Debt Disclosure [Abstract] Schedule of Short-term Debt [Table] Schedule of Short-term Debt [Table] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] Utility Holdings Utility Holdings [Member] Refers to an entity under the control of the same parent as another entity (that is, a sister company). Indiana Gas Indiana Gas [Member] Refers to an entity under the control of the same parent as another entity (that is, a sister company). SIGECO SIGECO [Member] Refers to an entity under the control of the same parent as another entity (that is, a sister company). Vectren Capital Corp. Vectren Capital Corp [Member] Refers to an entity under the control of the same parent as another entity (that is, a sister company). Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Fixed Rate Senior Unsecured Notes Unsecured Debt [Member] First Mortgage Bonds Mortgages [Member] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] 2018, 5.75% Fixed Rate Senior Unsecured Notes 2018, 5.75% [Member] A debt obligation not collateralized by pledge, mortgage or other lien in the entity's assets. 2020, 6.28% Fixed Rate Senior Unsecured Notes 2020, 6.28% [Member] A debt obligation not collateralized by pledge, mortgage or other lien in the entity's assets. 2021, 4.67% Fixed Rate Senior Unsecured Notes 2021, 4.67% [Member] A debt obligation not collateralized by pledge, mortgage or other lien in the entity's assets. 2023, 3.72% Fixed Rate Senior Unsecured Notes 2023, 3.72% [Member] Fixed Rate Senior Unsecured Notes 2023372 [Member] 2026, 5.02% Fixed Rate Senior Unsecured Notes 2026, 5.02% [Member] A debt obligation not collateralized by pledge, mortgage or other lien in the entity's assets. 2028, 3.20% Fixed Rate Senior Unsecured Notes 2028, 3.20% [Member] Fixed Rate Senior Unsecured Notes 2028320 [Member] 2032, 3.26% Fixed Rate Senior Unsecured Notes 2032, 3.26% [Member] Fixed Rate Senior Unsecured Notes 2032, 3.26% [Member] 2035, 6.10% Fixed Rate Senior Unsecured Notes 2035, 6.10% [Member] A debt obligation not collateralized by pledge, mortgage or other lien in the entity's assets. 2035, 3.90% Fixed Rate Senior Unsecured Notes 2035,3.90% [Member] Fixed Rate Senior Unsecured Notes 2035,3.90% [Member] 2041, 5.99% Fixed Rate Senior Unsecured Notes 2041, 5.99% [Member] A debt obligation not collateralized by pledge, mortgage or other lien in the entity's assets. 2042, 5.00% Fixed Rate Senior Unsecured Notes 2042, 5.00% [Member] 2043, 4.25% FixedRateSeniorGuaranteedNotes2043, 4.25% [Member] FixedRateSeniorGuaranteedNotes2043425 [Member] 2045, 4.36% Fixed Rate Senior Unsecured Notes 2045, 4.36% [Member] Fixed Rate Senior Unsecured Notes 2045,4.36% [Member] 2047, 3.93% Fixed Rate Senior Unsecured Notes 2047, 3.93% [Member] Fixed Rate Senior Unsecured Notes 2047, 3.93% [Member] 2055, 4.51% Fixed Rate Senior Unsecured Notes 2055, 4.51% [Member] Fixed Rate Senior Unsecured Notes 2055,4.51% [Member] 2025, Series E, 6.53% Fixed Rate Senior Unsecured Notes 2025 Series E 6.53% [Member] A debt obligation not collateralized by pledge, mortgage or other lien in the entity's assets. 2027, Series E, 6.42% Fixed Rate Senior Unsecured Notes 2027 Series E 6.42% [Member] A debt obligation not collateralized by pledge, mortgage or other lien in the entity's assets. 2027, Series E, 6.68% Fixed Rate Senior Unsecured Notes 2027 Series E 6.68% [Member] A debt obligation not collateralized by pledge, mortgage or other lien in the entity's assets. 2027, Series F, 6.34% Fixed Rate Senior Unsecured Notes 2027 Series F 6.34% [Member] A debt obligation not collateralized by pledge, mortgage or other lien in the entity's assets. 2028, Series F, 6.36% Fixed Rate Senior Unsecured Notes 2028 Series F 6.36% [Member] A debt obligation not collateralized by pledge, mortgage or other lien in the entity's assets. 2028, Series F, 6.55% Fixed Rate Senior Unsecured Notes 2028 Series F 6.55% [Member] A debt obligation not collateralized by pledge, mortgage or other lien in the entity's assets. 2029, Series G, 7.08% Fixed Rate Senior Unsecured Notes 2029 Series G 7.08% [Member] A debt obligation not collateralized by pledge, mortgage or other lien in the entity's assets. 2022, 2013 Series C, current adjustable rate 1.565%, tax-exempt First Mortgage Bonds 20222013 Series C 1565 Tax Exempt [Member] First Mortgage Bonds 20222013 Series C 1565 Tax Exempt [Member] 2024, 2013 Series D, current adjustable rate 1.565%, tax-exempt First Mortgage Bonds 20242013 Series D 1565 Tax Exempt [Member] First Mortgage Bonds 20242013 Series D 195 Tax Exempt [Member] 2025, 2014 Series B, current adjustable rate 1.565%, tax-exempt FirstMortgageBonds20252014CurrentAdjustbaleRate1565TaxExempt [Member] FirstMortgageBonds20252014CurrentAdjustbaleRate1565TaxExempt [Member] 2029, 1999 Series, 6.72% First Mortgage Bonds 20291999 Senior Notes 672 [Member] A loan to finance the purchase of utility property where the lender has a lien on the property as collateral for the loan. 2037, 2013 Series E, current adjustable rate 1.565%, tax-exempt First Mortgage Bonds 20372013 Series E 1565 Tax Exempt [Member] First Mortgage Bonds 20372013 Series E 1565 Tax Exempt [Member] 2038, 2013 Series A, 4.00%, tax-exempt First Mortgage Bonds 2038 2013 Series A 400 Tax Exempt [Member] First Mortgage Bonds 2038 2013 Series A 400 Tax Exempt [Member] 2043, 2013 Series B, 4.05%, tax-exempt FirstMortgageBonds20432013SeriesB405TaxExemptMember [Member] First Mortgage Bonds 2043, 2013 Series B 4.05% Tax Exempt [Member] 2044, 2014 Series A, 4.00% tax-exempt FirstMortgageBonds20442014SeriesA400TaxExempt [Member] [Member] FirstMortgageBonds20442014SeriesA400TaxExempt [Member] 2055, 2015 Series Mt. Vernon, 2.375%, tax-exempt Environmental Improvement Revenue Bonds, Mount Vernon, 2055, 2.375%, Series 2015 [Member] Environmental Improvement Revenue Bonds, Mount Vernon, 2055, 2.375%, Series 2015 [Member] 2055, 2015 Series Warrick County, 2.375%, tax-exempt Environmental Improvement Revenue Bonds, Warrick County, 2055, 2.375%, Series 2015 [Member] Environmental Improvement Revenue Bonds, Warrick County, 2055, 2.375%, Series 2015 [Member] 2017, 3.48% Fixed Rate Senior Unsecured Notes 2017348 [Member] A debt obligation not collateralized by pledge, mortgage or other lien in the entity's assets. 2019, 7.30% Fixed Rate Senior Unsecured Notes 2019730 [Member] A debt obligation not collateralized by pledge, mortgage or other lien in the entity's assets. 2022, 3.33% Fixed Rate Senior Unsecured Notes 2022, 3.33% [Member] Fixed Rate Senior Unsecured Notes 2022, 3.33% [Member] 2025, 4.53% Fixed Rate Senior Unsecured Notes 2025453 [Member] A debt obligation not collateralized by pledge, mortgage or other lien in the entity's assets. 2030, 3.90% Fixed Rate Senior Unsecured Notes 2030,3.90% [Member] Fixed Rate Senior Unsecured Notes 2030,3.90% [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Long term debt [Abstract] Long-term Debt, Unclassified [Abstract] Total long-term debt outstanding Long-term Debt, Gross Current maturities of long-term debt Long-term Debt, Current Maturities Debt issuance costs Debt Issuance Costs, Net Unamortized debt premium & discount-net Debt Instrument, Unamortized Discount (Premium), Net Total long-term debt-net Long-term Debt - Net of Current Maturities And Debt Subject to Tender Sum of the carrying values as of the balance sheet date of all long-term debt, which is debt initially having maturities due after one year from the balance sheet date or beyond the operating cycle, if longer, but excluding the portions thereof scheduled to be repaid within one year (current maturities) or the normal operating cycle, if longer, and after deducting unamortized discount or premiums, if any. Also excludes the portion of debt that could be repaid in one year at the option of the holder. Interest rate Debt Instrument, Interest Rate, Stated Percentage Property, Plant and Equipment [Abstract] Utility & Nonutility Plant Property, Plant and Equipment Disclosure [Text Block] Accounting Policies [Abstract] Principles of Consolidation Consolidation, Subsidiaries or Other Investments, Consolidated Entities, Policy [Policy Text Block] Subsequent Events Review Subsequent Events, Policy [Policy Text Block] Cash and Cash Equivalents Cash and Cash Equivalents, Policy [Policy Text Block] Allowance for Uncollectible Accounts Receivables, Policy [Policy Text Block] Inventories Inventory, Policy [Policy Text Block] Property, Plant & Equipment Property, Plant and Equipment, Policy [Policy Text Block] Investments in Unconsolidated Affiliates Equity Method Investments [Policy Text Block] Goodwill Goodwill and Intangible Assets, Goodwill, Policy [Policy Text Block] Regulation Public Utilities, Policy [Policy Text Block] Postretirement Obligations & Costs Postemployment Benefit Plans, Policy [Policy Text Block] Asset Retirement Obligations Asset Retirement Obligation [Policy Text Block] Product Warranties, Performance Guarantees & Other Guarantees Guarantees, Indemnifications and Warranties Policies [Policy Text Block] Energy Contracts & Derivatives Derivatives, Policy [Policy Text Block] Income Taxes Income Tax, Policy [Policy Text Block] Revenues Revenue Recognition, Policy [Policy Text Block] MISO Transactions Miso Transactions Policy [Policy Text Block] With the IURC's approval, the Company is a member of the MISO, a FERC approved regional transmission organization. The MISO serves the electrical transmission needs of much of the Midwest and maintains operational control over the Company's electric transmission facilities as well as that of other Midwest utilities. MISO-related purchase and sale transactions are accounted for on a net hourly position. Net Purchases are recorded in Cost of Fuel and Purchased