Guarantor Obligations [Line Items] Guarantor Obligations [Line Items] Award Timing Predetermined Award Timing Predetermined [Flag] Related Party Transaction [Axis] Related Party Transaction [Axis] Entity File Number Entity File Number Long-Term Debt and Other Long-Term Obligations Debt, Policy [Policy Text Block] Tabular List, Table Tabular List [Table Text Block] Miscellaneous Income Miscellaneous Income [Member] Miscellaneous Income New Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Other affiliate support services Other Affiliate Support Services [Member] Other Affiliate Support Services Schedule of Transactions with Affiliated Companies Schedule of Related Party Transactions [Table Text Block] Property taxes Property Taxes Receivable, Noncurrent Property Taxes, NonCurrent Assets Total Guarantees and Other Assurances Guarantor Obligations, Maximum Exposure, Undiscounted Trading Arrangements, by Individual Trading Arrangements, by Individual [Table] Senior Unsecured Notes Due 2031 at 5.00% Senior Unsecured Maturing 2036 At 5.02% [Member] Senior Unsecured Maturing 2036 At 5.02% Measurement Basis [Axis] Measurement Basis [Axis] Adjustment to Compensation: Adjustment to Compensation [Axis] TRANSACTIONS WITH AFFILIATED COMPANIES Related Party Transactions Disclosure [Text Block] Named Executive Officers, Footnote Named Executive Officers, Footnote [Text Block] REGULATORY MATTERS Public Utilities Disclosure [Text Block] REVENUE Revenue from Contract with Customer [Text Block] Accounts payable Increase (Decrease) in Accounts Payable, Trade Maximum capped percentage of face amount of debt Guarantor Obligations, Maximum Contractual Obligations, Capped Percentage of Face Amount of Debt Guarantor Obligations, Maximum Contractual Obligations, Capped Percentage of Face Amount of Debt Short-term borrowings- Short-Term Debt Regulatory Matters [Line Items] Regulatory Matters [Line Items] Regulatory matters. Adjustment to Compensation, Amount Adjustment to Compensation Amount Affiliated companies Affiliated Entity [Member] Consolidation Consolidation, Policy [Policy Text Block] Employee Stock Option Share-Based Payment Arrangement, Option [Member] Award Timing MNPI Disclosure Award Timing MNPI Disclosure [Text Block] Variable Interest Entity, Primary Beneficiary Variable Interest Entity, Primary Beneficiary [Member] Percent Effective Income Tax Rate Reconciliation, Percent [Abstract] Cash distribution declared Dividends, Common Stock, Cash Insider Trading Policies and Procedures [Line Items] Public Utilities, Regulatory Proceeding [Domain] Public Utilities, Regulatory Proceeding [Domain] Surety Bonds Surety Bond [Member] Asset removal costs Payments for Removal Costs Notes receivable from affiliated companies Financing Receivable, Accrued Interest, after Allowance for Credit Loss CURRENT ASSETS: Assets, Current [Abstract] TOTAL LIABILITIES AND EQUITY Liabilities and Equity Other current liabilities Increase (Decrease) in Other Current Liabilities Property taxes Property Taxes Payable, Noncurrent Property Taxes Payable, Noncurrent Fair Value of Financial Instruments [Table] Fair Value of Financial Instruments [Table] Fair Value Of Financial Instruments. LIABILITIES AND EQUITY Liabilities and Equity [Abstract] OTHER INCOME (EXPENSE): Other Nonoperating Income (Expense) [Abstract] Cover [Abstract] Cover [Abstract] Portion at Fair Value Measurement Portion at Fair Value Measurement [Member] PROPERTY, PLANT AND EQUIPMENT: Property, Plant and Equipment, Net [Abstract] Income attributable to noncontrolling interest Net Income (Loss) Attributable to Noncontrolling Interest Number of transmission projects Number Of Transmission Projects Number Of Transmission Projects Non-PEO NEO Average Total Compensation Amount Non-PEO NEO Average Total Compensation Amount Adjustment to Non-PEO NEO Compensation Footnote Adjustment to Non-PEO NEO Compensation Footnote [Text Block] Pay vs Performance Disclosure [Line Items] Grid Growth Grid Growth [Member] Grid Growth Forgone Recovery due to Disqualification of Tax Benefits, Amount Forgone Recovery due to Disqualification of Tax Benefits, Amount Non-Rule 10b5-1 Arrangement Terminated Non-Rule 10b5-1 Arrangement Terminated [Flag] INCOME BEFORE INCOME TAXES Income before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Entity Shell Company Entity Shell Company Other Other Liabilities, Noncurrent Less — Accumulated provision for depreciation Public Utilities, Property, Plant and Equipment, Accumulated Depreciation, Excluding Construction Work in Progress Public Utilities, Property, Plant and Equipment, Accumulated Depreciation, Excluding Construction Work in Progress Regulatory Asset [Line Items] Regulatory Asset [Line Items] Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] New financing- New Financing [Abstract] New Financing Abstract. Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Company Selected Measure Amount Company Selected Measure Amount Award Timing MNPI Considered Award Timing MNPI Considered [Flag] Interest income from affiliates Interest income Investment Income, Nonoperating Name Measure Name LOCs Letter of Credit [Member] Accumulated deferred income taxes Deferred Income Tax Liabilities, Net Document Fiscal Period Focus Document Fiscal Period Focus Unsecured Debt Unsecured Debt [Member] Award Timing Method Award Timing Method [Text Block] Award Type Award Type [Axis] Long-term debt and other long-term obligations Long-Term Debt Legal Entity [Axis] Legal Entity [Axis] TOTAL ASSETS Assets Assets Amortization of regulatory assets, net Amortization (Deferral) Of Regulatory Asset, Net Amortization (Deferral) Of Regulatory Asset, Net Transmission Revenues Transmission Revenues [Member] Transmission Revenues Investment, Name [Domain] Investment, Name [Domain] Members' Equity Member Units [Member] Excess deferred tax amortization Effective Income Tax Rate Reconciliation, Excess Deferred Tax Amortization, Amount Effective Income Tax Rate Reconciliation, Excess Deferred Tax Amortization, Amount Entity Address, City or Town Entity Address, City or Town CASH FLOWS FROM OPERATING ACTIVITIES: Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract] In service Public Utilities, Property, Plant and Equipment, Plant in Service Non-PEO NEO Average Compensation Actually Paid Amount Non-PEO NEO Average Compensation Actually Paid Amount Income Statement Location [Domain] Statement of Income Location, Balance [Domain] Compensation Actually Paid vs. Other Measure Compensation Actually Paid vs. Other Measure [Text Block] Regulatory Agency [Axis] Regulatory Agency [Axis] Entity Emerging Growth Company Entity Emerging Growth Company Entity Common Stock Shares Outstanding Entity Common Stock, Shares Outstanding Changes in current assets and liabilities- Increase (Decrease) in Operating Assets [Abstract] Pre-tax charge with interest recorded Public Utilities, Amount Awarded From Other Party Public Utilities, Amount Awarded From Other Party Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year [Member] Total Revenue from Contracts with Customers Revenue from Contract with Customer, Including Assessed Tax State and municipal income taxes, net of federal effect Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount Equity method investments Equity Method Investments Insider Trading Policies and Procedures Not Adopted Insider Trading Policies and Procedures Not Adopted [Text Block] Affiliates Related Party [Member] Additional successive term Lessee, Operating Lease, Renewal Term, Additional Successive Term Lessee, Operating Lease, Renewal Term, Additional Successive Term PEO PEO [Member] Schedule of Disaggregation of Revenue Disaggregation of Revenue [Table Text Block] Accrued taxes Accrued Income Taxes, Current Accrued Income Taxes, Current Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year [Member] Brookfield Brookfield [Member] Brookfield Retained Earnings Retained Earnings [Member] Number of additional successive periods Lessee, Operating Lease, Number Of Renewal Options Lessee, Operating Lease, Number Of Renewal Options Entity Address, Postal Zip Code Entity Address, Postal Zip Code Restatement Determination Date Restatement Determination Date Cash and cash equivalents, at beginning of period Cash and cash equivalents, at end of period Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Income Statement [Abstract] Income Statement [Abstract] Noncontrolling interest Members' Equity Attributable