Commitments under coal, gas and transportation contractual agreements Long-term Purchase Commitment [Table Text Block] Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Borrowings outstanding Line of Credit, Current Intangibles amortization (excluding goodwill) Deferred Tax Liabilities, Intangible Assets Target allocation of pension plan assets (as percent) Defined Benefit Plan, Plan Assets, Target Allocation, Percentage Receivable Type [Axis] Receivable Type [Axis] Aggregate Intrinsic Value Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value Other Comprehensive Income/(Loss), net of tax Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract] Pension and other post retirement benefit obligations Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] Expects to contribute to the pension plans Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] MSUs Market Stock Unit [Member] Market Stock Unit [Member] Agua Caliente Borrower 1, due 2038 Agua Caliente Borrower 1, due 2038 [Member] Agua Caliente Borrower 1, due 2038 [Member] NRG's net deferred tax position Deferred Tax Liabilities, Net, Classification [Abstract] Related Party [Axis] Related Party [Axis] Swingline facility Bridge Loan [Member] Fair value of plan assets for pension and other post retirement benefit Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] Pre-capitalized Trust Securities Pre-capitalized Trust Securities [Member] Pre-capitalized Trust Securities Noncontrolling Interest [Table] Noncontrolling Interest [Table] Non-nuclear Event Non-nuclear Event [Member] Non-nuclear Event [Member] Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at Beginning of Period Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at End of Period Cash and cash equivalents, funds deposited by counterparties and restricted cash shown in the statements of cash flows Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations Due to realization of previously deferred amounts Other Comprehensive Income (Loss), Derivative, Excluded Component, Increase (Decrease), after Adjustments and Tax Total operating revenues Operating Revenues [Member] Operating Revenues [Member] Deferred impact of state tax rate changes Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount Direct Energy Direct Energy [Member] Direct Energy Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract] Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract] Project Development Costs and Capitalized Interest Project Development Costs and Capitalized Interest [Abstract] Uncertain tax benefits Income Tax Uncertainties [Abstract] Range [Domain] Statistical Measurement [Domain] LIABILITIES AND STOCKHOLDERS' EQUITY Liabilities and Equity [Abstract] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Stock-Based Compensation Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Customers served (over) Customers added (over) Number of customers Number of customers Distributions to noncontrolling interest and dividends paid Distributions to redeemable noncontrolling interest Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders Redemption Period Prior to January 15, 2021 Redemption Period Prior to January 15, 2021 [Member] Redemption Period Prior to January 15, 2021 [Member] Finance lease cost Finance Lease, Right-of-Use Asset, Amortization Equity component of convertible senior notes Adjustments to Additional Paid in Capital, Equity Component of Convertible Debt Cash (used)/provided by continuing operations Net Cash Provided by (Used in) Investing Activities, Continuing Operations Security Exchange Name Security Exchange Name February 15, 2024 to February 14, 2025 Redemption Period February 15, 2024 to February 14, 2025 [Member] Redemption Period February 15, 2024 to February 14, 2025 Purchases Finite-Lived Intangible Assets, Purchases This element represents the finite-lived intangible assets purchased during the period. Fair value of plan assets at January 1 Fair value of plan assets at December 31 Fair value of plan assets Defined Benefit Plan, Plan Assets, Amount Proceeds from issuance of long-term debt Proceeds from Issuance of Long-term Debt Total current liabilities Current liabilities Liabilities, Current Other Other Asset Retirement Obligations [Member] Other Asset Retirement Obligations Increase to pension liability Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Curtailment Contributions from redeemable noncontrolling interest Redeemable Noncontrolling Interest, Cash Contributions from Noncontrolling Interest Holders Redeemable Noncontrolling Interest, Cash Contributions from Noncontrolling Interest Holders Emissions Emissions [Member] Details pertaining to the emission allowances, which is considered as a derivative commodity. Prepayments and other current assets Prepaid Expense and Other Assets, Current Non-vested at beginning of period (in usd per share) Non-vested at end of period (in usd per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Variable Rate [Domain] Variable Rate [Domain] 2025 Defined Benefit Plan, Expected Future Benefit Payment, Year Five Realized (losses) Debt Securities, Available-for-sale, Realized Loss Small Book Acquisitions 2020 Small Book Acquisitions 2020 [Member] Small Book Acquisitions 2020 Assets [Abstract] Assets [Abstract] Schedule of Property, Plant and Equipment [Table] Property, Plant and Equipment [Table] Investment, Name [Axis] Investment, Name [Axis] Accounting Policies [Abstract] Accounting Policies [Abstract] Commodity contracts current Commodity Contract Current [Member] The current portion of a derivative instrument whose primary underlying risk is tied to commodity prices. Counterparty Risk by Investment Grade [Axis] Counterparty Risk by Investment Grade [Axis] The counter party risk exposure by investment grades. Unrealized Losses Decommissioning Fund Investments, Unrealized Loss Decommissioning Fund Investments, Unrealized Loss Transfers out of Level 3 Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Transfers out of Level 3 Restricted Cash Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy [Policy Text Block] Balance outstanding at the beginning of the period, (in usd per share) Balance outstanding at the end of the period (in usd per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options Vested, Weighted Average Grant Date Fair Value The weighted-average fair value of vested awards on equity-based plans excluding option plans. Operating cash flows from operating leases Operating Lease, Payments 2018 Capital Allocation Plan 2018 Capital Allocation Plan [Member] 2018 Capital Allocation Plan [Member] 2023 Long-Term Debt, Maturity, Year Three Emission allowances held-for-sale Other Assets, Noncurrent, Emission Allowances This element represents the emission allowances held-for-sale that are included in other noncurrent assets on the entity's balance sheet. Fair Value, Balance Sheet Grouping, Financial Statement Captions Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items] Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items] Minimum purchase commitment obligations under purchased power agreements Unrecorded Unconditional Purchase Obligations Disclosure [Table Text Block] Unrealized gain on derivatives, net of income tax Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, after Tax East/West Other East And West [Member] East And West [Member] Weighted average useful life, years Acquired Finite-lived Intangible Assets, Weighted Average Useful Life Total deferred tax assets less deferred tax liabilities Deferred Tax Asset, Net of Deferred Tax Liability Deferred Tax Asset, Net of Deferred Tax Liability 2021 Lessee, Operating Lease, Liability, to be Paid, Year One Outstanding at the beginning of the period (in shares) Outstanding at the end of the period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number 2024 Lessee, Operating Lease, Liability, to be Paid, Year Four Put option agreement, semi-annual Interest rate Put Option Agreement, Semi-annual Interest Rate Put Option Agreement, Semi-annual Interest Rate Assets and Liabilities Measured and Recorded at Fair Value Measured on a Recurring Basis Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Unrecognized Total Cost Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount Long-term debt and finance lease Total long-term debt and finance leases Long-term Debt and Lease Obligation New Accounting Pronouncements or Change in Accounting Principle [Line Items] New Accounting Pronouncements or Change in Accounting Principle [Line Items] Canada CANADA State Current State and Local Tax Expense (Benefit) Outstanding principal after redemption, percentage (at least) Debt Instrument, Outstanding Amount After Redemption, Percentage Debt Instrument, Outstanding Amount After Redemption, Percentage Guarantee (up to) Guarantor Obligations, Maximum Exposure, Undiscounted Income from continuing operations per weighted average common share — diluted (in usd per share) Income (Loss) from Continuing Operations, Per Diluted Share Income/(loss) from discontinued operations per weighted average common share — diluted (in usd per share) Discontinued Operation, Income (Loss) from Discontinued Operation, Net of Tax, Per Diluted Share Common stock, par value (in usd per share) Common Stock, Par or Stated Value Per Share 2023 Defined Benefit Plan, Expected Future Benefit Payment, Year Three Other non-current liabilities Other Liabilities, Noncurrent Deferred income taxes Deferred tax asset Deferred Income Tax Assets, Net Financing cash flows from finance leases Finance Lease, Principal Payments Gross Receipts Tax Gross Receipts Tax Gross Receipts Tax East East Segment [Member] East Segment Net deferred tax asset (before valuation) Net Deferred Tax Asset, Before Valuation Allowance Net Deferred Tax Asset, before valuation allowance Income tax valuation allowance, deducted from deferred tax assets SEC Schedule, 12-09, Valuation Allowance, Deferred Tax Asset [Member] Inventory Total Inventory Inventory, Net Pension and post-retirement liability assumptions Discontinued Operation, Pension Liability Assumption Discontinued Operation, Pension Liability Assumption Fair Value, Measurement Frequency [Domain] Measurement Frequency [Domain] Accounts receivable, net - Derivative instruments Derivative Derivative [Member] Share-based Payment Arrangement, Tranche Three Share-based Payment Arrangement, Tranche Three [Member] Energy revenue Energy Revenue [Member] Energy Revenue [Member] Income from Continuing Operations Income from continuing operations Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest Concentration risk, percentage Concentration Risk, Percentage Maximum contractual term for outstanding options (in years) Share-based Compensation Arrangement by Share-based Payment Award, Maximum Contractual Term Share-based Compensation Arrangement by Share-based Payment Award, Maximum Contractual Term Valuation and Qualifying Accounts Disclosure SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items] Group of Individuals [Axis] Group of Individuals [Axis] Group of Individuals [Axis] Inventory [Axis] Inventory [Axis] Statement [Line Items] Statement [Line Items] Usage/Retirements Finite-Lived Intangible Assets, Usage and retirements The usage and retirement of finite-lived intangible assets during the period. The number of months a nuclear industry mutual insurance company will respond to retrospective premium adjustments Period of retrospective premium adjustments This represents number of months a nuclear industry mutual insurance company will respond to retrospective premium adjustments for policy purchased by company to guarantee financial obligations. Long Long [Member] February 15, 2027 to February 14, 2028 Redemption Period February 15, 2027 to February 14, 2028 [Member] Redemption Period February 15, 2027 to February 14, 2028 Nuclear decommissioning reserve Decommissioning Liability, Noncurrent Statement [Table] Statement [Table] Write-offs Accounts Receivable, Allowance for Credit Loss, Writeoff Interest cost on benefit obligation Interest cost Defined Benefit Plan, Interest Cost Range [Axis] Statistical Measurement [Axis] Period of estimated counterparty credit risk exposure under certain long term agreements, including California tolling agreements, South Central load obligations and solar power purchase agreements (in years) Estimated Counterparty Credit Risk Exposure to Certain Counterparties, Period Estimated Counterparty Credit Risk Exposure to Certain Counterparties, Period Redemption Period Prior to June 15, 2022 Redemption Period Prior to June 15, 2022 [Member] Redemption Period Prior to June 15, 2022 NRG Indian River Power 2020, tax exempt bonds, due 2045 Indian River Power 2020 