Power, and net sales are recorded in Electric Utility Revenues. Any revenues received from MISO for transactions not specifically assigned to a unit of power, such as use of the transmission system or other administrative amounts, are reflected in Electric Utility revenues. Any expenses incurred within the MISO market by the Company that are not specifically identified with a unit of power purchased, such as socialized administrative costs, are treated as Other Operating expense. Share-Based Compensation Compensation Related Costs, Policy [Policy Text Block] Excise & Utility Receipts Taxes Revenue Recognition Excise And Sales Taxes Disclosure [Policy Text Block] Describes the policy for accounting for excise and sales tax, i. e. whether the entity presents excise and sales taxes on a gross basis (included in revenues and costs) or a net basis (excluded from revenue). Operating Segments Segment Reporting, Policy [Policy Text Block] Fair Value Measurements Fair Value of Financial Instruments, Policy [Policy Text Block] Equity Method Investments and Joint Ventures [Abstract] Investment in ProLiance Holdings, LLC Equity Method Investments and Joint Ventures Disclosure [Text Block] Accounting Changes and Error Corrections [Abstract] New Accounting Pronouncements and Changes in Accounting Principles [Abstract] New Accounting Pronouncements and Changes in Accounting Principles [Abstract] Impact of Recently Issued Accounting Guidance New Accounting Pronouncements and Changes in Accounting Principles [Text Block] Commitments and Contingencies Disclosure [Abstract] Unrecorded Unconditional Purchase Obligation [Table] Unrecorded Unconditional Purchase Obligation [Table] Energy Systems Group Energy Systems Group [Member] Energy Systems Group [Member] Guarantor Obligations by Nature [Axis] Guarantor Obligations, Nature [Axis] Guarantor Obligations, Nature [Domain] Guarantor Obligations, Nature [Domain] Performance Guarantee Performance Guarantee [Member] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Maximum Maximum [Member] Unrecorded Unconditional Purchase Obligation [Line Items] Unrecorded Unconditional Purchase Obligation [Line Items] Commitments [Abstract] Commitments [Abstract] Future minimum operating lease payments due within one year of the balance sheet date Operating Leases, Future Minimum Payments Due, Next Twelve Months Future minimum operating lease payments due within the second year of the balance sheet date Operating Leases, Future Minimum Payments, Due in Two Years Future minimum operating lease payments due within the third year of the balance sheet date Operating Leases, Future Minimum Payments, Due in Three Years Future minimum operating lease payments due within the fourth year of the balance sheet date Operating Leases, Future Minimum Payments, Due in Four Years Future minimum operating lease payments due within the fifth year of the balance sheet date Operating Leases, Future Minimum Payments, Due in Five Years Future minimum operating lease payments due within after the fifth year of the balance sheet date Operating Leases, Future Minimum Payments, Due Thereafter Lease expense Operating Leases, Rent Expense Firm purchase commitment term one Purchase Commitment Contract Term One Purchase Commitment Contract Term One Firm purchase commitment term two Purchase Commitment Contract Term Two Purchase Commitment Contract Term Two Performance Guarantees and Product Warranties [Abstract] Performance Guarantees Product Warranties [Abstract] Number of surety bonds wholly owned subsidiary has outstanding in role as general contractor (in number of surety bonds) Number Of Surety Bond Obligations Outstanding For Wholly Owned Subsidiary Represents the absolute number of surety bonds the wholly owned subsidiary has outstanding in its role as general contractor Face amount of surety bonds Performance Guarantee Obligations Outstanding Face Amount Face amount of individual surety bonds the wholly owned subsidiary has outstanding. Work yet to be completed on surety bond projects Percentage Of Work Yet to be Completed On Projects With Open Surety Bonds Percentage of work yet to be completed on projects with open surety bonds Period for release of significant portion of surety bonds Guarantor Obligations, Term Warranty liability recognized Standard and Extended Product Warranty Accrual Corporate Guarantees [Abstract] Guarantees [Abstract] Maximum exposure by parent company on guarantees. Guarantor Obligations, Maximum Exposure, Undiscounted Letters of credit amount outstanding Letters of Credit Outstanding, Amount 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 Entity Well-known Seasoned Issuer Entity Well-known Seasoned Issuer Entity Voluntary Filers Entity Voluntary Filers Entity Current Reporting Status Entity Current Reporting Status Entity Public Float Entity Public Float Quarterly Financial Information Disclosure [Abstract] Quarterly Financial Data (Unaudited) Quarterly Financial Information [Text Block] Retirement Benefits [Abstract] Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Table] Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Table] Scenario [Axis] Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Forecast Scenario, Forecast [Member] Retirement Plan Type [Axis] Retirement Plan Type [Axis] Retirement Plan Type [Domain] Retirement Plan Type [Domain] Pension Benefits Pension Plan [Member] Other Benefits Other Postretirement Benefits Plan [Member] Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] Discount rate Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate Rate of compensation increase Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase Expected increase in Consumer Price Index Defined Benefit Plan Assumptions Used Calculating Benefit Obligation Expected Increase in Consumer Price Index The expected increase in the Consumer Price Index used in the calculation of benefit obligation. Assumption of percentage increase in medical claims cost for next fiscal year (in hundredths) Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year Ultimate trending increase of medical claims cost (in hundredths) Defined Benefit Plan, Ultimate Health Care Cost Trend Rate Dollar impact of a one-percentage point change in assumed health care cost trend rates Defined Benefit Plan, Effect of One Percentage Point Increase on Accumulated Postretirement Benefit Obligation Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization and Nature of Operations Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Earnings Per Share [Abstract] Earnings Per Share Earnings Per Share [Text Block] Defined Benefit Plan, Asset Categories [Axis] Defined Benefit Plan, Asset Categories [Axis] Plan Asset Categories [Domain] Plan Asset Categories [Domain] Equity Securities Equity Securities [Member] Debt Securities Debt Securities [Member] Real estate, commodity & other funds Real estate, commodities and other [Member] Investments in real estate, commodities and other investments. Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] Plan assets at fair value, beginning of period Defined Benefit Plan, Fair Value of Plan Assets Actual return on plan assets Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss) Employer contributions Defined Benefit Plan, Plan Assets, Contributions by Employer Plan participants' contributions Defined Benefit Plan, Plan Assets, Contributions by Plan Participant Benefit payments Defined Benefit Plan, Plan Assets, Benefits Paid Fair value of plan assets, end of period Target percentage of investments in equity instruments (in hundredths) Defined Benefit Plan, Plan Assets, Target Allocation, Percentage SERP Supplemental Employee Retirement Plan [Member] Fair Value, Hierarchy [Axis] Fair Value, Hierarchy [Axis] Fair Value Hierarchy [Domain] Fair Value Hierarchy [Domain] Level 2 Fair Value, Inputs, Level 2 [Member] Multiemployer Plan Type [Axis] Multiemployer Plan Type [Axis] Multiemployer Plans Type [Domain] Multiemployer Plans Type [Domain] Multiemployer Benefit Plans Multiemployer Plans, Pension [Member] Number of qualified defined benefit pension plans Number Of Defined Benefit Pension Plans Number Of Defined Benefit Pension Plans Portion of benefit costs capitalized as Utility plant Portion of benefit costs capitalized as Utility plant Portion of benefit costs capitalized as Utility plant Discount rate Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate Expected return on plan assets Defined Benefit Plan, Expected Return on Plan Assets, Next Fiscal Year An assumption as to the rate of return on plan assets reflecting the average rate of earnings expected on the funds invested or to be invested to provide for the benefits included in the benefit obligation. Maximum number of days restriction for exchange of shares in Common CTF's Maximum Number Of Days Restriction For Exchange Of Shares In Common Collective Trust Funds The maximum number of days that shares may be restricted in exchange for funds in Common Collective Trust Funds. Fair Value of guaranteed annuity contract [Roll Forward] Fair value of guaranteed annuity contract [Roll Forward] Fair value of guaranteed annuity contract Guaranteed Annuity Contract - estimate of undiscounted funds necessary to satisfy John Hancock's remaining obligation Estimate of undiscounted funds necessary to satisfy remaining obligation in guaranteed annuity contract Estimate of undiscounted funds necessary to satisfy John Hancock's remaining obligation in the guaranteed annuity contract. Guaranteed Annuity Contract - percent of composite investment return, net of manger fees and other charges Percent of composite investment return, net of manger fees and other charges Percent of composite investment