to Noncontrolling Interest INCOME TAXES Total income taxes Income Tax Expense (Benefit) Number of additional renewal options Lessee, Operating Lease, Number Of Additional Renewal Options Lessee, Operating Lease, Number Of Additional Renewal Options Common Class B Common Class B [Member] Accrued interest Increase (Decrease) in Interest Payable, Net Pension Adjustments Service Cost Pension Adjustments Service Cost [Member] Product and Service [Domain] Product and Service [Domain] Total Members' Equity Parent [Member] NET INCOME Net income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Restatement does not require Recovery Restatement Does Not Require Recovery [Text Block] Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] AFUDC equity income Effective Income Tax Rate Reconciliation, Tax Exempt Income, Amount Schedule of Guarantor Obligations [Table] Guarantor Obligation [Table] Capitalized cost of equity Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity Compensation Actually Paid vs. Company Selected Measure Compensation Actually Paid vs. Company Selected Measure [Text Block] City Area Code City Area Code Award Timing, How MNPI Considered Award Timing, How MNPI Considered [Text Block] All Trading Arrangements All Trading Arrangements [Member] Equity Awards Adjustments, Footnote Equity Awards Adjustments, Footnote [Text Block] Total Shareholder Return Vs Peer Group Total Shareholder Return Vs Peer Group [Text Block] Capitalized interest Interest Costs Capitalized AFUDC equity income Effective Income Tax Rate Reconciliation, Tax Exempt Income, Percent Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Transmission revenue collections, net Transmission Revenue Collection, Net Transmission Revenue Collection, Net CASH FLOWS FROM INVESTING ACTIVITIES: Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract] Pay vs Performance Disclosure Pay vs Performance Disclosure [Table] Net cash provided from operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation Investments Long-Term Investments Related Party Transactions [Abstract] Subsequent Event Subsequent Event [Member] Percent of face amount of debt Guarantor Obligations, Maximum Contractual Obligations, Percent of Face Amount of Debt Guarantor Obligations, Maximum Contractual Obligations, Percent of Face Amount of Debt Transmission solutions to the reliability issues Public Utilities, Transmission Solutions To The Reliability Issues, Amount Public Utilities, Transmission Solutions To The Reliability Issues, Amount Goodwill Goodwill Equity Valuation Assumption Difference, Footnote Equity Valuation Assumption Difference, Footnote [Text Block] PEO Total Compensation Amount PEO Total Compensation Amount Long-term Debt, Type [Axis] Long-Term Debt, Type [Axis] Provision for depreciation Depreciation Depreciation and amortization Depreciation, Depletion, Amortization And Impairments Depreciation, Depletion, Amortization And Impairments Equity Components [Axis] Equity Components [Axis] Non-Rule 10b5-1 Arrangement Adopted Non-Rule 10b5-1 Arrangement Adopted [Flag] Construction work in progress Public Utilities, Property, Plant and Equipment, Construction Work in Progress SUPPLEMENTAL CASH FLOW INFORMATION: Supplemental Cash Flow Information [Abstract] VARIABLE INTEREST ENTITIES Variable Interest Entity Disclosure [Text Block] Other Performance Measure, Amount Other Performance Measure, Amount Regulatory liabilities Regulatory Liability, Noncurrent Entity Address, State or Province Entity Address, State or Province FESC support services FESC Support Services [Member] FESC Support Services FERC Federal Energy Regulatory Commission [Member] Federal Energy Regulatory Commission Related Party [Domain] Related and Nonrelated Parties [Domain] Liabilities, Current, Total Liabilities, Current Amount Income Tax Expense (Benefit), Effective Income Tax Rate Reconciliation, Amount [Abstract] Capitalized financing costs Interest Costs Capitalized Adjustment Individual: Individual [Axis] Approved ROE Public Utilities, Approved Return on Equity, Percentage Corporate AMT credit carryforwards Deferred Tax Assets, Corporate AMT Credit Carryforwards Deferred Tax Assets, Corporate AMT Credit Carryforwards North American