Equity [Abstract] Accumulated Other Comprehensive Income Comprehensive Income (Loss) Note [Text Block] Regulatory Assets and Liabilities Disclosure [Abstract] Schedule of Regulatory Assets [Table] Schedule of Regulatory Assets [Table] Regulatory Agency [Axis] Regulatory Agency [Axis] Regulatory Agency [Domain] Regulatory Agency [Domain] Pennsylvania Public Utilities Commission Pennsylvania Public Utilities Commission [Member] Pennsylvania Public Utilities Commission [Member] Regulatory Asset [Axis] Regulatory Asset [Axis] Regulatory Asset [Domain] Regulatory Asset [Domain] Income taxes recoverable Income Taxes Recoverable [Member] Income taxes recoverable. Underfunded pension and postretirement plans Pension Costs [Member] Environmental costs Environmental Restoration Costs [Member] Removal costs, net Removal Costs, Net [Member] Removal costs net. Other Other Regulatory Assets [Member] Other regulatory assets. Regulatory Assets Regulatory Assets [Line Items] Regulatory assets Regulatory Assets Schedule of Regulatory Liabilities [Table] Schedule of Regulatory Liabilities [Table] Regulatory Liability [Axis] Regulatory Liability [Axis] Regulatory Liability [Domain] Regulatory Liability [Domain] Postretirement benefits Postretirement Benefit Costs [Member] Deferred fuel and power refunds Deferred Fuel and Power Refunds [Member] Deferred fuel and power refunds. State tax benefits — distribution system repairs Deferred Income Tax Charge [Member] PAPUC temporary rates order PUC Temporary Rates Order [Member] PUC Temporary Rates Order [Member] Excess federal deferred income taxes Excess Federal Deferred Income Taxes [Member] Excess Federal Deferred Income Taxes [Member] Other Other Liabilities [Member] Regulatory Liabilities Regulatory Liabilities [Line Items] Regulatory liabilities Regulatory Liabilities Accounting Changes and Error Corrections [Abstract] New Accounting Pronouncements or Change in Accounting Principle [Table] New Accounting Pronouncements or Change in Accounting Principle [Table] Adjustments for New Accounting Pronouncements [Axis] Adjustments for New Accounting Pronouncements [Axis] Type of Adoption [Domain] Type of Adoption [Domain] Accounting Standards Update 2018-02 Accounting Standards Update 2018-02 [Member] Accounting Standards Update 2018-02 [Member] Accounting Standards Update 2017-07 Accounting Standards Update 2017-07 [Member] Accounting Standards Update 2017-07 [Member] New Accounting Pronouncements or Change in Accounting Principle [Line Items] New Accounting Pronouncements or Change in Accounting Principle [Line Items] Tax cuts and jobs act of 2017, reclassification from AOCI to retained earnings, tax effect Tax Cuts and Jobs Act of 2017, Reclassification from AOCI to Retained Earnings, Tax Effect Tax Cuts and Jobs Act of 2017, Reclassification from AOCI to Retained Earnings, Tax Effect Net periodic benefits expense (reversal of expense) excluding service cost component Net Periodic Benefits Expense (Reversal of Expense) Excluding Service Cost Component Net Periodic Benefits Expense (Reversal of Expense) Excluding Service Cost Component Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income (Loss) [Table] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Postretirement Benefit Plans Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] Derivative Instruments Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] Total AOCI Attributable to Parent [Member] Derivative Instrument [Axis] Derivative Instrument [Axis] Derivative Contract [Domain] Derivative Contract [Domain] IRPAs Interest Rate Protection Agreements [Member] Interest rate protection agreements. Accumulated Other Comprehensive Income (Loss) Accumulated Other Comprehensive Income (Loss) [Line Items] AOCI, net of tax - beginning balance Stockholders' Equity Attributable to Parent Other comprehensive income (loss), before reclassifications, net of tax Other Comprehensive Income (Loss), before Reclassifications, Net of Tax Reclassifications, net of tax Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax AOCI, net of tax - end balance Defined Benefit Plan [Abstract] Schedule of Defined Benefit Plans Disclosures [Table] Schedule of Defined Benefit Plans Disclosures [Table] Retirement Plan Type [Axis] Retirement Plan Type [Axis] Retirement Plan Type [Domain] Retirement Plan Type [Domain] Pension Benefits Pension Plan [Member] Other Postretirement Benefits Other Postretirement Benefits Plan [Member] Defined Benefit Plan Disclosure Defined Benefit Plan Disclosure [Line Items] Service cost Defined Benefit Plan, Service Cost Interest cost Defined Benefit Plan, Interest Cost Expected return on assets Defined Benefit Plan, Expected Return (Loss) on Plan Assets Amortization of: Amortization [Abstract] Prior service cost (benefit) Defined Benefit