Document Type Document Type GOLDEN STATE WATER COMPANY Golden State Water Company Golden State Water Company [Member] Golden State Water Company [Member] Other, net Other Nonoperating Income (Expense) Contingencies Commitments and Contingencies Disclosure [Text Block] Business Segments [Axis] Segments [Axis] Segments [Axis] Regulatory assets — current Regulatory Assets, Current Employee Benefit Plans Retirement Benefits [Text Block] Regulatory asset-Wildfire mitigation Plans ( WMP) Regulatory asset-Wildfire mitigation Plans ( WMP) Regulatory asset-Wildfire mitigation Plans ( WMP) Schedule of Related Party Transactions, by Related Party [Table] Schedule of Restructuring and Related Costs [Table] 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 recognition of certain revenues that are included in rate-setting to the balance sheet. Statistical Measurement [Domain] Statistical Measurement [Domain] CAPITALIZATION AND LIABILITIES Liabilities and Equity [Abstract] Completion of Electric Utility Reorganization Plan[Line Items] Restructuring Cost and Reserve [Line Items] Receipt of advances for and contributions in aid of construction Proceeds from Advances for Construction Deferred income taxes Deferred Income Tax Liabilities, Net Derivative Instruments Derivative Instruments and Hedging Activities Disclosure [Text Block] Security Exchange Name Security Exchange Name Total other credits Liabilities, Other Than Long-Term Debt Related To Capitalization, Noncurrent Liabilities, Other Than Long-Term Debt Related To Capitalization, Noncurrent Weighted Average Dividends Common Stock Weighted Average Dividends Common Stock The aggregate cash, stock, and paid-in-kind dividends declared for common shareholders during the period calculated on a weighted average basis. Incremental expansion of borrowing capacity Line of Credit Facility, Incremental Expansion of Borrowing Capacity Line of Credit Facility, Incremental Expansion of Borrowing Capacity Property, Plant and Equipment Utilities Property Plant and Equipment Gross [Abstract] -- None. No documentation exists for this element. -- Other accounts receivable Increase (Decrease) in Accounts and Other Receivables Operating Income Operating income (loss) Operating Income (Loss) Unbilled revenue — receivable from U.S. government Unbilled Contracts Receivable From U S Government Unbilled Contracts Receivable From U S Government Total current liabilities Liabilities, Current Contract with Customer, Asset and Liability Contract with Customer, Contract Asset, Contract Liability, and Receivable [Table Text Block] Prepayments and other current assets Prepaid Expense and Other Assets, Current Commitments and Contingencies Commitments and Contingencies ASSETS Assets [Abstract] Accounting Policies [Abstract] Accounting Policies [Abstract] Income taxes payable Taxes Payable, Current Entity Address, State or Province Entity Address, State or Province Accounts payable Accounts Payable, Current Fair value of financial instruments Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Earnings reinvested in the business Retained Earnings (Accumulated Deficit) Operating lease right-of-use assets Operating Lease, Right-of-Use Asset Electric Service Utility Operations Electric Service Utility Operations [Member] Represents the electric service utility operations of the entity. Options outstanding (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number Basis of Presentation [Abstract] Basis of Presentation [Abstract] -- None. No documentation exists for this element. -- Undistributed earnings allocated to participating securities Undistributed Earnings (Loss) Allocated to Participating Securities, Basic Schedule of Capital Units [Table] Schedule of Capital Units [Table] Contracted Services Contracted Services [Member] Contracted Services [Member] Represents the contracted services unit of the entity. Accrued pension and other postretirement benefits Increase (Decrease) in Obligation, Pension and Other Postretirement Benefits Common Stock, Par or Stated Value Per Share Common Stock, Par or Stated Value Per Share Other Other Liabilities, Noncurrent Other investing activities Payments for (Proceeds from) Other Investing Activities Note receivable from AWR parent Origination of Notes Receivable from Related Parties Payments to affiliate for corporate office administrative and general costs Related Party Transaction, Amounts of Transaction Revenue from contract with customer, excluding assessed tax Revenue from Contract with Customer, Excluding Assessed Tax Golden State Water Company and Bear Valley Electric Service Inc. Golden State Water Company and Bear Valley Electric Service Inc. [Member] Golden State Water Company and Bear Valley Electric Service Inc. Regulatory Liability [Domain] Regulatory Liability [Domain] Concentration Risk, Percentage Concentration Risk, Percentage Regulatory adjustment — deferred Two-Way Pension balancing accounts Two-Way Pension balancing accounts Pension Plan's funded status and amounts recognized in balance sheets and the components of net pension cost and accrued post-retirement liability Defined Benefit Plan Disclosure [Line Items] Statement Statement [Line Items] Gain on investments held in a trust Unrealized Gain (Loss) on Investments Debt instrument term Debt Instrument, Term Diluted Earnings Per Share, Diluted, Two Class Method [Abstract] Description of derivative activity volume Derivative Activity Volume Derivative Activity Volume Operating income Results of Operations, Income