedule of Regulatory Assets and Liabilities [Table] A table of assets and liabilities that are created when regulatory agencies permit public utilities to defer certain costs and revenues that are included in rate-setting to the balance sheet. Payment for investment Payments to Acquire Equity Method Investments Operations: Operating Costs and Expenses [Abstract] Class of Stock [Line Items] Class of Stock [Line Items] Credit Facility [Axis] Credit Facility [Axis] Common Stock Common Stock [Member] Entity Address, Address Line One Entity Address, Address Line One Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities Portion at fair value measurement Portion at Fair Value Measurement [Member] Changes in operating assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Other income and expenses: Other Nonoperating Income (Expense) [Abstract] Net operating income Operating Income (Loss) Allowance for Credit Losses Financing Receivable, Allowance for Credit Losses, Policy for Uncollectible Amounts [Policy Text Block] Operating activities: Net Cash Provided by (Used in) Operating Activities [Abstract] 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 Total Regulatory Liabilities Regulatory Liability, Noncurrent Entity Shell Company Entity Shell Company Regulatory Asset [Axis] Regulatory Asset [Axis] Non-regulated revenue from contracts with customers Non-Regulated Services [Member] Non-Regulated Services [Member] Depreciation and amortization Utilities Operating Expense, Depreciation and Amortization Total current liabilities Liabilities, Current Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Document Fiscal Year Focus Document Fiscal Year Focus Income tax expense increase (decrease) Effective Income Tax Rate Reconciliation, Increase (Decrease), Amount Effective Income Tax Rate Reconciliation, Increase (Decrease), Amount Additional Paid-in Capital Additional Paid-in Capital [Member] Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Series 1 Mortgage Bonds Series 1 Mortgage Bonds [Member] Series 1 Mortgage Bonds Maximum borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Dividends paid on common stock (in dollars per share) Common Stock, Dividends, Per Share, Cash Paid Utility plant: Public Utilities, Property, Plant and Equipment, Net [Abstract] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Ownership [Domain] Ownership [Domain] Current Fiscal Year End Date Current Fiscal Year End Date Water production costs Utilities Operating Expense, Products and Services Recovery Period Regulatory Asset, Amortization Period Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Utility plant expenditures Payments to Acquire Water and Waste Water Systems Regulatory balancing accounts Short-term portion of the regulatory liabilities Regulatory Liability, Current Net other income Other Nonoperating Income (Expense) Customer assistance program (CAP) and Rate support fund (RSF) accounts receivable Low-income Rate Assistance And Rate Support Fund Accounts Receivable [Member] Low-income Rate Assistance And Rate Support Fund Accounts Receivable Adoption of New Accounting Standards New Accounting Pronouncements, Policy [Policy Text Block] Employer cash contributions Defined Benefit Plan, Plan Assets, Contributions by Employer Maximum Maximum [Member] Advances for construction Contract with Customer, Refund Liability, Noncurrent Share-based Payment Arrangement [Abstract] Share-based Payment Arrangement [Abstract] Statistical Measurement [Axis] Statistical Measurement [Axis] Property-related temporary differences (tax benefits flowed through to customers) Future tax benefits due to customers Deferred Income Tax Charge [Member] Receivables and unbilled revenue Increase (Decrease) in Receivables Award Type [Axis] Award Type [Axis] Financing activities: Net Cash Provided by (Used in) Financing Activities [Abstract] Goodwill Goodwill Revenue Revenue Recognition for Alternative Revenue Programs, Policy [Policy Text Block] Noncontrolling interests Stockholders' Equity Attributable to Noncontrolling Interest Asset retirement obligations, net Asset Retirement Obligation Costs [Member] BVRT Water Company BVRT Water Company [Member] BVRT Water Company City Area Code City Area Code Performance criteria adjustment (in dollars per share) Share-based Compensation Arrangement By Share-based Payment Award, Equity Instruments Other Than Options, Performance Criteria Adjustment, Weighted Average Grant Date Fair Value Share-based Compensation Arrangement By Share-based Payment Award, Equity Instruments Other Than Options, Performance Criteria Adjustment, Weighted Average Grant Date Fair Value Non-regulated expenses Other Nonoperating Expense Adjustments to reconcile net income (loss) to net cash provided by operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Pension Plan Pension Plan [Member] Regulated Operations [Abstract] Regulated Operations [Abstract] Entity Address, City or Town Entity Address, City or Town Lease revenue Lease Income Pension and retiree group health Pension And Post Retirement Benefits [Member] Discloses the amount of regulatory asset arising from the difference between net periodic pension and postretirement benefit costs, according to US GAAP, and the amount considered for rate-making purposes, according the actions of the regulator. Financing Receivable, Allowance for Credit Loss Accounts Receivable, Allowance for Credit Loss [Table Text Block] Repurchase of common stock Payments for Repurchase of Common Stock Net WRAM and MCBA long-term payable Net WRAM and MCBA Long-term Payable [Member] Net WRAM and MCBA Long-term Payable [Member] Utility plant Public Utilities, Property, Plant and Equipment, Plant in Service Average borrowing rate Line of Credit Facility, Interest Rate During Period Retirement Plan Type [Axis] Retirement Plan Type [Axis] Total operating expenses Utilities Operating Expense