Plan, Amortization of Prior Service Cost (Credit) Actuarial loss Defined Benefit Plan, Amortization of Gain (Loss) Net benefit cost (benefit) Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Change in associated regulatory liabilities Increase (Decrease) in Regulatory Liabilities Net benefit cost (benefit) after change in regulatory liabilities Net Periodic Benefit Cost after Change in Regulatory Liabilities Net periodic benefit cost after change in regulatory liabilities. Derivative Instruments and Hedging Activities Disclosure [Abstract] Balance Sheet Location and Fair Value of Derivative Assets and Liabilities Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block] Effects of Derivative Instruments on the Condensed Consolidated Statements of Income and Changes in AOCI and Noncontrolling Interest Derivative Instruments, Gain (Loss) [Table Text Block] Statement of Comprehensive Income [Abstract] Net losses on derivative instruments, tax Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax Reclassifications of net losses on derivative instruments, tax Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax Benefit plans reclassifications of actuarial losses and prior service costs, tax Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, Tax Accounting Policies [Abstract] Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Restricted cash Restricted Cash, Current Cash, cash equivalents and restricted cash Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Statement of Stockholders' Equity [Abstract] Statement [Table] Statement [Table] Common Stock Common Stock [Member] Retained Earnings Retained Earnings [Member] Additional Paid-in Capital Additional Paid-in Capital [Member] AOCI Including Portion Attributable to Noncontrolling Interest AOCI Including Portion Attributable to Noncontrolling Interest [Member] Statement [Line Items] Statement [Line Items] Balance, beginning of period Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Cumulative effect of change in accounting for employee share-based payments Cumulative Effect of New Accounting Principle in Period of Adoption Net income Net Income (Loss) Attributable to Parent Cash dividends on common stock Dividends, Common Stock, Cash Net loss on derivative instruments Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax Reclassifications of net losses on derivatives instruments Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax Reclassifications of benefits plans actuarial losses and net prior service costs Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, after Tax Balance, end of period Common stock, par value (in usd per share) Common Stock, Par or Stated Value Per Share Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Derivative assets Derivative Financial Instruments, Assets [Member] Derivative liabilities Derivative Financial Instruments, Liabilities [Member] Hedging Designation [Axis] Hedging Designation [Axis] Hedging Designation [Domain] Hedging Designation [Domain] Designated as Hedging Instrument Designated as Hedging Instrument [Member] Derivatives subject to PGC and DS mechanisms Derivatives Subject to PGC and DS Mechanisms [Member] Derivatives Subject to PGC and DS Mechanisms [Member] Not designated as hedging instruments Not Designated as Hedging Instrument [Member] Interest rate contracts Interest Rate Contract [Member] Commodity contracts Commodity Contract [Member] Derivatives, Fair Value Derivatives, Fair Value [Line Items] Derivative assets: Derivative Asset, Fair Value, Amount Not Offset Against Collateral [Abstract] Derivative assets Derivative Asset, Fair Value, Gross Asset Gross amounts offset in the balance sheet Derivative Asset, Fair Value, Gross Liability Total derivative assets — net (a) Derivative Asset, Fair Value, Amount Not Offset Against Collateral Derivative liabilities: Derivative Liability, Fair Value, Amount Not Offset Against Collateral [Abstract] Derivative liabilities Derivative Liability, Fair Value, Gross Liability Gross amounts offset in the balance sheet Derivative Liability, Fair Value, Gross Asset Total derivative liabilities — net (a) Derivative Liability, Fair Value, Amount Not Offset Against Collateral Revenue from Contract with Customer [Abstract] Summary of Disaggregation of Revenue Disaggregation of Revenue [Table Text Block] Statement of Financial Position [Abstract] ASSETS Assets [Abstract] Current assets: Assets, Current [Abstract] Restricted cash Restricted Cash and Cash Equivalents, Current Accounts receivable (less allowances for doubtful accounts of $11,694, $9,760 and $6,398, respectively) Accounts Receivable, Net, Current Accounts receivable — related parties Accounts Receivable, Related Parties, Current Accrued utility revenues Accrued Utility Revenues Estimated amount due from natural gas and electric utility customers for distribution service and commodities rendered but not yet billed at the end of the period. Inventories Inventory, Net Prepaid income taxes Prepaid Taxes Regulatory assets Deferred Fuel Cost Derivative instruments Derivative Instruments and Hedges, Assets Prepaid expenses Prepaid Expense, Current Other current assets Other Assets, Current Total current assets Assets, Current Property, plant and equipment, at cost (less accumulated depreciation of $1,091,212, $1,074,521 and $1,026,450, respectively) Property, Plant and Equipment, Net Goodwill Goodwill Regulatory assets Regulatory Assets, Noncurrent Other assets Other Assets, Noncurrent Total assets Assets LIABILITIES AND STOCKHOLDER’S EQUITY Liabilities and Equity [Abstract] Current liabilities: Liabilities, Current [Abstract] Current maturities of long-term debt Long-term Debt and Capital Lease Obligations, Current Short-term borrowings Short-term Bank Loans and Notes Payable Accounts payable Accounts Payable, Current Accounts payable — related parties Accounts Payable, Related Parties Regulatory liabilities Regulatory Liability, Current Derivative instruments Derivative Instruments and Hedges, Liabilities Other current liabilities Other Liabilities, Current Total current liabilities Liabilities, Current Long-term debt Long-term Debt and Capital Lease Obligations Deferred income taxes Deferred Tax Liabilities, Net, Noncurrent Pension and postretirement benefit obligations Liability, Defined Benefit Plan, Noncurrent Regulatory liabilities Regulatory Liability, Noncurrent Other noncurrent liabilities Other Liabilities, Noncurrent Total liabilities Liabilities Commitments and contingencies (Note 9) Commitments and Contingencies Common stockholder’s equity: Stockholders' Equity Attributable to Parent [Abstract] Common Stock, $2.25 par value (authorized — 40,000,000 shares; issued and outstanding — 26,781,785 shares) Common Stock, Value, Issued Additional paid-in capital Additional Paid in Capital, Common Stock Retained earnings Retained Earnings (Accumulated Deficit) Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax Total common stockholder’s equity Total liabilities and stockholder’s equity Liabilities and Equity Inventory Disclosure [Abstract] Schedule of Inventories Schedule of Inventory, Current [Table Text Block] Revenue from Contract with Customer Revenue from Contract with Customer [Text Block] Related Party Transactions [Abstract] Schedule of Related Party Transactions, by Related Party [Table] Schedule of Related Party Transactions, by Related Party [Table] Related Party [Axis] Related Party [Axis] Related Party [Domain] Related Party [Domain] UGI and Subsidiaries UGI And Subsidiaries [Member] UGI And Subsidiaries [Member] Energy Services UGI Energy Services, Inc. [Member] UGI Energy Services, Inc. [Member] Related Party Transaction [Axis] Related Party Transaction [Axis] Related Party Transaction Detail [Domain] Related Party Transaction [Domain] Administrative Services Administrative Services [Member] Administrative Services [Member] SCAAs Storage Contract Administrative Agreements [Member] Storage Contract Administrative Agreements [Member] Exclusive of Transactions Pursuant SCAAs Exclusive of transactions pursuant SCAAs [Member] Exclusive of transactions pursuant SCAAs [Member] Related Party Transaction Related Party Transaction [Line Items] Amount of related party transaction Related Party Transaction, Amounts of Transaction SCAA contract term (in years) Contract Term Contract Term Related party costs incurred Related Party Transaction, Expenses from Transactions with Related Party Related party security deposits Related Party Deposit Liabilities Volume of gas storage inventory (in bcf of natural gas) Volume Of Gas Storage Inventory Volume Of Gas Storage Inventory Natural gas storage inventory, related parties, current Natural Gas Storage Inventory, Related Parties, Current Natural Gas Storage Inventory, Related Parties, Current Revenue from related parties Revenue from Related Parties Term of agreements (in years) Storage Agreement, Term Storage Agreement, Term Purchases from related party Related Party Transaction, Purchases from Related Party Segment Reporting [Abstract] Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Segments [Axis] Segments [Axis] Segments [Domain] Segments [Domain] Gas Utility Gas Utility [Member] Gas utility. Electric Utility Electric Utility [Member] Electric utility. Segment Reporting Information Segment Reporting Information [Line Items] Revenues Revenues Cost of sales Cost of Goods Sold, Excluding Depreciation, Depletion, and Amortization Depreciation and amortization Depreciation, Depletion and Amortization Operating income Operating Income (Loss) Pension and other postretirement plans non-service income Pension