before Income Taxes Effective income tax rate Effective Income Tax Rate [Line Items] -- None. No documentation exists for this element. -- Advances for construction Advances For Construction Advances For Construction Statement [Table] Statement [Table] Receivable from the U.S. government (Note 2) Accounts Receivable from U S Government Net, Current This element represents the amount, at the balance sheet date, current portion of receivables that are derived from government contracts. Interest cost Defined Benefit Plan, Interest Cost Statistical Measurement [Axis] Statistical Measurement [Axis] Contract assets Contract with Customer, Asset, before Allowance for Credit Loss, Current Intercompany receivable Related Party Transaction, Due from (to) Related Party, Current Deferred income taxes and investment tax credits Deferred Income Taxes and Tax Credits Alternative revenues program [Member] Alternative revenues program [Member] Alternative revenues program [Member] Net change in intercompany borrowings Payments for Proceeds from Related Party Debt This element represents the net change during the reporting period in amount of payments for proceeds from related party debt. Outstanding borrowings Line of Credit Facility, Fair Value of Amount Outstanding Restructuring and Related Activities [Abstract] Restructuring and Related Activities [Abstract] Total capitalization Capitalization, Long-term Debt and Equity Entity Small Business Entity Small Business Increase (Decrease) in Stockholders' Equity Increase (Decrease) in Stockholders' Equity [Roll Forward] Bear Valley Electric Service, Inc. Bear Valley Electric Service, Inc. [Member] Bear Valley Electric Service, Inc. Debt Instrument Redemption Premium as Percentage of Par Value after Specified Period Debt Instrument Redemption Premium as Percentage of Par Value after Specified Period Debt Instrument Redemption Premium as Percentage of Par Value after Specified Period Fair Value, Measurements, Fair Value Hierarchy [Domain] Fair Value Hierarchy and NAV [Domain] Period of fixed price contracts to operate and maintain water systems at various military bases Period of Fixed Price Contracts to Operate and Maintain Water Systems at Various Military Bases Period of Fixed Price Contracts to Operate and Maintain Water Systems at Various Military Bases Represents the period of fixed price contracts to operate and maintain the water and/or wastewater systems at various military bases. Amendment Flag Amendment Flag Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Undistributed earnings allocated to common shareholders Undistributed Earnings Allocated to Common Stock Represents the earnings allocated (not distributed) to common stock under the two-class method to the extent that common shareholders may share in earnings as if all of the earnings for the period had been distributed. Note Payable 2.9 Percent Due 2040 [Member] Note Payable 2.9 Percent Due 2040 [Member] Note Payable 2.9 Percent Due 2040 Defined Benefit Plan, Plan Assets, Category [Axis] Defined Benefit Plan, Plan Assets, Category [Axis] Water Revenue Adjustment Mechanism Net of Modified Cost Balancing Account [Member] Water Revenue Adjustment Mechanism and Modified Cost Balancing Account Water Revenue Adjustment Mechanism Net of Modified Cost Balancing Account [Member] Represents the regulatory assets arising from water revenue adjustment mechanism, net of modified cost balancing account. Net Cash Provided by (Used in) Operating Activities Net cash provided from operating activities Net Cash Provided by (Used in) Operating Activities Notes payable to bank Notes Payable to Bank, Noncurrent Entity Central Index Key Entity Central Index Key Completion of Electric Utility Reorganization Plan Restructuring and Related Activities Disclosure [Text Block] Line of Credit Facility, Current Borrowing Capacity Line of Credit Facility, Current Borrowing Capacity Contributions in aid of construction - net Contributions In Aid Construction, Net Contributions In Aid Construction, Net Derivative Instrument [Axis] Derivative Instrument [Axis] COVID-19 Impact Receivables, Trade and Other Accounts Receivable, Allowance for Doubtful Accounts, Policy [Policy Text Block] Schedule of estimates of the fair value of long-term debt Schedule of Carrying Values and Estimated Fair Values of Debt Instruments [Table Text Block] ASUS American States Utility Services [Member] Represents activity related to American States Utility Services, Inc. (ASUS). Expected return on plan assets Defined Benefit Plan, Expected Return (Loss) on Plan Assets Fair Value Measurement [Domain] Fair Value Measurement [Domain] Accrued payables for investment in utility plant Capital Expenditures Incurred but Not yet Paid Income taxes receivable Income Taxes Receivable, Current Undistributed earnings Undistributed Earnings, Basic Undistributed Earnings, Basic Segments [Domain] Segments [Domain] Amount spent in clean-up and remediation activities [Abstract] Site Contingency, Recovery from Third Party of Environmental Remediation Cost Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Other accounts receivable, allowance for doubtful accounts Allowance for Doubtful Accounts Receivable Other, Current This element represents the valuation allowance for other receivables not separately presented elsewhere in the balance sheet, within one year (or the normal operating cycle, whichever is longer) that are expected to be uncollectible. Accounting Policies [Table] Accounting Policies [Table] Schedule