return, net of manger fees and other charges for the guaranteed annuity contract. Expected contributions in fiscal year 2018 Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year Payments expected to be made to SERP participants in the next fiscal year Payments Expected To Be Made To Serp Participants In Next Fiscal Year Payments expected to be made to SERP participants in the next fiscal year. Other postretirement benefit payments to be made during the next fiscal year Other Post Rretirement Payments To BE Made During Next Fiscal Year Other postretirement benefit payments to be made during the next fiscal year Estimated future benefit payments [Abstract] Defined Benefit Plan, Expected Future Benefit Payment [Abstract] Expected future benefit payments, 2018 Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months Expected future benefit payments, 2019 Defined Benefit Plan, Expected Future Benefit Payment, Year Two Expected future benefit payments, 2020 Defined Benefit Plan, Expected Future Benefit Payment, Year Three Expected future benefit payments, 2021 Defined Benefit Plan, Expected Future Benefit Payment, Year Four Expected future benefit payments, 2022 Defined Benefit Plan, Expected Future Benefit Payment, Year Five Expected future benefit payments, 2022-2026 Defined Benefit Plan, Expected Future Benefit Payment, Five Fiscal Years Thereafter Amounts that will be amortized from Accumulated Other Comprehensive Income (Loss) in next year [Abstract] Defined Benefit Plan, Expected Amortization, Next Fiscal Year [Abstract] Prior service cost expected to be amortized in next year Defined Benefit Plan, Expected Amortization of Prior Service Cost (Credit), Next Fiscal Year Actuarial gain/loss expected to be amortized in next year Defined Benefit Plan, Expected Amortization of Gain (Loss), Next Fiscal Year Multiemployer Plans [Abstract] Multiemployer Plans [Abstract] Multiemployer contributions Multiemployer Plan, Contributions by Employer Approximate number of unions the Company contributed to on behalf of employees Approximate number of unions the Company contributed to on behalf of employees The approximate number of unions the Company contributed to during the year on behalf of employees Average contribution Multiemployer Plans Average Contributions The average contribution made by the Company to unions within multiemployer plans during the period. Largest contribution Multiemployer Plans Largest Contribution The largest contribution made by the Company to a single union multiemployer plan during the period. Number of multiemployer plans contributed to Number of multiemployer plans contributed to Number of multi-employer plans contributed to Defined benefit plan, number of significant plans Defined benefit plan, number of significant plans Defined benefit plan, number of significant plans Number of plans in red zone status receiving company contributions Defined benefit plan, number of plans in red zone status receiving company contributions Defined benefit plan, number of plans in red zone status receiving company contributions Number of plans whereby company contributions exceed 5% of plan balance Defined benefit plan, number of plans whereby company contributions exceed 5% of plan balance Number of plans whereby company contributions exceed 5% of plan balance Percentage threshold by which plan contributions are considered significant Defined benefit plan, percentage threshold by which plan contributions are considered significant Percentage threshold in which plan contributions are considered significant Number of plans in red zone status considered significant by the Company Number of plans in red zone status considered significant by the Company Number of plans in red zone status considered significant by the Company Defined Contribution Plan [Abstract] Defined Contribution Plan [Abstract] Contributions to defined contribution plan Defined Contribution Plan, Cost Valuation and Qualifying Accounts [Abstract] Valuation and Qualifying Accounts Disclosure [Table] Valuation and Qualifying Accounts Disclosure [Table] Valuation Allowances and Reserves Type [Axis] Valuation Allowances and Reserves Type [Axis] Valuation Allowances and Reserves [Domain] Valuation Allowances and Reserves [Domain] Accumulated Provision for Uncollectible Accounts Allowance for Doubtful Accounts [Member] Reserve for Impaired Notes Receivable Allowance for Loans and Leases Receivable [Member] Valuation and Qualifying Accounts Disclosure [Line Items] Valuation and Qualifying Accounts Disclosure [Line Items] Movement in Valuation Allowances and Reserves [Roll Forward] Movement in Valuation Allowances and Reserves [Roll Forward] Balance, at beginning of year Valuation Allowances and Reserves, Balance Additions Charged to Expenses Valuation Allowances and Reserves, Additions for Charges to Cost and Expense Additions Charged to Other Accounts Valuation Allowances and Reserves, Additions for Charges to Other Accounts Deductions from Reserves, Net Valuation Allowances and Reserves, Deductions Balance, at end of period Vectren Utility Holdings Inc Vectren Utility Holdings Inc [Member] Information related to the wholly owned subsidiary, Vectren Utility Holdings, Inc. Line of Credit Line of Credit [Member] VUHI Credit Agreement VUHI Credit Agreement [Member] VUHI Credit Agreement [Member] Vectren Capital Credit Agreement Vectren Capital Credit Agreement [Member] Vectren Capital Credit Agreement [Member] Credit Facility [Axis] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Revolving Credit Facility Revolving Credit Facility [Member] Bridge Loan Bridge Loan [Member] Letter of Credit Letter of Credit [Member] Segments [Axis] Segments [Axis] Segment [Domain] Segments [Domain] Utility Group Utility Group [Member] Nonutility Group Nonutility Group [Member] Nonutility Group Short-term Debt [Line Items] Short-term Debt [Line Items] Short-term borrowings [Abstract] Short-term Debt [Abstract] Short-term borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Increase (decrease) of credit facility Line of Credit Facility, Increase (Decrease), Net Short term borrowings available Line of Credit Facility, Remaining Borrowing Capacity Balance outstanding, as of year end Short-term Debt Weighted average interest rate, as of year end Short-term Debt, Weighted Average Interest Rate, at Point in Time Balance outstanding, annual average Short-term Debt, Average Outstanding Amount Weighted average interest rate, annual average (in hundredths) Weighted Average Interest Rate, annual average This element reflects the calculation of the average interest rate weighted by the amount of debt outstanding by type or by instrument during the period under review. Maximum Month End Balance Outstanding Short-term Debt, Maximum Month-end Outstanding Amount Income Tax Disclosure [Abstract] Operating Loss Carryforwards [Table] Operating Loss Carryforwards [Table] Segments [Domain] Corporate and Other Corporate and Other [Member] Operating Loss Carryforwards [Line Items] Operating Loss Carryforwards [Line Items] Tax Cuts and Jobs Act of 2017 tax benefit Tax Cuts and Jobs Act of 2017, Change in Tax Rate, Income Tax Expense (Benefit) Tax Cuts and Jobs Act of 2017, Change in Tax Rate, Income Tax Expense (Benefit) Excess federal deferred income taxes from Tax Cuts and Jobs Act of 2017 Tax Cuts and Jobs Act of 2017, Change in Tax Rate, Deferred Tax Asset, Income Tax Expense (Benefit) Tax Cuts and Jobs Act of 2017, Change in Tax Rate, Deferred Tax Asset, Income Tax Expense (Benefit) Investment tax credits Investment Tax Credit State net operating loss carryforwards Deferred Tax Assets, Operating Loss Carryforwards, State and Local Charitable contributions carryforwards Deferred Tax Assets, Charitable Contribution Carryforwards Valuation allowance Operating Loss Carryforwards, Valuation Allowance Uncertain tax positions [Abstract] Income Tax Uncertainties [Abstract] Net liability for unrecognized tax benefits inclusive of interest, penalties and net of secondary impacts which are a component of the deferred income taxes and are benefits Net liability for recognized tax benefits inclusive of interest, penalties and net of secondary impacts which are a component of the Deferred income taxes Net liability for recognized tax benefits inclusive of interest, penalties and net of secondary impacts which are a component of the Deferred income taxes SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS AND RESERVES Schedule of Valuation and Qualifying Accounts Disclosure [Text Block] Retirement Plans & Other Postretirement Benefits Pension and Other Postretirement Benefits Disclosure [Text Block] Net income Net Income (Loss) Attributable to Parent Weighted average common shares outstanding (Basic and Diluted EPS) (in shares) Weighted Average Number of Shares Outstanding, Basic and Diluted Basic and Diluted earnings per share (in dollars per share) Earnings Per Share, Basic and Diluted Long term senior unsecured obligations and first mortgage bonds outstanding by subsidiary Schedule of Long-term Debt Instruments [Table Text Block] Short term borrowing arrangements Schedule of Short-term Debt [Table Text Block] Additional Balance Sheet and Operational Information [Abstract] Investments in unconsolidated Affiliates [Table] Investments in and Advances to Affiliates [Table] Investments in and Advances to Affiliates Categorization [Axis] Investments in and Advances to Affiliates Categorization [Axis] Investments in and Advances to Affiliates Categorization [Domain] Investments in and Advances to Affiliates Categorization [Domain] ProLiance Holdings, LLC Proliance Holdings Llc [Member] Information related to the legal entity ProLianceHoldings, LLC. Other