Tax Exempt Bonds Due 2045 [Member] Indian River Power 2020 Tax Exempt Bonds Due 2045 Capital expenditures Capital Expenditures Represents amount of total Capital expenditures including accruals pertaining to repowering of entity's projects, major maintenance and meeting environmental commitments. Sale of assets to NRG Yield, Inc Sale of Assets Under Common Control Sale of Assets Under Common Control Weighted Average Weighted Average [Member] Balance sheet Segment Reporting Information, Additional Information [Abstract] Entity Small Business Entity Small Business Derivatives by Underlying Assets [Axis] Derivatives by Underlying Assets [Axis] Derivatives by the underlying asset from which its value is derived. Principles of Consolidation Consolidation, Policy [Policy Text Block] Total Unrecorded Unconditional Purchase Obligation Gross Amounts of Recognized Assets / Liabilities Fair Value of Gross Derivative Assets/(Liabilities), Net Fair value of gross derivative assets less fair value of gross derivative liabilities. Receivable Securitization and Repurchase Facility Long-term Debt and Finance Leases Debt Disclosure [Text Block] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Operating revenue Disposal Group, Including Discontinued Operation, Revenue Multiplier that the industry mutual insurance company may assess against insureds premium Industry Mutual Insurance Company Multiplier The industry mutual insurance company may assess the company: 10 times the amount of the total annual premium. Cash provided by discontinued operations Cash Provided by (Used in) Financing Activities, Discontinued Operations Cost of operations Cost of Revenue Amendment Flag Amendment Flag Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract] Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract] Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Accrued interest and penalties related to unrecognized tax benefits Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued Permanent differences Effective Income Tax Rate Reconciliation, Permanent Differences, Amount Effective Income Tax Rate Reconciliation, Permanent Differences, Amount Number of shares authorized for issuance under plan (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized Fort Bend County, tax exempt bonds, due 2038 Fort Bend County, tax exempt bonds, due 2038 [Member] Fort Bend County, tax exempt bonds, due 2038 [Member] Deferred tax assets: Deferred Tax Assets, Gross [Abstract] Corporate Corporate, Non-Segment [Member] Number of shares available for grant under plan (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant Accrued expenses and other current liabilities Other Accrued Liabilities, Current Provinces in which entity operates Number of Provinces in which Entity Operates Number of Provinces in which Entity Operates Mark-to-market of cash flow hedge accounting contracts Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, after Tax Measurement Frequency [Axis] Measurement Frequency [Axis] Initial Application Period Cumulative Effect Transition [Axis] Initial Application Period Cumulative Effect Transition [Axis] Power Power [Member] Details pertaining to the power, which is considered as a derivative commodity. Financial Instruments [Domain] Financial Instruments [Domain] Credit Losses Credit Loss, Financial Instrument [Policy Text Block] Expected return on plan assets Defined Benefit Plan, Expected Return (Loss) on Plan Assets Estimated Carrying Amounts and Fair Values of Financial Instruments Not Carried at Fair Value Fair Value, by Balance Sheet Grouping [Table Text Block] Investments Accounted for by the Equity Method Equity Method Investments [Policy Text Block] Fair Value Measurement [Domain] Fair Value Measurement [Domain] Adequate Assurance Clauses Adequate Assurance Clauses [Member] Adequate Assurance Clauses [Member] Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Table] Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Table] Intercompany secured revolving credit facility and accrued interest and fees Due from Related Parties Derivative Financial Instruments Derivatives, Policy [Policy Text Block] Weighted- average maturities (in years) Decommissioning Trust Assets, Weighted Average Maturity Period The weighted-average maturity period for securities of nuclear decommissioning trust funds assets. Postretirement Benefit Obligation Postretirement Benefit Obligation [Member] Postretirement Benefit Obligation [Member] Renewal term Lessee, Operating Lease, Renewal Term Accrued Interest On Borrowings Accrued Interest On Borrowings [Member] Accrued Interest On Borrowings [Member] Lease Revenue and Lessor Accounting Sale-Leaseback Arrangements Lessor, Leases [Policy Text Block] Contracts added from acquisitions Fair Value, Net Derivative Asset (Liability) Measured On Recurring Basis, Unobservable Inputs Reconciliation, Acquisition Fair Value, Net Derivative Asset (Liability) Measured On Recurring Basis, Unobservable Inputs Reconciliation, Acquisition Revolving accounts receivable financing facility Receivables Facility Receivables Facility [Member] Receivables Facility Loss on deconsolidation Deconsolidation, Revaluation of Retained Investment, Gain (Loss), Amount Property, Plant and Equipment, Type [Axis] Long-Lived Tangible Asset [Axis] Balance at Beginning of Period Balance at End of Period SEC Schedule, 12-09, Valuation Allowances and Reserves, Amount Emission Allowances Emission Allowances Emission Allowances [Member] An asset acquired in a business combination representing an entity's emission allowances. Payment for asset acquisition Payment for Asset Acquisition Payment for Asset Acquisition Over 5 Years Guarantee Maturity, Greater than Five Years Maximum potential amount of future payments that the guarantor could be required to make after five years of the balance sheet date under the guarantee. Units Share-Based Compensation Arrangement By Share-Based Payment Award, Equity Instruments Other Than Options, Vested Number [Roll Forward] Share-Based Compensation Arrangement By Share-Based Payment Award, Equity Instruments Other Than Options, Vested Number [Roll Forward] Company's contributions to 401(k) plans Defined Contribution Plans [Abstract] Defined Contribution Plans Nuclear decommissioning trust liability Nuclear Decommissioning Trust Fund Liability Noncurrent The company is a beneficiary of a trust funded through collections from electric utility ratepayers. In the event that the trust funds are ultimately determined to be inadequate to decommission the company's nuclear facility, all additional amounts required to fund the decommissioning obligations may be collected through non-by-passable charges to the ratepayers. Following the completion of the decommissioning, if surplus funds remain in the decommissioning trusts, any excess funds will be refunded to the respective ratepayers. Consequently, the liability represents a liability to ratepayers in the state of Texas related to decommissioning of the company's Texas nuclear facility. This liability is the sum of the nuclear decommission trust fund asset, the nuclear decommissioning retirement obligation asset included within property, plant and equipment, less the nuclear decommissioning reserve. The total carrying value of all assets and liabilities associated with the decommissioning and the trusts net to zero and none of the activities related to the decommissioning of the STP nuclear facility are recorded in the income statement as ultimately the ratepayers in the state of Texas are liable for decommissioning the facility. Income Statement Location [Domain] Income Statement Location [Domain] 2022 Lessee, Operating Lease, Liability, to be Paid, Year Two State and Local Jurisdiction State and Local Jurisdiction [Member] Net (purchases)/sales of emissions allowances Payments For Proceeds From Intangible Assets Payments For Proceeds From Intangible Assets Cash Flows from Financing Activities Net Cash Provided by (Used in) Financing Activities [Abstract] Selling, general and administrative costs Selling, General and Administrative Expense Lease Cost Lease, Cost [Table Text Block] Ownership interest in STP (as a percent) Limited Liability Company or Limited Partnership, Members or Limited Partners, Ownership Interest 2023 Lessee, Operating Lease, Liability, to be Paid, Year Three Other non-current assets Other Assets, Noncurrent Plan Name [Axis] Plan Name [Axis] Commodity contracts long-term Commodity Contract Non Current [Member] The noncurrent portion of a derivative instrument whose primary underlying risk is tied to commodity prices. Preferred stock, shares authorized (in shares) Temporary Equity, Shares Authorized Income from continuing operations, net of income tax Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent Total Assets Total assets Assets Related Party Transactions Related Party Transactions Disclosure [Text Block] 6.25% Senior Notes due 2024 6.25% Senior Notes due 2024 Senior Notes 2024 [Member] Senior Notes 2024 [Member] Other Other [Member] Other [Member] Schedule of Comparison of Pension Benefit obligation, Other Postretirement Benefit Obligations and Related Plan Assets on a Combined Basis Schedule of Net Funded Status [Table Text Block] Foreign government fixed income securities Debt Security, Government, Non-US [Member] Redemption Period Prior to February 15, 2026 Redemption Period Prior to February 15, 2026 [Member] Redemption Period Prior to February 15, 2026 Non-vested at beginning of period (in shares) Non-vested at end of period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Corporate Corporate Segment [Member] Schedule of Performance Benchmarks Schedule of Performance Benchmarks [Table Text Block] Tabular disclosure of the major categories of plan assets and their related performance benchmark. Eligible compensation withholding, minimum, percentage Employee Stock Purchase Plan, Minimum Percentage of Compensation Eligible Employee Stock Purchase Plan, Minimum Percentage of Compensation Eligible Amortization of unrecognized prior service cost Defined Benefit Plan, Amortization of Prior Service Cost (Credit) NRG's expected future benefit payments Defined Benefit Plan, Expected Future Benefit Payment [Abstract] Transmission and distribution charges not yet billed Cost of Services Energy Services Unbilled The estimated transmission and distribution charges not yet billed by the transmission and distribution utilities for the period. Subsequent Event Type [Axis] Subsequent Event Type [Axis] NRG Yield Inc. And Zephyr Renewables NRG Yield Inc. And Zephyr Renewables [Member] NRG Yield, Inc. and Zephyr Renewables [Member] Sale of NRG Yield and other business Sale of NRG Yield and the Renewables Platform Noncontrolling Interest, Decrease from Deconsolidation Cost of operations Cost of Sales [Member] Changes in NRG's common shares issued and outstanding Schedule of Common Stock Outstanding Roll Forward [Table Text Block] Concentrations of Credit Risk Concentration Risk, Credit Risk, Policy [Policy Text Block] Acquisitions, Discontinued Operations and Dispositions Mergers, Acquisitions and Dispositions Disclosures [Text Block] Other Intangible Assets Other Intangible Assets [Member] Cash and cash equivalents Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents Commercial mortgage-backed securities Commercial Mortgage Backed Securities [Member] Total Liabilities Total Liabilities Liabilities Liability for uncertainty in income taxes, noncurrent Liability for Uncertainty in Income Taxes, Noncurrent Taxes receivable and payable Income Tax Contingency [Line Items] Aon Hewitt above median yield curve discount rate (in years) Aon Hewitt Above Median Yield Curve Discount Rate Years Aon Hewitt Above Median Yield Curve Discount Rate Years Interest crediting rate Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Weighted-Average Interest Crediting Rate July 15, 2022 to July 14, 2023 Redemption Period From 15 July 2022 to 14 July 2023 [Member] Redemption Period From 15 July 2022 to 14 July 2023 [Member] Operating revenue Sales [Member] Changes in derivative instruments Changes in Derivatives The net unrealized change in the aggregate value of derivative instruments used in operating activities and included in earnings in the period, including trading securities and risk management instruments. Schedule of Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income Schedule of Amounts Recognized in Other Comprehensive Income (Loss) [Table Text Block] Expected volatility Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate Retirement Plan Type [Axis] Retirement Plan Type [Axis] Accumulated benefit obligation Defined Benefit Plan, Accumulated Benefit Obligation