detailing accounting policies of the entity. Accounts Receivable, Allowance for Credit Loss, Current Accounts Receivable, Allowance for Credit Loss, Current Entity Common Stock, Shares Outstanding (in shares) Entity Common Stock, Shares Outstanding Stock-based compensation, net of taxes paid from shares withheld from employees related to net share settlements APIC, Share-based Payment Arrangement, Option, Increase for Cost Recognition Unrealized losses on purchased power contracts Energy Marketing Contract Liabilities, Current Other Other Assets, Noncurrent Business Segments Segment Reporting Disclosure [Text Block] 'Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate, Increase (Decrease) 'Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate, Increase (Decrease) 'Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate, Increase (Decrease) Total Assets Assets Scenario [Axis] Scenario [Axis] Net assets transferred Restructuring And Related Costs, Net Assets Transferred Restructuring And Related Costs, Net Assets Transferred Restricted stock units outstanding (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Title of 12(b) Security Title of 12(b) Security Amortization of prior service cost Defined Benefit Plan, Amortization of Prior Service Cost (Credit) Subsequent Event Type [Axis] Subsequent Event Type [Axis] Add: Addition [Abstract] -- None. No documentation exists for this element. -- Interest expense Interest Expense Depreciation and amortization Depreciation, Depletion and Amortization Revenue, Initial Application Period Cumulative Effect Transition [Line Items] Revenue, Initial Application Period Cumulative Effect Transition [Line Items] Product and Service [Axis] Product and Service [Axis] Sales Sales [Member] Retirement Plan Type [Axis] Retirement Plan Type [Axis] Contract with Customer, Liability, Revenue Recognized Contract with Customer, Liability, Revenue Recognized Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Total income available to common shareholders, basic Net Income (Loss) Available to Common Stockholders, Basic Fair Value, Inputs, Level 1 Fair Value, Inputs, Level 1 [Member] Regulated Operations [Abstract] Regulated Operations [Abstract] Net change in notes payable to banks Increase (Decrease) in Notes Payable, Current Number of States in which Entity Operates Number of States in which Entity Operates Accounts payable Increase (Decrease) in Accounts Payable Derivative unrealized (gain) loss Gain (Loss) on Derivative Instruments [Member] Dividends Declared Per Common Share (in dollars per share) Common Stock, Dividends, Per Share, Cash Paid Purchase Commitment, Excluding Long-term Commitment [Domain] Purchase Commitment, Excluding Long-term Commitment [Domain] Debt Instrument [Axis] Debt Instrument [Axis] Less: Distributed earnings to participating securities Preferred Stock Dividends and Other Adjustments Preferred Stock Dividends and Other Adjustments Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Asset Class [Axis] Asset Class [Axis] Unbilled receivable Unbilled Contracts Receivable Catastrophic Event Memo Account (CEMA) [Member] Catastrophic Event Memo Account (CEMA) [Member] Catastrophic Event Memo Account for COVID-19 Revenue from Contract with Customer [Abstract] Revenue from Contract with Customer [Abstract] Environmental Remediation Expense Environmental Remediation Expense Common Stock, Shares, Outstanding Common Stock, Shares, Outstanding Less - Accumulated depreciation Public Utilities, Property, Plant and Equipment, Accumulated Depreciation Entity Information [Line Items] Entity Information [Line Items] Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Funding for overdue electric bills per Budget Act of 2021 Funding for overdue electric bills per Budget Act of 2021 Funding for overdue electric bills per Budget Act of 2021 COVID-19 Impact [Line Items] COVID-19 Impact [Abstract] COVID-19 Impact Alternative revenue program Regulated Operating Revenue Revolving Credit Facility [Member] Revolving Credit Facility [Member] Loss Contingency Nature [Axis] Loss Contingency Nature [Axis] Term of derivative contract Derivative, Term of Contract Other Products and Services Other Products and Services [Member] Other Products and Services [Member] Regulatory assets Regulatory assets Net Regulatory Assets Common Stock, Shares Authorized Common Stock, Shares Authorized Concentration Risk Type [Axis] Concentration Risk Type [Axis] Stock-based compensation (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Total Property, Plant and Equipment, Gross Capital stock Capital Unit [Line Items] Schedule of reporting segments information Schedule of Segment Reporting Information, by Segment [Table Text Block] Retained Earnings [Member] Retained Earnings, Unappropriated [Member] Undistributed earnings for dilutive stock-based awards Dilutive Securities, Effect on Basic Earnings Per Share, Options and Restrictive Stock Units Regulatory asset not accruing carrying costs Regulatory Asset Not Accruing Carrying Costs Represents the regulatory asset not accruing carrying costs as of the balance sheet date. Estimate of Fair Value Measurement Estimate of Fair Value Measurement [Member] Commercial paper, term Investment Term Represents the term associated with a fixed-term security. Income Statement [Abstract] Income Statement [Abstract] Operating lease liabilities Operating Lease, Liability, Noncurrent Prepayments and other assets Increase (Decrease) in Prepaid Expense and Other