Transmission Company II LLC North American Transmission Company II LLC [Member] North American Transmission Company II LLC Prepaid taxes and other Other Assets, Current MAIT Mid-Atlantic Interstate Transmission, LLC [Member] Mid-Atlantic Interstate Transmission, LLC [Member] Entity [Domain] Entity [Domain] Net cash used for investing activities Cash Provided by (Used in) Investing Activity, Including Discontinued Operation Variable interest entities percentage of high voltage transmission line project owned by variable interest entity one in joint venture party two Variable Interest Entities Percentage Of High Voltage Transmission Line Project Owned By Variable Interest Entity One In Joint Venture Party Two Variable Interest Entities Percentage of high voltage transmission line project owned By variable interest entity one in joint venture party two. Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table [Member] Document Fiscal Year Focus Document Fiscal Year Focus Equity contribution from FE First Energy (FE) [Member] First Energy (FE) Basis of Accounting Basis of Accounting, Policy [Policy Text Block] Operating lease right-of-use asset Operating Lease, Right-of-Use Asset Operating Lease, Right-of-Use Asset Forgone Recovery, Explanation of Impracticability Forgone Recovery, Explanation of Impracticability [Text Block] Repayments of debt Repayments of Long-Term Debt Total income taxes Effective Income Tax Rate Reconciliation, Percent Entity Interactive Data Current Entity Interactive Data Current Carrying value Reported Value Measurement [Member] Number of directors Number Of Directors Number Of Directors Grid Growth Formula Transmission Rate Grid Growth Formula Transmission Rate [Member] Grid Growth Formula Transmission Rate Service area Service Area Service Area. Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Currently payable long-term debt Long-Term Debt and Lease Obligation, Current Variable Interest Entities [Abstract] Variable Interest Entities [Abstract] Variable Interest Entities Abstract. Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Transource Energy, LLC Transource Energy, LLC [Member] Transource Energy, LLC Ownership [Domain] Ownership [Domain] Compensation Actually Paid vs. Total Shareholder Return Compensation Actually Paid vs. Total Shareholder Return [Text Block] Capital investments Payments to Acquire Productive Assets Other Other Assets, Noncurrent Other Assets, Noncurrent Customer [Domain] Customer [Domain] Accrued interest Interest Payable, Current Entity Central Index Key Entity Central Index Key PEO Name PEO Name Total revenues Total revenues Revenues Revenues Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year [Member] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Outstanding Aggregate Erroneous Compensation Amount Outstanding Aggregate Erroneous Compensation Amount Arrangement Duration Trading Arrangement Duration Operating expenses capitalized Utilities Operating Expense, Maintenance, Operations, Costs Capitalized Utilities Operating Expense, Maintenance, Operations, Costs Capitalized Prepaid taxes and other current assets Increase (Decrease) in Prepaid Expense and Other Assets Grid Growth EHV Holdings, LLC Grid Growth EHV Holdings, LLC [Member] Grid Growth EHV Holdings, LLC Exercise Price Award Exercise Price Entity Filer Category Entity Filer Category Class of Stock [Domain] Class of Stock [Domain] Local Phone Number Local Phone Number Capitalization, Long-Term Debt and Equity [Abstract] Capitalization, Long-Term Debt and Equity [Abstract] Additional 402(v) Disclosure Additional 402(v) Disclosure [Text Block] Federal statutory income tax Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Other Payment for (Proceeds from) Other Investing Activity Other Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Other Item Subsequent Event Type [Axis] Subsequent Event Type [Axis] ASSETS Assets [Abstract] Non-affiliates Nonrelated Party [Member] Underlying Security Market Price Change Underlying Security Market Price Change, Percent Debt Instrument [Axis] Debt Instrument [Axis] FAIR VALUE MEASUREMENTS Fair Value Disclosures [Text Block] MEMBERS' EQUITY: Equity, Attributable to Parent [Abstract] Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year [Member] Short-term borrowings, net Proceeds from Short-Term Debt Entity Address, Address Line One Entity Address, Address Line One Allowance for equity funds used during construction Public Utilities, Allowance for Funds Used During Construction, Additions Interest rate Debt Instrument, Interest Rate, Stated Percentage Investment, Name [Axis] Investment, Name [Axis] Noncurrent operating lease obligation Operating Lease, Liability, Noncurrent Ownership [Axis] Ownership [Axis] Fair Value as of Grant Date Award Grant Date Fair Value Entity Registrant Name Entity Registrant Name Stock Price or TSR Estimation Method Stock Price or TSR Estimation Method [Text Block] Defined benefit plan, plan assets, other pension and OPEB net periodic costs (credits) Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Total operating expenses Costs and Expenses Regulated Operations [Abstract] Regulated Operations [Abstract] Related Party Transaction [Line Items] Related Party Transaction [Line Items] Document Quarterly Report Document Quarterly Report Deferred income taxes and investment tax credits, net Deferred Income Taxes and Tax Credits Changed Peer Group, Footnote Changed Peer Group, Footnote [Text Block] Counterparty Name [Domain] Counterparty Name [Domain] Revenues from affiliates Electric Transmission [Member] Number of operating segments Number of Operating Segments Adjustment To PEO Compensation, Footnote Adjustment To PEO Compensation, Footnote [Text Block] Related Party [Axis] Related and Nonrelated Parties [Axis] Title Trading Arrangement, Individual Title Peer Group Total Shareholder Return Amount Peer Group Total Shareholder Return Amount Capital structure, percentage Public Utilities, Approved Debt Capital Structure, Percentage Service Service [Member] Restatement Determination Date: Restatement Determination Date [Axis] Non-PEO NEO Non-PEO NEO [Member] Total members' equity Members' Equity Other Proceeds from (Payment for) Other Financing Activity Name Trading Arrangement, Individual Name All Award Types Award Type [Domain] Loans with affiliated companies, net Payments for (Proceeds from) Loans Receivable Equity Awards Adjustments Equity Awards Adjustments [Member] Pension Benefits Adjustments, Footnote Pension Benefits Adjustments, Footnote [Text Block] Capped portion of surety bond obligations Guarantor Obligations, Capped Portion of Surety Bond Obligations Guarantor Obligations, Capped Portion of Surety Bond Obligations Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Receivables Increase (Decrease) in Accounts and Other Receivables Compensation Amount Outstanding Recovery Compensation Amount Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Other Effective Income Tax Rate Reconciliation, Other Reconciling Items, Percent Nominal voltage (in kV) Transmission Line, Nominal Voltage 4 Transmission Line, Nominal Voltage 4 Nominal voltage (in kV) Transmission Line, Nominal Voltage 5 Transmission Line, Nominal Voltage 5 Recovery of Erroneously Awarded Compensation Disclosure [Line Items] Fair value Estimate of Fair Value Measurement [Member] Nominal voltage (in kV) Transmission Line, Nominal Voltage 6 Transmission Line, Nominal Voltage 6 Nominal voltage (in kV) Transmission Line, Nominal Voltage 7 Transmission Line, Nominal Voltage 7 Nominal voltage (in kV) Transmission Line, Nominal Voltage 1 Transmission Line, Nominal Voltage 1 Nominal voltage (in kV) Transmission Line, Nominal Voltage 2 Transmission Line, Nominal Voltage 2 Nominal voltage (in kV) Transmission Line, Nominal Voltage 3 Transmission Line, Nominal Voltage 3 MNPI Disclosure Timed for Compensation Value MNPI Disclosure Timed for Compensation Value [Flag] Name Awards Close in Time to MNPI Disclosures, Individual Name Aggregate Erroneous Compensation Not Yet Determined Aggregate Erroneous Compensation Not Yet Determined [Text Block] REVENUES: Revenues [Abstract] Long-term debt and other long-term obligations Long-Term Debt and Lease Obligation Income Statement Location [Axis] Statement of Income Location, Balance [Axis] Aggregate Pension Adjustments Service Cost Aggregate Pension Adjustments Service Cost [Member] Senior Unsecured Notes Due 2030 At 5.00% Senior