Less present value adjustment Lessee, Operating Lease, Liability, Undiscounted Excess Amount Employee and retiree contributions Defined Benefit Plan, Plan Assets, Contributions by Plan Participant May 15, 2024 and thereafter Redemption Period From 15 May 2024 And Thereafter [Member] Redemption Period From 15 May 2024 And Thereafter [Member] Schedule of Related Party Transactions, by Related Party [Table] Schedule of Related Party Transactions, by Related Party [Table] 3.625% Senior Unsecured Notes Due 2031 [Member] 3.625% Senior Unsecured Notes Due 2031 [Member] 3.625% Senior Unsecured Notes Due 2031 Fort Bend County, tax exempt bonds, due 2042 Fort Bend County, tax exempt bonds, due 2042 [Member] Fort Bend County, tax exempt bonds, due 2042 [Member] Changes in redeemable noncontrolling interest Redeemable Noncontrolling Interest [Table Text Block] Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Sale of NRG Yield and Renewables Other Comprehensive Income (Loss), Reclassification Adjustment From AOCI, Divestiture Of Business, Net Of Tax Other Comprehensive Income (Loss), Reclassification Adjustment From AOCI, Divestiture Of Business, Net of Tax May 15, 2021 to May 14, 2022 Redemption Period From 15 May 2021 to 14 May 2022 [Member] Redemption Period From 15 May 2021 to 14 May 2022 [Member] Level 1 Quoted Prices in Active Markets for Identical Assets (Level 1) Fair Value, Inputs, Level 1 [Member] Thereafter Unrecorded Unconditional Purchase Obligation, to be Paid, after Year Five Regulated Operations [Abstract] Inventory Increase (Decrease) in Inventories 2022 Unrecorded Unconditional Purchase Obligation, to be Paid, Year Two Weighted average interest rate Debt, Weighted Average Interest Rate Number of states in which the entity operates Number of States in which Entity Operates Derivative Instruments Derivative Liability, Fair Value, Gross Asset NRG Indian River Power 2020, tax exempt bonds, due 2040 Indian River Power2020 Tax Exempt Bonds Due 2040 [Member] Indian River Power2020 Tax Exempt Bonds Due 2040 Capacity revenue Capacity Revenue [Member] Capacity Revenue [Member] Units Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Basis point increase to interest rate Debt Instrument, Basis Spread on Variable Rate, Increase Debt Instrument, Basis Spread on Variable Rate, Increase Other assets and liabilities Increase (Decrease) in Other Operating Assets and Liabilities, Net Facility agreement in connection with sale of pre-capitalized trust securities Facility Agreement, Pre-capitalized Trust Securities [Member] Facility Agreement, Pre-capitalized Trust Securities Watson Cogeneration Company Watson Cogeneration Company [Member] Watson Cogeneration Company [Member] Reduction to interest expense Interest Income (Expense), Net Additional Paid-In Capital Additional Paid-in Capital [Member] Assets Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] West/Other West and Other Segment [Member] West and Other Segment Impaired Long-Lived Assets Held and Used by Type [Axis] Impaired Long-Lived Assets Held and Used by Type [Axis] Credit facility, lien basket, percentage of total assets Line of Credit Facility, Lien Basket, Percentage of Total Assets Line of Credit Facility, Lien Basket, Percentage of Total Assets Noncontrolling Interest [Roll Forward] Noncontrolling Interest [Roll Forward] Noncontrolling Interest Income from continuing operations per weighted average common share —basic (in usd per share) Income (Loss) from Continuing Operations, Per Basic Share Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Environmental Matters Disclosure [Abstract] Environmental Matters Disclosure [Abstract] -- None. No documentation exists for this element. -- Repurchase of redeemable noncontrolling interest Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests Fair Value of Financial Instruments Fair Value of Financial Instruments, Policy [Policy Text Block] Common stock, shares outstanding (in shares) Beginning balance, common shares outstanding (in shares) Ending balance, common shares outstanding (in shares) Common Stock, Shares, Outstanding Equity investments in affiliates Equity method investments Equity Method Investments Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Operating Costs and Expenses Operating Costs and Expenses [Abstract] Other trust fund investments Financial Instruments, Owned, US Government and Agency Obligations, at Fair Value Revolving Credit Facility Revolving Credit Facility [Member] February 15, 2026 and thereafter Redemption Period February 15, 2026 and thereafter [Member] Redemption Period February 15, 2026 and thereafter Income from Continuing Operations Before Income Taxes Income from continuing operations before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest NQSOs Non-Qualified Stock Options [Member] Represents details pertaining to non-qualified stock options. Outstanding (in usd per share) Outstanding (in usd per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price Retail Revenue Products And Services, Retail Revenue [Member] Products And Services, Retail [Member] Common stock, shares authorized (in shares) Common Stock, Shares Authorized Summary of Company's non-vested RSU awards and changes during the year Share-based Payment Arrangement, Restricted Stock Unit, Activity [Table Text Block] Cash received from options exercised Proceeds from Stock Options Exercised Incremental shares attributable to the issuance of equity compensation (treasury stock method) (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements U.S. Federal Deferred Federal Income Tax Expense (Benefit) 2022 Defined Benefit Plan, Expected Future Benefit Payment, Year Two Nuclear operator maximum annual assessment Nuclear Insurance Financial Protection Pool Nuclear Operator Maximum Annual Assessment Nuclear Insurance Financial Protection Pool Nuclear Operator Maximum Annual Assessment Other net current and non-current working capital Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Working Capital, Other, Net Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Working Capital, Other, Net Segment Reporting Schedule of Segment Reporting Information, by Segment [Table Text Block] January 15, 2023 to January 14, 2024 Redemption Period From 15 January 2023 to 14 January 2024 [Member] Redemption Period From 15 January 2023 to 14 January 2024 Regulatory Matters Disclosure [Abstract] Regulatory Matters Disclosure [Abstract] -- None. No documentation exists for this element. -- Funded status at December 31 — excess of obligation over assets Funded status — STPNOC benefit plans Defined Benefit Plan, Funded (Unfunded) Status of Plan Guarantor Obligations, Nature [Axis] Guarantor Obligations, Nature [Axis] SEC Schedule, 12-09, Valuation Allowances and Reserves Type [Axis] SEC Schedule, 12-09, Valuation Allowances and Reserves Type [Axis] Goodwill Goodwill and Intangible Assets, Goodwill, Policy [Policy Text Block] 3.625% Senior Notes due 2031 3.625% Senior Unsecured Notes Due February 2031 [Member] 3.625% Senior Unsecured Notes Due February 2031 Income Statement Income Statement [Abstract] 2025 Unrecorded Unconditional Purchase Obligation, to be Paid, Year Five Accumulated Other Comprehensive Loss AOCI Attributable to Parent [Member] Prepayments and other current assets Increase (Decrease) in Prepaid Expense and Other Assets Percentage of contribution to the retirement plan obligation reimbursed Percentage of Contribution to Retirement Plan Obligations Reimbursed by Entity This element represents the percentage of contribution to the retirement plan obligation reimbursed by the entity. PSUs Performance Stock Units [Member] Performance Stock Units are comprised of Market Stock Units and Relative Performance Stock Units Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Variable Interest Entity, Primary Beneficiary Variable Interest Entity, Primary Beneficiary [Member] Asset Retirement Obligations [Line Items] Asset Retirement Obligations [Line Items] Asset Retirement Obligations Reversal of acquired loss/(gain) positions related to economic hedges Reversal Previously Recognized, Unrealized Gains (Losses) Acquired as Part of Acquisition Economic Hedges Amount reversed into entity's statement of operations for previously recognized unrealized (gains) losses on settled positions related to acquired economic hedges. Cash provided by discontinued operations Cash Provided by (Used in) Operating Activities, Discontinued Operations State net operating loss carryforwards Deferred Tax Assets, Operating Loss Carryforwards, State and Local Disposal Groups, Including Discontinued Operations [Table] Disposal Groups, Including Discontinued Operations [Table] Use of Estimates Use of Estimates, Policy [Policy Text Block] Recognized amount in statement of financial position, statement of operations and accumulated OCI related to STP Amount Recognized in Statement of Financial Position and Accumulated Other Comprehensive Income, Related to Equity Method Investment [Abstract] AOCI Including Portion Attributable to Noncontrolling Interest AOCI Including Portion Attributable to Noncontrolling Interest [Member] Income Tax Authority [Domain] Income Tax Authority [Domain] Schedule of Assumptions Used to Calculate Benefit Expense Defined Benefit Plan, Assumptions [Table Text Block] Gross Receipts and Sales Taxes Gross Receipts and Sales Taxes [Policy Text Block] Describes an entity's accounting policy for gross receipts and sales taxes, which may include its accounting policies, disclosure of the amount recognized in consolidated statement of operations, and method of recognition. Consolidated Entities [Axis] Consolidated Entities [Axis] Other guarantees Guarantee Type, Other [Member] Deferred customer acquisition costs Capitalized Contract Cost, Net Decrease to long-term debt outstanding Increase (Decrease) In Long-Term Debt Increase (Decrease) In Long-Term Debt Scenario, Unspecified [Domain] Scenario [Domain] Bad debt reserve Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Allowance for Doubtful Accounts Additions Costs Incurred, Asset Retirement Obligation Incurred Counterparty Name [Domain] Counterparty Name [Domain] Capital expenditures Payments to Acquire Property, Plant, and Equipment Consolidation Items [Domain] Consolidation Items [Domain] Non Recourse Debt Non Recourse Debt [Member] Represents the non-recourse debt. Return to provision adjustments Effective Income Tax Rate Reconciliation, Prior Year Income Taxes, Amount Asset Acquisition [Domain] Asset Acquisition [Domain] Asset Acquisition Goodwill and Other Intangibles Goodwill and Intangible Assets Disclosure [Text Block] Property, Plant and Equipment Property, Plant and Equipment [Abstract] Actual return on plan assets Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss) Long-term incentive plans (in shares) Common Stock, Capital Shares Reserved for Future Issuance Prior service credit Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), after Reclassification Adjustment, before Tax Equity in earnings of unconsolidated affiliates Equity in (losses)/earnings of unconsolidated affiliates Income (Loss) from Equity Method Investments Nuclear property insurance coverage limit per individual insured Mutual Property Insurance Individual Maximum Property Coverage Limit Maximum coverage limit per individual insured for property insurance from an industry mutual insurance company. Schedule of Guarantor Obligations [Table] Schedule of Guarantor Obligations [Table] Age 65 and after Age 65 and after [Member] Age 65 and after [Member] Hedging Designation [Axis] Hedging Designation [Axis] Current liabilities Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Proceeds from issuance of long-term debt Proceeds from Issuance of Senior Long-term Debt 2026-2030 Defined Benefit Plan, Expected Future Benefit Payment, after Year Five for Next Five Years Schedule of Inventory Schedule of Inventory, Current [Table Text Block] U.S. Federal net operating loss carryforwards Deferred Tax Assets, Operating Loss Carryforwards, Domestic Reduction Of Settlement Payment Reduction Of Settlement Payment [Member] Reduction Of Settlement Payment [Member] Entity [Domain] Entity [Domain] Minimum tax withholdings Payment, Tax Withholding, Share-based Payment Arrangement Lease and easement agreement, number of extensions Lease And Easement Agreement, Number Of Extensions Lease And Easement Agreement, Number Of Extensions Convertible Debt Deferred Tax Liabilities, Deferred Expense, Debt Issuance Costs SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS SEC Schedule, 12-09, Schedule of Valuation and Qualifying Accounts Disclosure [Table Text Block] SEC Schedule, 12-09, Schedule of Valuation and Qualifying Accounts Disclosure Counterparty Risk by Institution [Axis] Counterparty Risk by Institution [Axis] The counter party risk exposure by institutions involved. Summary of Aggregate Fair Values and Unrealized Gains And Losses (Including Other-Than-Temporary Impairments) for the Securities Held in The Nuclear Decommissioning Trust Fund Decommissioning Trust Assets [Table Text Block] Disclosure related to investments held in a trust fund to pay for the costs of decommissioning facilities. Pre-tax Effects of Economic Hedges That Have Not Been Designated As Cash Flow Hedges, Ineffectiveness On Cash Flow Hedges And Trading Activity on the Company's Statement of Operations Derivatives Not Designated as Hedging Instruments [Table Text Block] Depreciable lives (in years) Property, Plant and Equipment, Useful Life Mark-to-market for economic hedging activities Total unrealized mark-to-market (losses)/gains for economic hedging activities Unrealized Gain (Loss) on Derivatives, Mark To Market, Economic Hedging Activities Unrealized Gain (Loss) on Derivatives, Mark To Market, Economic Hedging Activities Amortization of nuclear fuel Amortization of Nuclear Fuel The current period expense charged against earnings for the periodic recognition of the entity's ownership in nuclear fuel based on units of production over the estimated useful life. As a noncash (income) expense, this element is added back to net income when calculating cash provided by (used in) operations using the indirect method. Counterparty credit risk exposure to certain counterparties, threshold (as a percent) Counterparty Credit Risk Exposure, Percentage Threshold Represents the threshold percentage for disclosure of counterparty credit exposure. Accounts receivable, net - Affiliate GenOn Affiliated Entity [Member] Transfers into Level 3 Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Transfers into Level 3 Other trust fund investments: Financial Instruments, Owned, at Fair Value, by Type, Alternative [Abstract] Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Income/(expense) from California property tax indemnification Disposal Group, Including Discontinued Operation, Income (Expense) Property Tax Indemnification Disposal Group Including Discontinued Operation, Income (Expense) Property Tax Indemnification Subtotal long-term debt and finance leases (including current maturities) Debt and Lease Obligation Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income [Roll Forward] Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income [Roll Forward] Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income Counterparty Risk by Investment Grade [Domain] Counterparty Risk by Investment Grade [Domain] Represents the counter party risk exposure by investment grades. Fuel Oil Crude Oil [Member] Net deferred tax asset Deferred tax asset Deferred Tax Assets, Net Investments in securities (classified within other current and non-current assets) Debt Securities, Available-for-sale Summary of Company's DSU awards and non-vested PSU Awards changes during the year Share-based Payment Arrangement, Activity [Table Text Block] Account receivable Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Share-based Payment Arrangement [Abstract] Changes in investments in unconsolidated affiliates (Investments in) Proceeds From Sales of Unconsolidated Affiliates (Investments in) Proceeds From Sales of Unconsolidated Affiliates Accounts Receivable, Allowance for Credit Loss Accounts Receivable, Allowance for Credit Loss [Table Text Block] Consolidated Entities [Domain] Consolidated Entities [Domain] Federal agency mortgage-backed securities Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] Current portion of operating lease liabilities Operating Lease, Liability, Current Payments for acquisitions of assets, businesses and leases Payments To Acquire Assets And Businesses, Net Of Cash Acquired Payments To Acquire Assets And Businesses, Net Of Cash Acquired Right-of-use assets obtained in exchange for new finance lease liabilities Right-of-Use Asset Obtained in Exchange for Finance Lease Liability Impaired Long-Lived Assets Held and Used, Asset Name [Domain] Impaired Long-Lived Assets Held and Used, Asset Name [Domain] Jointly Owned Utility Plant Interests [Table] Jointly Owned Utility Plant Interests [Table] Credit default swap facility Credit Default Swap Facility [Member] Credit Default Swap Facility Dunkirk Power LLC, tax exempt bonds, due 2042 Dunkirk Power LLC Tax Exempt Bonds Due 2042 [Member] Represents Dunkirk Power LLC tax exempt bonds, which are due 2042. Forfeited (in usd per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Current assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets Undistributed earnings by equity investment Schedule of Equity Method Investments, Undistributed Earnings [Table Text Block] Disclosure of details relating to undistributed earnings by equity method investments. Fair Value of Financial Instruments Fair Value Disclosures [Text Block] Jointly Owned Plants Jointly Owned Plants [Text Block] Describes that the entity has a proportionate interest in a jointly owned plant. Should include a table showing separately for each interest the amount of plant in service; the accumulated provision for depreciation; the balance of property plant and equipment; the amount of plant under construction; and the proportionate share. Should include statements that the amounts represent the entity's share in each joint plant and that it must provide its own financing. Information concerning two or more generating plants on the same site may be combined. Should state that the entity's share of direct expenses of the joint plants is included in the corresponding operating expenses on its income statement (for example, fuel, maintenance of plant, other operating expense). Interest Rate Swap Interest Rate Swap [Member] Reversal of previously recognized unrealized (gains) on settled positions related to trading activity Reversal Previously Unrecognized, Unrealized Gains (Losses) Settled Positions Trading Activity Amount reversed into entity's statement of operations for previously recognized unrealized (gains) losses on settled positions related to trading activities. Customer [Domain] Customer [Domain] Cumulative Effect, Period of Adoption, Adjustment Cumulative Effect, Period of Adoption, Adjustment [Member] Defined Contribution Plan Contributions Defined Contribution Plan Disclosures [Table Text Block] Intangible Assets Goodwill and Intangible Assets, Intangible Assets, Policy [Policy Text Block] Additional paid-in capital Additional Paid in Capital, Common Stock Depreciation and amortization Depreciation, Amortization and Accretion, Net Entity Registrant Name Entity Registrant Name Cumulative translation adjustment Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax Subsequent Event Type [Domain] Subsequent Event Type [Domain] Business Acquisition [Line Items] Business Acquisition [Line Items] Weighted average discount rate Operating Lease, Weighted Average Discount Rate, Percent Assets Assets, Fair Value Disclosure [Abstract] Impairment losses Impairment losses Asset Impairment Charges Corporate/Eliminations Eliminations Intersegment Eliminations [Member] Total other assets Regulated Entity, Other Assets, Noncurrent Less debt issuance costs Debt Issuance Costs, Net Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract] Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract] Other repurchases Capital Allocation Plan, Open Market Repurchases [Member] Capital Allocation Plan, Open Market Repurchases [Member] Net Period Benefit Cost/Credit Net Period Benefit Cost/Credit [Member] Net Period Benefit Cost/Credit [Member] Payments of dividends to common stockholders Payments of Ordinary Dividends, Common Stock Shares repurchased under May 24, 2018 Accelerated Repurchase Agreement Capital Allocation Plan, Accelerated Repurchase Agreement May 2018 [Member] Capital Allocation Plan, Accelerated Repurchase Agreement May 2018 [Member] Common stock, annual dividends increase, percentage Common Stock, Annual Dividends Increase (Decrease), Percentage Common Stock, Annual Dividends Increase (Decrease), Percentage Other changes in plan assets and benefit obligations recognized in other comprehensive income Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax [Abstract] Long-term capital allocation, target allocation, cash generated allocated returned to shareholders, percentage Long-term Capital Allocation, Target Allocation, Cash Generated Allocated Returned to Shareholders, Percentage Long-term Capital Allocation, Target Allocation, Cash Generated Allocated Returned to Shareholders, Percentage Equity securities Equity Securities [Member] Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Held-for-sale Disposal Group, Held-for-sale, Not Discontinued Operations [Member] Schedule of Impaired Long-Lived Assets Held and Used [Table] Schedule of Impaired Long-Lived Assets Held and Used [Table] Adjusted Base Rate Adjusted Base Rate [Member] Adjusted Base Rate [Member] Entity Address, Postal Zip Code Entity Address, Postal Zip Code Jointly Owned Plants Disclosure [Abstract] Jointly Owned Plants Disclosure [Abstract] -- None. No documentation exists for this element. -- Goodwill Goodwill Nuclear decommissioning trust fund disclosure Debt Securities, Available-for-sale [Line Items] Schedule of Significant Unobservable Inputs used in Developing Fair Value of Level 3 Positions Fair Value Measurement Inputs and Valuation Techniques [Table Text Block] (Decreases)/additions to fixed assets for accrued capital expenditures Increase (Decrease) Capital Expenditures Incurred but Not yet Paid Increase (Decrease) Capital Expenditures Incurred but Not yet Paid UPMC Thermal Project UPMC Thermal Project [Member] UPMC Thermal Project [Member] Dividends per common share (in usd per share) Common Stock, Dividends, Per Share, Declared Aggregate principal amount Debt Instrument, Face Amount June 15, 2027 and thereafter Redemption Period From June 15, 2027 And Thereafter [Member] Redemption Period From June 15, 2027 And Thereafter Other current assets Other Assets, Current Senior Secured First Lien Notes, due 2027 2.450% Senior Secured Notes Due 2027 [Member] 2.450% Senior Secured Notes Due 2027 Forfeited (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period Shared service, selling, general and administrative Related Party Transaction, Selling, General and Administrative Expenses from Transactions with Related Party Equity [Abstract] Equity [Abstract] Underlying Asset Class [Domain] Underlying Asset Class [Domain] Total assets Assets, Fair Value Disclosure Mass customers Mass Customer [Member] Mass Customer [Member] PRSUs Phantom Restricted Stock Units, PRSUs [Member] Phantom Restricted Stock Units, PRSUs February 15, 2025 to February 14, 2026 Redemption Period February 15, 2025 to February 14, 2026 [Member] Redemption Period February 15, 2025 to February 14, 2026 Redemption Period Prior to February 15, 2024 Redemption Period Prior to February 15, 2024 [Member] Redemption Period Prior to February 15, 2024 Net Amount Derivative Asset, Fair Value, Amount Offset Against Collateral Net Of Derivative Liability, Fair Value, Amount Offset Against Collateral Derivative Asset, Fair Value, Amount Offset Against Collateral Net Of Derivative Liability, Fair Value, Amount Offset Against Collateral Derivative, nonmonetary notional amount, energy measure in (millions of btu) and (megawatt hours) Derivative, Nonmonetary Notional Amount, Energy Measure Customer Concentration Risk Customer Concentration Risk [Member] Schedule of Estimated Amortization of Intangible Assets for Next Five Years Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Derivative Contract [Domain] Derivative Contract [Domain] Weighted average number of common shares outstanding — diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Letter of Credit Letter of Credit [Member] Repurchases under February 28, 2019 Accelerated Share Repurchase Agreement Capital Allocation Plan, Accelerated Repurchase Agreement February [Member] Capital Allocation Plan, Accelerated Repurchase Agreement February 2019 [Member] Senior Secured First Lien Notes, due 2024, 2025, 2027 and 2029 Senior Secured First Lien Notes, Due 2024, 2025, 2027 and 2029 [Member] Senior Secured First Lien Notes, Due 2024, 2025, 2027 and 2029 Forfeited (in shares) Forfeited (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Debt Disclosure [Abstract] Debt Disclosure [Abstract] Total derivative liabilities valued with prices provided by models and other valuation techniques, percentage Derivative Liability, Fair Value Determined Using Valuation Techniques, Percentage Derivative Liability, Fair Value Determined Using Valuation Techniques, Percentage 1-3 Years Guarantee Maturity, Between One to Three Years Maximum potential amount of future payments that the guarantor could be required to make between one to three years of the balance sheet date under the guarantee. Inventory, Current [Table] Inventory, Current [Table] Recoveries collected Accounts Receivable, Allowance for Credit Loss, Recovery NRG Solar Guam, LLC NRG Solar Guam, LLC [Member] NRG Solar Guam, LLC [Member] Group of Individuals [Domain] Group of Individuals [Domain] [Domain] for Group of Individuals [Axis] BETM BETM [Member] BETM Restructuring Plan [Axis] Restructuring Plan [Axis] Amortization of financing costs and debt discounts Amortization of Debt Issuance Costs and Discounts Repayment of debt Repayments of Long-term Debt Net Cash (Used)/Provided by Financing Activities Net Cash Provided by (Used in) Financing Activities Estimated future fixed fee performance obligation Revenue, Remaining Performance Obligation, Amount January 15, 2025 to January 14, 2026 Redemption Period From 15 January 2025 to 14 January 2026 [Member] Redemption Period From 15 January 2025 to 14 January 2026 Underlying Assets [Domain] Underlying Assets [Domain] Major types of referenced/ underlying assets. Increase in the number of shares available for issuance (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Number of Shares, Period Increase (Decrease) Uncertain tax benefits Balance as of January 1 Uncertain tax benefits as of December 31 Unrecognized Tax Benefits Counterparty Name [Axis] Counterparty Name [Axis] Increase in revolving commitments Line Of Credit Facility, Borrowing Capacity, Increase Line Of Credit Facility, Borrowing Capacity, Increase Intercompany Credit Agreement Intercompany Credit Agreement [Member] Intercompany Credit Agreement [Member] Common stock; $0.01 par value; 500,000,000 shares authorized; 423,057,848 and 421,890,790 shares issued; and 244,231,933 and 248,996,189 shares outstanding at December 31, 2020 and 2019 Common Stock, Value, Issued 2024 Defined Benefit Plan, Expected Future Benefit Payment, Year Four Goodwill and Other Intangibles Finite-Lived Intangible Assets [Line Items] Finite-Lived Intangible Assets [Line Items] Document Fiscal Year Focus Document Fiscal Year Focus 2022 Finite-Lived Intangible Asset, Expected Amortization, Year Two Equivalent shares purchased in lieu of tax withholding on equity compensation issuances Equivalent Shares In Lieu Of Tax Withholding on Equity Compensation Issuances [Member] Equivalent Shares In Lieu Of Tax Withholding on Equity Compensation Issuances Additional collateral required Additional Collateral, Aggregate Fair Value SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract] SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract] 3-5 Years Guarantee Maturity, Between Three to Five Years Maximum potential amount of future payments that the guarantor could be required to make between three to five years of the balance sheet date under the guarantee. Settlements, payments and statute closure Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities Capital Allocation Plan [Domain] Capital Allocation Plan [Domain] Explains details pertaining to the different capital allocation plans. Benefit obligation at January 1 Benefit obligation at December 31 Projected benefit obligation Defined Benefit Plan, Benefit Obligation Entity Current Reporting Status Entity Current Reporting Status NOLs utilized Net Operating Loss Carryforwards Utilized Net Operating Loss Carryforwards Utilized Redemption Period Prior To 15 July 2021 Redemption Period Prior To 15 July 2021 [Member] Redemption Period Prior To 15 July 2021 [Member] Derivative assets: Derivative Asset [Abstract] City of Texas City, tax exempt bonds, due 2045 Fort Bend County, tax exempt bonds, due 2045 [Member] Fort Bend County, tax exempt bonds, due 2045 [Member] Settlement consideration Restructuring and Related Cost, Expected Cost Schedule of Amounts Recognized in OCI Not Yet Recognized as Components of Net Periodic Benefit Costs Schedule of Net Periodic Benefit Cost Not yet Recognized [Table Text Block] Related Party Transaction [Axis] Related Party Transaction [Axis] Derivative liabilities: Derivative Liability, Fair Value, Amount Not Offset Against Collateral [Abstract] Investments in nuclear decommissioning trust fund securities Payments to Acquire Debt Securities, Available-for-sale Company's exposure before collateral expected to roll off (as a percent) Counterparty Credit Risk Exposure Percentage Of Credit Risk Roll Off The percentage of net counterparty credit exposure that rolls-off by the end of 2012. Comprehensive Income Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Inventory Disclosure [Abstract] Inventory Disclosure [Abstract] Award vesting right, percentage Award vesting, percentage Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage Common stock, shares issued (in shares) Beginning balance, common shares issued (in shares) Ending balance, common shares issued (in shares) Common Stock, Shares, Issued Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value July 15, 2023 to July 14, 2024 Redemption Period From 15 July 2023 to 14 July 2024 [Member] Redemption Period From 15 July 2023 to 14 July 2024 [Member] Investment grade External Credit Rating, Investment Grade [Member] Operating lease liability Operating lease liability Operating Lease, Liability Eligible compensation withholding, maximum, percentage Employee Stock Purchase Plan, Maximum Percentage of Compensation Eligible This element represents the maximum percentage of eligible compensation, which can be withheld by employees to purchase shares of the entity. Segment Reporting [Abstract] Segment Reporting [Abstract] Accounts receivable, net Accounts Receivable, after Allowance for Credit Loss Redemption percentage of principal Debt Instrument, Redemption Price, Percentage of Principal Amount Redeemed Debt Instrument [Line Items] Debt Instrument [Line Items] Other Other Debt [Member] Represents other debt instruments not separately accounted disclosed. Reduction of assets due to deconsolidation Increase (Decrease) in Operating Assets Utilities, energy merchants, marketers and other Utilities Energy Merchants Marketers And Other [Member] Represents the information pertaining to utilities, energy, merchants, marketers and other. Nature of Business Nature of Operations [Text Block] Accretion of asset retirement obligations Accretion Expense, Including Asset Retirement Obligations Interest disallowance carryforward per §163(j) of the Tax Act Deferred Tax Asset, Interest Carryforward Purchase price Business Combination, Consideration Transferred 2024 Unrecorded Unconditional Purchase Obligation, to be Paid, Year Four Gains for the period included in earnings attributable to the change in unrealized gains or losses relating to assets or liabilities still held at the end of period Fair Value, Net Derivative Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss) Entity Address, City or Town Entity Address, City or Town Ivanpah Master Holdings, LLC Ivanpah Master Holdings LLC Ivampah Master Holdings LLC [Member] Ivampah Master Holdings LLC [Member] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Changes in collateral deposits in support of risk management activities Changes in Collateral Deposits Supporting Energy Risk Management Activities Changes in cash collateral deposits for contracts supporting energy risk management activities. RSUs Restricted Stock Units (RSUs) [Member] Net contributions to discontinued operations Net (Contributions) To Distributions From Discontinued Operations Net (Contributions) To Distributions From Discontinued Operations Health care trend rate Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year Other Assets Other Assets, Noncurrent [Abstract] 2025 Lessee, Operating Lease, Liability, to be Paid, Year Five Financial Instrument [Axis] Financial Instrument [Axis] Financial Instrument [Axis] Short-term lease cost Short-term Lease, Cost Before age 65 Before age 65 [Member] Before age 65 [Member] Discontinued Operations Discontinued Operations, Policy [Policy Text Block] Indefinite-lived Intangible Assets [Axis] Indefinite-lived Intangible Assets [Axis] Gross Receipts and Sales Taxes Gross Receipts and Sales Taxes [Abstract] Effects on the Company's Accumulated OCI Balance Attributable to Cash Flow Hedge Derivatives, Net of Tax Schedule of Cash Flow Hedges Included in Accumulated Other Comprehensive Income (Loss) [Table Text Block] Construction in Progress Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress Income/(loss) from discontinued operations, net of income tax Income (Loss) From Discontinued Operations, Including Adjustment For Discontinued Operations Noncontrolling Interest, Net Of Tax,Attributable To Parent Income (Loss) From Discontinued Operations, Including Adjustment For Discontinued Operations Noncontrolling Interest, Net Of Tax, Attributable To Parent Valuation allowance Valuation allowance Deferred Tax Assets, Valuation Allowance 2023 Finite-Lived Intangible Asset, Expected Amortization, Year Three Construction in progress Construction in Progress Construction in Progress [Member] Cash Collateral (Held) / Posted Derivative, Collateral, Obligation to Return Cash Net Of Derivative, Collateral, Right to Reclaim Cash Derivative, Collateral, Obligation to Return Cash Net Of Derivative, Collateral, Right to Reclaim Cash Contract Amortization Revenue Recognition Revenue from Contract with Customer [Policy Text Block] Net Notional Volume Buy/(sell) of NRG's Open Derivative Transactions Broken Out By Commodity Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block] Wholesale counterparties with net exposure Number Of Wholesale Counterparties With Credit Risk Exposure Number Of Wholesale Counterparties With Credit Risk Exposure Funds deposited by counterparties Funds Deposited by Counterparties The amount of cash collateral received from hedge counterparties in support of energy risk management activities for which there is an offsetting liability within current liabilities. These amounts are segregated into separate accounts that are not contractually restricted but, based on the entity's intention, are not available for the payment of the entity's general corporate obligations. Depending on market fluctuations and the settlement of the underlying contracts, the entity will refund this collateral to the counterparties pursuant to the terms and conditions of the underlying trades. Investment, Name [Domain] Investment, Name [Domain] Investment, Name [Domain] Other comprehensive (loss) Other comprehensive loss Other Comprehensive Income (Loss), Net of Tax Common/collective trust investment — non-core assets Emerging Market Equities [Member] Emerging Market Equities [Member] Lessor Accounting Leases [Abstract] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Total current assets Assets, Current Less: Comprehensive income attributable to noncontrolling interests and redeemable noncontrolling interests Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest Deduction for GenOn tax losses Operating loss carryforwards Operating Loss Carryforwards Earnings/(Loss) Per Share Attributable to NRG Energy, Inc. Common Stockholders Earnings Per Share [Abstract] Company's deferred tax assets and liabilities Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Summary of NRG's net deferred tax position Schedule of Deferred Tax Component [Table Text Block] Disclosure of the current and non-current portion of net deferred tax assets and liabilities. Home Solar Home Solar [Member] Home Solar Amortization of prior service cost Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax Auction Prices (USD per MWh) Derivative, Auction Price Derivative, Auction Price Net income/(loss) attributable to continuing and discontinued operations Additional Financial Information Disclosure [Table Text Block] Additional Financial Information Disclosure [Table Text Block] Fair Value Measured at Net Asset Value Per Share Fair Value Measured at Net Asset Value Per Share [Member] (Loss) gain on sale of business Gain (Loss) on Disposition of Business Disposal Group Name [Domain] Disposal Group Name [Domain] Disposal Group Name [Domain] Derivative instruments Derivative Instruments and Hedges, Noncurrent Amortization of emission allowances, out-of-market contracts and REC retirements Amortization of Intangibles and Out of Market Contracts The aggregate (income) expense recorded in earnings to allocate the cost of out-of-market contracts and intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash (income) expense, this element is added back