nonutility partnerships & corporations Other Nonutility Partnerships and Corporations [Member] Information on equity investments in non-utility partnerships and corporations. Other utility investments Other Utility Investments [Member] Information on other utility equity investments. Other Other Unconsolidated Affiliates [Member] Information on other unconsolidated affiliates not individually identified. Subsegments [Axis] Subsegments [Axis] Subsegments [Domain] Subsegments [Domain] Gas Utility Services Gas Utility Services [Member] Infrastructure Services Infastructure Services [Member] Energy Services Energy Services [Member] Investments in unconsolidated Affiliates [Line Items] Investments in and Advances to Affiliates [Line Items] Inventories Inventory, Net [Abstract] Gas in storage – at LIFO cost Gas in storage - at LIFO cost The amount of gas in storage, at the balance sheet date, valued using the LIFO (last in, first out) cost method. Coal & oil for electric generation - at average cost Coal and Oil for electric generation - at average cost The amount of coal and oil for electric generation recorded using the average cost method of costing for inventory present at the reporting date. Materials & supplies Inventory, Raw Materials and Supplies, Gross Other Other Inventory, Gross Total inventories Inventory, Net Amount by which cost of replacing inventories carried at LIFO cost exceeded carrying value Excess of Replacement or Current Costs over Stated LIFO Value Prepayments and other current assets Prepaid Expense and Other Assets, Current [Abstract] Prepaid gas delivery service Prepaid gas delivery service Carrying amount as of the balance sheet date of capitalized payments for gas delivery service which will be transported within one year or the normal operating cycle, if longer. Prepaid taxes Prepaid Taxes Other prepayments & current assets Other Assets, Current Total prepayments & other current assets Prepaid Expense and Other Assets, Current Investments in unconsolidated affiliates Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures [Abstract] Investments in unconsolidated affiliates Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures Other utility & corporate investments Other Utility And Corporate Investments [Abstract] Cash surrender value of life insurance policies Cash Surrender Value of Life Insurance Restricted cash & other investments Restricted Cash and Investments, Noncurrent Total other utility & corporate investments Other utility and corporate investments Other long-term utility and corporate investments not classified elsewhere in the taxonomy. Goodwill Goodwill Accrued liabilities Accrued Liabilities, Current [Abstract] Refunds to customers & customer deposits Customer Refund Liability, Current Accrued taxes Taxes Payable, Current Accrued interest Interest Payable, Current Deferred compensation & post retirement benefits Liability, Pension and Other Postretirement and Postemployment Benefits, Current Accrued salaries & other Accrued Salaries, Current Total accrued liabilities Accrued Liabilities, Current Asset Retirement Obligation Asset Retirement Obligation, Roll Forward Analysis [Roll Forward] Asset retirement obligation, beginning balance Asset Retirement Obligation Accretion Asset Retirement Obligation, Accretion Expense Changes in estimates, net of cash payments Asset Retirement Obligation, Period Increase (Decrease) Asset retirement obligation, ending balance Equity in earnings (loss) of unconsolidated affiliates Equity Method Investment, Financial Statement, Reported Amounts [Abstract] Equity in earnings (losses) of unconsolidated affiliates Income (Loss) from Equity Method Investments Other - income (expense) - net Other Nonoperating Income (Expense) [Abstract] AFUDC – borrowed funds Public Utilities Allowance For Funds Used During Construction Capitalized Interest Including Certain Post In Service Activities The component of the allowance for funds used during construction during the period comprised of interest on borrowed funds used in financing the construction of regulated assets, which may be reflected as a reduction of interest expense. Also includes capitalized interest for certain post-in-service activities, namely bare steel/cast iron replacement program, where AFUDC continues to accrue after in-service and until recovered through rates. AFUDC – equity funds Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity Nonutility plant capitalized interest Interest Costs Capitalized Adjustment Interest income, net Interest Income (Expense), Net Other nonutility investment impairment charges Other Asset Impairment Charges All other income Other Non-operating Income (Expense), Net Other Non-operating Income (Expense), Net Total other income – net Other Nonoperating Income (Expense) Supplemental cash flow information Supplemental Cash Flow Information [Abstract] Cash paid (received) for: Cash paid for [Abstract] Interest Interest Paid Income taxes Income Taxes Paid, Net Accruals related to utility and nonutility plant purchases Noncash Investing and Financing Items [Abstract] Accruals related to utility and nonutility plant purchases Capital Expenditures Incurred but Not yet Paid Nonutility Real Estate Other Legacy Holdings [Abstract] Schedule of Equity Method Investments [Table] Schedule of Equity Method Investments [Table] Investment, Name [Axis] Investment, Name [Axis] Investment, Name [Domain] Investment, Name [Domain] Legacy Investments, Other Than ProLiance Legacy Investments, Other Than ProLiance [Member] Legacy Investments, Other Than ProLiance [Member] Segments [Axis] Schedule of Equity Method Investments [Line Items] Schedule of Equity Method Investments [Line Items] Restricted cash & other investments Other Investments Debt security related to the sale of commercial real estate Held-to-maturity Securities Other nonutility investments Other nonutility investments Other long-term nonutility investments not classified elsewhere in the taxonomy. Income Statement [Abstract] OPERATING REVENUES Revenue, Net [Abstract] Gas utility Regulated Operating Revenue, Gas Electric utility Electric Domestic Regulated Revenue Nonutility Other Revenue, Net Total operating revenues Revenue, Net OPERATING EXPENSES Operating Expenses [Abstract] Cost of gas sold Cost of Natural Gas Purchases Cost of fuel & purchased power Cost of Domestic Regulated Electric Cost of nonutility revenues Other Cost of Operating Revenue Other operating Other Cost and Expense, Operating Depreciation & amortization Depreciation, Depletion and Amortization Taxes other than income taxes Taxes other than income taxes All taxes not related to income of the entity. Total operating expenses Operating Expenses OPERATING INCOME Operating Income (Loss) OTHER INCOME Nonoperating Income (Expense) [Abstract] Other income – net Total other income Nonoperating Income (Expense) Interest expense Interest Expense INCOME BEFORE INCOME TAXES Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Income taxes Income Tax Expense (Benefit) NET INCOME WEIGHTED AVERAGE AND DILUTED COMMON SHARES OUTSTANDING BASIC AND DILUTED EARNINGS PER SHARE OF COMMON STOCK (in dollars per share) Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Reconciliation of total cost of share-based awards to the after tax effect on net income Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block] Performance based units outstanding Performance Based Units Outstanding [Table Text Block] Schedule of equity and liability awards outstanding. Stockholders' Equity Note [Abstract] Common Shareholder's Equity Stockholders' Equity Note Disclosure [Text Block] Reconciliation of the Federal Statutory Rate to Effective Income Tax Rate Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Significant Components of Net Deferred Tax Liability Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Components of Income Tax Expense Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] Segment Reporting [Abstract] Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Number of operating groups Number Of Operating Groups Number Of Operating Groups Portion of Indiana that is provided natural gas distribution and transportation services by the Gas Utility Services segment (in hundredths) Portion Of Indiana That Is Provided Natural Gas Distribution And Transportation Services By Gas Utility Services Segment The percentage of Indiana that is provided natural gas distribution and transportation services by the Gas Utility Services segment. Number of customers Number of Customers Number of Customers Number of operating segments Number of Operating Segments Fees incurred for pipeline construction and repair services Related Party Transaction, Expenses from Transactions with Related Party Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Award Type [Axis] Award Type [Axis] Equity Award [Domain] Equity Award [Domain] Equity Awards Performance Based Units Equity Method [Member] Incremental common shares attributable to performance based units accounted for on the equity method of accounting that were not included in diluted earnings per share (EPS) because to do so would increase EPS amounts or decrease loss per share amounts for the period presented. Performance based units are awards for which sale is contractually or governmentally restricted for a given period of time. Liability Awards Performance Based Units Liability Method [Member] Performance Based Units Liability Method [Member] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Performance based awards at beginning of period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Vested (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Forfeited (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Performance based awards at end of period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Weighted average grant date fair value at beginning of period (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Granted (in dollars 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 Vested (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Forfeited (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Weighted average grant date fair value at end of period (in dollars per share) Summarized Financial Information of Equity Investment Summarized Financial Information of Equity Investment [Table Text Block] Tabular disclosure of financial information of ProLiance Holdings, LLC. Statement of Cash Flows [Abstract] CASH FLOWS FROM OPERATING ACTIVITIES Net Cash Provided by (Used in) Operating Activities [Abstract] NET INCOME Adjustments to reconcile net income to cash from operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Deferred income taxes & investment tax credits Deferred Income Taxes and Tax Credits Provision for uncollectible accounts Provision for Doubtful Accounts Expense portion of pension & postretirement benefit cost Pension and Other Postretirement Benefits Cost (Reversal of Cost) Other non-cash items - net Other Noncash Income (Expense) Changes in working capital accounts: Increase (Decrease) in Operating Capital [Abstract] Accounts receivable & accrued unbilled revenues Increase (Decrease) in Receivables Inventories Increase (Decrease) in Inventories Recoverable/refundable fuel & natural gas costs Increase (Decrease) in Recoverable Refundable Gas Costs Prepayments & other current assets Increase (Decrease) in Prepaid Expense and Other Assets Accounts payable, including to affiliated companies Increase (Decrease) in Accounts Payable Accrued liabilities Increase (Decrease) in Accrued Liabilities Employer contributions to pension & postretirement plans Payment for Pension and Other Postretirement Benefits Changes in noncurrent assets Increase (Decrease) in Other Operating Assets Changes in noncurrent liabilities Increase (Decrease) in Other Operating Liabilities Net cash from operating activities Net Cash Provided by (Used in) Operating Activities CASH FLOWS FROM FINANCING ACTIVITIES Net Cash Provided by (Used in) Financing Activities [Abstract] Proceeds from: Proceeds From Financing Activities [Abstract] Long-term debt, net of issuance costs Proceeds from Issuance of Long-term Debt Dividend reinvestment plan & other common stock issuances Proceeds from Issuance of Shares under Incentive and Share-based Compensation Plans, Including Stock Options Requirements for: Requirements For Financing Activities [Abstract] Dividends on common stock Payments of Ordinary Dividends, Common Stock Retirement of long-term debt Repayments of Long-term Debt Other financing activities Proceeds from (Payments for) Other Financing Activities Net change in short-term borrowings Proceeds from (Repayments of) Short-term Debt Net cash from financing activities Net Cash Provided by (Used in) Financing Activities CASH FLOWS FROM INVESTING ACTIVITIES Net Cash Provided by (Used in) Investing Activities [Abstract] Proceeds from sale of assets and other collections Proceeds from Investing Activities [Abstract] Proceeds from sale of assets and other collections Proceeds from Collection of Other Receivables Requirements for: Requirements For Investing Activities [Abstract] Capital expenditures, excluding AFUDC equity Payments to Acquire Property, Plant, and Equipment Other costs Payments for (Proceeds from) Other Investing Activities Changes in restricted cash Increase (Decrease) in Restricted Cash Net cash from investing activities Net Cash Provided by (Used in) Investing Activities Net change in cash & cash equivalents Cash and Cash Equivalents, Period Increase (Decrease) Cash & cash equivalents at beginning of period Cash and Cash Equivalents, at Carrying Value Cash & cash equivalents at end of period Environmental Matters Disclosure [Abstract] Environmental and Sustainability Matters Environmental Loss Contingency Disclosure [Text Block] Current: Current Income Tax Expense (Benefit), Continuing Operations [Abstract] Federal Current Federal Tax Expense (Benefit) State Current State and Local Tax Expense (Benefit) Total current taxes Current Income Tax Expense (Benefit) Deferred: Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract] Federal Deferred Federal Income Tax Expense (Benefit) State Deferred State and Local Income Tax Expense (Benefit) Total deferred taxes Deferred Income Tax Expense (Benefit) Amortization of investment tax credits Effective Income Tax Rate Reconciliation, Tax Credit, Investment, Amount Total income tax expense Public Utilities, General Disclosures [Abstract] Public Utilities General Disclosures [Table] Public Utilities General Disclosures [Table] Public Utilities, Regulatory Proceeding [Axis] Public Utilities, Regulatory Proceeding [Axis] Public Utilities, Regulatory Proceeding [Domain] Public Utilities, Regulatory Proceeding [Domain] Electric Modernization Program - SB 560 Electric Modernization Program - SB 560 [Member] Electric Modernization Program - SB 560 [Member] Renewable Generation - SB 29 Renewable Generation - SB 29 [Member] Renewable Generation Project - SB 29 [Member] SIGECO Electric Environmental Compliance Filing SIGECO Electric Environmental Compliance Filing [Member] SIGECO Electric Environmental Compliance Filing [Member] Electric Demand Side Management Filing Electric Demand Side Management Filing [Member] Electric Demand Side Management Filing [Member] Electric Generation and Compliance [Member] Electric Generation and Compliance [Member] Electric Generation and Compliance [Member] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event Subsequent Event [Member] Minimum Minimum [Member] Public Utilities, General Disclosures [Line Items] Public Utilities, General Disclosures [Line Items] Capital expenditures under plan Total Capital Expenditures Under Seven Year Plan Total Capital Expenditures Under Seven Year Plan Length of project plan required for recovery under new legislation Length of project plan required for recovery under new legislation Length of project plan required for recovery under new legislation Project spend life to date Project spend life to date Project spend life to date Investment under plan Investment In Plan Investment In Plan Requested recovery in rates of investments Public Utilities, Requested Recovery in Rates of Investments Public Utilities, Requested Recovery in Rates of Investments Regulatory assets Regulatory Assets Number of solar projects filed for authority to recover costs Number Of Solar Projects With Authority To Recover Costs Number Of Solar Projects With Authority To Recover Costs Additional solar generation resulting from project Public Utilities, Electric Power, Additional Solar Generation Resulting From Project Public Utilities, Electric Power, Additional Solar Generation Resulting From Project Additional battery storage resources resulting from project Public Utilities, Electric Power, Additional Battery Storage Resources Resulting From Project Public Utilities, Electric Power, Additional Battery Storage Resources Resulting From Project Estimated cost of project Estimated Capital Expenditures Under Project Plan Estimated Capital Expenditures Under Project Plan Amount of capital investments to date in equipment for mercury control Amount of capital investments to date in equipment for mercury control Amount of capital investments to date in equipment for coal fired generation units to control mercury emissions in air and water. Amount of capital investments to date in equipment to control sulfur trioxide emissions Amount of capital investments to date in equipment to control sulfur trioxide emissions Amount of capital investments to date in equipment to control sulfur trioxide emissions. Estimated cost of equipment to comply with MATS Estimated cost of equipment to comply with MATS Estimated cost of equipment to comply with MATS Estimated cost of equipment required by the NOV Estimated cost of equipment required by the NOV Estimated cost of equipment required by the NOV SIGECO Electric Demand Side Managements (DSM) Program Filing Vectren South Electric Demand Side Management Program Filing [Abstract] Vectren South Electric Demand Side Management Program Filing [Abstract] Maximum period for recovery under energy efficiency program Maximum period for recovery under energy efficiency program Maximum period for recovery under energy efficiency program Life of the plan Estimated Average Measure Life Of Lost Margin Recovery Plan Estimated Average Measure Life Of Lost Margin Recovery Plan Electric utility revenue FERC Return On Equity Complaint [Abstract] FERC Return On Equity Complaint [Abstract] FERC Return On Equity Complaint [Abstract] Current return on equity used in MISO transmission owners rates Current return on equity used in MISO transmission owners rates Current return on equity percentage used in MISO transmission owners rates, which includes SIGECO's formula transition rates. Reduced return on equity percentage sought by third party through joint complaint Reduced return on equity percentage sought by third party through joint complaint Reduced return on equity percentage sought by third party under joint complaint filed with the FERC under Section 206 of the Federal Power Act against MISO and various MISO transmission owners, including SIGECO. FERC authorized base ROE percentage for first refund period FERC authorized base ROE percentage for first refund period FERC authorized base ROE percentage FERC authorized base ROE percentage for second refund period FERC authorized base ROE percentage for second refund period FERC authorized base ROE percentage for second refund period FERC authorized incentive ROE percentage for first refund period FERC Authorized Incentive ROE Percentage for First Refund Period FERC Authorized Incentive ROE Percentage for First Refund Period Gross investment in qualifying projects Gross Investment In Qualifying Transmission Projects Gross investment in qualifying electric transmission projects constructed by the Company in its service territory that meet certain MISO criteria. Net plant balance for qualifying projects Net Investment in Qualifying Transmission Projects Net investment in qualifying electric transmission projects constructed by the Company in its service territory that meet certain MISO criteria. Gas combined cycle generating facility Public Utilities, Gas Combined Cycle Generating Facility Public Utilities, Gas Combined Cycle Generating Facility Gas combined cycle generating facility cost Public Utilities, Gas Combined Cycle Generating Facility, Cost Public Utilities, Gas Combined Cycle Generating Facility, Cost Requested recovery of environmental investments Public Utilities, Requested Recovery Of Environmental Investments Public Utilities, Requested Recovery Of Environmental Investments Universal solar energy power Public Utilities, Universal Solar Energy Public Utilities, Universal Solar Energy Borrowing Arrangements Debt Disclosure [Text Block] Statement of Financial Position [Abstract] ASSETS Assets [Abstract] Current Assets Assets, Current [Abstract] Reserves Allowance for Doubtful Accounts Receivable, Current LIABILITIES & SHAREHOLDERS' EQUITY Liabilities and Equity [Abstract] Common Shareholders' Equity Stockholders' Equity Attributable to Parent [Abstract] Common stock, shares issued (in shares) Common Stock, Shares, Issued Common stock shares outstanding (in shares) Common Stock, Shares, Outstanding Basic and dilutive earnings per share calculation Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Cost of Utility Plant Public Utility Property, Plant, and Equipment [Table Text Block] Nonutility Plant, Net of Depreciation and Amortization Nonutility Plant, Net of Depreciation and Amortization [Table Text Block] Disclosure of the useful life and salvage value of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale. Examples include land, buildings, machinery and equipment, and other types of furniture and equipment including, but not limited to, office equipment, furniture and fixtures, and computer equipment and software. Statement of Comprehensive Income [Abstract] Pension & other benefits Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax [Abstract] Amounts arising during the year Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, after Tax Reclassifications to periodic cost Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, after Tax Deferrals to regulatory assets Other Comprehensive Income Deferrals To Regulatory Assets After Tax Portion of other comprehensive income deferrals to regulatory assets associated with pension and other postretirment benefit plans, before tax. Pension & other benefits costs, net of tax Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAX Other Comprehensive Income (Loss), Net of Tax TOTAL COMPREHENSIVE INCOME Comprehensive Income (Loss), Net of Tax, Attributable to Parent Statement of Stockholders' Equity [Abstract] Dividends (in dollars per share) Common Stock, Dividends, Per Share, Declared Total cost of share-based compensation Share-based Compensation Less capitalized cost Employee Service Share-based Compensation, Allocation of Recognized Period Costs, Capitalized Amount Total in other operating expense Allocated Share-based Compensation Expense Less income tax benefit in earnings Employee Service Share-based Compensation, Tax Benefit from Compensation Expense After tax effect of share-based compensation Allocated Share-based Compensation Expense, Net of Tax Share-based Compensation Arrangements by Share-based Payment Award, Award Type and Plan Name [Domain] Vesting period for performance-based awards to executives and key non-officer employees Vesting Period For Performance-Based Awards To Executives And key Non-Officer Employees Description of the period of time over which an employee's right to the share based award is no longer contingent on satisfaction of either a service condition, market condition, and/or performance condition. Measurement time frame for grants to executives and key nonofficer employees Performance Measurement Time Frame For Grants To Executives And Key Nonofficer Emplyees In Years Vesting period for awards to non-employee directors Vesting period for awards to non-employee directors Description of the period of time over which a non-employee director's right to a share based award is fully vested. Non-employee director must be an active director at the date of lift. Upper range of share based awards that may potentially be taken in cash (in units) Upper range of share based awards that may potentially be taken in cash Upper range of share based awards that may potentially be taken in cash due to ability to participate in the Company's deferred compensation plan. Total unrecognized compensation cost related to performance based awards Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized Weighted-average life of unrecognized compensation cost Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition Total fair value of liability awards vested Share Based Compensation Arrangement By Share Based Payment Award Liability Awards Vested In Period Total Fair Value The total fair value of liability awards for which the grantee gained the right during the reporting period, by satisfying performance, and/or service requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement. Total fair value of equity awards vested Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value Deferred Compensation Plans [Abstract] Deferred Compensation Arrangements [Abstract] Liability associated with deferred compensation plans Deferred Compensation Liability, Current and Noncurrent Portion of liability classified in Accrued liabilities Deferred Compensation Liability, Current Impact of deferred compensation plans on Other operating expenses Deferred Compensation Plan (Income) Expense in Other Operating Expenses This amount represents the impact of gains and losses, as well as savings and match amounts and pass through dividends that were recognized in the income statement. Amount recorded in earnings related to the investment activities in phantom stock associated with deferred compensation plans (Income) Expense Impact Of Phantom Stock Activites Associated With Deferred Comp Plans This amount represents the portion of gain or loss recognized in the income statement specifically related to Vectren phantom stock in the deferred compensation plans. Cash surrender value of life insurance policies Earnings (loss) from investments in corporate-owned life insurance policies Life Insurance, Corporate or Bank Owned, Change in Value Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract] Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income (Loss) [Table] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Pension & other benefit costs Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] Accumulated other comprehensive income (loss) AOCI Attributable to Parent [Member] Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss) [Line Items] Deferred income taxes AOCI Tax, Attributable to Parent AOCI Attributable to Parent, Net of Tax [Roll Forward] AOCI Attributable to Parent, Net of Tax [Roll Forward] Beginning of year Stockholders' Equity Attributable to Parent Change during the year Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent End of year Commitments & Contingencies Commitments and Contingencies Disclosure [Text Block] Income Taxes Income Tax Disclosure [Text Block] Additional Balance Sheet & Operational Information Additional Balance Sheet And Operational Information [Text Block] Disclosure related to additional balance sheet and operational information, including inventories, prepayments and other current assets, investments in unconsolidated affiliates, other utility and corporate investments, goodwill, accrued liabilities, asset retirement obligations, equity in earnings (losses) of unconsolidated affiliates, other income - net, and supplemental cash flow information. Accumulated Other Comprehensive Income Accumulated Other Comprehensive Income Note Disclosure [Text Block] The entire disclosure for accumulated other comprehensive income. Goodwill and Intangible Assets Disclosure [Abstract] Schedule of Finite-Lived Intangible Assets [Table] Schedule of Finite-Lived Intangible Assets [Table] Indefinite-lived Intangible Assets [Axis] Indefinite-lived Intangible Assets [Axis] Indefinite-lived Intangible Assets, Major Class Name [Domain] Indefinite-lived Intangible Assets, Major Class Name [Domain] Customer-related assets Customer Related Assets [Member] Information about assets related to customers such as customer lists, relationships, etc. Market-related assets Market Related Assets [Member] Represents 1/2 of the value of the Miller Pipeline trademark name. 