Regulated Operations [Abstract] Regulatory Rate Filings Regulatory Rate Filings [Text Block] Regulatory Rate Filings [Text Block] Segment Reporting [Abstract] Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Business Segments [Axis] Segments [Axis] Segment [Domain] Segments [Domain] Water Utility Services Reportable Segment One [Member] Reportable Segment One [Member] Real Estate Services Reportable Segment Two [Member] Reportable Segment Two [Member] All Other Other Segments [Member] SJW Corp. Corporate Segment [Member] Regulation Status [Axis] Regulation Status [Axis] Regulated and Unregulated Operation [Domain] Regulated and Unregulated Operation [Domain] Regulated Regulated Operation [Member] Non-tariffed Unregulated Operation [Member] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Number of Subsidiaries Number of Subsidiaries Number of Subsidiaries Operating revenue Regulated Operating Revenue Operating expense Utilities Operating Expense Operating income (loss) Operating Income (Loss) Net income (loss) Net Income (Loss) Attributable to Parent Depreciation and amortization Utilities Operating Expense, Depreciation and Amortization Senior note, mortgage and other interest expense Interest Expense Income tax expense (benefit) in net income Income Tax Expense (Benefit) Assets Assets Regulatory Assets and Liabilities Disclosure [Abstract] Schedule of Regulatory Assets Schedule of Regulatory Assets [Table Text Block] Accounting Changes and Error Corrections [Abstract] New Accounting Pronouncements or Change in Accounting Principle [Table] New Accounting Pronouncements or Change in Accounting Principle [Table] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Infrastructure [Member] Infrastructure [Member] Infrastructure [Member] Adjustments for New Accounting Pronouncements [Axis] Adjustments for New Accounting Pronouncements [Axis] Type of Adoption [Domain] Type of Adoption [Domain] Adjustments for New Accounting Pronouncement [Member] Adjustments for New Accounting Pronouncement [Member] New Accounting Pronouncements or Change in Accounting Principle [Line Items] New Accounting Pronouncements or Change in Accounting Principle [Line Items] Intangible assets Finite-Lived Intangible Assets, Gross Accumulated amortization Finite-Lived Intangible Assets, Accumulated Amortization Cumulative effect of prospective application of new accounting principle New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets Statement of Financial Position [Abstract] ASSETS Assets [Abstract] Utility plant: Public Utilities, Property, Plant and Equipment, Net [Abstract] Land Public Utilities, Property, Plant and Equipment, Land Depreciable plant and equipment Public Utilities, Property, Plant and Equipment, Plant in Service Construction in progress Public Utilities, Property, Plant and Equipment, Construction Work in Progress Property, Plant and Equipment, Gross Property, Plant and Equipment, Gross Less accumulated depreciation and amortization Public Utilities, Property, Plant and Equipment, Accumulated Depreciation Public Utilities, Property, Plant and Equipment, Net Public Utilities, Property, Plant and Equipment, Net Real estate investments Real Estate Investment Property, at Cost Less accumulated depreciation and amortization Real Estate Investment Property, Accumulated Depreciation Total Property, Plant and Equipment, Net CURRENT ASSETS: Assets, Current [Abstract] Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Accounts receivable: Accounts Receivable, Net, Current [Abstract] Customers, net of allowances for uncollectible accounts Accounts Receivable, Net, Current Income tax Income Taxes Receivable, Current Other Nontrade Receivables, Current Accrued unbilled utility revenue Receivables, Long-term Contracts or Programs Current regulatory assets, net Regulatory Assets, Current Other current assets Other Assets, Current Assets, Current Assets, Current OTHER ASSETS: Other Assets, Noncurrent [Abstract] Investment in California Water Service Group Available-for-sale Securities, Equity Securities, Noncurrent Unamortized debt issuance, broker and reacquisition costs Unamortized Debt Issuance Expense and Broker Fees The remaining balance of debt issuance expenses and broker fees that were capitalized and are being amortized against income over the