to net income when calculating cash provided by (used in) operations using the indirect method. STP Defined Benefit Plans Defined Benefit Plans of Affiliates [Abstract] Stockholders' Equity Stockholders' Equity Attributable to Parent [Abstract] 2025 Finite-Lived Intangible Asset, Expected Amortization, Year Five Net unrealized gains on open positions related to trading activity Derivative Unrealized Gains on Open Positions Related to Trading Activity, Net This element represents the amount recorded in the entity's statement of operations for net unrealized gains (losses) on open positions related to trading activities. Document Fiscal Period Focus Document Fiscal Period Focus LC Agreement Letter Of Credit Agreement [Member] Letter Of Credit Agreement SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Table] SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Table] South Texas Project South Texas Project Units 1 and 2, Bay City, TX South Texas Project Units 1 And 2 [Member] This element represents the information pertaining to South Texas Project Units 1 and 2, Bay City, TX. Sale Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Sales Employer contributions Defined Benefit Plan, Plan Assets, Contributions by Employer Total Fair Value, Inputs, Level 1, 2 and 3 [Member] Derivative Instruments Derivative Asset Fair Value Gross Liability Net Of Derivative Liability Fair Value Gross Asset Derivative Asset Fair Value Gross Liability Net Of Derivative Liability Fair Value Gross Asset Lease term Lessor, Operating Lease, Term of Contract Redemption percentage Debt Instrument, Redemption Price, Percentage Entity Filer Category Entity Filer Category Common Stock Common Stock [Member] Product and Service [Domain] Product and Service [Domain] Other(b) Other Finite Lived Intangible Assets Member All other assets acquired in a business combination not specified elsewhere in the taxonomy. Powerton Facility And Units 7 And 8 Of The Joliet Facility Powerton Facility And Units 7 And 8 Of The Joliet Facility [Member] Powerton Facility And Units 7 And 8 Of The Joliet Facility Company contributions to defined contribution plans Defined Contribution Plan, Cost Weighted average discount rate Finance Lease, Weighted Average Discount Rate, Percent Other Commitments [Axis] Other Commitments [Axis] Income tax provision from continuing operations Income Tax Expense (Benefit), Continuing Operations [Abstract] Non-Investment grade/Non-Rated External Credit Rating Not Rated [Member] Represents underlying referenced credits or entities, with respect to guarantees, for which ratings are not available. 2021 Unrecorded Unconditional Purchase Obligation, to be Paid, Year One Secured Debt Secured Debt [Member] Class of Treasury Stock [Table] Class of Treasury Stock [Table] Partnerships/joint ventures Partnership [Member] Other Finite-Lived Intangible Assets, Other Changes This element represents other additions or reductions to finite-lived intangible assets during the period. Purchase of and distributions to noncontrolling interests from subsidiaries Proceeds from (Payments to) Noncontrolling Interests Number of facilities Number Of Facilities Number Of Facilities Amounts recognized in balance sheet Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract] Other Investments Other Equity Method Investments [Member] Other Equity Method Investments Investments Accounted for by the Equity Method Schedule of Equity Method Investments [Line Items] Schedule of Equity Method Investments [Line Items] Interest rate, stated percentage Debt Instrument, Interest Rate, Stated Percentage Revenue, remaining performance obligation, period Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period Long-term incentive plans Share-based Payment Arrangement [Member] Write off of deferred debt issuance cost Write off of Deferred Debt Issuance Cost Notes receivable Financing Receivable, before Allowance for Credit Loss Asset Acquisition [Axis] Asset Acquisition [Axis] Asset Acquisition Summary of NRG's material related-party transactions with affiliates Schedule of Related Party Transactions [Table Text Block] Canal Three Canal Three [Member] Canal Three [Member] GenOn Mid-Atlantic GenOn Mid-Atlantic [Member] GenOn Mid-Atlantic [Member] Marketing Partnerships Marketing Partnerships [Member] Marketing Partnerships [Member] Exercised (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Net Increase/(Decrease) in Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Total other expense Nonoperating Income (Expense) Loss Contingency, Nature [Domain] Loss Contingency, Nature [Domain] Fair Value Measurement Inputs and Valuation Techniques [Abstract Fair Value Measurement Inputs and Valuation Techniques [Abstract] Repurchase facility Repurchase Facility Repurchase Facility [Member] Repurchase Facility Other Income/(Expense) Costs and Expenses [Abstract] Treasury stock, shares (in shares) Beginning balance, treasury shares (in shares) Ending balance, treasury shares (in shares) Treasury Stock, Shares Foreign currency translation adjustments, net of income tax Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Impairment losses Asset Impairment Charges Including Equity Method Investments Asset Impairment Charges Including Equity Method Investments May 15, 2023 to May 14, 2024 Redemption Period From 15 May 2023 to 14 May 2024 [Member] Redemption Period From 15 May 2023 to 14 May 2024 [Member] July 15, 2024 and thereafter Redemption Period From 15 July 2024 And Thereafter [Member] Redemption Period From 15 July 2024 And Thereafter [Member] Unrealized Gains Decommissioning Fund Investments, Unrealized Gains Decommissioning Fund Investments, Unrealized Gains Impairment losses on investments Impairment losses on investments Other than Temporary Impairment Losses, Investments State Deferred State and Local Income Tax Expense (Benefit) Ownership [Domain] Ownership [Domain] 2025 Long-Term Debt, Maturity, Year Five U.S.  Income (Loss) from Continuing Operations before Income Taxes, Domestic Expected return on plan assets Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets Income/(expense) from other commitments, indemnification and fees Disposal Group, Including Discontinued Operation, Other Income (Expense) Disposal Group, Including Discontinued Operation, Other Income (Expense) Interest paid, net of amount capitalized Interest Paid, Excluding Capitalized Interest, Operating Activities Amount reimbursed to STPNOC towards defined benefit plans Defined Benefit Plan, Amount Reimbursed to Sponsor This element represents the amount reimbursed to the sponsor of defined benefit plans. Eurodollar Eurodollar Applicable Margin Rate [Member] Eurodollar Applicable Margin Rate [Member] January 15, 2026 and thereafter Redemption Period From 15 January 2026 And Thereafter [Member] Redemption Period From 15 January 2026 And Thereafter Summary of Significant Accounting Policies Disclosure Summary of Significant Accounting Policies Disclosure [Line Items] Number of qualified pension plans Number Of Defined Benefit Plans Number Of Defined Benefit Plans Total Stockholders' Equity Beginning balance Adoption of new accounting standards Ending balance Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Redeemable noncontrolling interest Redeemable Noncontrolling Interest [Member] Redeemable Noncontrolling Interest [Member] 2021 Finite-Lived Intangible Asset, Expected Amortization, Year One Total operating revenues Revenues Revenues Generation capacity (in MW) Power Generation Capacity, Megawatts The generation capacity of the entity's power generation facilities as of the balance sheet date, expressed in megawatts. Income taxes paid, net of refunds Income Taxes Paid, Net Proceeds from sale Cash received Proceeds from Divestiture of Businesses Effect of exchange rate changes on cash and cash equivalents Effect of Exchange Rate on Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations New Accounting Pronouncements or Change in Accounting Principle [Table] Accounting Standards Update and Change in Accounting Principle [Table] Total liabilities Financial and Nonfinancial Liabilities, Fair Value Disclosure Net Income per Weighted Average Common Share - Diluted (in usd per share) Income per weighted average common share — diluted (in usd per share) Earnings Per Share, Diluted Derivative, non-monetary notional amount (in shares) Derivative, Non-monetary Notional Amount, Other Derivative, Non-monetary Notional Amount, Other Ivanpah Ivanpah Credit Agreement [Member] Ivanpah Credit Agreement [Member] Proceeds from sales of nuclear decommissioning trust fund securities Proceeds from Sale of Debt Securities, Available-for-sale Reconciliation of total amounts of uncertain tax benefits Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block] Total unrealized mark-to-market (losses)/gains for trading activity Unrealized Gain (Loss) on Derivatives, Mark To Market, Trading Activities Unrealized Gain (Loss) on Derivatives, Mark To Market, Trading Activities Guarantees [Abstract] Guarantees [Abstract] Long-term Debt and Finance Leases Schedule of Debt [Table Text Block] Noncontrolling Interest [Line Items] Noncontrolling Interest [Line Items] Schedule Of Contract Assets And Liabilities [Table] Schedule Of Contract Assets And Liabilities [Table] Schedule Of Contract Assets And Liabilities [Table] Nuclear trust fund investments Decommissioning Fund Investments Schedule of Tax Exempt Bonds Schedule of Long-term Debt Instruments [Table Text Block] Depreciation Depreciation Entity Address, Address Line One Entity Address, Address Line One Mutual property insurance additional blanket policy property coverage Mutual Property Insurance Additional Blanket Policy Property Coverage Additional property insurance coverage under a single limit blanket policy purchased from an industry mutual insurance company in order to insure property beyond the individual maximum coverage limit per insured. Entity Emerging Growth Company Entity Emerging Growth Company Carrying value Indefinite-lived Intangible Assets (Excluding Goodwill) Total — deferred Deferred Income Tax Expense (Benefit) Purchased Energy and Other Cost of Sales for Customer Operations Cost of Energy for Retail Operations [Abstract] Commodity contracts Derivative liabilities Derivative Liability, Fair Value, Gross Liability Credit Risk Related Contingent Features [Abstract] Credit Risk Related Contingent Features [Abstract] -- None. No documentation exists for this element. -- Net Amount Derivative Liability, Fair Value, Amount Offset Against Collateral Net loss (income) Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest Intangible assets, accumulated amortization Less accumulated amortization Finite-Lived Intangible Assets, Accumulated Amortization Number of months beyond which company can not predict the holding of collateral (in months) Period Beyond which Comapny Can Not Predict Holding of Collateral This element represents the period beyond which company can not predict the holding of collateral. Redeemable Noncontrolling Interest Redeemable Noncontrolling Interest [Policy Text Block] Redeemable Noncontrolling Interest [Policy Text Block] High Maximum Maximum [Member] Noncon- trolling Interest Noncontrolling Interest [Member] Cash used by discontinued operations Cash Provided by (Used in) Investing Activities, Discontinued Operations Equity compensation Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Share-based Compensation Cost Payments for short and long-term debt Repayments of Other Debt Common stock dividends Dividends, Common Stock, Cash Premium percentage of principal amount of note discount factor (as percent) Premium Percentage of Principal of Senior Notes, Discount Factor Percentage above the Treasury rate over the principal amount of the note used as a discount factor in determining the redemption price of Senior Notes prior to maturity. Estimated counterparty credit risk exposure under certain long term agreements, including California tolling agreements, South Central load obligations and solar power purchase agreements for the next 5 years Estimated Counterparty Credit Risk Exposure to Certain Counterparties This element represents the estimated amount of the counterparty credit risk exposure. Receivable from affiliate Payments of Distributions to Affiliates Effective income tax rate (as a percent) Effective Income Tax Rate Reconciliation, Percent Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Forward Market Price (USD per MWh) Derivative, Forward Price Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Beginning balance Ending balance Accounts Receivable, Allowance for Credit Loss Total property, plant, and equipment Public Utilities, Property, Plant