Assets Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Refunds on advances for construction Repayments of Advances for Construction Basic Earnings Per Share, Basic, Two Class Method [Abstract] Current Assets Assets, Current [Abstract] Interest income Investment Income, Interest Cash Flows From Investing Activities: Net Cash Provided by (Used in) Investing Activities, Continuing Operations [Abstract] Due to Related Parties, Noncurrent Due to Related Parties, Noncurrent Consolidated Entities [Axis] Consolidated Entities [Axis] Scenario [Domain] Scenario [Domain] Counterparty Name [Domain] Counterparty Name [Domain] Capital expenditures Payments to Acquire Property, Plant, and Equipment City Area Code City Area Code Legal Entity [Axis] Legal Entity [Axis] Consolidation Items [Domain] Consolidation Items [Domain] Other Assets Regulatory and Other Assets [Abstract] -- None. No documentation exists for this element. -- General Rate Case Memorandum Accounts General Rate Case Memorandum Accounts [Member] Discloses the amount of regulatory assets and liabilities pertaining to the general rate case memorandum accounts. Document Period End Date Document Period End Date Number of registrants filing combined report Number of Registrants Filing Combined Report Represents the number of registrants filing combined report during the period. Disaggregation of Revenue Disaggregation of Revenue [Table Text Block] Income from operations before income tax expense Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest Other accounts receivable, less allowance for doubtful accounts Accounts and Other Receivables, Net, Current Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] 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 Continuing Operations [Abstract] -- None. No documentation exists for this element. -- Deferred Income Tax Charge Deferred Income Tax Charge [Member] Net change in cash and cash equivalents Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Excluding Exchange Rate Effect Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Stock-based compensation expense Share-based Payment Arrangement, Noncash Expense Entity [Domain] Entity [Domain] Other financing activities Payment, Tax Withholding, Share-based Payment Arrangement Payment, Tax Withholding, Share-based Payment Arrangement Total other assets Regulatory and Other Assets This element represents aggregate carrying amount, at the balance sheet date, of noncurrent regulatory assets held by public utility entities and other noncurrent assets not separately disclosed in the balance sheet. Surcharges (Cost-recovery Activities) Surcharges (Cost-recovery Activities) [Member] Surcharges (Cost-recovery Activities) [Member] Cover [Abstract] Cover [Abstract] Completion of Electric utility reorganization plan -selected information for the results of operations and its cash flows Restructuring and Related Costs [Table Text Block] Regulatory Asset [Domain] Regulatory Asset [Domain] Derivative Instruments, Gain (Loss) [Table] Derivative Instruments, Gain (Loss) [Table] Schedule of regulatory assets, less regulatory liabilities in the consolidated balance sheets for continuing operations Schedule of Regulatory Assets Liabilities [Table Text Block] Tabular disclosure of regulatory assets, less regulatory liabilities, included in consolidated balance sheets for continuing operations. Taxes Payable Taxes Payable Contract Liability Increase (Decrease) in Contract with Customer, Liability Electric Regulated Operating Revenue, Electric, Non-Nuclear Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Other Property and Investments Property, Plant and Equipment, Other, Net [Abstract] Service cost Defined Benefit Plan, Service Cost Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Axis] Total operating expenses Costs and Expenses Equity Components [Axis] Equity Components [Axis] Modified Cost Balancing Account Modified Cost Balancing Account [Member] Represents the regulatory assets arising from modified cost balancing account. Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Minimum Minimum [Member] Minimum [Member] Consolidated Entities [Domain] Consolidated Entities [Domain] Operating lease liabilities Operating Lease, Liability, Current Defined Benefit Plan, Plan Assets, Category [Domain] Defined Benefit Plan, Plan Assets, Category [Domain] Notes Payable, Related Parties Notes Payable, Related Parties Sensitivity Analysis For Defined Benefit Plan, Benefit Obligation, Impact Of 65 Basis Point Increase In Discount Rate, Percent Sensitivity Analysis For Defined Benefit Plan, Benefit Obligation, Impact Of 65 Basis Point Increase In Discount Rate, Percent Sensitivity Analysis For Defined Benefit Plan, Benefit Obligation, Impact Of 65 Basis Point Increase In Discount Rate, Percent Amortization of actuarial (gain) loss Defined Benefit Plan, Amortization of Gain (Loss) Derivative Instruments, Gain (Loss) [Line Items] Derivative Instruments, Gain (Loss) [Line Items] Entity Interactive Data Current Entity Interactive Data Current Net periodic benefits costs under accounting standards Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Operating Revenues Revenues [Abstract] Fair Value of Financial Instruments Fair Value Disclosures [Text Block] Property installed by developers and conveyed Contribution of Property Regulatory Assets Regulatory Assets, Noncurrent Commodity Contract Commodity Contract [Member] Costs deferred for future recovery on Aerojet case Costs Deferred for Future Recovery on Aerojet Case [Member] Represents