and Other Postretirement Benefits Cost (Reversal of Cost) Interest expense Interest and Debt Expense Income before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Capital expenditures (including the effects of accruals) Property, Plant and Equipment, Additions Total assets Goodwill Schedule of Changes in Accumulated Other Comprehensive Income Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Public Utilities, Inventory [Table] Public Utilities, Inventory [Table] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Maximum Maximum [Member] Public Utilities, Inventory Public Utilities, Inventory [Line Items] Number of storage agreements Number of Storage Agreements Number of Storage Contract Administrative Agreements Term of agreements (in years) Term of Agreements Term of Agreement Number of storage agreements with Energy Services Number of Storage Agreements with Energy Services Number of storage agreements with Energy Services Number of storage agreements with non-affiliates Number of Storage Agreements with Non-Affiliates Number of Storage Agreements with Non-Affiliates Volume of gas storage inventories released under SCAAs with non-affiliates (in bcf) Volume of Gas Storage Inventories Released Volume of gas storage inventories released. Carrying value of gas storage inventories released under SCAAs with non-affiliates Storage Inventory Released Carrying amount as of the balance sheet date of natural gas storage inventories released under SCAA's. Security deposit liability Security Deposit Liability Derivative [Table] Derivative [Table] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Unsecured Debt Unsecured Debt [Member] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] Electric Utility Electric Utility - Forward Contract [Member] Electric utility - forward contract. Electric Utility Electric Transmission Congestion Electric Utility electric transmission congestion [Member] Electric utility electric transmission congestion. Derivative Derivative [Line Items] Notional amount (energy measure) (in mmbtu) Derivative, Nonmonetary Notional Amount Maximum length of time hedged in price risk cash flow hedges (in months) Maximum Length of Time Hedged in Price Risk Cash Flow Hedges Maximum length of time hedged in price risk cash flow hedges. Derivative, fixed interest rate Derivative, Fixed Interest Rate Notional amount of unsettled IRPA contracts Derivative, Notional Amount Amount of net losses associated with interest rate hedges to be reclassified with interest rate hedges during the next 12 months Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net Debt Disclosure [Abstract] Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event Subsequent Event [Member] UGI Utilities UGI Utilities [Member] UGI Utilities [Member] Senior Notes Senior Notes [Member] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] 4.55% Senior Notes due February 2049 4.55% Senior Notes due February 2049 [Member] 4.55% Senior Notes due February 2049 [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Aggregate principal amount Debt Instrument, Face Amount Debt instrument, interest rate, stated percentage Debt Instrument, Interest Rate, Stated Percentage Debt instrument, covenant terms, consolidated debt to consolidated total capital ratio Debt Instrument, Covenant Terms, Consolidated Debt to Consolidated Total Capital Ratio Debt Instrument, Covenant Terms, Consolidated Debt to Consolidated Total Capital Ratio Segment Information Segment Reporting Disclosure [Text Block] Income Statement [Abstract] Costs and expenses: Costs and Expenses [Abstract] Cost of sales — gas and purchased power (excluding depreciation shown below) Operating and administrative expenses Operating Expenses Operating and administrative expenses — related parties Depreciation Depreciation Other operating expense, net Other Operating Income (Expense), Net Total costs and expenses Costs and Expenses Operating income Interest expense Income tax expense Income Tax Expense (Benefit) Net income Pennsylvania PUC Pennsylvania Public Utility Commission [Member] Pennsylvania Public Utility Commission UGI South UGI South [Member] UGI South [Member] UGI North UGI North [Member] UGI North [Member] UGI Central UGI Central [Member] UGI Central [Member] UGI Gas UGI Gas [Member] UGI Gas [Member] CPG CPG [Member] CPG [Member] Electric Utilities Electric Utilities [Member] Electric Utilities [Member] Fair value of unrealized gains (losses) Derivative, Fair Value, Net PUC termporary rates order, percent of reduction in base revenues PUC Termporary Rates Order, Percent Of Reduction In Base Revenues PUC Termporary Rates Order, Percent Of Reduction In Base Revenues Requested operating revenue increase Public Utilities, Requested Rate Increase (Decrease), Amount Proposed negative surcharge in customer distribution service bills, percentage Public Utilities, Proposed Negative Surcharge In Customer Distribution Service Bills Public Utilities, Proposed Negative Surcharge In Customer Distribution Service Bills Public Utilities, Tax Benefits Received Public Utilities, Tax Benefits Received To Be Returned Public Utilities, Tax Benefits Received To Be Returned Tax Cuts And Jobs Act Of 2017, Customer Billing Credit Tax Cuts And Jobs Act Of 2017, Customer Billing Credit Tax Cuts And Jobs Act Of 2017, Customer Billing Credit Increase in annual base distribution rate Public Utilities, Approved Rate Increase (Decrease), Amount Distribution system improvement charge, percent of amount billed to customers Distribution System Improvement Charge, Percent of Amount Billed to Customers Distribution System Improvement Charge, Percent of Amount Billed to Customers Public utilities, civil penalties Public Utilities, Civil Penalties Public Utilities, Civil Penalties Basis of Presentation Consolidation, Policy [Policy Text Block] Derivative Instruments Derivatives, Policy [Policy Text Block] Use of Estimates Use of Estimates, Policy [Policy Text Block] Reclassifications Reclassification, Policy [Policy Text Block] Adoption of New Accounting Standard and Accounting Standards Not Yet Adopted New Accounting Pronouncements, Policy [Policy Text Block] Revenue From Contracts With Customers Revenue From Contracts With Customers [Policy Text Block] Revenue From Contracts With Customers [Policy Text Block] Debt Debt Disclosure [Text Block] Related Party Transactions Related Party Transactions Disclosure [Text Block] Inventories Inventory Disclosure [Text Block] Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Products and Services [Axis] Products and Services [Axis] Products and Services [Domain] Products and Services [Domain] Residential Residential [Member] Residential [Member] Commercial & industrial Commercial and Industrial [Member] Commercial and Industrial [Member] Large delivery service Large Delivery Service [Member] Large Delivery Service [Member] Off-system sales and capacity releases Off System Sales and Capacity Releases [Member] Off System Sales and Capacity Releases [Member] Other Utility, Other [Member] Utility, Other [Member] Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Revenue from contracts with customers Revenue from Contract with Customer, Excluding Assessed Tax Other revenue, net Other Revenues Other Revenues Public utilities, negative surcharge in revenue Public Utilities, Negative Surcharge In Revenue Public Utilities, Negative Surcharge In Revenue Fair Value Disclosures [Abstract] Fair Value Measurements Fair Value Disclosures [Text Block] Schedule of Financial Assets and Financial Liabilities that are Measured at Fair Value on a Recurring Basis Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Schedule of Carrying Amount and Estimated Fair Value of Long-term Debt Fair Value, by Balance Sheet Grouping [Table Text Block] Defined Benefit Pension and Other Postretirement Plans Pension and Other Postretirement Benefits Disclosure [Text Block] Commitments and Contingencies Disclosure [Abstract] Loss Contingencies [Table] Loss Contingencies [Table] Business Acquisition [Axis] Business Acquisition [Axis] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] PNG and CPG PNG and CPG [Member] PNG and CPG [Member] Environmental Remediation Site [Axis] Environmental Remediation Site [Axis] Environmental Remediation Site [Domain] Environmental Remediation Site [Domain] PNG MGP PNG MGP [Member] PNG MGP. CPG, PNG and UGI Gas COAs CPG-COA, PNG-COA and UGI Gas-COA [Member] CPG-COA, PNG-COA and UGI Gas-COA [Member] Loss Contingency Nature [Axis] Loss Contingency Nature [Axis] Loss Contingency, Nature [Domain] Loss Contingency, Nature [Domain] Environmental Issue Environmental Issue [Member] Loss Contingencies [Line Items] Loss Contingencies [Line Items] Number of subsidiaries acquired with similar histories Number of Subsidiaries Acquired Number of Subsidiaries Acquired Environmental expenditures cap during year Environmental Expenditures Cap During Year Environmental Expenditures Cap During Year Accrual for environmental loss contingencies Accrual for Environmental Loss Contingencies Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value by Measurement Frequency [Axis] Measurement Frequency [Axis] Fair Value, Measurement Frequency [Domain] Fair Value, Measurement Frequency [Domain] Fair Value, Measurements, Recurring Fair Value, Measurements, Recurring [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] Level 2 Fair Value, Inputs, Level 2 [Member] Level 3 Fair Value, Inputs, Level 3 [Member] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Assets: Assets, Fair Value Disclosure [Abstract] Derivative Asset Derivative Asset Liabilities: Liabilities, Fair Value Disclosure [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Number of counties of operation Counties Of Operation, Number Counties Of Operation, Number Derivative Instruments and Hedging Activities Derivative Instruments and Hedging Activities Disclosure [Text Block] Schedule of Components of Net Periodic Pension Expense and Other Postretirement Benefit Costs Schedule of Net Benefit Costs [Table Text Block] New Accounting Pronouncements and Changes in Accounting Principles [Abstract] Accounting Changes Description of New Accounting Pronouncements Not yet Adopted [Text Block] Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Nature of Operations Nature of Operations [Text Block] Income Tax Disclosure [Abstract] Operating Loss Carryforwards [Table] Operating Loss Carryforwards [Table] Operating Loss Carryforwards [Line Items] Operating Loss Carryforwards [Line Items] Federal statutory income tax rate Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Tax Cuts and Jobs Act of 2017, reduction of net deferred income tax liabilities Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Change In Tax Rate, Deferred Tax Liability, Provisional Income Tax (Expense) Benefit, Including Unrecognized Deferred Tax Liability Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Change In Tax Rate, Deferred Tax Liability, Provisional Income Tax (Expense) Benefit, Including Unrecognized Deferred Tax Liability Tax Cuts and Jobs Act of 2017, reduction of income tax expense Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Change In Tax Rate, Deferred Tax Liability, Provisional Income Tax Expense (Benefit) Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Change In Tax Rate, Deferred Tax Liability, Provisional Income Tax Expense (Benefit) Tax Cuts and Jobs Act of 2017, change in tax rate, provisional unrecognized deferred tax liability Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Change In Tax Rate, Provisional Unrecognized Deferred Tax Liability Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Change In Tax Rate, Provisional Unrecognized Deferred Tax Liability Increase in regulatory liabilities, excess deferred income taxes Increase (Decrease) In Regulatory Liabilities, Excess Deferred Income Taxes Increase (Decrease) In Regulatory Liabilities, Excess Deferred Income Taxes Restrictions on Cash and Cash Equivalents Restrictions on Cash and Cash Equivalents [Table Text Block] Net income Other comprehensive income (loss): Other Comprehensive Income (Loss), Net of Tax [Abstract] Net losses on derivative instruments (net of tax of $487 and $0, respectively) Reclassifications of net losses on derivative instruments (net of tax of $(252) and $(279), respectively) Reclassifications of benefit plans actuarial losses and net prior service benefits (net of tax of $(54) and $(104), respectively) Other comprehensive (loss) income Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Comprehensive income Comprehensive Income (Loss), Net of Tax, Attributable to Parent Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Measurement Basis [Axis] Measurement Basis [Axis] Fair Value Measurement [Domain] Fair Value Measurement [Domain] Portion at Fair Value Measurement Portion at Fair Value Measurement [Member] Carrying amount Reported Value Measurement [Member] Estimated fair value Estimate of Fair Value Measurement [Member] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Long-term debt Long-term Debt, Fair Value Number of reportable segments Number of Reportable Segments Accounting Standards Update 2014-09 Accounting Standards Update 2014-09 [Member] Scenario [Axis] Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Scenario, Previously Reported Scenario, Previously Reported [Member] Revenue, remaining performance obligation Revenue, Remaining Performance Obligation Increase (decrease) in restricted cash Increase (Decrease) in Restricted Cash Contract with Customer, Basis of Pricing [Axis] Contract with Customer, Basis of Pricing [Axis] Contract with Customer, Basis of Pricing [Domain] Contract with Customer, Basis of Pricing [Domain] Fixed-price Contract Fixed-price Contract [Member] Contract with customer, liability, current Contract with Customer, Liability, Current Income Tax Disclosure Income Tax Disclosure [Text Block] Public Utilities, Inventory [Axis] Inventory [Axis] Public Utilities, Inventory, Type [Domain] Inventory [Domain] Gas Utility natural gas Gas Utility Natural Gas [Member] Gas Utility natural gas. Materials, supplies and other Materials, Supplies and Other [Member] Materials, supplies and other. Total inventories Summary of Significant Accounting Policies Basis of Presentation and Significant Accounting Policies [Text Block] Derivative Instruments, Gain (Loss) by Hedging Relationship, by