Business Segments [Axis] Regulated [Member] Non - Regulated [Member] Consolidation Items [Axis] Inter-segment Elimination [Member] Class of Stock [Axis] Convertible Preferred Stock $7.00 Series [Member] Convertible Preferred Stock $8.00 Series [Member] Nonredeemable Preferred Stock $7.00 Series [Member] Nonredeemable Preferred Stock $4.75 Series [Member] State Revolving Trust Note, due February 1, 2036 [Member] Debt Instrument [Axis] First Mortgage Bonds - Series RR [Member] First Mortgage Bonds - Series SS [Member] First Mortgage Bonds - Series TT [Member] First Mortgage Bonds - Series UU [Member] First Mortgage Bonds - Series VV [Member] First Mortgage Bonds - Series WW [Member] First Mortgage Bonds - Series LL [Member] First Mortgage Bonds - Series MM [Member] First Mortgage Bonds - Series NN [Member] First Mortgage Bonds - Series OO [Member] First Mortgage Bonds - Series PP [Member] First Mortgage Bonds - Series QQ [Member] First Mortgage Bonds - Series FF [Member] First Mortgage Bonds - Series GG [Member] First Mortgage Bonds - Series HH [Member] First Mortgage Bonds - Series II [Member] First Mortgage Bonds - Series JJ [Member] First Mortgage Bonds - Series KK [Member] First Mortgage Bonds - Series Y [Member] First Mortgage Bonds - Series Z [Member] First Mortgage Bonds - Series AA [Member] First Mortgage Bonds - Series BB [Member] First Mortgage Bonds - Series CC [Member] First Mortgage Bonds - Series EE [Member] Amortizing Secured Note 7.05%, due January 20, 2030 [Member] Amortizing Secured Note 5.69%, due January 20, 2030 [Member] Amortizing Secured Note, due April 20, 2040 [Member] State Revolving Trust Note, due July 1, 2031 [Member] State Revolving Trust Note, due November 30, 2030 [Member] First Mortgage Bonds - Series X [Member] State Revolving Trust Bond 4.00% to 5.00%, due August 1, 2021 [Member] State Revolving Trust Bond 0.00%, due August 1, 2021 [Member] State Revolving Trust Note, due July 1, 2028 [Member] State Revolving Trust Note, due January 1, 2028 [Member] State Revolving Trust Note, due August 1, 2031 [Member] Amortizing Secured Note, due April 20, 2029 [Member] Amortizing Secured Note, due September 19, 2031 [Member] State Revolving Trust Note, due December 31, 2022 [Member] State Revolving Trust Note, due May 1, 2025 [Member] State Revolving Trust Note, due March 1, 2026 [Member] State Revolving Trust Note, due January 25, 2027 [Member] State Revolving Trust Note, due December 1, 2026 [Member] Amortizing Secured Note, due December 20, 2021 [Member] Amortizing Secured Note, due May 19, 2028 [Member] Amortizing Secured Note, due August 25, 2030 [Member] Construction Loans [Member] Legal Entity [Axis] Tidewater Utilities Inc [Member] Measurement Basis [Axis] Carrying Amount [Member] Fair Value [Member] Tax Period [Axis] Tax Year 2014 [Member] Amortizing Secured Note, due April 20, 2040 [Member] State Revolving Fund Bond 0.00%, due August 1, 2021 [Member] Retirement Plan Type [Axis] Other Benefits Plan [Member] Pension Benefit Plan [Member] Middlesex [Member] Long-term Debt, Type [Axis] Series XX [Member] Series YY [Member] Purchase Commitment, Excluding Long-term Commitment [Axis] NJ Water Supply Authority [Member] Regulated Water Authority [Member] City of Dover [Member] Range [Axis] Minimum [Member] Maximum [Member] Legal Entity [Axis] New Jersey Board Of Public Utilities [Member] Lender Name [Axis] New Jersey NJIB Program [Member] New Jersey Infrastructure Bank [Member] First Mortgage Bonds - Series XX [Member] First Mortgage Bonds - Series YY [Member] 0.00%, Series 2018A, due August 1, 2047 [Member] 3.00% to 5.00%, Series 2018B, due August 1, 2047 [Member] Subsequent Event Type [Axis] Subsequent Event [Member] Delaware State Revolving Fund [Member] Series 2018A [Member] Series 2018B [Member] Document And Entity Information [Abstract] Entity Registrant Name Entity Central Index Key Document Type Document Period End Date Amendment Flag Current Fiscal Year End Date Entity Filer Category Entity Common Stock, Shares Outstanding Document Fiscal Period Focus Document Fiscal Year Focus Income Statement [Abstract] Operating Revenues Operating Expenses: Operations and Maintenance Depreciation Other Taxes Total Operating Expenses Operating Income Other Income (Expense): Allowance for Funds Used During Construction Other Income (Expense), net Total Other Income, net Interest Charges Income before Income Taxes Income Taxes Net Income Preferred Stock Dividend Requirements Earnings Applicable to Common Stock Earnings per share of Common Stock: Basic Diluted Average Number of Common Shares Outstanding: Basic Diluted Cash Dividends Paid per Common Share Statement of Financial Position [Abstract] ASSETS UTILITY PLANT: Water Production Transmission and Distribution General Construction Work in Progress TOTAL Less Accumulated Depreciation UTILITY PLANT - NET CURRENT ASSETS: Cash and Cash Equivalents Accounts Receivable, net Unbilled Revenues Materials and Supplies (at average cost) Prepayments TOTAL CURRENT ASSETS AND OTHER ASSETS: Preliminary Survey and Investigation Charges Regulatory Assets Operations Contracts, Developer and Other Receivables Restricted Cash Non-utility Assets - Net Other TOTAL DEFERRED CHARGES AND OTHER ASSETS TOTAL ASSETS CAPITALIZATION AND LIABILITIES CAPITALIZATION: Common Stock, No Par Value Retained Earnings TOTAL COMMON EQUITY Preferred Stock Long-term Debt TOTAL CAPITALIZATION CURRENT LIABILITIES: Current Portion of Long-term Debt Notes Payable Accounts Payable Accrued Taxes Accrued Interest Unearned Revenues and Advanced Service Fees Other TOTAL CURRENT LIABILITIES COMMITMENTS AND CONTINGENT LIABILITIES (Note 7) DEFERRED CREDITS AND OTHER LIABILITIES: Customer Advances for Construction Accumulated Deferred Income Taxes Employee Benefit Plans Regulatory Liabilities Other TOTAL DEFERRED CREDITS AND OTHER LIABILITIES CONTRIBUTIONS IN AID OF CONSTRUCTION TOTAL CAPITALIZATION AND LIABILITIES Statement of Cash Flows [Abstract] CASH FLOWS FROM OPERATING ACTIVITIES: Net Income Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities: Depreciation and Amortization Provision for Deferred Income Taxes Equity Portion of Allowance for Funds Used During Construction (AFUDC) Cash Surrender Value of Life Insurance Stock Compensation Expense Changes in Assets and Liabilities: Accounts Receivable Unbilled Revenues Materials & Supplies Prepayments Accounts Payable Accrued Taxes Accrued Interest Employee Benefit Plans Unearned Revenue & Advanced Service Fees Other Assets and Liabilities NET CASH PROVIDED BY OPERATING ACTIVITIES CASH FLOWS FROM INVESTING ACTIVITIES: Utility Plant Expenditures, Including AFUDC of $125 in 2018, $94 in 2017 NET CASH USED IN INVESTING ACTIVITIES CASH FLOWS FROM FINANCING ACTIVITIES: Redemption of Long-term Debt Proceeds from Issuance of Long-term Debt Net Short-term Bank Borrowings Deferred Debt Issuance Expense Proceeds from Issuance of Common Stock Payment of Common Dividends Payment of Preferred Dividends Construction Advances and Contributions-Net NET CASH PROVIDED BY FINANCING ACTIVITIES NET CHANGES IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH CASH, CASH EQUIVALENTS AND RESTRICTED CASH AT BEGINNING OF PERIOD CASH, CASH EQUIVALENTS AND RESTRICTED CASH AT END OF PERIOD SUPPLEMENTAL DISCLOSURE OF NON-CASH ACTIVITY: Utility Plant received as Construction Advances and Contributions SUPPLEMENTAL DISCLOSURE OF CASH FLOWS INFORMATION: Cash Paid During the Year for: Interest Interest Capitalized Income Taxes Allowance for funds used during construction Statement [Table] Statement [Line Items] TOTAL COMMON EQUITY TOTAL PREFERRED STOCK SUBTOTAL LONG-TERM DEBT Add: Premium on Issuance of Long-term Debt Less: Unamortized Debt Expense Less: Current Portion of Long-term Debt TOTAL LONG-TERM DEBT Common Stock, Shares Authorized Common Stock, Shares Outstanding Preferred Stock, Shares Authorized Preferred Stock, Shares Outstanding Interest rate Due date of debt Basis of Presentation and Recent Developments [Abstract] Basis of Presentation and Recent Developments Regulated Operations [Abstract] Rate and Regulatory Matters Capitalization, Long-term Debt and Equity [Abstract] Capitalization Earnings Per Share [Abstract] Earnings Per Share Segment Reporting [Abstract] Business Segment Data Short-term Debt [Abstract] Short-term Borrowings Commitments and Contingencies Disclosure [Abstract] Commitments and Contingent Liabilities Retirement Benefits [Abstract] Employee Benefit Plans Revenue from Contract with Customer [Abstract] Revenue Recognition from Contracts with Customers Income Tax Disclosure [Abstract] Income Taxes Schedule of carrying amount and fair value of bonds Schedule of earnings per share Schedule of segment reporting information, by segment Short-term Borrowings Schedule of Credit Lines Schedule of purchased water cost Schedule of periodic costs for employee retirement benefit plan Schedule of Operating Revenue Schedule of Product Information [Table] Product Information [Line Items] Cash, Cash Equivalents and Restricted Cash Other Income (Expense) Professional services contract Wastewater system description Schedule of Regulatory Liabilities [Table] Regulatory Liabilities [Line Items] Regulatory Agency [Axis] Approved increase in annual operating revenues Originally filed increase in annual operating revenue Amended filed increase in annual operating revenue Projected annual revenue Corporate tax rate Base rate amount Return on equity Deferred income tax benefits Amortization period Regulatory liabilities Schedule of Capitalization [Table] Schedule of Capitalization [Line Items] Issuance of shares under the DRP, shares Issuance of shares under the DRP Maximum borrowing amount Maximum borrowing capacity, construction loan Loan amount Proceeds from issuance of first mortgage bond Other long term debt Customer advances Amount drawn First Mortgage Bonds Schedule of Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Table] Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items] Basic: Preferred Dividend Earnings Applicable to Common Stock Basic EPS Weighted average number of basic shares outstanding Diluted: Preferred Dividend Common Shares Attributable to Dilutive Effect of Conversion of Preferred Stock (in shares) Adjusted Earnings Applicable to Common Stock Diluted EPS Weighted average number of diluted shares outstanding Schedule of Segment Reporting Information, by Segment [Table] Segment Reporting Information [Line Items] Segments [Axis] Number of Reportable Segments Operating Income Capital Expenditures Assets Lines Of Credit Facility Established lines of credit Increase in lines of credit Established lines of credit, amount outstanding Weighted average interest rate at period end Average Daily Amounts Outstanding Weighted Average Interest Rates Purchase Commitment, Excluding Long-term Commitment [Table] Purchase Commitment, Excluding Long-term Commitment [Line Items] Guaranty liabilty for AWM's performance Budgeted construction cost for construction program, 2018 Period of wastewater agreement Purchase commitment expiration date of contract Water purchase per commitment Rental expenses under operating leases Purchased Water Treated Untreated Total Costs Schedule of Defined Benefit Plans Disclosures [Table] Defined Benefit Plan Disclosure [Line Items] Benfit plan, cash contributions Expected cash contributions Annual benefits paid to retired participants Periodic costs for employee retirement benefit plans Service Cost Interest Cost Expected Return on Assets Amortization of Unrecognized Losses Amortization of Unrecognized Prior Service Cost (Credit) Net Periodic Benefit Cost Regulated Tariff Sales Residential Commercial Industrial Fire Protection Wholesale Non-Regulated Contract Operations Total Revenue from Contracts with Customers Other Regulated Revenues Other Non-Regulated Revenues Inter-segment Elimination Total Revenue Operating Loss Carryforwards [Table] Operating Loss Carryforwards [Line Items] Net reduction in taxes due to the federal government Income tax refund receivable Interest expense Basis Of Presentation And Recent Developments [Abstract ]. Budgeted construction cost for construction program, next year. The entire disclosure for Capitalization. Cash Paid During the Year for: The maximum borrowing capacity for the construction loan as outlined in the closed agreement. Borrowings will take place when construction on a qualifying project is substantially complete. Refers to series of convertible prederred stock. Purchased Water Refers to cost of treated water during the period. Refers to cost of untreated water during the period. 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 [Abstract]. Document And Entity Information [Abstract]. Loan secured by real property that has a first (highest) lien on such property in the event of default by the borrower. Loan secured by real property that has a first (highest) lien on such property in the event of default by the borrower. Loan secured by real property that has a first (highest) lien on such property in the event of default by the borrower. Loan secured by real property that has a first (highest) lien on such property in the event of default by the borrower. Loan secured by real property that has a first (highest) lien on such property in the event of default by the borrower. Loan secured by real property that has a first (highest) lien on such property in the event of default by the borrower. Loan secured by real property that has a first (highest) lien on such property in the event of default by the borrower. Loan secured by real property that has a first (highest) lien on such property in the event of default by the borrower. Loan secured by real property that has a first (highest) lien on such property in the event of default by the borrower. Loan secured by real property that has a first (highest) lien on such property in the event of default by the borrower. Loan secured by real property that has a first (highest) lien on such property in the event of default by the borrower. Loan secured by real property that has a first (highest) lien on such property in the event of default by the borrower. Loan secured by real property that has a first (highest) lien on such property in the event of default by the borrower. Loan secured by real property that has a first (highest) lien on such property in the event of default by the borrower. Loan secured by real property that has a first (highest) lien on such property in the event of default by the borrower. Loan secured by real property that has a first (highest) lien on such property in the event of default by the borrower. Loan secured by real property that has a first (highest) lien on such property in the event of default by the borrower. Loan secured by real property that has a first (highest) lien on such property in the event of default by the borrower. Loan secured by real property that has a first (highest) lien on such property in the event of default by the borrower. Loan secured by real property that has a first (highest) lien on such property in the event of default by the borrower. Loan secured by real property that has a first (highest) lien on such property in the event of default by the borrower. Loan secured by real property that has a first (highest) lien on such property in the event of default by the borrower. Loan secured by real property that has a first (highest) lien on such property in the event of default by the borrower. Loan secured by real property that has a first (highest) lien on such property in the event of default by the borrower. Loan secured by real property that has a first (highest) lien on such property in the event of default by the borrower. Represents the aggregate of the first mortgage bonds reported on the balance sheet at period end measured at fair value by the entity. Series XX [Member] Series YY [Member] The expiration date of a long-term purchase commitment. Middlesex [Member] Net Income [Member] Construction Loans [Member] New Jersey SRF Program [Member] Refers to amount of non utility fixed assets as of the balance sheet date. 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. Costs incurred and are directly related to operations and maintenance. Refers to amount of receivables under operations contracts or from developers that are not expected to be collected in less than one year. The maximum borrowing amount for other loan sources not specifically stated in the taxonomy. The amount of preliminary survey and investigation charges that are deferred as of the balance sheet date. The projected annual revenue from new water operations. Purchase Commitment1 [Member]. Purchase Commitment2 [Member]. The reduction of taxes previously paid to the IRS resulting from the adoption of new IRS regulations. Amortizing Secured Note 4.45%, due April 20, 2040 [Member] Amortizing Secured Note 4.47%, due April 20, 2040 [Member] Collateralized debt obligation backed by, for example, but not limited to, pledge, mortgage or other lien on the entity''s assets. Collateralized debt obligation backed by, for example, but not limited to, pledge, mortgage or other lien on the entity''s assets. Collateralized debt obligation backed by, for example, but not limited to, pledge, mortgage or other lien on the entity''s assets. Collateralized debt obligation backed by, for example, but not limited to, pledge, mortgage or other lien on the entity''s assets. Collateralized debt obligation backed by, for example, but not limited to, pledge, mortgage or other lien on the entity''s assets. Collateralized debt obligation backed by, for example, but not limited to, pledge, mortgage or other lien on the entity''s assets. Collateralized debt obligation backed by, for example, but not limited to, pledge, mortgage or other lien on the entity''s assets. Collateralized debt obligation backed by, for example, but not limited to, pledge, mortgage or other lien on the entity''s assets. Secured Debt Zero [Member] Refers to state revolving fund bond. Refers to state revolving trust bond. Refers to state revolving trust bond. State Revolving Trust Note, due February 1, 2036 [Member] Refers to state revolving trust note. Refers to state revolving trust note. Refers to state revolving trust note. Refers to state revolving trust note. Refers to state revolving trust note. Refers to state revolving trust note. Refers to state revolving trust note. Refers to state revolving trust note. State Revolving Trust Note 9 [Member]. Refers to state revolving trust note. Statement Consolidated Statements Of Capital Stock And Longterm Debt [Abstract] Tidewater Refers to total equity attributable to common stockholders. 2017 Renew Program [Member] New Jersey Board Of Public Utilities [Member] The base amount used for water rates. New Jersey NJIB Program [Member] Delaware State Revolving Fund [Member] New Jersey Infrastructure Bank [Member] Non-regualted contract operations revenue. Wholesale municipal revenue. Residential, Commercial, Industrial and fire protection revenue. First Mortgage Bonds - Series XX [Member] First Mortgage Bonds - Series YY [Member] Residential operating revenues. Commercial operating revenues. Industrial operating revenues. Other Non-Regulated Revenues operating revenue. Inter-segment Elimination. 0.00%, Series 2018A, due August 1, 2047 [Member] 3.00% to 5.00%, Series 2018B, due August 1, 2047 [Member] Wastewater system description. Series 2018A [Member] Series 2018A [Member] Series 2018B [Member] State Revolving Trust Note, due December 1, 2026 [Member] [Default Label] Operating Expenses Nonoperating Income (Expense) Public Utilities, Property, Plant and Equipment, Plant in Service Public Utilities, Property, Plant and Equipment, Net Assets, Current Deferred Charges And Other Assets Capitalization, Long-term Debt and Equity Other Liabilities, Current Liabilities, Current Other Liabilities, Noncurrent Liabilities, Other than Long-term Debt, Noncurrent Liabilities and Equity Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity Life Insurance, Corporate or Bank Owned, Change in Value Increase (Decrease) in Accounts Receivable Increase (Decrease) in Unbilled Receivables Increase (Decrease) in Raw Materials, Packaging Materials and Supplies Inventories Increase (Decrease) in Prepaid Expense Increase (Decrease) in Accounts Payable Increase (Decrease) in Accrued Taxes Payable Increase (Decrease) in Interest Payable, Net Increase (Decrease) in Obligation, Pension and Other Postretirement Benefits Increase (Decrease) in Other Operating Assets and Liabilities, Net Net Cash Provided by (Used in) Operating Activities Net Cash Provided by (Used in) Investing Activities Repayments of Long-term Debt Payments of Debt Issuance Costs Payments of Ordinary Dividends, Common Stock Payments of Ordinary Dividends, Preferred Stock and Preference Stock Net Cash Provided by (Used in) Financing Activities Cash and Cash Equivalents, Period Increase (Decrease) Income Taxes Paid, Net Debt Instrument, Unamortized Discount Pension and Other Postretirement Benefits Disclosure [Text Block] Income Tax Disclosure [Text Block] Cost of Purchased Water Defined Benefit Plan, Expected Return (Loss) on Plan Assets Defined Benefit Plan, Amortization of Gain (Loss) Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Revenue from Contract with Customer, Including Assessed Tax