the regulatory assets arising from costs deferred for future recovery on Aerojet case. Entity Registrant Name Entity Registrant Name Subsequent Event Type [Domain] Subsequent Event Type [Domain] Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Related Party Transactions and Financing Activities Related Party Transactions and Financing Activities [Policy Text Block] Related Party Transactions and Financing Activities Other liabilities Increase (Decrease) in Other Operating Liabilities Intersegment Eliminations Intersegment Eliminations [Member] Unrealized gains on purchased power contracts Energy Marketing Contracts Assets, Current Other operation Other Cost and Expense, Operating Other Regulatory Assets Net [Member] Other Regulatory Assets Net [Member] Represents the regulatory assets arising from other regulatory matters not specified in the taxonomy. Number of reportable segments Number of Reportable Segments Retirement Plan Type [Domain] Retirement Plan Type [Domain] Consolidation Items [Axis] Consolidation Items [Axis] Schedule of reconciliation of total utility plant (a key figure for rate-making) to total consolidated assets Schedule Showing Reconciliation of Total Utility Plant to Total Consolidated Assets [Table Text Block] Tabular disclosure of reconciliation of total utility plant (a key figure for rate-making) to total consolidated assets. Effective Income Tax Rate [Table] Effective Income Tax Rate [Table] Income tax rate reconciliations and adjustments that are made in order to arrive at the effective income tax rate of the entity. Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Accounts receivable - customers, less allowance for doubtful accounts Accounts Receivable, after Allowance for Credit Loss, Current Gain (loss) on asset transfer Restructuring And Related Costs, Gain (Loss) On Transfer Gain (loss) on asset transfer between GSWC and BVESI Depreciation and amortization Depreciation, Depletion and Amortization, Nonproduction Other property and investments Property Plant and Equipment and Investments Other Net This element represents capitalized assets classified as property, plant and equipment and other noncurrent investments not otherwise defined in the taxonomy. Nature of Operations: Nature of Operations [Abstract] -- None. No documentation exists for this element. -- Entity Address, Postal Zip Code Entity Address, Postal Zip Code Water Utility Relief Funding for Overdue Water Bills per Budget Act of 2021 [Line Items] Water Utility Relief Funding for Overdue Water Bills per Budget Act of 2021 Water Utility Relief Funding for Overdue Water Bills per Budget Act of 2021 Income taxes receivable/payable Increase (Decrease) in Income Taxes Fair value at beginning of the period Fair value at end of the period Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs Increase (Decrease) in Other Regulatory Assets Increase (decrease) in other regulatory assets Increase (Decrease) in Other Regulatory Assets Goodwill Goodwill Notes Receivable from AWR parent Notes Receivable, Related Parties, Noncurrent Document Transition Report Document Transition Report Water Service Utility Operations Water Service Utility Operations [Member] Water Service Utility Operations [Member] Represents the water service utility operations of the entity. Power purchased for resale Utilities Operating Expense, Purchased Power Water purchased Cost of Purchased Water Dividend equivalent rights on stock-based awards not paid in cash Dividends Equivalent Rights on Share Based Compensation Not Paid in Cash Net of Tax This element represents equity impact of dividend equivalent rights on stock-based awards which is not paid in cash during the reporting period. Other Income and Expenses Nonoperating Income (Expense) [Abstract] Debt Instrument, Face Amount Debt Instrument, Face Amount Document Quarterly Report Document Quarterly Report Groundwater production assessment Groundwater Production Assessment This element represents the aggregate expenses on groundwater production assessment. Fair Value by Asset Class [Domain] Asset Class [Domain] Term estimate for the environmental cleanup Term estimate for the environmental cleanup Term estimate to complete the environmental clean-up Components of Net Periodic Benefits Cost: Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] Contract liabilities (Note 2) Contract with Customer, Liability, Current Related Party Transaction, Terms and Manner of Settlement Related Party Transaction, Terms and Manner of Settlement Entities [Table] Entities [Table] Customer Concentration Risk Customer Concentration Risk [Member] Derivative Contract [Domain] Derivative Contract [Domain] Weighted Average Number of Diluted Shares (in shares) Weighted Average Number of Shares Outstanding, Diluted Basic Earnings Per Common Share (in dollars per share) Basic earnings per Common Share (in dollars per share) Earnings Per Share, Basic Contract assets (Note 2) Contract with Customer, Asset, before Allowance for Credit Loss, Noncurrent Entity File Number Entity File Number Accrued pension and other postretirement benefits Liability, Defined Benefit Plan, Noncurrent Public Utilities Property Plant and Equipment Depreciation on Transportation Equipment Depreciation on transportation equipment Public Utilities Property Plant and Equipment Depreciation on Transportation Equipment The amount of expense recognized in the current period that reflects the allocation of the cost of transportation equipment over the assets' useful lives. SERP