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] Finite-Lived Intangible Assets [Line Items] Finite-Lived Intangible Assets [Line Items] Amortizing Finite-Lived Intangible Assets, Net Non-amortizing Indefinite-Lived Intangible Assets (Excluding Goodwill) Reclassification of market-related assets from non-amortizing to amortizing Intangible Assets, Reclassification From Indefinite to Finite-lived Intangible Assets, Reclassification From Indefinite to Finite-lived Weighted average remaining life for amortizing customer-related assets and all amortizing intangibles (in years) Finite-Lived Intangible Asset, Useful Life Residual values Finite Lived Intangible Assets, Residual Value Finite Lived Intangible Assets, Residual Value Accumulated amortization Finite-Lived Intangible Assets, Accumulated Amortization Amortization expense Amortization of Intangible Assets Amortization expense - 2018 Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months Amortization expense - 2019 Finite-Lived Intangible Assets, Amortization Expense, Year Two Amortization expense - 2020 Finite-Lived Intangible Assets, Amortization Expense, Year Three Amortization expense - 2021 Finite-Lived Intangible Assets, Amortization Expense, Year Four Amortization expense - 2022 Finite-Lived Intangible Assets, Amortization Expense, Year Five Schedule of Segment Reporting Information Schedule of Segment Reporting Information, by Segment [Table Text Block] Gas Rate and Regulatory Matters Public Utilities General Disclosures - Gas [Text Block] Public Utilities General Disclosures - Gas [Text Block] Intangible assets Schedule of Intangible Assets, Excluding Goodwill, By Major Class [Table Text Block] Tabular disclosure of the carrying value of intangible assets, excluding goodwill, in total and by major class. A major class is composed of intangible assets that can be grouped together because they are similar, either by their nature or by their use in the operations of the company. Common stock, shares authorized for issue (in shares) Common Stock, Shares Authorized Preferred stock , shares authorized for issue (in shares) Preferred Stock, Shares Authorized Number of shares reserved for issuance under share-based compensation plans, benefit plans, and dividend reinvestment plan (in shares) Number of shares reserved for issuance under share-based compensation plans, benefit plans, and dividend reinvestment plan The maximum number of shares authorized for issuance under the stock based compensation plans, benefit plans and dividend reinvestment plan as of the balance sheet date. Authorized shares of common stock available for issuance (in shares) Common Stock, Capital Shares Reserved for Future Issuance Authorized shares of preferred stock available for issuance (in shares) Preferred Stock, Capital Shares Reserved for Future Issuance Schedule of Defined Benefit Plans Disclosures [Table] Schedule of Defined Benefit Plans Disclosures [Table] Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] Service cost Defined Benefit Plan, Service Cost Interest cost Defined Benefit Plan, Interest Cost Expected return on plan assets Defined Benefit Plan, Expected Return (Loss) on Plan Assets Amortization of prior service cost (benefit) Defined Benefit Plan, Amortization of Prior Service Cost (Credit) Amortization of actuarial loss Defined Benefit Plan, Amortization of Gain (Loss) Settlement charge Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement Net periodic benefit cost (benefit) Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] Projected benefit obligation, beginning of period Defined Benefit Plan, Benefit Obligation Service cost – benefits earned during the period Interest cost on projected benefit obligation Plan participants' contributions Defined Benefit Plan, Benefit Obligation, Contributions by Plan Participant Plan amendments Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment Actuarial loss (gain) Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) Settlement loss Defined Benefit Plan, Benefit Obligation, Payment for Settlement Benefit payments Defined Benefit Plan, Benefit Obligation, Benefits Paid Projected benefit obligation, end of period Accumulated benefit obligation for all defined benefit pension plans Defined Benefit Plan, Accumulated Benefit Obligation LA Storage LA Storage [Member] LA Storage [Member] Consolidated Entities [Axis] Consolidated Entities [Axis] Consolidated Entities [Domain] Consolidated Entities [Domain] Affiliated Entity Affiliated Entity [Member] Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Investments in unconsolidated affiliates Investments In Unconsolidated Affiliates [Member] Investments In Unconsolidated Affiliates [Member] Other nonutility investments Prepaid Expenses and Other Current Assets [Member] Ownership percentage Equity Method Investment, Ownership Percentage Governance and voting rights Equity Method Investment, Voting and Governance Rights Equity method investment, voting and governance rights Summarized balance sheet information [Abstract] Equity Method Investment, Summarized Financial Information [Abstract] Cash Equity method investment, Summarized Financial Information, Cash The amount of cash reported by an equity method investment of the entity. Investment in LA Storage Equity Method investment, Summarized Financial Information, Storage Assets The amount of the storage assets reported by an equity method investment of the entity. Total investment in ProLiance Equity method investment, gross investment in equity method investee Equity method investment, gross investment in equity method investee Total investment in Proliance included in Investments in unconsolidated affiliates and other nonutility investments Combined Joint Venture Ownership Percentage Combined Joint Venture Ownership Percentage Equity method investment, combined joint venture ownership percentage ProLiance's investment in joint venture Equity Method Investments Schedule of Property, Plant and Equipment [Table] Property, Plant and Equipment [Table] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Domain] Property, Plant and Equipment, Type [Domain] Gas utility plant Natural Gas Processing Plant [Member] Electric utility plant Electricity Generation Plant, Non-Nuclear [Member] Common utility plant Common Utility Plant [Member] Plant used in connection with both electric transmission and distribution and natural gas operations Construction work in progress Construction in Progress [Member] Asset retirement obligations Asset Retirement Obligations [Member] Asset Retirement Obligations [Member] Jointly Owned Utility Plant [Axis] Jointly Owned Utility Plant [Axis] Jointly Owned Utility Plant [Domain] Jointly Owned Utility Plant [Domain] Warrick Power Plant Warrick Power Plant [Member] Warrick Power Plant [Member] Property, Plant and Equipment [Line Items] Property, Plant and Equipment [Line Items] Original Cost Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment Depreciation Rates as a Percent of Original Cost Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service Size of Unit 4 Warrick Power Plant (in megawatts) Power Plant Maximum Capacity Power Plant Maximum Capacity SIGECO's share of cost of Warrick unit 4 Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service SIGECO's share of accumulated depreciation of Warrick unit 4 Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation Rate of compensation increase Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase Expected return on plan assets Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets Expected increase in Consumer Price Index Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Expected Increase in Consumer Price Index The expected increase in the Consumer Price Index used in the calculation of net periodic benefit costs. Fair Value Disclosures [Abstract] Fair Value Measurements Fair Value Disclosures [Text Block] Goodwill impairments Goodwill, Impairment Loss Excise taxes and a portion of utility receipts taxes Excise and Sales Taxes Number of operating segments in Utility group Number of operating segments in Utility group The number of operating segments in the Utility group for which income is reviewed to make operating decisions. Electric Rate and Regulatory Matters Public Utilities, General Disclosures - Electric [Text Block] Public Utilities, General Disclosures - Electric [Text Block] Geographical [Axis] Geographical [Axis] Geographical [Domain] Geographical [Domain] INDIANA INDIANA OHIO OHIO Indiana Recovery and Deferral Mechanisms Indiana Recovery and Deferral Mechanisms [Member] Indiana Recovery and Deferral Mechanisms [Member] Senate Bill 251 and 560 Senate Bill 251 and 560 [Member] Senate Bill 251 and 560 [Member] Ohio Recovery and Deferral Mechanisms Ohio Recovery and Deferral Mechanisms [Member] Ohio Recovery and Deferral Mechanisms [Member] Ohio House Bill 95 Ohio House Bill95 [Member] Information on the Ohio House Bill 95. Senate Bill 251 Senate Bill 251 [Member] Senate Bill 251 [Member] Allowable capital expenditures under Vectren programs Capital Expenditures Allowed Under Program Capital Expenditures Allowed Under Program Regulatory assets Regulatory Assets, Noncurrent Amount of project investment approved Expected Seven Year Period Modernization Investment Expected Seven Year Period Modernization Investment Amount of projects not approved for recovery Expected Seven Year Period Modernization Investment, Not Approved For Recovery Expected Seven Year Period Modernization Investment, Not Approved For Recovery Additional investment increase Capital Expenditure Increases Amount of capital expenditure increases included in update to seven-year plan. Payments for capital improvements Payments for Capital Improvements Bill impact per customer per month Impact on Customer Bill Per Month The limit on the deferrals, represented as a bill impact per customer per month, allowed under VEDO's Capital Expenditure Program filed under Ohio House Bill 95. Period to recover costs of capital investments Public Utilities, Period To Recover Costs Of Capital Investments Public Utilities, Period To Recover Costs Operating expenses