lives of the respective note issues and leases. Net regulatory assets, less current portion Regulatory Assets, Noncurrent Other Other Assets, Noncurrent Assets, Noncurrent Assets, Noncurrent Assets CAPITALIZATION AND LIABILITIES Liabilities and Equity [Abstract] CAPITALIZATION: Capitalization, Long-term Debt and Equity [Abstract] Shareholders' equity: Stockholders' Equity, Number of Shares, Par Value and Other Disclosures [Abstract] Common stock, $0.521 par value; authorized 36,000,000 shares; issued and outstanding 20,381,949 shares on September 30, 2015 and 20,286,840 on December 31, 2014 Common Stock, Value, Issued Additional paid-in capital Additional Paid in Capital, Common Stock Retained earnings Retained Earnings (Accumulated Deficit) Accumulated other comprehensive income Accumulated Other Comprehensive Income (Loss), Net of Tax Total shareholders' equity Stockholders' Equity Attributable to Parent Long-term debt, less current portion Long-term Debt, Excluding Current Maturities Capitalization, Long-term Debt and Equity Capitalization, Long-term Debt and Equity CURRENT LIABILITIES: Liabilities, Current [Abstract] Line of credit Line of Credit, Current Current portion of long-term debt Long-term Debt, Current Maturities Accrued groundwater extraction charges, purchased water and power Accrued groundwater extraction charges, purchased water and power Accrued groundwater extraction charges, purchased water and power Accounts payable Accounts Payable, Current Accrued interest Interest Payable, Current Accrued property taxes and other non-income taxes Accrual for Taxes Other than Income Taxes, Current Accrued payroll Employee-related Liabilities, Current Other current liabilities Other Liabilities, Current Liabilities, Current Liabilities, Current DEFERRED INCOME TAXES Deferred Tax Liabilities, Net, Noncurrent ADVANCES FOR CONSTRUCTION Customer Advances for Construction CONTRIBUTIONS IN AID OF CONSTRUCTION Contributions in Aid of Construction POSTRETIREMENT BENEFIT PLANS Pension and Other Postretirement Defined Benefit Plans, Liabilities, Noncurrent REGULATORY LIABILITY Regulatory Liability, Noncurrent OTHER NONCURRENT LIABILITIES Other Liabilities, Noncurrent COMMITMENTS AND CONTINGENCIES Commitments and Contingencies Liabilities and Equity Liabilities and Equity Schedule of Regulatory Assets [Table] Schedule of Regulatory Assets [Table] Regulatory Liability [Axis] Regulatory Liability [Axis] Regulatory Liability [Domain] Regulatory Liability [Domain] Balancing and memorandum accounts, net Balancing and Memorandum Accounts [Member] Balancing and Memorandum Accounts [Member] Regulatory Asset [Axis] Regulatory Asset [Axis] Regulatory Asset [Domain] Regulatory Asset [Domain] Income tax temporary differences, net Deferred Income Tax Charge [Member] Postretirement pensions and other medical benefits Postretirement Pensions and Other Medical Benefits [Member] Postretirement Pensions and Other Medical Benefits [Member] Other, net Other Regulatory Assets [Member] Other Regulatory Assets [Member] Regulatory Assets [Line Items] Regulatory Assets [Line Items] Regulatory assets: Regulatory Assets Net Regulatory Assets Net Regulatory Assets Less: current regulatory asset, net Regulatory Liabilities Regulatory Liabilities Organization, Consolidation and Presentation of Financial Statements [Abstract] GENERAL Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Basis of Accounting, Policy Basis of Accounting, Policy [Policy Text Block] New Accounting Pronouncements, Policy New Accounting Pronouncements, Policy [Policy Text Block] Earnings Per Share, Policy Earnings Per Share, Policy [Policy Text Block] Debt Disclosure [Abstract] Long-Term Liabilities and Bank Borrowings Long-term Debt [Text Block] Disclosure of Compensation Related Costs, Share-based Payments [Abstract] EQUITY PLANS Shareholders' Equity and Share-based Payments [Text Block] Public Utilities General Disclosures Public Utilities General Disclosures [Table Text Block] Investments, Debt and Equity Securities [Abstract] Schedule of Regulatory Liabilities [Table] Schedule of Regulatory Liabilities [Table] Scenario [Axis] Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Scenario, Forecast [Member] Scenario, Forecast [Member] Regulatory Liabilities [Line Items] Regulatory Liabilities [Line