Regulated Operations [Abstract] 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. Regulatory Liability [Axis] Regulatory Liability [Axis] Regulatory Liability [Domain] Regulatory Liability [Domain] Various refunds to customers Revenue Subject to Refund [Member] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] GOLDEN STATE WATER COMPANY Golden State Water Company [Member] Represents the activity related to Golden State Water Company. Regulatory Asset [Axis] Regulatory Asset [Axis] Regulatory Asset [Domain] Regulatory Asset [Domain] Water Revenue Adjustment Mechanism, net of 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. Base Revenue Requirement Adjustment Mechanism Base Revenue Requirement Adjustment Mechanism [Member] Represents the regulatory assets arising from base revenue requirement adjustment mechanism. 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. 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. Flow-through taxes, net Flow Through Taxes Net [Member] Represents the regulatory assets arising from flow-through taxes, net. Low income rate assistance balancing accounts Low Income Rate Assistance Balancing Accounts [Member] Represents the regulatory assets arising from low income rate assistance balancing accounts. 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. Other regulatory assets Other Regulatory Assets Net [Member] Represents the regulatory assets arising from other regulatory matters not specified in the taxonomy. Regulatory matters: Regulatory Assets and Liabilities [Line Items] -- None. No documentation exists for this element. -- 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. Regulatory assets Net Regulatory Assets Fair Value Disclosures [Abstract] Fair Value of Financial Instruments Fair Value Disclosures [Text Block] Segment Reporting [Abstract] Business Segments Segment Reporting Disclosure [Text Block] GSWC La Serena Plant Improvement Project La Serena Plant Improvement Project [Member] Represents the regulatory assets arising from La Serena Plant improvement project. Litigation Status [Axis] Litigation Status [Axis] Litigation Status [Domain] Litigation Status [Domain] CPUC Rehearing Matter Pending Litigation [Member] Costs included in rehearing matter Payments for Capital Improvements Disallowed costs and related refunds Disallowed Cost and Revenue Represents the disallowed costs and related refunds. Separate independent audits Number of Separate Independent Audits of Procurement Practices Agreed under Settlement Agreement Represents the number of separate independent audits of procurement practices agreed as a part of the settlement agreement. Separate independent audits, period of years after settlement date Number of Years of Separate Independent Audits of Procurement Practices Agreed under Settlement Agreement Number of Years of Separate Independent Audits of Procurement Practices Agreed under Settlement Agreement Schedule of reporting segments information Schedule of Segment Reporting Information, by Segment [Table Text Block] 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. Income Tax Disclosure [Abstract] 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. Effective income tax rate Effective Income Tax Rate [Line Items] -- None. No documentation exists for this element. -- ETRs (as a percent) Effective Income Tax Rate Reconciliation, Percent Compensation and Retirement Disclosure [Abstract] Schedule of Defined Benefit Plans Disclosures [Table] Schedule of Defined Benefit Plans Disclosures [Table] Defined Benefit Plans and Other Postretirement Benefit Plans [Axis] Defined Benefit Plans and Other Postretirement Benefit Plans [Axis] Defined Benefit Plans and Other Postretirement Benefit Plans [Domain] Defined Benefit Plan and Other Postretirement Benefit Plan [Domain] Pension Benefits Pension Plan [Member] Other Postretirement Benefits Other Postretirement Benefit Plan [Member] SERP Supplemental Employee Retirement Plan [Member] 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] Defined Benefit Plan, Expected Contributions in Current Fiscal Year Defined Benefit Plan, Expected Contributions in Current Fiscal Year Components of Net Periodic Benefits Cost: Defined Benefit Plan, Net Periodic Benefit Cost [Abstract] Service cost Defined Benefit Plan, Service Cost Interest cost Defined Benefit Plan, Interest Cost Expected return on plan assets Defined Benefit Plan, Expected Return on Plan Assets Amortization of transition Defined Benefit Plan, Amortization of Transition Obligations (Assets) Amortization of prior service cost (benefit) Defined Benefit Plan, Amortization of Prior Service Cost (Credit) Amortization of actuarial (gain) loss Defined Benefit Plan, Amortization of Gains (Losses) Net periodic pension cost under accounting standards Defined Benefit Plan, Net Periodic Benefit Cost Regulatory adjustment — deferred Increase (Decrease) in Other Regulatory Assets Total expense recognized, 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. Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum Minimum [Member] Maximum Maximum [Member] Majority Majority [Member] Represents the majority range. Other regulatory assets, net Net regulatory assets increase (decrease) due to settlement of rate case Net Regulatory Assets Increase (Decrease) Due to Settlement of Rate Case Represents the amount of increase or decrease to net regulatory assets due to settlement of rate case during the period. Regulatory asset recovery periods Regulatory Asset Recovery Periods Represents the recovery periods of the surcharge billed to the customers. Number of Customers in new service territory Number of Customers in new service territory Earnings Per Share [Abstract] Schedule of Capital Units [Table] Schedule of Capital Units [Table] Share Repurchase Program [Axis] Share Repurchase Program [Axis] Share Repurchase Program [Domain] Share Repurchase Program [Domain] AWR Parent Company [Member] Award Type [Axis] Award Type [Axis] Award Type [Domain] Equity Award [Domain] Restricted Stock Units Restricted Stock Units (RSUs) [Member] Capital stock Capital Unit [Line Items] Additional disclosure Earnings Per Share, Basic and Diluted, Other Disclosures [Abstract] Options outstanding (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number Restricted stock units outstanding (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Stock options included in the calculation of diluted EPS (in shares) Share Based Compensation Arrangement by Share Based Payment Award, Options Outstanding Included in Calculation of Diluted Earnings Per Share, Number Represents the stock options included in the calculation of diluted earnings per share. Stock options not included in the calculation of diluted EPS (in shares) Share Based Compensation Arrangement by Share Based Payment Award, Options Outstanding Not Included in Calculation of Diluted Earnings Per Share, Number Share Based Compensation Arrangement by Share Based Payment Award, Options Outstanding Not Included in Calculation of Diluted Earnings Per Share, Number Anti-dilutive stock options not included in the computation of diluted EPS (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Common Shares issued under DRP and the 2000 and 2008 Employee Plans Stock Issued During Period, Shares, New Issues Value of Common Shares issued under DRP and the 2000 and 2008 Employee Plans Stock Issued During Period, Value, New Issues Common Shares repurchased in the open market under DRP and 401(k) Plan Stock Repurchased During Period, Shares Dividends paid Payments of Dividends Quarterly dividends paid, per share of common stock (in dollars per share) Common Stock, Dividends, Per Share, Cash Paid Percent change in quarterly dividend Percent change in quarterly dividend Percent change in quarterly dividend Authorized shares to be repurchased Stock Repurchase Program, Number of Shares Authorized to be Repurchased Dividends, Preferred Stock, Cash Common Stock, Dividends, Per Share, Declared Debt Disclosure [Abstract] Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Fair value of financial instruments Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] 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] Statement of Financial Position [Abstract] Statement [Table] Statement [Table] Statement Statement [Line Items] Accounts receivable - customers, allowance for doubtful accounts Allowance for Doubtful Accounts Receivable, Current 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. Statement of Cash Flows [Abstract] Cash Flows From Operating Activities: Net Cash Provided by (Used in) Operating Activities, Continuing Operations [Abstract] Net income Net Income (Loss) Attributable to Parent 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. -- Depreciation and amortization Depreciation, Depletion and Amortization, Nonproduction Provision for doubtful accounts Provision for Doubtful Accounts Deferred income taxes and investment tax credits Deferred Income Taxes and Tax Credits Stock-based compensation expense Share-based Compensation Other — net Other Noncash Income (Expense) Changes in assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Accounts receivable — customers Increase (Decrease) in Accounts Receivable Unbilled revenue Increase (Decrease) in Unbilled Receivables Other accounts receivable Increase (Decrease) in Accounts and Other Receivables Receivable from the U.S. government Increase (Decrease) Receivable from Government The net change during the reporting period in amount receivable from the government. Materials and supplies Increase (Decrease) in Materials and Supplies Prepayments and other current assets Increase (Decrease) in Prepaid Expense and Other Assets Regulatory assets — supply cost balancing accounts Costs and estimated earnings in excess of billings on uncompleted contracts Increase (Decrease) in Costs in Excess of Billings on Uncompleted Contracts or Programs The increase (decrease) during the reporting period in the amounts costs and estimated earnings in excess of billings on uncompleted contracts. Other assets (including other regulatory assets) Increase (Decrease) in Other Operating Assets Accounts payable Increase (Decrease) in Accounts Payable Inter-company 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. Income taxes receivable/payable Increase (Decrease) in Income Taxes Income taxes receivable/payable from/to Parent Increase (Decrease) in Receivable/Payable from Related Parties, Income Taxes The increase (decrease) during the reporting period in the amounts payable to/receivable from affiliated parties for income taxes Billings in excess of costs and estimated earnings on uncompleted contracts Increase (Decrease) in Billing in Excess of Cost of Earnings Accrued pension and other postretirement benefits Increase (Decrease) in Pension and Postretirement Obligations Other liabilities Increase (Decrease) in Other Operating Liabilities Net cash provided Net Cash Provided by (Used in) Operating Activities, Continuing Operations Cash Flows From Investing Activities: Net Cash Provided by (Used in) Investing Activities, Continuing Operations [Abstract] Construction expenditures Payments to Acquire Property, Plant, and Equipment Note receivable from AWR parent Increase (Decrease) in Notes Receivable, Related Parties Receipt of payment of note receivable from AWR parent Repayment of Notes Receivable from Related Parties Other investments Payments to Acquire Other Investments Proceed from sale of property Proceeds from Sale of Property, Plant, and Equipment Net cash used Net Cash Provided by (Used in) Investing Activities, Continuing Operations Cash Flows From Financing Activities: Net Cash Provided by (Used in) Financing Activities, Continuing Operations [Abstract] Proceeds from issuance of common shares and 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. Repurchase of common shares Payments for Repurchase of Common Stock Receipt of advances for and contributions in aid of construction Proceeds from Contribution in Aid of Construction Refunds on advances for construction Repayments of Advances for Construction Repayments of long-term debt Repayments of Long-term Debt Proceeds from the issuance of long-term debt Proceeds from Issuance of Long-term Debt Dividends paid Other — net Proceeds from (Payments for) Other Financing Activities Net cash used Net Cash Provided by (Used in) Financing Activities, Continuing Operations Net change in cash and cash equivalents Cash and Cash Equivalents, Period Increase (Decrease) Cash and cash equivalents, beginning of period Cash and Cash Equivalents, at Carrying Value Cash and cash equivalents, end of period Regulatory Matters Schedule of Regulatory Assets and Liabilities [Text Block] WRAM, net of MCBA WRAM Water Revenue Adjustment Mechanism [Member] Represents the regulatory assets arising from water revenue adjustment mechanism. Modified Cost Balancing Account Modified Cost Balancing Account [Member] Represents the regulatory assets arising from modified cost balancing account. Base revenue requirement adjustment mechanism Commercial paper, term Investment Term Represents the term associated with a fixed-term security. Amount billed to customers as surcharges Regulatory Asset Amount Billed to Customers as Surcharges Represents amount billed to customers as surcharges. Under (over) collection BVES General Rate Case B V E S General Rate Case [Member] Represents the regulatory liabilities arising from BVES General Rate Case. Net regulatory assets Portion of deferred rate case costs required to be written off, if DRA prevails Percentage of Deferred Rate Costs Required to be Written Off if D R A Prevails Represents the portion of deferred rate case costs required to be written off, if DRA prevails. Percentage of deferred rate case cost to be borne by shareholders Percentage of Deferred Rate Case Cost Borne by Shareholders Represents the portion of deferred rate case cost borne by shareholders. 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. Earnings per Share/Capital Stock Earnings Per Share [Text Block] Income Taxes Income Tax Disclosure [Text Block] 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 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] Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Details of reportable segment Segment Reporting Information [Line Items] Total utility plant Property, Plant and Equipment, Net 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. Total Assets Assets Accounting Policies [Abstract] Accounting Policies [Table] Accounting Policies [Table] Schedule detailing accounting policies of the entity. Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event Subsequent Event [Member] Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Axis] Concentration Risk Type [Domain] Concentration Risk Benchmark [Domain] Sales Sales [Member] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Fourth Amendment to Revolving Credit Agreement Fourth Amendment to Revolving Credit Agreement [Member] Fourth Amendment to Revolving Credit Agreement [Member] 6.87% Medium-Term Notes Series A 6.87% Medium-Term Notes Series A [Member] 6.87% Medium-Term Notes Series A [Member] 7.00% Medium-Term Notes Series A 7.00% Medium-Term Notes Series A [Member] [Member] 7.00% Medium-Term Notes Series A [Member] [Member] ASUS American States Utility Services [Member] Represents activity related to American States Utility Services, Inc. (ASUS). Business Segments [Axis] Segments [Axis] Segment [Domain] Segments [Domain] Purchase, production, distribution and sale of water Water Service Utility Operations [Member] Represents the water service utility operations of the entity. Electricity distribution Electric Service Utility Operations [Member] Represents the electric service utility operations of the entity. Contracts Contracted Services [Member] Represents the contracted services unit of the entity. Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Promissory Note Notes Payable, Other Payables [Member] Syndicated Credit Facility Syndicated Revolving Credit Facility [Member] Represents activity related to the syndicated revolving credit facility. Summary of significant accounting policies Accounting Policies [Line Items] -- None. No documentation exists for this element. -- Nature of Operations: Nature of Operations [Abstract] -- None. No documentation exists for this element. -- Number of customers served Number of Customers Represents the number of customers who are served by the entity. Percentage of total revenue Concentration Risk, Percentage Period of fixed price contracts to operate and maintain the water and/or wastewater 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. Term of contract with US Military Bases Contract, Term Contract, Term Basis of Presentation: Basis of Presentation [Abstract] -- None. No documentation exists for this element. -- Number of registrants filing combined report Number of Registrants Filing Combined Report Represents the number of registrants filing combined report during the period. Stock split, conversion ratio Stockholders' Equity Note, Stock Split, Conversion Ratio Related Party Transactions Related Party Transactions [Abstract] Debt instrument, face amount Debt Instrument, Face Amount Debt instrument, maximum borrowing capacity Debt Instrument, Maximum Borrowing Capacity Debt Instrument, Maximum Borrowing Capacity Maximum borrowing capacity on line of credit Line of Credit Facility, Maximum Borrowing Capacity Long term debt Debt Instruments [Abstract] Rate of interest Debt Instrument, Interest Rate, Stated Percentage Debt instrument, face amount Repurchase amount Debt Instrument, Redemption Price, Percentage of Principal Amount Redeemed Notes Payable to Banks: Line of Credit Facility [Abstract] Maximum borrowing capacity on line of credit Maximum borrowing capacity on line of credit, potential election to increase Line of Credit Facility, Maximum Borrowing Capacity, Potential Election to Increase Line of Credit Facility, Maximum Borrowing Capacity, Potential Election to Increase Sales and Use Taxes: Sales and Use Taxes [Abstract] -- None. No documentation exists for this element. -- Franchise fees billed to customers and recorded as operating revenue Cost of Reimbursable Expense Period of fixed price contracts to operate and maintain the water and/or wastewater systems at various military bases Non-income tax assessments accounted on a gross basis Taxes, Miscellaneous Consolidation Items [Axis] Consolidation Items [Axis] Consolidation Items [Domain] Consolidation Items [Domain] Reportable Entities Reportable Legal Entities [Member] Intersegment Eliminations Intersegment Eliminations [Member] Water Electric Number of reportable segments Number of Reportable Segments Operating revenues Revenue, Net Operating income (loss) Operating Income (Loss) Interest expense, net Interest Income (Expense), Nonoperating, Net Utility plant Depreciation and amortization expense Depreciation, Depletion and Amortization Income tax expense (benefit) Income Tax Expense (Benefit) Capital additions Property, Plant and Equipment, Additions 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. ASSETS Assets [Abstract] Property, Plant and Equipment Utilities Property Plant and Equipment Gross [Abstract] -- None. No documentation exists for this element. -- 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. 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. Utility plant, at cost Property, Plant and Equipment, Gross Less - Accumulated depreciation Public Utilities, Property, Plant and Equipment, Accumulated Depreciation Net property, plant and equipment Other Property and Investments Property, Plant and Equipment, Other, Net [Abstract] Goodwill Goodwill 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. 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. Current Assets Assets, Current [Abstract] Cash and cash equivalents Accounts receivable - customers, less allowance for doubtful accounts Accounts Receivable, Net, Current Unbilled revenue Unbilled Receivables, Current Receivable from the U.S. government 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. Inter-company receivable Due from Related Parties, Current Other accounts receivable, less allowance for doubtful accounts Accounts and Other Receivables, Net, Current Income taxes receivable Income Taxes Receivable, Current Income taxes receivable from Parent Due from Related Parties, Income Taxes, Current The amount of aggregate amount of current tax-related receivables to be collected from related parties where one party can exercise control or significant influence over another party, which are usually due within one year (or one business cycle). Note receivable from Parent Notes Receivable, Related Parties, Current Materials and supplies, at average cost Inventory, Raw Materials and Supplies, Gross Regulatory assets — current Regulatory Assets, Current Prepayments and other current assets Prepaid Expense and Other Assets, Current Costs and estimated earnings in excess of billings on uncompleted contracts Costs in Excess of Billings, Current Deferred income taxes — current Deferred Tax Assets, Net, Current Total current assets Assets, Current Regulatory and Other Assets Regulatory and Other Assets [Abstract] -- None. No documentation exists for this element. -- Regulatory assets Regulatory Assets, Noncurrent Other accounts receivable Other Accounts Receivable, Noncurrent This element represent the noncurrent portion of amount due from customers, clients, or other third-parties, or arising from transactions not separately disclosed, net of allowances established for the purpose of reducing such receivables to an amount that approximates their net realizable value. Costs and estimated earnings in excess of billings on uncompleted contracts Costs in Excess of Billings, Noncurrent Receivable from the U.S. government, less allowance for doubtful accounts Receivable from U S Government Net Non Current This element represents the amount, at the balance sheet date, noncurrent portion of receivables that are derived from government contracts. Other Other Assets, Noncurrent Total regulatory and 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. CAPITALIZATION AND LIABILITIES Liabilities and Equity [Abstract] Capitalization Capitalization, Long-term Debt and Equity [Abstract] Common shares, no par value Common Stock, Value, Issued Earnings reinvested in the business Retained Earnings (Accumulated Deficit) Total common shareholders’ equity Stockholders' Equity Attributable to Parent Long-term debt Long-term Debt, Excluding Current Maturities Total capitalization Capitalization, Long-term Debt and Equity Current Liabilities Liabilities, Current [Abstract] Long-term debt — current Long-term Debt, Current Maturities Accounts payable Accounts Payable, Current Income taxes payable Taxes Payable, Current Accrued other taxes Franchise and Assessment Fees Taxes Represents franchise and assessment fees taxes. Accrued employee expenses Employee-related Liabilities, Current Accrued interest Accrued Liabilities, Current Billings in excess of costs and estimated earnings on uncompleted contracts Billings in Excess of Cost, Current Dividends payable Interest and Dividends Payable, Current Other Other Liabilities, Current Total current liabilities Liabilities, Current Other Credits Liabilities, Other than Long-term Debt, Noncurrent [Abstract] Advances for construction Customer Advances for Construction Contributions in aid of construction - net Contributions in Aid of Construction Deferred income taxes Deferred Tax Liabilities, Net, Noncurrent Unamortized investment tax credits Accumulated Deferred Investment Tax Credit Accrued pension and other postretirement benefits Pension and Other Postretirement Defined Benefit Plans, Liabilities, Noncurrent Other Other Liabilities, Noncurrent Total other credits Liabilities, Other than Long-term Debt, Noncurrent Commitments and Contingencies (Note 7) Commitments and Contingencies Total Capitalization and Liabilities Liabilities and Equity Income Statement [Abstract] Operating Revenues Revenue, Net [Abstract] Water Regulated Operating Revenue, Water Electric Electric Domestic Regulated Revenue Contracted services Contracts Revenue Total operating revenues Operating Expenses Operating Expenses [Abstract] Water purchased Cost of Purchased Water Power purchased for pumping Power Purchased for Pumping This element represents Power purchased for pumping expenses. Groundwater production assessment Groundwater Production Assessment This element represents the aggregate expenses on groundwater production assessment. Power purchased for resale Cost of Purchased Power 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. Other operation Other Cost and Expense, Operating Administrative and general General and Administrative Expense Depreciation and amortization Maintenance Cost of Property Repairs and Maintenance Property and other taxes ASUS construction Other Cost of Operating Revenue Net gain on sale of property Gain (Loss) on Disposition of Property Plant Equipment Total operating expenses Operating Expenses Operating Income Other Income and Expenses Nonoperating Income (Expense) [Abstract] Interest expense Interest Expense Interest income Investment Income, Interest Other, net Other Nonoperating Income (Expense) Total other income and expenses Nonoperating Income (Expense) Income from operations before income tax expense Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest Income tax expense Net Income (Loss) Attributable to Parent Weighted Average Number of Common Shares Outstanding (in shares) Weighted Average Number of Shares Outstanding, Basic Basic Earnings Per Common Share (in dollars per share) Earnings Per Share, Basic Weighted Average Number of Diluted Shares (in shares) Weighted Average Number of Shares Outstanding, Diluted Fully Diluted Earnings Per Common Share (in dollars per share) Earnings Per Share, Diluted Dividends Paid Per Common Share (in dollars per share) Asset Class [Axis] Asset Class [Axis] Fair Value by Asset Class [Domain] Asset Class [Domain] Mutual Funds Mutual Funds [Member] Mutual Funds [Member] Fair Value, by Balance Sheet Grouping, Disclosure Item Amounts [Axis] Measurement Basis [Axis] Fair Value, Disclosure Item Amounts [Domain] Fair Value Measurement [Domain] Portion at Fair Value Measurement [Member] Portion at Fair Value Measurement [Member] Carrying Amount Reported Value Measurement [Member] Total Estimate of Fair Value Measurement [Member] Fair Value, Hierarchy [Axis] Fair Value, Hierarchy [Axis] Fair Value, Measurements, Fair Value Hierarchy [Domain] Fair Value Hierarchy [Domain] Level 1 Fair Value, Inputs, Level 1 [Member] Investments Investments, Fair Value Disclosure Financial liabilities: Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract] Long-term debt-GSWC Long-term Debt, Fair Value Commitments and Contingencies Disclosure [Abstract] Loss Contingencies [Table] Loss Contingencies [Table] Litigation Case [Axis] Litigation Case [Axis] Litigation Case Type [Domain] Litigation Case [Domain] City of Claremont City of Claremont [Member] Information pertaining to City of Claremont, California. Ojai FLOW Ojai F L O W [Member] Information pertaining to an organization called Ojai FLOW (Friends of Locally Owned Water). Loss Contingency Nature [Axis] Loss Contingency Nature [Axis] Loss Contingency, Nature [Domain] Loss Contingency, Nature [Domain] Condemnation of Properties Condemnation of Properties [Member] Represents the acquisition of public utility property by governmental agencies through their power of eminent domain, also known as condemnation of properties. Environmental Clean-Up and Remediation Environmental Issue [Member] Contingencies Loss Contingencies [Line Items] Condemnation Potential amount of city bonds to be issued Potential amount of city bonds to be issued Number of customers served through water systems Loss Contingency Number of Customers Served Represents the number of customers served by the entity. Amount spent in clean-up and remediation activities Environmental Remediation Expense Amount paid by the State of California Underground Storage Tank Fund for clean-up and remediation of plant facilities Environmental Loss Contingencies Paid by Third Party Represents the amount of environmental remediation costs paid by the third party. Accrued liability for the estimated additional cost to complete the clean-up at the site Accrual for Environmental Loss Contingencies Employee Benefit Plans Pension and Other Postretirement Benefits Disclosure [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] Summary of Significant Accounting Policies Organization, Consolidation, Basis of Presentation, Business Description and Accounting Policies [Text Block] Basic Earnings Per Share, Basic, Two Class Method [Abstract] Less: Distributed earnings to common shareholders 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. Less: Distributed earnings to participating securities Preferred Stock Dividends and Other Adjustments Undistributed earnings Undistributed Earnings, Basic 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. Undistributed earnings allocated to participating securities Undistributed Earnings (Loss) Allocated to Participating Securities, Basic Total income available to common shareholders, basic Net Income (Loss) Available to Common Stockholders, Basic Weighted average Common Shares outstanding, basic (in shares) Basic earnings per Common Share (in dollars per share) Diluted Earnings Per Share, Diluted, Two Class Method [Abstract] Undistributed earnings for dilutive stock options Dilutive Securities, Effect on Basic Earnings Per Share, Options and Restrictive Stock Units Total common shareholders earnings, diluted Net Income (Loss) Available to Common Stockholders, Diluted Stock-based compensation (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Weighted average common shares outstanding, diluted (in shares) Diluted earnings per Common Share (in dollars per share) Document and Entity Information -- None. No documentation exists for this element. -- Document Information [Table] Document Information [Table] Document Information, Document [Axis] Document Information, Document [Axis] Document [Domain] Document [Domain] Document Information [Line Items] Document Information [Line Items] Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Document Type Document Type Document Period End Date Document Period End Date Amendment Flag Amendment Flag Current Fiscal Year End Date Current Fiscal Year End Date Entity Current Reporting Status Entity Current Reporting Status Entity Filer Category Entity Filer Category Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Contingencies Legal Matters and Contingencies [Text Block] Nature of Operations and Basis of Presentation Basis of Accounting, Policy [Policy Text Block] GSWC's Related Party Transactions Related Party Transactions [Policy Text Block] Disclosure of accounting policy related to transactions with related parties. Sales and Use Taxes Sales and Use Taxes [Policy Text Block] Disclosure of accounting policy relating to sales and use taxes. Recently Adopted Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block]