Supplemental Employee Retirement Plan [Member] Summary of significant accounting policies Accounting Policies [Line Items] -- None. No documentation exists for this element. -- Cash Flows From Operating Activities: Net Cash Provided by (Used in) Operating Activities, Continuing Operations [Abstract] Net Cash Provided by (Used in) Financing Activities Net cash provided from financing activities (1) Net Cash Provided by (Used in) Financing Activities Retirement or repayments of long-term debt Repayments of Long-term Debt Dividends on Common Shares Dividends, Common Stock Revenue, Remaining Performance Obligation, Amount Revenue, Remaining Performance Obligation, Amount Counterparty Name [Axis] Counterparty Name [Axis] Additional disclosure Earnings Per Share, Basic and Diluted, Other Disclosures [Abstract] Common Stock, Value, Issued Common Stock, Value, Issued Schedule of reconciliation of Registrant's net income and weighted average Common Shares outstanding for calculating diluted net income per share Schedule of Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Table Text Block] Document Fiscal Year Focus Document Fiscal Year Focus Dividend equivalent rights on stock-based awards not paid in cash Dividends Equivalent Rights on Share Based Compensation Net of Tax This element represents dividend equivalent rights on stock based awards, net of tax effect. Defined Benefit Plan, Benefit Obligation Defined Benefit Plan, Benefit Obligation Entity Current Reporting Status Entity Current Reporting Status Capital additions Property, Plant and Equipment, Additions Retirement Benefits [Abstract] Retirement Benefits [Abstract] Receipt of payment of note receivable from AWR parent Repayment of Notes Receivable from Related Parties Operating expenses Utilities Operating Expense, Operations Pension and other post-retirement obligations Pension Costs and Other Postretirement Benefit Costs [Member] Represents the regulatory assets arising from pensions and other post-retirement obligations. Increase (Decrease) in Obligation, Pension Benefits Increase (Decrease) in Obligation, Pension Benefits Contract assets Increase (Decrease) in Contract with Customer, Asset Unbilled receivable Increase (Decrease) In Unbilled Contracts Receivables Increase (Decrease) In Unbilled Contracts Receivables Balance (in shares) Balances (in shares) Common Stock, Shares, Issued Cash and cash equivalents Cash and cash equivalents, beginning of period Cash and cash equivalents, end of period Cash and Cash Equivalents, at Carrying Value Maintenance Utilities Operating Expense, Maintenance and Operations Schedule of Defined Benefit Plans Disclosures [Table] Schedule of Defined Benefit Plans Disclosures [Table] Various refunds to customers Revenue Subject to Refund [Member] Revenue Subject to Refund [Member] Wastewater Wastewater [Member] Wastewater [Member] Long-term debt Long-term Debt, Excluding Current Maturities Segment Reporting [Abstract] Segment Reporting [Abstract] Purchase Commitment, Excluding Long-term Commitment [Axis] Purchase Commitment, Excluding Long-term Commitment [Axis] Accounts receivable — customers Increase (Decrease) in Accounts Receivable Contracted services Regulated Operating Revenue, Other Total common shareholders’ equity Beginning balances Ending balances Stockholders' Equity Attributable to Parent Concentration Risk Type [Domain] Concentration Risk Type [Domain] Total Capitalization and Liabilities Liabilities and Equity Loss Contingencies [Line Items] Loss Contingencies [Line Items] Income Taxes Income Tax Disclosure [Text Block] Unrealized gains (losses) on purchased power contracts Fair Value, Net Derivative Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss) Entity Address, City or Town Entity Address, City or Town Portion at Fair Value Measurement Portion at Fair Value Measurement [Member] Accrued employee expenses Employee-related Liabilities, Current Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Restricted Stock Units Restricted Stock Units (RSUs) [Member] Parent [Member] Parent [Member] Long-term debt-GSWC Other Investments and Securities, at Cost Number of customers Number of Customers Represents the number of customers who are served by the entity. Administrative and general General and Administrative Expense Regulatory Asset Recovery Periods Regulatory Asset Recovery Periods Represents the recovery periods of the surcharge billed to the customers. Anti-dilutive stock options not included in the computation of diluted EPS (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Other — net Other Noncash Income (Expense) Capitalization Capitalization, Long-term Debt and Equity [Abstract] Equity Component [Domain] Equity Component [Domain] Dividends paid Dividends paid Payments of Dividends Net property, plant and equipment Net property, plant and equipment Total utility plant Property, Plant and Equipment, Net Reportable Legal Entities Reportable Legal Entities [Member] Entity Tax Identification Number Entity Tax Identification Number Interest expense, net Interest Income (Expense), Nonoperating, Net Non-utility property, at cost Non Utilities Property Plant and Equipment, Gross This element represents the gross amount, at the balance sheet date, of non utility property assets used in the normal conduct of business and not intended for resale owned by a utility entity. Net Income Net income Net income Net Income (Loss) Attributable to Parent Receivable from the U.S. government Government Contract Receivable Changes in assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Cost of Capital, Proceeding for Water Regions [Member] Cost of Capital, Proceeding for Water Regions [Member] Represents information pertaining to Cost of Capital Proceeding for Water Regions. Other Other Liabilities, Current Pro Forma Pro Forma [Member] Regulated utility plant, at cost Utilities Property Plant and Equipment, Gross This element represents the gross amount, at the balance sheet date, of long-lived physical assets used in the normal conduct of business and not intended for resale owned by a utility entity used in the operations of the entity. Regulatory Asset [Axis] Regulatory Asset [Axis] Property and other taxes Taxes, Miscellaneous Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Total current assets Assets, Current Current Fiscal Year End Date Current Fiscal Year End Date Operating Expenses Operating Expenses [Abstract] Earnings Per Share [Abstract] Earnings Per Share [Abstract] Defined Benefit Plan, Net Periodic Benefit Cost before Allocation to Overhead Pool Defined Benefit Plan, Net Periodic Benefit Cost before Allocation to Overhead Pool The total amount of net periodic benefit cost for defined benefit plans during the period, before allocation to overhead pool. Proceeds from stock option exercises Proceeds from Issuance of Common Shares and Stock Option Exercises The cash inflow from the additional capital contribution to the entity and amount received from holders exercising their stock options. Regulatory asset CEMA - Storm Regulatory asset CEMA - Storm Regulatory asset CEMA - Storm Syndicated Revolving Credit Facility member [Member] Syndicated Revolving Credit Facility member [Member] Syndicated Revolving Credit Facility member Other Credits Liabilities, Other than Long-term Debt, Noncurrent [Abstract] Document Fiscal Period Focus Document Fiscal Period Focus Regulatory Matters Schedule of Regulatory Assets and Liabilities [Text Block] AWR Parent Company [Member] Parent Company [Member] Financial liabilities: Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract] Water Regulated Operating Revenue, Water Total common shareholders earnings, diluted Net Income (Loss) Available to Common Stockholders, Diluted Water Revenue Adjustment Mechanism [Member] Water Revenue Adjustment Mechanism [Member] Represents the regulatory assets arising from water revenue adjustment mechanism. Deduct: Deduction [Abstract] -- None. No documentation exists for this element. -- Entity Filer Category Entity Filer Category Common Stock [Member] Common Stock [Member] Product and Service [Domain] Product and Service [Domain] Concentration Risk Benchmark [Domain] Concentration Risk Benchmark [Domain] Water Water [Member] Exercise of stock options and other issuance of Common Shares (in shares) Common Shares issued under DRP and the 2000 and 2008 Employee Plans Stock Issued During Period, Shares, New Issues Regulatory assets Increase (Decrease) in Regulatory Assets and Liabilities Increase (Decrease) in Regulatory Assets and Liabilities Total other property and investments Property Plant and Equipment and Investments Other and Goodwill Net This element represents aggregate amount of capitalized assets classified as property, plant and equipment and other noncurrent investments not otherwise defined in the taxonomy, and also include goodwill, as of the balance sheet date. Expected contributions in current fiscal year Defined Benefit Plan, Expected Future Employer Contributions, Current Fiscal Year Debt Instrument, Interest Rate, Stated Percentage Debt Instrument, Interest Rate, Stated Percentage Provision for doubtful accounts Accounts Receivable, Credit Loss Expense (Reversal) Intercompany receivable/payable Increase (Decrease) in Related Party Receivable Payable, Current The increase (decrease) during the reporting period of related party receivables/payables which are due within one year or one business cycle. Non-cash transactions: Noncash Investing and Financing Items [Abstract] Fully Diluted Earnings Per Share Earnings Per Share, Diluted [Abstract] Regulatory matters: Regulatory Assets and Liabilities [Line Items] -- None. No documentation exists for this element. -- Related Party Transactions Related Party Transactions [Abstract] Total other income and expenses Nonoperating Income (Expense) Environmental Clean-Up and Remediation Environmental Issue [Member] Loss Contingency, Nature [Domain] Loss Contingency, Nature [Domain] Tariff-based Revenues Tariff-based Revenues [Member] Tariff-based Revenues [Member] Basis of Accounting, Policy Basis of Accounting, Policy [Policy Text Block] Power purchased for pumping Power Purchased for Pumping This element represents Power purchased for pumping expenses. Net change in cash and cash equivalents Cash and Cash Equivalents, Period Increase (Decrease) Weighted Average Number of Common Shares Outstanding (in shares) Weighted average Common Shares outstanding, basic (in shares) Weighted Average Number of Shares Outstanding, Basic Unamortized investment tax credits Accumulated Deferred Investment Tax Credit Loss Contingencies [Table] Loss Contingencies [Table] Reported Value Measurement Reported Value Measurement [Member] Revenue from Contract with Customer Revenue from Contract with Customer [Text Block] Receivable from the U.S. government (Note 2) Account Receivable from US Government, Net,Noncurrent Account Receivable from US Government, Net,Noncurrent Other assets Assets Other than Property Plant and Equipment, Net Sum of the carrying amounts as of the balance sheet date of all assets except utility plant that are recognized. Notes Payable, Noncurrent Notes Payable, Noncurrent Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Explanation Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Explanation Long-term Debt, Fair Value Long-term Debt, Fair Value Total operating revenues Revenues Revenues Income tax expense Income Tax Expense (Benefit) Receivables from the U.S. government Increase (Decrease) Receivable from Government The net change during the reporting period in amount receivable from the government. Cash and cash equivalents, beginning of period Cash and cash equivalents, end of period Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Regulatory asset-CEMA Regulatory asset-CEMA Regulatory asset-Catastrophic Event Memo Account (CEMA) Accrued interest Accrued Liabilities, Current Fully Diluted Earnings Per Common Share (in dollars per share) Diluted earnings per Common Share (in dollars per share) Earnings Per Share, Diluted Local Phone Number Local Phone Number Derivative Instruments and Hedging Activities Disclosure [Abstract] Derivative Instruments and Hedging Activities Disclosure [Abstract] Accrued liability for the estimated additional cost to complete the clean-up at the site Accrual for Environmental Loss Contingencies Supply cost balancing accounts Supply Cost Balancing Accounts This element represents the supply cost balancing accounts maintained for under-collections and over-collections of revenues designed to recover such costs. Entity Address, Address Line One Entity Address, Address Line One Contract liabilities Contract with Customer, Liability Entity Emerging Growth Company Entity Emerging Growth Company Exercise of stock options and other issuances of Common Shares Stock Issued During Period, Value, Stock Options Exercised Derivative Instruments Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Maximum borrowing capacity on line of credit Line of Credit Facility, Maximum Borrowing Capacity Consolidated Balance Sheets(Parenthetical) Allowance for Doubtful Accounts [Abstract] Allowance for Doubtful Accounts [Abstract] Award Type [Axis] Award Type [Axis] Maximum [Member] Maximum Maximum [Member] Materials and supplies, at weighted average cost Inventory, Raw Materials and Supplies, Gross Measurement Basis [Axis] Measurement Basis [Axis] Schedule of reconciliation of Registrant's net income and weighted average Common Shares outstanding for calculating basic net income per share Schedule of Earnings Per Share, Basic, by Common Class, Including Two Class Method [Table Text Block] Schedule of components of net periodic benefit costs, before allocation to the overhead pool, for Registrant's pension plan, postretirement plan, and SERP Schedule of Net Benefit Costs [Table Text Block] ETRs ( as a percent) Effective Income Tax Rate Reconciliation, Percent Significant Accounting Policies Significant Accounting Policies [Text Block] Net Cash Provided by (Used in) Investing Activities Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities Amount billed to customers as surcharges Regulatory Asset Amount Billed to Customers as Surcharges Represents amount billed to customers as surcharges. Award Type [Domain] Award Type [Domain] Other Postretirement Benefits Other Postretirement Benefits Plan [Member] Trading Symbol Trading Symbol Mutual Funds Mutual Funds [Member] Mutual Funds [Member] Sensitivity Analysis For Defined Benefit Plan, Benefit Obligation, Impact Of 65 Basis Point Increase In Discount Rate, Amount Sensitivity Analysis For Defined Benefit Plan, Benefit Obligation, Impact Of 65 Basis Point Increase In Discount Rate, Amount Sensitivity Analysis For Defined Benefit Plan, Benefit Obligation, Impact Of 65 Basis Point Increase In Discount Rate, Amount Regulatory Liability [Axis] Regulatory Liability [Axis] Note Payable 2.17 Percent Due 2030 [Member] Note Payable 2.17 Percent Due 2030 [Member] Note Payable 2.17 Percent Due 2030 [Abstract] Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Revenue, Initial Application Period Cumulative Effect Transition [Table] Revenue, Initial Application Period Cumulative Effect Transition [Table] Redemption price of debt instrument Redemption price of debt instrument Redemption price of debt instrument Contract assets Contract with Customer, Asset, after Allowance for Credit Loss Pension Benefits Pension Plan [Member] Earnings per Share/Capital Stock Earnings Per Share [Text Block] Accrued other taxes Franchise and Assessment Fees Taxes Represents franchise and assessment fees taxes. Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate Flow-through taxes, net Flow Through Taxes Net [Member] Represents the regulatory assets arising from flow-through taxes, net. ASUS construction Cost of Construction Cost of Construction Current Liabilities Liabilities, Current [Abstract] Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Cash Flows From Financing Activities: Net Cash Provided by (Used in) Financing Activities, Continuing Operations [Abstract] Entity Shell Company Entity Shell Company Details of reportable segment Segment Reporting Information [Line Items] Recently Issued Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Long-term debt — current Other Notes Payable, Current Consolidated Balance Sheets(Parenthetical) Statement of Financial Position [Abstract] Basic Earnings Per Common Share Earnings Per Share, Basic [Abstract] Materials and supplies Increase (Decrease) in Materials and Supplies