Items] Authorized Regulatory Surcharge, Gross Authorized Regulatory Surcharge, Gross Authorized Regulatory Surcharge, Gross Regulatory Rate Filings, Requested Rate Increase, Year One Regulatory Rate Filings, Requested Rate Increase, Year One Regulatory Rate Filings, Requested Rate Increase, Year One Regulatory Rate Filings, Requested Rate Increase as Percentage of Total Revenue at Time of Request, Year One Regulatory Rate Filings, Requested Rate Increase as Percentage of Total Revenue at Time of Request, Year One Regulatory Rate Filings, Requested Rate Increase as Percentage of Total Revenue at Time of Request, Year One Regulatory Rate Filings, Requested Rate Increase, Year Two Regulatory Rate Filings, Requested Rate Increase, Year Two Regulatory Rate Filings, Requested Rate Increase, Year Two Regulatory Rate Filings, Proposed Rate Increase, Percent of Authorized Revenue, Year Two Regulatory Rate Filings, Proposed Rate Increase, Percent of Authorized Revenue, Year Two Regulatory Rate Filings, Proposed Rate Increase, Percent of Authorized Revenue, Year Two Regulatory Rate Filings, Requested Rate Increase, Year Three Regulatory Rate Filings, Requested Rate Increase, Year Three Regulatory Rate Filings, Requested Rate Increase, Year Three Regulatory Rate Filings, Requested Rate Increase, Percent of Authorized Revenue, Year Three Regulatory Rate Filings, Requested Rate Increase, Percent of Authorized Revenue, Year Three Regulatory Rate Filings, Requested Rate Increase as Percentage of Total Revenue at Time of Request, Year Three Balancing Account, Recovery Request Balancing Account, Recovery Request A request to the regulatory authority for authorization to recover under (over) -collected amounts. Memorandum Account, Recovery Request Memorandum Account, Recovery Request A request to the regulatory authority for authorization to refund over (under) collected amounts. Regulatory Rate Filings, Recommended Rate Increase, Year One Regulatory Rate Filings, Recommended Rate Increase, Year One Regulatory Rate Filings, Recommended Rate Increase, Year One Regulatory Rate Filings, Recommended Rate Increase as Percentage of Total Revenue at Time of Request, Year One Regulatory Rate Filings, Recommended Rate Increase as Percentage of Total Revenue at Time of Request, Year One Regulatory Rate Filings, Recommended Rate Increase as Percentage of Total Revenue at Time of Request, Year One Regulatory Rate Filings, Recommended Rate Increase, Year Two Regulatory Rate Filings, Recommended Rate Increase, Year Two Regulatory Rate Filings, Recommended Rate Increase, Year Two Regulatory Rate Filings, Recommended Rate Increase as Percentage of Total Revenue at Time of Request, Year Two Regulatory Rate Filings, Recommended Rate Increase as Percentage of Total Revenue at Time of Request, Year Two Regulatory Rate Filings, Recommended Rate Increase as Percentage of Total Revenue at Time of Request, Year Two Regulatory Rate Filings, Recommended Rate Increase, Year Three Regulatory Rate Filings, Recommended Rate Increase, Year Three Regulatory Rate Filings, Recommended Rate Increase, Year Three Regulatory Rate Filings, Recommended Rate Increase as Percentage of Total Revenue at Time of Request, Year Three Regulatory Rate Filings, Recommended Rate Increase as Percentage of Total Revenue at Time of Request, Year Three Regulatory Rate Filings, Recommended Rate Increase as Percentage of Total Revenue at Time of Request, Year Three Regulatory Rate Filings, Requested Rate Increase, Authorized Revenue Regulatory Rate Filings, Requested Rate Increase, Authorized Revenue Regulatory Rate Filings, Requested Rate Increase, Authorized Revenue Regulatory Rate Filings, Increase Requested, Percent of Authorized Revenue Regulatory Rate Filings, Increase Requested, Percent of Authorized Revenue Regulatory Rate Filings, Total Increase Requested, Percentage Regulatory Rate Filings, Requested Issuance of Debt and Equity Securities Regulatory Rate Filings, Requested Issuance of Debt and Equity Securities Regulatory Rate Filings, Requested Issuance of Debt and Equity Securities Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Title of Individual [Axis] Title of Individual [Axis] Relationship to Entity [Domain] Relationship to Entity [Domain] Board Member [Member] Board Member [Member] Board Member [Member] Executive Officer [Member] Executive Officer [Member] Officer [Member] Officer [Member] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum Minimum [Member] Maximum Maximum [Member] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] Common Stock Common Stock [Member] Award Type [Axis] Award Type [Axis] Award Type [Domain] Equity Award [Domain] Restricted stock and deferred restricted stock Restricted Stock and Deferred Restricted Stock [Member] Restricted Stock and Deferred Restricted Stock [Member] Stock options Employee Stock Option [Member] Restricted Stock Units (RSUs) Restricted Stock Units (RSUs) [Member] Performance Shares [Member] Performance Shares [Member] Plan Name [Axis] Plan Name [Axis] Plan Name [Domain] Plan Name [Domain] Incentive Plan Incentive Plan [Member] Incentive Plan [Member] Employee Stock Purchase Plan (ESPP) Employee Stock [Member] Dividend Reinvestment and Stock Purchase Plan (DRSPP) Dividend Reinvestment and Stock Purchase Plan [Member] Dividend Reinvestment and Stock Purchase Plan [Member] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Remaining shares available for issuance under the Incentive Plan (shares) Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant Shares issuable upon exercise of Incentive Plan awards (shares) Share-based Compensation Arrangement by Share-based Payment Award, Shares Issuable upon Exercise Number of shares reserved for issuance under equity instrument agreements awarded that validly exist and are outstanding, including vested instruments. Compensation costs charged to income: Allocated Share-based Compensation Expense Excess tax benefits realized from share options exercised and stock issuance: Excess Tax Benefit from Share-based Compensation, Financing Activities Proceeds from the exercise of stock options and similar instruments: Proceeds from Issuance of Shares under Incentive and Share-based Compensation Plans, Including Stock Options Number of equity instruments granted (shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Number of equal successive installments for vesting of stock awards (vesting installments) Number of Equal Successive Installments for Vesting of Stock Awards Number of Equal Successive Installments for Vesting of Stock Awards Grant date fair value of equity instruments granted (usd per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Target vesting percentage Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage Unrecognized compensation costs Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized Recognition period for unrecognized compensation cost Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition Purchase price of common stock under ESPP (percent) Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent Maximum percentage of base compensation employees can designate for stock purchases under ESPP (percent) Share-based Compensation Arrangement by Share-based Payment Award, Maximum Employee Subscription Rate Number of shares authorized for issuance under the plan (shares) Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized Plan expense Stock or Unit Option Plan Expense Number of shares issued under the DRSPP (shares) Stock Issued During Period, Shares, Dividend Reinvestment and Stock Purchase Plan Number of shares issued during the period from a dividend reinvestment and stock purchase plan (DRSPP). A dividend reinvestment and stock purchase plan allows the shareholders to reinvest dividends paid to them by the entity on new issues of stock by the entity and to purchase additional shares. SEGMENT AND NONREGULATED BUSINESS REPORTING Segment Reporting Disclosure [Text Block] Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] Lender Name [Axis] Lender Name [Axis] Line of Credit Facility, Lender [Domain] Line of Credit Facility, Lender [Domain] Credit Facility [Axis] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Debt Instrument [Line Items] Debt Instrument [Line Items] Document and Entity Information [Abstract] Document and Entity Information [Abstract] Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Document Type Document Type Document Period End Date Document Period End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Amendment Flag Amendment Flag Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Accounting Policies [Abstract] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Restricted Stock and Stock Options Restricted Stock and Stock Options [Member] Restricted Stock and Stock Options [Member] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Anti-dilutive restricted common stock units excluded from computation of earnings per share (shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Regulatory Assets and Liabilities Schedule of Regulatory Assets and Liabilities [Text Block] Real Estate Investments, Net [Abstract] Schedule of Investments [Table] Schedule of Investments [Table] Long Lived Assets Held-for-sale by Asset Type [Axis] Long Lived Assets Held-for-sale by Asset Type [Axis] Long Lived Assets Held-for-sale, Name [Domain] Long Lived Assets Held-for-sale, Name [Domain] California Non-Utility Property Portfolio [Domain] California Non-Utility Property Portfolio [Domain] California Non-Utility Property Portfolio [Domain] California Non-Utility Property [Member] California Non-Utility Property [Member] California Non-Utility Property Texas Retail Buildings [Member] Texas Retail Buildings [Member] Texas Retail Buildings [Member] Schedule of Investments [Line Items] Schedule of Investments [Line Items] Land Land Buildings and improvements Investment Building and Building Improvements Intangibles Real Estate Investments, Intangibles Gross carrying amount before accumulated amortization as of the balance sheet date of intangible assets related to Real Estate Investments having a reasonably expected period of economic benefit. Subtotal Estimated useful life SEC Schedule III, Real Estate and Accumulated Depreciation, Life Used for Depreciation Proceeds from Sale of Real Estate Held-for-investment Proceeds from Sale of Real Estate Held-for-investment Gain on sale of real estate investment Gain (Loss) on Sale of Properties Real Estate Selling Expenses Real Estate Selling Expenses Real Estate Selling Expenses REAL ESTATE INVESTMENTS SEC Schedule III, Real Estate and Accumulated Depreciation Disclosure [Text Block] BALANCING AND MEMORANDUM ACCOUNT RECOVERY PROCEDURES Public Utilities Disclosure [Text Block] Common stock, par value (usd per share) Common Stock, Par or Stated Value Per Share Common stock, shares authorized (shares) Common Stock, Shares Authorized Common stock, shares issued (shares) Common Stock, Shares, Issued Common stock, shares outstanding (shares) Common Stock, Shares, Outstanding Compensation and Retirement Disclosure [Abstract] DEFINED BENEFIT PLAN Pension and Other Postretirement Benefits Disclosure [Text Block] Fair Value Disclosures [Abstract] FAIR VALUE MEASUREMENT Fair Value Disclosures [Text Block] Schedule of Segment Reporting Information, by Segment Schedule of Segment Reporting Information, by Segment [Table Text Block] Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Fair Value, Hierarchy [Axis] Fair Value, Hierarchy [Axis] Fair Value, Measurements, Fair Value Hierarchy [Domain] Fair Value Hierarchy [Domain] Quoted Prices in Active Markets for Identical Assets Fair Value, Inputs, Level 1 [Member] Significant Observable Inputs Fair Value, Inputs, Level 2 [Member] Significant Unobservable Inputs Fair Value, Inputs, Level 3 [Member] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Long-term debt, fair value Long-term Debt, Fair Value Long-term debt Long-term Debt Investment in California Water Service Group Available-for-sale Securities Public Utilities General Disclosures [Table] Public Utilities General Disclosures [Table] Drought Surcharges [Member] Drought Surcharges [Member] Drought Surcharges [Member] Water supply balancing accounts Water Supply Balancing Accounts [Member] Water Supply Balancing Accounts [Member] Pension balancing account Pension Balancing Account [Member] Pension Balancing Account [Member] 2012 General Rate Case true-up 2012 General Rate Case True-up [Member] 2012 General Rate Case True-up [Member] Public Utilities, General Disclosures [Line Items] Public Utilities, General Disclosures [Line Items] Memorandum Accounts [Roll Forward] Memorandum Accounts [Roll Forward] Memorandum Accounts [Roll Forward] Beginning Balance Memorandum Account, Net This represents the memorandum accounts that track under-collection or over-collection for approved activities as directed by the CPUC. Rate recovery for these memorandum accounts is generally allowed in the next general rate cases. Revenue Increase(Reduction) Memorandum Account, Revenue Increase (Reduction) Memorandum Account, Revenue Increase (Reduction) Refunds (Collections) Memorandum Account, Refunds (Collections) Memorandum Account, Refunds (Collections) Ending Balance Balancing Accounts [Roll Forward] Balancing Accounts [Roll Forward] Balancing Accounts [Roll Forward] Beginning Balance Balancing Account, Net This represents the under-collection or over-collection associated with expense changes and the revenue authorized by the CPUC to offset those expense changes. Pursuant to Section 792.5 of the California Public Utilities Code, a balancing account must be maintained for expense items for which revenue offsets have been authorized. Since the amounts in the balancing accounts must be approved by the CPUC before they can be incorporated into rates, the Company does not recognize balancing accounts in its revenue until CPUC approval occurs. It is typical for the CPUC to incorporate any over-collected and/or under-collected balances in balancing accounts into customer rates at the time rate decisions are made as part of the Company’s general rate case proceedings by assessing temporary surcredits and/or surcharges. Revenue Increase(Reduction) Balancing Account, Revenue Increase (Reduction) Balancing Account, Revenue Increase (Reduction) Refunds (Collections) Balancing Account, Refunds (Collections) Balancing Account, Refunds (Collections) Ending Balance Balancing and Memorandum Account [Roll Forward] Balancing and Memorandum Account [Roll Forward] Balancing and Memorandum Account [Roll Forward] Balancing and Memorandum Accounts, Net Assets Balancing and Memorandum Accounts, Net Assets Balancing and Memorandum Accounts, Net Assets Revenue Increase(Reduction) Balancing and Memorandum Account, Revenue Increase (Reduction), Net Balancing and Memorandum Account, Revenue Increase (Reduction), Net Refunds (Collections) Balancing and Memorandum Account, Refunds (Collections) Balancing and Memorandum Account, Refunds (Collections) Balancing and Memorandum Accounts, Net Assets Balancing Account, Liability Balancing Account, Liability Balancing Account, Liability Balancing and Memorandum Account, Revenue Increase (Reduction), Net Liability Balancing and Memorandum Account, Revenue Increase (Reduction), Net Liability Balancing and Memorandum Account, Revenue Increase (Reduction), Net Liability Balancing and Memorandum Account, Net Liability, Refunds (Collections) Balancing and Memorandum Account, Net Liability, Refunds (Collections) Balancing and Memorandum Account, Net Liability, Refunds (Collections) Balancing Account, Liability Net under-collected balancing and memorandum accounts Regulatory Balancing and Memorandum Accounts, Net Under-Collected Regulatory Balancing and Memorandum Accounts,, Net Under-Collected Public Utility, Property, Plant and Equipment [Table] Public Utility, Property, Plant and Equipment [Table] Income Statement Location [Axis] Income Statement Location [Axis] Income Statement Location [Domain] Income Statement Location [Domain] General and Administrative Expense General and Administrative Expense [Member] Public Utility, Property, Plant and Equipment [Line Items] Public Utility, Property, Plant and Equipment [Line Items] Depreciation Depreciation Schedule of Net Benefit Costs Schedule of Net Benefit Costs [Table Text Block] Schedule of Allocation of Plan Assets Schedule of Allocation of Plan Assets [Table Text Block] Commitments and Contingencies Disclosure [Abstract] LEGAL PROCEEDINGS Commitments and Contingencies Disclosure [Text Block] Income Statement [Abstract] OPERATING REVENUE OPERATING EXPENSE: Costs and Expenses [Abstract] Production Expenses: Water Production Costs [Abstract] Water Production Costs [Abstract] Purchased water Cost of Purchased Water Power Utilities Operating Expense, Purchased Power Groundwater extraction charges Groundwater Extraction Charges Groundwater Extraction Charges Other production expenses Utilities Operating Expense, Other Total production expenses Water Production Costs Administrative and general General and Administrative Expense Maintenance Utilities Operating Expense, Maintenance Property taxes and other non-income taxes Utilities Operating Expense, Taxes Total operating expense OPERATING INCOME OTHER (EXPENSE) INCOME: Other Nonoperating Income (Expense) [Abstract] Interest on long-term debt Interest Expense, Debt Mortgage and other interest expense Interest Expense, Other Gain on sale of California Water Service Group stock Available-for-sale Securities, Gross Realized Gain (Loss) Dividend income Investment Income, Dividend Other, net Other Nonoperating Income (Expense) Income before income taxes Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest Provision for income taxes NET INCOME Other comprehensive income (loss), net of tax: Other Comprehensive Income (Loss), Net of Tax [Abstract] Unrealized loss on investment Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax Reclassification adjustment for gain realized on sale of investments Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax COMPREHENSIVE INCOME Comprehensive Income (Loss), Net of Tax, Attributable to Parent EARNINGS PER SHARE Earnings Per Share [Abstract] Basic (usd per share) Earnings Per Share, Basic Diluted (usd per share) Earnings Per Share, Diluted DIVIDENDS PER SHARE (usd per share) Common Stock, Dividends, Per Share, Declared WEIGHTED AVERAGE SHARES OUTSTANDING Weighted Average Number of Shares Outstanding Basic and Diluted [Abstract] Weighted Average Number of Shares Outstanding Basic and Diluted [Abstract] Basic (shares) Weighted Average Number of Shares Outstanding, Basic Diluted (shares) Weighted Average Number of Shares Outstanding, Diluted Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs by Plan Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs by Plan [Table Text Block] Statement of Cash Flows [Abstract] OPERATING ACTIVITIES: Net Cash Provided by (Used in) Operating Activities [Abstract] Net income Adjustments to reconcile net income to net cash provided by operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Depreciation and amortization Depreciation, Depletion and Amortization Deferred income taxes Deferred Income Tax Expense (Benefit) Share-based compensation Share-based Compensation Gain on sale of real estate investment Gain on sale of California Water Service Group stock Changes in operating assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Accounts receivable and accrued unbilled utility revenue Increase (Decrease) in Receivables Accounts payable and other current liabilities Increase (Decrease) in Accounts Payable Accrued groundwater extraction charges, purchased water and power Increase (Decrease) in Accrued Groundwater Extraction Charges, Purchased Water and Power Increase (Decrease) in Accrued Groundwater Extraction Charges, Purchased Water and Power Tax receivable and accrued taxes Increase (Decrease) in Accrued Taxes Payable Postretirement benefits Increase (Decrease) in Pension and Postretirement Obligations Regulatory assets and liability related to balancing and memorandum accounts Increase (Decrease) to Regulatory Asset Related to Balancing and Memorandum Accounts Increase (Decrease) to Regulatory Asset Related to Balancing and Memorandum Accounts Other changes, net Increase (Decrease) in Other Operating Assets and Liabilities, Net NET CASH PROVIDED BY OPERATING ACTIVITIES Net Cash Provided by (Used in) Operating Activities INVESTING ACTIVITIES: Net Cash Provided by (Used in) Investing Activities [Abstract] Company-funded Payments to Acquire Water Systems Contributions in aid of construction Payments to Acquire Water Systems using Contributions In Aid of Construction Payments to Acquire Water Systems using Contributions In Aid of Construction Additions to real estate investments Payments to Acquire Real Estate Payments for business/asset acquisition and water rights Payments to Acquire Businesses, Assets and Water Rights Payments to Acquire Businesses, Assets and Water Rights Payments to retire utility plant, net of salvage Payments for (Proceeds from) Removal Costs Proceeds from sale of real estate investment Proceeds from Sale of Property Held-for-sale Proceeds from sale of California Water Service Group stock Proceeds from Sale of Available-for-sale Securities, Equity NET CASH USED IN INVESTING ACTIVITIES Net Cash Provided by (Used in) Investing Activities FINANCING ACTIVITIES: Net Cash Provided by (Used in) Financing Activities [Abstract] Borrowings from line of credit Proceeds from Lines of Credit Repayments of line of credit Repayments of Lines of Credit Long-term borrowings Proceeds from Issuance of Long-term Debt Repayments of long-term borrowings Repayments of Long-term Debt Dividends paid Payments of Ordinary Dividends, Common Stock Exercise of stock options and similar instruments Tax benefits realized from share options exercised Receipts of advances and contributions in aid of construction Proceeds from Contribution in Aid of Construction Refunds of advances for construction Repayments of Advances for Construction NET CASH PROVIDED BY FINANCING ACTIVITIES Net Cash Provided by (Used in) Financing Activities 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, END OF PERIOD Cash paid during the period for: Supplemental Cash Flow Information [Abstract] Interest Interest Paid Income taxes Income Taxes Paid, Net Supplemental disclosure of non-cash activities: Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Increase (decrease) in accrued payables for construction costs capitalized Noncash or Part Noncash Acquisition, Payables Assumed Utility property installed by developers Utility Property Installed by Developer Utility Property Installed by Developer Schedule of Defined Benefit Plans Disclosures [Table] Schedule of Defined Benefit Plans Disclosures [Table] Defined Benefit Plan, Asset Categories [Axis] Defined Benefit Plan, Asset Categories [Axis] Plan Asset Categories [Domain] Plan Asset Categories [Domain] Cash and cash equivalents Cash and Cash Equivalents [Member] Actively Managed Actively Managed Investments [Member] Actively Managed Investments [Member] Fixed Income Fixed Income Funds [Member] Investment Type [Axis] Investment Type [Axis] Investment Type Categorization [Domain] Investments [Domain] Equity Securities [Member] Equity Securities [Member] All Cap Equity All Cap Equity Fund [Member] All Cap Equity Fund [Member] U.S. Large Cap Equity U.S. Large Cap Equity [Member] U.S. Large Cap Equity [Member] U.S. Mid Cap Equity U.S. Mid Cap Equity [Member] U.S. Mid Cap Equity [Member] U.S. Small Cap Equity U.S. Small Cap Equity [Member] U.S. Small Cap Equity [Member] Non-U.S. Large Cap Equity Non-U.S. Large Cap Equity [Member] Non-U.S. Large Cap Equity [Member] REIT 6798 Real Estate Investment Trusts [Member] Fixed Income Securities [Member] Fixed Income Securities [Member] Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] Components of Net Periodic Benefit Cost [Abstract] Defined Benefit Plan, Net Periodic Benefit Cost [Abstract] Service cost Defined Benefit Plan, Service Cost Interest cost Defined Benefit Plan, Interest Cost Other cost Defined Benefit Plan, Other Costs Expected return on assets Defined Benefit Plan, Expected Return on Plan Assets Net periodic benefit cost Defined Benefit Plan, Net Periodic Benefit Cost Plan Assets [Abstract] Plan Assets [Abstract] Plan Assets [Abstract] Fair value of plan assets Defined Benefit Plan, Fair Value of Plan Assets Target plan asset allocations Defined Benefit Plan, Target Plan Asset Allocations Employer Contributions [Abstract] Pension and Other Postretirement Benefit Contributions [Abstract] Estimated employer contributions for the current fiscal year Defined Benefit Plan, Estimated Total Employer Contributions for the Current Fiscal Year The employer's best estimate of total contributions expected to be paid to the plan for the current fiscal period. Estimated contributions may be presented in the aggregate combining (1) contributions required by funding regulations or laws, (2) discretionary contributions, and (3) noncash contributions. Defined Contribution Plan, Employer Required and Discretionary Contribution Amount Defined Contribution Plan, Employer Required and Discretionary Contribution Amount The total amount of required and discretionary contributions made by an employer to a defined contribution plan during the period. Schedule of Real Estate Investments Schedule of Real Estate Investments [Table Text Block] Tabular disclosure of real estate investments. Water reduction target goal (percent) Water Reduction Target Goal, Percentage Water Reduction Target Goal, Percentage Mandatory Water Reduction, Percentage Mandatory Water Reduction, Percentage Mandatory Water Reduction, Percentage