Unsecured Maturing 2033 At 5.19% [Member] Senior Unsecured Maturing 2033 At 5.19% Company Selected Measure Name Company Selected Measure Name Fair Value Measurement [Domain] Fair Value Measurement [Domain] Senior Notes Senior Notes [Member] ATSI ATSI [Member] ATSI. Aggregate Available Trading Arrangement, Securities Aggregate Available Amount Recovery of project abandonment costs (percent) Public Utilities, Recovery Of Project Abandonment, Prior To Effective Date Costs, Percentage Public Utilities, Recovery Of Project Abandonment, Prior To Effective Date Costs, Percentage Stock Appreciation Rights (SARs) Stock Appreciation Rights (SARs) [Member] Regulatory Matters [Table] Regulatory Matters [Table] Regulatory matters. All Executive Categories All Executive Categories [Member] PJM 2024 RTEP Window 1 PJM 2024 RTEP Window 1 [Member] PJM 2024 RTEP Window 1 COMMITMENTS, GUARANTEES AND CONTINGENCIES Commitments and Contingencies Disclosure [Text Block] Property, Plant and Equipment [Table] Regulated Operation, Regulatory Asset [Table] Segment Information Segment Reporting, Policy [Policy Text Block] COMMITMENTS, GUARANTEES AND CONTINGENCIES (NOTE 7.) Commitments and Contingencies Non-GAAP Measure Description Non-GAAP Measure Description [Text Block] FET FET [Member] FET Entity Small Business Entity Small Business Fair Value of Financial Instruments [Line Items] Fair Value of Financial Instruments [Line Items] Fair Value of Financial Instruments. Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Other operating expenses Other operating expenses: Other Cost and Expense, Operating Noncontrolling Interest Noncontrolling Interest [Member] Document Transition Report Document Transition Report Interest expense Interest Costs Incurred Equity method investment, ownership percentage Equity Method Investment, Ownership Percentage Dominion HV Dominion HV [Member] Dominion HV Underlying Securities Award Underlying Securities Amount Basis point adder associated with RTO membership Utilities, Basis Point Adder Associated With RTO Membership Utilities, Basis Point Adder Associated With RTO Membership Equity Component [Domain] Equity Component [Domain] Document Period End Date Document Period End Date PEO Actually Paid Compensation Amount PEO Actually Paid Compensation Amount INCOME TAXES Income Tax Disclosure [Text Block] Common Class A Common Class A [Member] Awards Close in Time to MNPI Disclosures, Table Awards Close in Time to MNPI Disclosures [Table Text Block] Transmission ROE Incentive Transmission ROE Incentive [Member] Transmission ROE Incentive Revenue from Contract with Customer [Abstract] Revenue from Contract with Customer [Abstract] Receivables- Receivables, Net, Current [Abstract] PJM Interconnection, LLC PJM Interconnection, LLC [Member] PJM Interconnection, LLC Document Type Document Type Name Outstanding Recovery, Individual Name Product and Service [Axis] Product and Service [Axis] Total investments and other noncurrent assets Deferred Charges And Other Assets, Noncurrent Deferred Charges And Other Assets, Noncurrent All Individuals All Individuals [Member] Long-term Debt, Type [Domain] Long-Term Debt, Type [Domain] Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Name Forgone Recovery, Individual Name General taxes Utilities Operating Expense, Taxes Assets, Current, Total Assets, Current Regulatory Agency [Domain] Regulatory Agency [Domain] Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested [Member] Special purpose membership interest held, percentage of distributions Special Purpose Membership Interest Held, Percentage Of Distributions Special Purpose Membership Interest Held, Percentage Of Distributions Aggregate Erroneous Compensation Amount Aggregate Erroneous Compensation Amount Peer Group Issuers, Footnote Peer Group Issuers, Footnote [Text Block] Erroneous Compensation Analysis Erroneous Compensation Analysis [Text Block] Property, plant and equipment in service net of accumulated provision for depreciation Net Plant Excluding Construction Work In Progress Amount, net of accumulated depreciation of long-lived physical assets, excluding construction in progress, used in the normal conduct of business and not intended for resale. CURRENT LIABILITIES: Liabilities, Current [Abstract] Guarantor Obligations, Nature [Domain] Guarantor Obligations, Nature [Domain] Rule 10b5-1 Arrangement Terminated Rule 10b5-1 Arrangement Terminated [Flag] Related Party Transaction [Table] Related Party Transaction [Table] Erroneously Awarded Compensation Recovery Erroneously Awarded Compensation Recovery [Table] Affiliated companies Accounts Receivable, after Allowance for Credit Loss, Current Significant non-cash transactions: Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Accounts payable - Affiliated companies Accounts Payable Other Effective Income Tax Rate Reconciliation, Other Reconciling Items, Amount Total other expense Nonoperating Income (Expense) Ownership percentage by parent Subsidiary, Ownership Percentage, Parent Variable Interest Entity, Not Primary Beneficiary Variable Interest Entity, Not Primary Beneficiary [Member] Path WV Path Wv [Member] PATH-WV [Member]. TrAIL Trail [Member] TRAIL. Transource Transource [Member] Transource Award Timing Disclosures [Line Items] Senior Unsecured Notes Maturing Due 2025 At 3.85% Senior Unsecured Notes Maturing 2026 At 4.00% [Member] Senior Unsecured Notes Maturing 2026 At 4.00% Renewal term of lease yet to be commenced Lessee, Operating Lease, Renewal Term Transmission Related Vegetation Management Programs Transmission Related Vegetation Management Programs [Member] Transmission Related Vegetation Management Programs MAIT Mid-Atlantic Interstate Transmission, LLC (MAIT) [Member] Mid-Atlantic Interstate Transmission, LLC (MAIT) EARNINGS ATTRIBUTABLE TO FIRSTENERGY TRANSMISSION, LLC Net Income (Loss) Attributable to Parent Expiration Date Trading Arrangement Expiration Date NONCURRENT LIABILITIES: Liabilities, Noncurrent [Abstract] Total property, plant and equipment Public Utilities, Property, Plant and Equipment, Net Public Utilities, Property, Plant and Equipment, Net Capital structure, percentage Public Utilities, Requested Debt Capital Structure, Percentage Ground lease expense Ground Lease Expense [Member] Ground Lease Expense Schedule of Effective Income Tax Rate Reconciliation Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Equity ratio, percentage Public Utilities, Requested Equity Capital Structure, Percentage Sale of ownership interest by parent Equity Method Investment, Ownership Percentage, Acquired Equity Method Investment, Ownership Percentage, Acquired TOTAL EQUITY Beginning balance Ending balance Limited Liability Company (LLC) Members' Equity, Including Portion Attributable to Noncontrolling Interest Other revenue unrelated to contracts with customers Revenue Not from Contract with Customer Adoption Date Trading Arrangement Adoption Date Reclassifications Reclassification, Comparability Adjustment [Policy Text Block] Compensation Actually Paid vs. Net Income Compensation Actually Paid vs. Net Income [Text Block] Entity Current Reporting Status Entity Current Reporting Status Customer [Axis] Customer [Axis] Awards Close in Time to MNPI Disclosures Awards Close in Time to MNPI Disclosures [Table] OPERATING INCOME Operating Income (Loss) Consolidated Entities [Domain] Consolidated Entities [Domain] Retained earnings Retained Earnings (Accumulated Deficit) Federal statutory income tax Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount Excess deferred tax amortization Effective Income Tax Rate Reconciliation, Excess Deferred Tax Amortization, Percent Effective Income Tax Rate Reconciliation, Excess Deferred Tax Amortization, Percent Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested [Member] Executive Category: Executive Category [Axis] State and municipal income taxes, net of federal effect Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent Proceeds from issuance of long-term debt Proceeds from Issuance of Long-Term Debt Ownership interest Limited Liability Company or Limited Partnership, Members or Limited Partners, Ownership Interest Class of Stock [Axis] Class of Stock [Axis] Current Fiscal Year End Date Current Fiscal Year End Date Subsequent Event Type [Domain] Subsequent Event Type [Domain] Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table [Member] Curing period Guarantor Obligations, Curing Period Guarantor