Income Statement Location, by Derivative Instrument Risk [Table] Derivative Instruments, Gain (Loss) [Table] Derivative Instruments, Gain (Loss) by Hedging Relationship [Axis] Hedging Relationship [Axis] Hedging Relationship [Domain] Hedging Relationship [Domain] Cash Flow Hedges Cash Flow Hedging [Member] Commodity contracts Derivative Instruments, Gain (Loss) by Income Statement Location [Axis] Income Statement Location [Axis] Income Statement and Other Comprehensive Income (Loss) Location [Domain] Income Statement Location [Domain] Interest expense Interest Expense [Member] Operating and administrative expenses Operating and administrative expenses/other income, net [Member] Operating and administrative expenses/other income, net [Member] Derivative Instruments, Gain (Loss) Derivative Instruments, Gain (Loss) [Line Items] Loss Recognized in AOCI Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss) Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss) Location of Loss Reclassified from AOCI into Income Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net Location of (Loss) Gain Recognized in Income Derivative, Gain (Loss) on Derivative, Net Schedule of Regulatory Assets Associated with Gas Utility and Electric Utility Schedule of Regulatory Assets [Table Text Block] Schedule of Regulatory Liabilities Associated with Gas Utility and Electric Utility Schedule of Regulatory Liabilities [Table Text Block] VEBA Contribution made to Pension Plan Defined Benefit Plan, Plan Assets, Contributions by Employer Expected contribution to pensions plans in the remainder of current fiscal year Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year Document and Entity Information [Abstract] 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 Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Allowance for doubtful accounts Allowance for Doubtful Accounts Receivable, Current Accumulated depreciation and amortization Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Common stock, shares authorized (in shares) Common Stock, Shares Authorized Common stock, shares issued (in shares) Common Stock, Shares, Issued Common stock, shares outstanding (in shares) Common Stock, Shares, Outstanding Regulatory Assets and Liabilities and Regulatory Matters Public Utilities Disclosure [Text Block] Statement of Cash Flows [Abstract] CASH FLOWS FROM OPERATING ACTIVITIES Net Cash Provided by (Used in) Operating Activities [Abstract] 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 Deferred income taxes, net Deferred Income Tax Expense (Benefit) Provision for uncollectible accounts Provision for Doubtful Accounts Other, net Other Noncash Income (Expense) Net change in: Increase (Decrease) in Operating Capital [Abstract] Accounts receivable and accrued utility revenues Increase (Decrease) in Accounts and Other Receivables Inventories Increase (Decrease) in Inventories Deferred fuel and power costs, net of changes in unsettled derivatives Increase (Decrease) in Deferred Fuel Costs Accounts payable Increase (Decrease) in Accounts Payable, Trade Other current assets Increase (Decrease) in Prepaid Expense and Other Assets Other current liabilities Increase (Decrease) in Other Current Liabilities Net cash provided (used) by operating activities Net Cash Provided by (Used in) Operating Activities CASH FLOWS FROM INVESTING ACTIVITIES Net Cash Provided by (Used in) Investing Activities [Abstract] Expenditures for property, plant and equipment Payments to Acquire Property, Plant, and Equipment Net costs of property, plant and equipment disposals Payments For (Proceeds From) Property, Plant, And Equipment Disposal Payments For (Proceeds From) Property, Plant, And Equipment Disposal Net cash used by investing activities Net Cash Provided by (Used in) Investing Activities CASH FLOWS FROM FINANCING ACTIVITIES Net Cash Provided by (Used in) Financing Activities [Abstract] Payment of dividends Payments of Ordinary Dividends, Common Stock Issuances of long-term debt, net of issuance costs Proceeds from Issuance of Long-term Debt Repayments of long-term debt Repayments of Long-term Debt Other Proceeds from (Payments for) Other Financing Activities Increase in short-term borrowings Proceeds from (Repayments of) Short-term Debt, Maturing in Three Months or Less Net cash provided by financing activities Net Cash Provided by (Used in) Financing Activities CASH AND CASH EQUIVALENTS Cash and Cash Equivalents, Period Increase (Decrease) [Abstract] Cash, cash equivalents, and restricted cash, period end Cash, cash equivalents, and restricted cash, period beginning Cash, cash equivalents and restricted cash increase Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Schedule of Segment Information Schedule of Segment Reporting Information, by Segment [Table Text Block]