Regulatory Matters, Operation Expenses Requested For Recovery Regulatory Matters, Operation Expenses Requested For Recovery Capital investments Regulatory Matters, Capital Investments Requested For Recovery Regulatory Matters, Capital Investments Requested For Recovery Recovery period beginning in 2018 Regulatory Matters, Recovery Term Regulatory Matters, Recovery Term Regulatory Assets and Liabilities Disclosure [Abstract] Regulated Operations, Schedule of Regulatory Assets [Table] Schedule of Regulatory Assets [Table] Regulatory Assets by Category[Axis] Regulatory Assets by Category[Axis] The list of the regulatory asset itemized in a table of regulatory assets. Asset that is created when regulatory agencies permits public utilities to defer costs to the balance sheet. These amounts would otherwise be required to appear on the company's income statement and would be charged against current expenses or revenues. Regulatory Assets by Group [Domain] Regulatory Assets by Group [Domain] The name of the group of regulatory assets itemized in a table of regulatory assets. Asset that is created when regulatory agencies permits public utilities to defer costs to the balance sheet. These amounts would otherwise be required to appear on the company's income statement and would be charged against current expenses or revenues. Future amounts recoverable from ratepayers related to: Future Amounts Recoverable From Ratepayers [Member] Group of Items Classified as Future Amounts Recoverable From Ratepayers Amounts deferred for future recovery related to: Amounts Deferred for Future Recovery [Member] Group of Items Classified as Amounts Deferred for Future Recovery Amounts currently recovered in customer rates related to: Amounts Currently Recovered in Customer Rates [Member] Group of Items Classified as Amounts Currently Recovered in Customer Rates Regulatory Asset [Axis] Regulatory Asset [Axis] Regulatory Asset [Domain] Regulatory Asset [Domain] Benefit Obligations Pension Costs [Member] Net deferred income taxes Deferred Income Tax Charge [Member] Asset retirement obligations & other Asset Retirement Obligation Costs [Member] Cost recovery riders & other Cost Recovery Riders Other [Member] Costs deferred as a Regulatory Asset per Commission Orders. These costs are expected to be recovered from customers through future ratemaking processes. Indiana authorized trackers Indiana Authorized Trackers [Member] Annual recovery mechanisms approved by the Indiana Commission to recover Midwest ISO administrative costs, integrity management costs, gas conservation costs, and various other costs. Balance represents costs deferred and not yet fully recovered. Ohio authorized trackers Ohio Authorized Trackers [Member] Annual recovery mechanisms approved by the Ohio Commission to recover bad debt expense, gas conservation costs, and other infrastructure replacement expenses. Balance represents costs deferred and not yet fully recovered. Loss on reacquired debt & hedging costs Unamortized Debt Issue Costs, Reaquisition Premiums and Hedging Proceeds [Member] Amounts amortized over the life of the related debt instrument, and included for recovery in customer rates via the total cost of debt (interest expense). Deferred coal costs and other Deferred Coal Costs [Member] Coal costs deferred as a regulatory asset, per Commission approval, that are expected to be recovered in rates charged to customers in a future period. Regulatory asset or liability is recognized for differences in the timing of recognition of the period costs for financial reporting and rate-making purposes. Regulatory Liability [Axis] Regulatory Liability [Axis] Regulatory Liability [Domain] Regulatory Liability [Domain] Removal Costs Removal Costs [Member] Regulatory Assets [Line Items] Regulatory Assets [Line Items] Regulatory liabilities Regulatory Liability, Noncurrent Regulatory asset amount earning a return Regulatory Assets, Amounts Earning A Return Regulatory Assets, Amounts Earning A Return Regulatory assets currently being recovered in base rates Regulatory Assets Currently Being Recovered in Base Rates Total amount of regulatory assets currently being recovered in base rates Weighted average recovery period of regulatory assets currently being recovered (in years) Weighted average recovery period of regulatory assets currently being recovered The weighted average recovery period of regulatory assets currently being recovered, in years. Deferred tax regulatory liability due to revaluation of deferred taxes at reduced federal tax rate Tax Cuts and Jobs Act of 2017, Change in Tax Rate, Deferred Tax Liability, Income Tax (Expense) Benefit Tax Cuts and Jobs Act of 2017, Change in Tax Rate, Deferred Tax Liability, Income Tax (Expense) Benefit Nonutility Legacy Holdings Nonutility Real Estate Other Legacy Holdings [Text Block] The entire disclosure of the investments included in the Nonutility business segment. Retirement Plan Tax Status [Axis] Retirement Plan Tax Status [Axis] Retirement Plan Tax Status [Domain] Retirement Plan Tax Status [Domain] Qualified Plans Qualified Plan [Member] Projected benefit obligation, end of period Fair value of plan assets, end of period Funded (unfunded) status of plan Defined Benefit Plan, Funded (Unfunded) Status of Plan Accrued liabilities Liability, Defined Benefit Plan, Current Deferred credits & other liabilities Liability, Defined Benefit Plan, Noncurrent Summarized quarterly financial data Quarterly Financial Information [Table Text Block] Property, Plant and Equipment [Table] Vehicles & equipment Vehicles And Equipment [Member] Vehicles And Equipment [Member] Computer hardware & software Computer Hardware And Software [Member] Computer Hardware And Software [Member] Land & buildings Land and Building [Member] All other Other Capitalized Property Plant and Equipment [Member] Change in Accounting Estimate by Type [Axis] Change in Accounting Estimate by Type [Axis] Change in Accounting Estimate, Type [Domain] Change in Accounting Estimate, Type [Domain] Change in Accounting Method Accounted for as Change in Estimate Change in Accounting Method Accounted for as Change in Estimate [Member] Nonutility plant - net Property, Plant and Equipment, Net Accumulated depreciation and amortization Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Capitalized interest on nonutility plant construction projects Interest Costs Capitalized Depreciation Depreciation Regulatory Assets & Liabilities Schedule of Regulatory Assets and Liabilities [Text Block] Customer [Axis] Customer [Axis] Customer [Domain] Customer [Domain] Natural Gas Customers Natural Gas Customers [Member] Natural Gas Customers [Member] Electric Customers Electric Customers [Member] Electric Customers [Member] Vectren Energy Delivery of Ohio Vectren Energy Delivery of Ohio [Member] Vectren Energy Delivery of Ohio [Member] Number of public utility subsidiaries owned by wholly owned subsidiary, Vectren Utility Holdings, Inc. (in number of subsidiaries) Number Of Public Utility Subsidiaries Owned By Wholly Owned Subsidiary Of Company Pertains to the number of public utility subsidiaries owned by wholly owned subsidiary, Vectren Utility Holdings, Inc. Approximate number of customers Approximate Number Of Customers Pertains to the approximate number customers serviced by the Company. Number of primary business areas Number Of Primary Business Areas Number Of Primary Business Areas Schedule of Regulatory Assets Schedule of Regulatory Assets [Table Text Block] Operating revenues Operating income Earnings per share [Abstract] Earnings Per Share, Basic and Diluted [Abstract] Level 3 Fair Value, Inputs, Level 3 [Member] Fair value of guaranteed annuity contract [Abstract] Fair value, beginning of year Fair value, beginning of year Fair value, beginning of year Unrealized gains related to investments still held at reporting date Unrealized gains related to investments still held at reporting date Unrealized gains related to investments still held at reporting date Purchases, sales & settlements, net Purchases, sales and settlements, net Purchases, sales and settlements, net Fair value, end of year Fair value, end of year Fair value, end of year Statement [Table] Statement [Table] Statement, Equity Components [Axis] Common Stock Common Stock [Member] Retained Earnings Retained Earnings [Member] Statement [Line Items] Statement [Line Items] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Balance at beginning of period (in shares) Balance at beginning of period Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Other comprehensive income (loss) Common stock: Common Stock [Abstract] Issuance: option exercises & dividend reinvestment plan (in shares) Stock Issued During Period Shares Stock Options Exercised And Dividend Reinvestment Plan Number of shares issued during the period as a result of the exercise of stock options and from a dividend reinvestment plan (DRIP). A dividend reinvestment plan allows the holder of the stock to reinvest dividends paid to them by the entity on new issues of stock by the entity. Issuance: option exercises & dividend reinvestment plan Stock Issued During Period Value Stock Options Exercised And Dividend Reinvestment Plan Value stock issued during the period as a result of the exercise of stock options and from a dividend reinvestment plan (DRIP). A dividend reinvestment plan allows the holder of the stock to reinvest dividends paid to them by the entity on new issues of stock by the entity. Dividends Dividends, Common Stock, Cash Other Stockholders' Equity, Other Balance at end of period (in shares) Balance at end of period Cash & cash equivalents Accounts receivable - less reserves of $5.1 & $6.0, respectively