Obligations, Curing Period Schedule of Potential Amount of Future Payments Schedule of Guarantor Obligations [Table Text Block] Miscellaneous income, net Other Nonoperating Income (Expense) Statement [Table] Statement [Table] Adjustments to reconcile net income to net cash from operating activities- Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity [Abstract] CASH FLOWS FROM FINANCING ACTIVITIES: Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract] Equity Awards Adjustments, Excluding Value Reported in Compensation Table Equity Awards Adjustments, Excluding Value Reported in the Compensation Table [Member] Senior Unsecured Maturing 2033 Senior Unsecured Maturing 2033 [Member] Senior Unsecured Maturing 2033 Members' equity Members' Capital All Adjustments to Compensation All Adjustments to Compensation [Member] Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Amendment Flag Amendment Flag INVESTMENTS AND OTHER NONCURRENT ASSETS: Deferred Charges And Other Assets [Abstract] Deferred Charges And Other Assets Abstract. Termination Date Trading Arrangement Termination Date Net cash provided from financing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation Insider Trading Policies and Procedures Adopted Insider Trading Policies and Procedures Adopted [Flag] Measure: Measure [Axis] ORGANIZATION AND BASIS OF PRESENTATION Basis of Presentation and Significant Accounting Policies [Text Block] Related Party Transaction [Domain] Related Party Transaction [Domain] Pay vs Performance Disclosure, Table Pay vs Performance [Table Text Block] Forgone Recovery due to Violation of Home Country Law, Amount Forgone Recovery due to Violation of Home Country Law, Amount Entity Tax Identification Number Entity Tax Identification Number Valley Link Valley Link [Member] Valley Link OPERATING EXPENSES: Costs and Expenses [Abstract] Forgone Recovery due to Expense of Enforcement, Amount Forgone Recovery due to Expense of Enforcement, Amount Equity ratio, percentage Public Utilities, Approved Equity Capital Structure, Percentage Consolidated Entities [Axis] Consolidated Entities [Axis] Public Utilities, Regulatory Proceeding [Axis] Public Utilities, Regulatory Proceeding [Axis] MAIT MAIT [Member] MAIT Use of Estimates Use of Estimates, Policy [Policy Text Block] Guarantor Obligations, Nature [Axis] Guarantor Obligations, Nature [Axis] Valley Link Transmission Rate Valley Link Transmission Rate [Member] Valley Link Transmission Rate Distribution payments Payments of Dividends Interest expense Interest Expense, Nonoperating Trading Arrangement: Trading Arrangement [Axis] Recovery of project abandonment costs incurred thereafter (percent) Public Utilities, Recovery Of Project Abandonment, Costs Incurred Thereafter, Percentage Public Utilities, Recovery Of Project Abandonment, Costs Incurred Thereafter, Percentage Accrued taxes Increase (Decrease) in Income Taxes Payable Total Shareholder Return Amount Total Shareholder Return Amount Insider Trading Arrangements [Line Items] Schedule of Fair Value and Related Carrying Amounts of Long-term Debt Fair Value And Related Carrying Amounts Of Long Term Debt And Other Long Term Obligations [Table Text Block] Fair value and related carrying amounts of long-term debt and other long-term obligations. Liabilities, Noncurrent, Total Liabilities, Noncurrent TOTAL LIABILITIES Liabilities Liabilities Accrued capital investments Capital Expenditures Incurred but Not yet Paid Pension Adjustments Prior Service Cost Pension Adjustments Prior Service Cost [Member] Material Terms of Trading Arrangement Material Terms of Trading Arrangement [Text Block] Other Other Liabilities, Current Statement [Line Items] Statement [Line Items] Rule 10b5-1 Arrangement Adopted Rule 10b5-1 Arrangement Adopted [Flag] Cash and cash equivalents Cash and Cash Equivalent Counterparty Name [Axis] Counterparty Name [Axis] Company posted collateral related to net liability positions Company Posted Collateral Related To Net Liability Positions Company Posted Collateral Related To Net Liability Positions. Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Non-NEOs Non-NEOs [Member] Net change in cash and cash equivalents Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation