Cover [Abstract] Entity Central Index Key Document Fiscal Period Focus Document Fiscal Year Focus Current Fiscal Year End Date Amendment Flag Document Type Document Annual Report Document Period End Date Document Transition Report Entity File Number Entity Registrant Name Entity Incorporation State Country Code Entity Tax Identification Number Entity Address, Address Line One Entity Address, Address Line Two Entity Address, City or Town Entity Address, State or Province Entity Address, Postal Zip Code City Area Code Local Phone Number Title of 12(b) Security Trading Symbol Name of Exchange on which Security is Registered Entity a Well-known Seasoned Issuer Entity a Voluntary Filer Entity Reporting Status Current Entity Interactive Data Current Entity Filer Category Entity Small Business Entity Emerging Growth Company Auditor Attestation Flag Entity Shell Company Entity Public Float Entity Common Stock, Shares Outstanding Documents Incorporated By Reference Text Block Auditor Name Auditor Location Auditor Firm Id Income Statement [Abstract] Operating Revenues Total Revenue Revenues Operating Expenses: Operations and Maintenance Costs incurred and are directly related to operations and maintenance. Depreciation Other Taxes Total Operating Expenses Operating Expenses Operating Income Operating Income Other Income (Expense): Allowance for Funds Used During Construction Other Income (Expense), net Total Other Income, net Nonoperating Income (Expense) Interest Charges Interest Expense Income before Income Taxes Income Taxes Total Income Tax (Benefit) Expense Income taxes Paid Net Income Net Income Preferred Stock Dividend Requirements Preferred Dividend Earnings Applicable to Common Stock Earnings Applicable to Common Stock Earnings per share of Common Stock: Basic Basic EPS Basic Earnings per Share Diluted Diluted EPS Diluted Earnings per Share Average Number of Common Shares Outstanding : Basic Weighted-average number of basic shares outstanding, shares Diluted Weighted-average diluted shares outstanding, shares Statement of Financial Position [Abstract] ASSETS UTILITY PLANT: Water Production Transmission and Distribution General Construction Work in Progress TOTAL Public Utilities, Property, Plant and Equipment, Plant in Service Less Accumulated Depreciation UTILITY PLANT - NET Public Utilities, Property, Plant and Equipment, Net CURRENT ASSETS: Cash and Cash Equivalents Accounts Receivable, net of allowance for uncollectible accounts of $2,574 and $2,053, respectively Unbilled Revenues Materials and Supplies (at average cost) Prepayments TOTAL CURRENT ASSETS Assets, Current OTHER ASSETS: Deferred Charges And Other Assets [Abstract]. Operating Lease Right of Use Asset Preliminary Survey and Investigation Charges Deferred balance for preliminary survey charges and investigation charges. Regulatory Assets Restricted Cash Non-utility Assets - Net Refers to amount of non utility fixed assets as of the balance sheet date. Other TOTAL OTHER ASSETS This element represents aggregate carrying amount, at the balance sheet date, of noncurrent deferred charges held by public utility entities and other noncurrent assets not separately disclosed in the balance sheet. Deferred Charges And Other Assets TOTAL ASSETS Assets CAPITALIZATION AND LIABILITIES CAPITALIZATION: Capitalization, Long-term Debt and Equity [Abstract] Common Stock, No Par Value Retained Earnings TOTAL COMMON EQUITY TOTAL COMMON EQUITY Balance Balance Refers to total equity attributable to common stockholders. Preferred Stock TOTAL PREFERRED STOCK Long-term Debt TOTAL LONG-TERM DEBT TOTAL CAPITALIZATION Capitalization, Long-term Debt and Equity CURRENT LIABILITIES: Current Portion of Long-term Debt Notes Payable Accounts Payable Accrued Taxes Accrued Interest Unearned Revenues and Advanced Service Fees Unearned revenues and advanced service fees. Other Other Liabilities, Current TOTAL CURRENT LIABILITIES Liabilities, Current COMMITMENTS AND CONTINGENT LIABILITIES (Note 4) OTHER LIABILITIES: Customer Advances for Construction Customer advances Construction advances from customers. Lease Obligations Accumulated Deferred Income Taxes Employee Benefit Plans Regulatory Liabilities Other Other Liabilities, Noncurrent TOTAL OTHER LIABILITIES Liabilities, Other than Long-term Debt, Noncurrent CONTRIBUTIONS IN AID OF CONSTRUCTION TOTAL CAPITALIZATION AND LIABILITIES Liabilities and Equity Consolidated Balance Sheets Allowance for uncollectible accounts Statement of Cash Flows [Abstract] CASH FLOWS FROM OPERATING ACTIVITIES: Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities: Depreciation and Amortization Provision for Deferred Income Taxes Deferred income tax benefits Equity Portion of Allowance for Funds Used During Construction (AFUDC) Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity Cash Surrender Value of Life Insurance Life Insurance, Corporate or Bank Owned, Change in Value Stock Compensation Expense Changes in Assets and Liabilities: Accounts Receivable Increase (Decrease) in Accounts Receivable Unbilled Revenues Increase (Decrease) in Other Operating Assets Materials & Supplies Increase (Decrease) in Raw Materials, Packaging Materials and Supplies Inventories Prepayments Increase (Decrease) in Prepaid Expense Accounts Payable Increase (Decrease) in Accounts Payable Accrued Taxes Increase (Decrease) in Accrued Taxes Payable Accrued Interest Increase (Decrease) in Interest Payable, Net Employee Benefit Plans Increase (Decrease) in Obligation, Pension and Other Postretirement Benefits Unearned Revenue & Advanced Service Fees Increase (decrease) in deferred revenue for the period. Other Assets and Liabilities Increase (Decrease) in Other Operating Assets and Liabilities, Net NET CASH PROVIDED BY OPERATING ACTIVITIES Net Cash Provided by (Used in) Operating Activities CASH FLOWS FROM INVESTING ACTIVITIES: Utility Plant Expenditures, Including AFUDC of $1,148 in 2021, $1,513 in 2020 and $1,149 in 2019 Capital Expenditures NET CASH USED IN INVESTING ACTIVITIES Net Cash Provided by (Used in) Investing Activities CASH FLOWS FROM FINANCING ACTIVITIES: Redemption of Long-term Debt Repayments of Long-term Debt Proceeds from Issuance of Long-term Debt Proceeds from Premium Issuance of Long-term Debt The cash inflow from amount of debt premium that was originally recognized at the issuance of the instrument . Net Short-term Bank Borrowings Deferred Debt Issuance Expense Payments of Debt Issuance Costs Common Stock Issuance Expense Payments of Stock Issuance Costs Proceeds from Issuance of Common Stock Payment of Common Dividends Payments of Ordinary Dividends, Common Stock Payment of Preferred Dividends Payments of Ordinary Dividends, Preferred Stock and Preference Stock Construction Advances and Contributions-Net NET CASH PROVIDED BY FINANCING ACTIVITIES Net Cash Provided by (Used in) Financing Activities NET CHANGES IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Excluding Exchange Rate Effect CASH, CASH EQUIVALENTS AND RESTRICTED CASH AT BEGINNING OF PERIOD CASH, CASH EQUIVALENTS AND RESTRICTED CASH AT END OF PERIOD Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents SUPPLEMENTAL DISCLOSURE OF NON-CASH ACTIVITY: Utility Plant received as Construction Advances and Contributions Long-term Debt Deobligation Refers to value of long term debt deobligation in noncash investing and financing activities. SUPPLEMENTAL DISCLOSURE OF CASH FLOWS INFORMATION: Cash Paid During the Year for: Cash Paid During the Year for: Interest Interest Capitalized Income Taxes Income Taxes Paid, Net Allowance for funds used during construction Statement [Table] Debt Instrument [Axis] First Mortgage Bonds [Member] First Mortgage Bonds [Member] FirstMortgageOne1Member Amortizing Secured Notes [Member] Amortizing Secured Notes [Member] State Revolving Trust Notes [Member] State Revolving Trust Notes [Member] State Revolving Fund Bond [Member] State Revolving Fund Bond [Member] Construction Loans [Member] Construction Loans [Member] Class of Stock [Axis] Convertible Preferred Stock $7.00 Series Nonredeemable Preferred Stock $7.00 Series Nonredeemable Preferred Stock $4.75 Series [Member] Preferred shares that are not redeemable before liquidation of the entity. Preferred shares may provide a preferential dividend to the dividend on common stock and may take precedence over common stock in the event of a liquidation. Preferred shares typically represent an ownership interest in the company. Statement [Line Items] SUBTOTAL LONG-TERM DEBT Long-term debt Add: Premium on Issuance of Long-term Debt Less: Unamortized Debt Expense Debt Instrument, Unamortized Discount Less: Current Portion of Long-term Debt Long-term Debt, Current Maturities First Mortgage Bonds due 2023-2059 [Member] First Mortgage Bonds due 2021-2059 [Member] Amortizing Secured Notes due 2028-2046 [Member] Amortizing Secured Notes due 2021-2046 [Member] State Revolving Trust Notes due 2022-2038 [Member] State Revolving Trust Notes due 2022-2038 [Member] State Revolving Fund Bond due 2021 [Member] State Revolving Fund Bond due 2021 [Member] Range [Axis] Statistical Measurement [Axis] Minimum [Member] Maximum [Member] Common Stock, Shares Authorized Common Stock, Shares Outstanding Preferred Stock, Shares Authorized Preferred Stock, Shares Outstanding Interest rate Long term debt maturity period Statement of Stockholders' Equity [Abstract]