and Equipment, Plant in Service Proceeds from sale of businesses, net of working capital adjustments Proceeds From Divestiture Of Businesses, Net Of Working Capital Adjustments Proceeds From Divestiture Of Businesses, Net Of Working Capital Adjustments Unrecognized tax benefits, income tax penalties expense Unrecognized Tax Benefits, Income Tax Penalties Expense Other Postretirement Benefits Plan Other Postretirement Benefits Plan [Member] Trading Symbol Trading Symbol Revenues from Related Parties Included in Operating Revenues Revenue from Related Parties Disposal Group Classification [Domain] Disposal Group Classification [Domain] Ownership Interest (as a percent) Jointly Owned Utility Plant, Proportionate Ownership Share Jointly Owned Utility Plant [Axis] Jointly Owned Utility Plant [Axis] Offsetting of Derivatives by Counterparty Master Agreement Level and Collateral Received or Paid Offsetting Assets and Liabilities [Line Items] [Line Items] for Offsetting Assets and Liabilities [Table] Redemption Period Prior To 15 May 2021 Redemption Period Prior To 15 May 2021 [Member] Redemption Period Prior To 15 May 2021 [Member] Cash collateral posted in support of energy risk management activities Cash Collateral (Held)/Posted Derivative, Collateral, Right to Reclaim Cash Cash Paid Payment amount Debt Instrument, Repurchase Amount Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Foreign Income (Loss) from Continuing Operations before Income Taxes, Foreign Entity Shell Company Entity Shell Company Segment Reporting Information Segment Reporting Information [Line Items] Fair Value, Measurements, Recurring Fair Value, Recurring [Member] Segment Reporting Segment Reporting, Policy [Policy Text Block] Entity Public Float Entity Public Float Business Combinations Business Combinations Policy [Policy Text Block] Letters of credit and surety bonds, maximum expiration period (in years) Guarantee Obligations, Letters of Credit and Surety Bonds, Maximum Expiration Period This element represents the maximum expiration period of letters of credit and surety bonds for entity is contingently obliged. Residential customer equivalents acquired Business Acquisition, Residential Customer Equivalents Acquired Business Acquisition, Residential Customer Equivalents Acquired Document Type Document Type Number of solar electric generating projects Number Of Solar Electric Generating Projects Number of Solar Electric Generating Projects ICFR Auditor Attestation Flag ICFR Auditor Attestation Flag Other income, net Other income, net Other Nonoperating Income (Expense) Nuclear fuel Nuclear Fuel [Member] Other expenses Disposal Group, Including Discontinued Operation, Other Expense Shares granted during the period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross Treasury Stock Treasury Stock Treasury Stock [Member] Segments [Axis] Segment Reporting Information, by Segment [Axis] Segments [Axis] SEC Schedule, 12-09, Valuation Allowances and Reserves [Domain] SEC Schedule, 12-09, Valuation Allowances and Reserves [Domain] Benefit Plans and Other Postretirement Benefits Retirement Benefits [Text Block] Vested (in usd 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 Goodwill Deferred Tax Liabilities, Goodwill Level 3 Fair Value, Inputs, Level 3 [Member] Guarantor Obligations, Nature [Domain] Total guarantees Guarantor Obligations, Nature [Domain] January 15, 2024 to January 14, 2025 Redemption Period From 15 January 2024 to 14 January 2025 [Member] Redemption Period From 15 January 2024 to 14 January 2025 Share repurchases (in shares) Shares repurchased (in shares) Total number of shares purchased (in shares) Stock Repurchased During Period, Shares Small Book Acquisitions 2019 Small Book Acquisitions 2019 [Member] Small Book Acquisitions 2019 [Member] Long-term Purchase Commitment, Category of Item Purchased [Domain] Long-term Purchase Commitment, Category of Item Purchased [Domain] Senior Notes, due 2028 5.750% Senior Notes due 2028 Senior Notes due 2028 [Member] Senior Notes due 2028 Benefit payments Defined Benefit Plan, Plan Assets, Benefits Paid Minimum purchase commitment Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract] Underlying Asset Class [Axis] Underlying Asset Class [Axis] Line of Credit Line of Credit [Member] Operating Leases [Abstract] Operating Leases [Abstract] Operating Leases Pensions and Other Postretirement Benefits Pension and Other Postretirement Plans, Policy [Policy Text Block] Deferred income taxes Deferred tax liability Deferred Income Tax Liabilities, Net Accounting for Derivative Instruments and Hedging Activities Derivative Instruments and Hedging Activities Disclosure [Text Block] Common/collective trust investment — fixed income Common Trust Investment Fixed Income Securities [Member] Represents the investments in common/collective trust in fixed income securities. Cash proceeds Proceeds from Issuance of Debt Marketing and Advertising Costs Marketing and Advertising Expense [Abstract] 2024 Defined Benefit Plan, Expected Future Prescription Drug Subsidy Receipt, Year Four Market value on offering date percentage Share-based Compensation Arrangement by Share-based Payment Award, Discount from Market Price, Purchase Date Operating Income Operating income/(loss) Operating Income (Loss) 2025 Defined Benefit Plan, Expected Future Prescription Drug Subsidy Receipt, Year Five Working capital adjustments Business Acquisition, Consideration Transferred, Working Capital And Other Adjustments Business Acquisition, Consideration Transferred, Working Capital And Other Adjustments Payments of debt issuance costs Payments of Debt Issuance Costs Cash collateral received in support of energy risk management activities Cash Collateral (Held)/Posted Derivative, Collateral, Obligation to Return Cash 2021 Defined Benefit Plan, Expected Future Prescription Drug Subsidy Receipt, Year One Settlement consideration, insurance and services credit Discontinued Operation, Settlement Consideration And Prior Service Cost (Credit) Discontinued Operation, Settlement Consideration And Prior Service Cost (Credit) Midwest Generation Midwest Generation [Member] Midwest Generation [Member] NRG Yield, Inc. NRG Yield, Inc. [Member] NRG Yield, Inc. [Member] Contract Assets and Liabilities Contract with Customer, Contract Asset, Contract Liability, and Receivable [Table Text Block] Gain on derivative Derivative, Gain on Derivative Cash provided by continuing operations Net Cash Provided by (Used in) Operating Activities, Continuing Operations Variable Rate [Axis] Variable Rate [Axis] Cash and Cash Equivalents Cash and Cash Equivalents, Unrestricted Cash and Cash Equivalents, Policy [Policy Text Block] Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [Table] Commitments and Contingencies Commitments and Contingencies Share-based Payment Arrangement, Tranche Two Share-based Payment Arrangement, Tranche Two [Member] Payments for share repurchase activity Payments for Repurchase of Common Stock Award vesting period Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Put option agreement, covenant, mandatory exercise of Issuance Right, consolidated stockholder's equity (below) Put Option Agreement, Covenant, Mandatory Exercise of Issuance Right, Consolidated Stockholder's Equity, Minimum Put Option Agreement, Covenant, Mandatory Exercise of Issuance Right, Consolidated Stockholder's Equity, Minimum Thereafter Lessee, Operating Lease, Liability, to be Paid, after Year Five Entity Address, State or Province Entity Address, State or Province Vested (in shares) Converted to Common Stock (in shares) Vested (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Schedule of Benefit Costs and Other Changes Recognized in the Financial Statements Related to its Interest in STP Schedule of Defined Benefit Plans Disclosures [Table Text Block] Coal Coal [Member] Details pertaining to the coal, which is considered as a derivative commodity. Interest income-affiliate Disposal Group, Including Discontinued Operation, Interest Income Tax at federal statutory tax rate Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount Accounts payable  Accounts Payable, Current Sublease income Sublease Income Nuclear Decommission Nuclear Decommission [Member] Nuclear Decommission Accumulated deficit Retained Earnings (Accumulated Deficit) Operating lease right-of-use assets, net Operating Lease, Right-of-Use Asset February 15, 2029 and thereafter Redemption Period February 15, 2029 and thereafter [Member] Redemption Period February 15, 2029 and thereafter Loss on debt extinguishment, net Loss on debt extinguishment Loss on debt extinguishment Gain (Loss) on Extinguishment of Debt Property, Plant & Equipment Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service South Central Portfolio South Central Portfolio [Member] South Central Portfolio [Member] Leased Assets, Powerton facility and Units 7 and 8 of the Joliet facility Leased Assets, Powerton facility and Units 7 and 8 of the Joliet facility [Member] Leased Assets, Powerton facility and Units 7 and 8 of the Joliet facility Reconciliation of Beginning and Ending Balances for Financial Instruments that are Recognized at Fair Value using Significant Unobservable Inputs Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Property, plant and equipment Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment Schedule of ARO Obligations and Related Additions, Reductions and Accretion Schedule of Change in Asset Retirement Obligation [Table Text Block] Customer [Axis] Customer [Axis] RPSUs Relative Performance Stock Units [Member] Relative Performance Stock Units Net unrealized (losses)/gains on open positions related to economic hedges Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net Income Taxes Income Tax, Policy [Policy Text Block] Hedging Designation [Domain] Hedging Designation [Domain] Shares repurchased under September 5, 2018 Accelerated Repurchase Agreement Capital Allocation Plan, Accelerated Repurchase Program September 2018 [Member] Capital Allocation Plan, Accelerated Repurchase Program September 2018 [Member] Total lease cost Lease, Cost Nuclear Decommissioning Policy Nuclear Decommissioning [Policy Text Block] Describes an entity's policy regarding nuclear decommissioning trust fund assets and compliance with regulatory treatment. Accidental outage weekly recovery limit for loss revenues from a nuclear industry mutual insurance company in the event of insurable loss Additional Mutual Lost Revenue Insurance Weekly Maximum This represents the additional policy for weekly lost revenues insured by a nuclear industry mutual insurance company. Contribution in cash Payments to Acquire Equity Method Investments Exercisable at the end of the period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number Collateral required for contracts in net liability positions that have adequate assurance clauses Collateral Already Posted, Aggregate Fair Value Payments for debt extinguishment costs Payment for Debt Extinguishment or Debt Prepayment Cost Natural gas Energy Related Inventory, Natural Gas in Storage Other Payments for (Proceeds from) Other Investing Activities Number of years board of directors of industry mutual insurance company can adjust policy after policy expires Number Of Years Board Of Directors Of Industry Mutual Insurance Company Can Adjust Policy After Policy Expires This represents the number of years after the policy expires that the industry mutual insurance company’s board of directors can make premium adjustments. Equity-based awards activity, net APIC, Share-based Payment Arrangement, Increase for Cost Recognition Balance as of December 31, 2019 Balance as of December 31, 2020 Asset Retirement Obligation Restructuring Support Agreement Restructuring Support Agreement [Member] Restructuring Support Agreement [Member] Difference between Revenue Guidance in Effect before and after Topic 606 Difference between Revenue Guidance in Effect before and after Topic 606 [Member] Parent guarantee Guarantees by Remaining Maturity, Total Guarantee obligation Guarantee Obligations, Estimated Exposure The estimated amount of future payments the guarantor could be required to make under guarantees, indemnities and other contingent liability obligations. Capital Allocation Plan [Axis] Capital Allocation Plan [Axis] Explains the different capital allocation plans. GenOn settlement, net of insurance proceeds Nondebtor Reorganization Items, Net (Gain) Loss on Settlement of Other Claims Thereafter Long-Term Debt, Maturity, after Year Five Revenue from contract with customer Revenue from Contract with Customer, Excluding Assessed Tax Advertising expense Advertising Expense Inventory [Line Items] Inventory [Line Items] Business Acquisition [Axis] Business Acquisition [Axis] Geographical [Domain] Geographical [Domain] Benefit Plans and Other Postretirement Benefits Defined Benefit Plan Disclosure [Line Items] Conversion ratio Debt Instrument, Convertible, Conversion Ratio Under 1 Year Guarantee Maturity, Less than One Year Maximum potential amount of future payments that the guarantor could be required to make within one year of the balance sheet date under the guarantee. Foreign Deferred Foreign Income Tax Expense (Benefit) Scenario, Forecast Forecast [Member] Basic income per share attributable to NRG, Inc; Earnings Per Share, Basic and Diluted [Abstract] Domestic and foreign components of income from continuing operations before income tax expense Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest [Abstract] Proceeds from revolving Credit Facility Proceeds from Long-term Lines of Credit Capital Allocation Plan Capital Allocation Plan [Member] Capital Allocation Plan [Member] Non-current liabilities Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities Entity Voluntary Filers Entity Voluntary Filers Cedar Bayou Unit 4, Baytown, TX Cedar Bayou Unit 4 [Member] This element represents the information pertaining to Cedar Bayou Unit 4, Baytown, TX. Acquisition costs Business Combination, Acquisition Related Costs Keystone Keystone [Member] This element represents the information pertaining to Keystone, Shelocta, PA. Sierra Club Et Al V. Midwest Generation L L C Sierra Club Et Al V. Midwest Generation L L C [Member] Sierra Club Et Al V. Midwest Generation L L C Credit Facility [Axis] Credit Facility [Axis] Long-term debt, including current portion Debt Instrument, Fair Value Disclosure Liabilities Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities [Abstract] Weighted-Average Assumptions Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract] Fair Value Within the Derivative Instrument Valuation On the Balance Sheet Schedule of Derivatives Instruments Statements of Financial Performance and Financial Position, Location [Table Text Block] Derivative instruments Derivative Liability, Noncurrent Common stock, dividends, proposed annual amount, per share (usd per share) Common Stock, Dividends, Proposed Annual Amount, Per Share Common Stock, Dividends, Proposed Annual Amount, Per Share Non-cash adjustments to redeemable noncontrolling interest Noncontrolling Interest, Noncash Adjustments Noncontrolling Interest, Noncash Adjustments Foreign Tax Authority Foreign Tax Authority [Member] Business Combinations [Abstract] Reorganization Costs Restructuring and Related Activities [Abstract] Asset Retirement Obligation Disclosure [Abstract] Asset Retirement Obligation Disclosure [Abstract] Lease Revenue Revenue Recognition [Abstract] Increase (Decrease) in Stockholders' Equity Increase (Decrease) in Stockholders' Equity (in shares) Increase (Decrease) in Stockholders' Equity [Roll Forward] Indian River Power, tax exempt bonds, due 2040 Indian River Power LLC Tax Exempt Bonds Due 2040 [Member] Represents Indian River Power LLC tax exempt bonds, which are due 2040. Weighted Average Remaining Contractual Term, Exercisable (in years) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term Proceeds from issuance of common stock Proceeds from Issuance of Common Stock Contingent rental income Operating Leases, Income Statement, Contingent Revenue Reconciliation of NRG's basic and diluted earnings per share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Long-term capital allocation policy, target allocation of cash generated allocated to growth investments, percentage Long-term Capital Allocation, Target Allocation, Cash Generated Allocated to Growth Investments, Percentage Long-term Capital Allocation, Target Allocation, Cash Generated Allocated to Growth Investments, Percentage GenConn Gen Conn Energy LLC [Member] Represents the information pertaining to GenConn Energy LLC. Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] XOOM Energy Litigation XOOM Energy Litigation [Member] XOOM Energy Litigation Schedule of Purchase Price Allocation Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block] Summary of shares repurchased Class of Treasury Stock [Table Text Block] Schedule of Fair Value of Pension Plan Assets by Asset Category and Level within the Fair Value Hierarchy Fair Value, Assets Measured on Recurring Basis [Table Text Block] 1.841% Senior Secured First Lien Notes due 2023 1.841% Senior Secured First Lien Notes due 2023 [Member] 1.841% Senior Secured First Lien Notes due 2023 Buckthorn Renewables, LLC Buckthorn Renewables, LLC [Member] Buckthorn Renewables, LLC [Member] Summary NRG's equity method investments Equity Method Investments [Table Text Block] Target allocations Defined Benefit Plan, Plan Assets, Allocations [Abstract] Defined Benefit Plan by Plan Asset Categories [Axis] Defined Benefit Plan, Plan Assets, Category [Axis] Net Cash Provided by Operating Activities Net Cash Provided by (Used in) Operating Activities Nuclear Decommissioning Trust Fund Nuclear Decommissioning Trust Fund [Text Block] This item represents the disclosure regarding the nuclear decommissioning trust fund assets investments held in trust to pay for the cost of decommissioning a facility at the end of its economic life as a single block text. The disclosure may include the following: the aggregate fair values and unrealized gains and losses (including other-than-temporary impairments) for the securities held as well as information about the contractual maturities of those securities; summarized proceeds from sales of available for sale securities and the related realized gains and losses from these sales. The disclosure also includes that such funds are contributed and owned by the ratepayers but reported by the entity. Other Liabilities Other Liabilities, Noncurrent [Abstract] Entity Central Index Key Entity Central Index Key Operating expenses Cost of revenue including selling marketing and general administrative Cost of revenue including selling marketing and general administrative Leases, Weighted Average Discount Rate [Abstract] Leases, Weighted Average Discount Rate [Abstract] Leases, Weighted Average Discount Rate Related Party [Domain] Related Party [Domain] Letters of credit facility Line of Credit Facility, Current Borrowing Capacity Related Party Transaction [Line Items] Related Party Transaction [Line Items] Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member] Derivative Instrument [Axis] Derivative Instrument [Axis] Remaining payments and other balances due under settlement agreement Related Party Transaction, Due from (to) Related Party Percentage of ownership sold Percentage of Ownership Sold of Subsidiary Percentage of Ownership Sold of Subsidiary Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Total retail revenue Products And Services, Total Retail [Member] Products And Services, Total Retail [Member] Regulatory Matters Regulatory Matters [Text Block] Describes all of the specific regulatory matters that are pending, including the regulatory authorities involved and the potential impacts. Maximum liability per nuclear incident Nuclear Insurance Financial Protection Pool Nuclear Operator Total Assessment Maximum total assessment to be paid by a nuclear reactor for a nuclear incident under the financial protection pool mandated by the Price-Anderson Act. The total amount is calculated by multiplying the maximum assessment per nuclear reactor, by NRG’s ownership percentage. Summary of the Components of Intangible Assets Subject to Amortization Schedule of Finite-Lived Intangible Assets [Table Text Block] Nuclear decommissioning trust fund Fair Value Decommissioning Fund Investments, Fair Value Required nuclear liability insurance Nuclear Insurance Requirement Per Site Nuclear Insurance Requirement Per Site Debt assumed Disposal Group, Including Discontinued Operation, Liabilities Midway-Sunset Cogeneration Company Midway-Sunset Midway-Sunset Cogeneration Company [Member] Midway-Sunset Cogeneration Company [Member] Senior Notes Senior Notes [Member] Cash Flow Information Cash Flow, Supplemental Disclosures [Text Block] Expected reimbursement of contribution to retirement plan obligations to STPNOC in 2014 Defined Benefit Obligation, Reimbursement of Contribution to Affiliates in Next Fiscal Year This element represents the expected reimbursement of contribution to retirement plan obligations to affiliates in the next fiscal year. Undistributed earnings by equity investment Retained Earnings, Undistributed Earnings from Equity Method Investees Geographical [Axis] Geographical [Axis] Changes in valuation allowance Valuation allowance - current period activities Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount Total Increases to Liquidity and Collateral Facilities Total Liquidity and Collateral Facilities [Member] Total Liquidity and Collateral Facilities Charged to Other Accounts SEC Schedule, 12-09, Valuation Allowances and Reserves, Additions, Charge to Other Account Redemption Period Prior to June 15, 2024 Redemption Period Prior to June 15, 2024 [Member] Redemption Period Prior to June 15, 2024 Tax Equity Arrangements Tax Equity Arrangements, Policy [Policy Text Block] Tax Equity Arrangements, Policy [Policy Text Block] Segments [Domain] Segments [Domain] Segments [Domain] Derivatives, net Deferred Tax Assets, Derivative Instruments Derivative revenue Products And Services, Derivative Revenue [Member] Products And Services, Derivative Revenue [Member] Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] 2024 Long-Term Debt, Maturity, Year Four NRG GenOn LTIP NRG GenOn LTIP [Member] NRG GenOn LTIP [Member] Texas Texas Segment [Member] Texas Segment Senior Secured First Lien Notes, Due 2024 and 2029 Senior Secured First Lien Notes, Due 2024 and 2029 [Member] Senior Secured First Lien Notes, Due 2024 and 2029 Schedule of Collective Collateral Facilities Schedule of Line of Credit Facilities [Table Text Block] Maximum assessment Forty-Four Percent Maximum Assessment NRG’s percentage of ownership in STP. Amount of interest capitalized Interest Costs Capitalized Income Statement Location [Axis] Income Statement Location [Axis] Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Average price paid per share (in shares) Treasury Stock Acquired, Average Cost Per Share Total recognized in OCI Other changes in plan assets and benefit obligations recognized in other comprehensive income/(loss) Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax (Loss)/income on disposal of discontinued operations, net of tax Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax Credit facility, lien basket (greater of) Line of Credit Facility, Lien Basket, Minimum Line of Credit Facility, Lien Basket, Minimum Interest rate hedge Sale pre-capitalized trust securities Derivative, Notional Amount Total amortization Amortization of Intangible Assets Line of Credit Facility [Table] Line of Credit Facility [Table] Total nuclear property insurance coverage Mutual Property Insurance Total Property Coverage Total coverage for property insurance from an industry mutual insurance company. Investments Accounted for by the Equity Method and Variable Interest Entities Equity Method Investments and Joint Ventures Disclosure [Text Block] Segment Reporting Segment Reporting Disclosure [Text Block] Issuance of common stock Stock Issued During Period, Value, New Issues Asset Retirement Obligation, Roll Forward Analysis [Roll Forward] Asset Retirement Obligation, Roll Forward Analysis [Roll Forward] Scenario [Axis] Scenario [Axis] Schedule of Benefit Obligations Significant Components Defined Benefit Plan, Plan with Projected Benefit Obligation in Excess of Plan Assets [Table Text Block] Tax-exempt bonds Tax-exempt Bonds [Member] Tax-exempt Bonds [Member] Derivative instruments Derivative Liability, Current Title of 12(b) Security Title of 12(b) Security Disposal Group Classification [Axis] Disposal Group Classification [Axis] Treasury Rate Treasury Rate [Member] Treasury Rate Revolving Credit Facility commitment increase Revolving Credit Facility Commitment Increase [Member] Revolving Credit Facility Commitment Increase Intangible assets, net Net carrying amount Finite-Lived Intangible Assets, Net Current taxes payable Accrued Income Taxes, Current Lost revenue insurance maximum weekly recovery Mutual Lost Revenue Insurance Maximum Weekly Recovery This represents the maximum total weekly recovery for lost revenues insured by a nuclear industry mutual insurance company. Senior Notes, due 2029 3.375% Senior Notes Due 2029 3.375% Senior Notes due 2029 3.375% Senior Unsecured Notes Due 2029 [Member] 3.375% Senior Unsecured Notes Due 2029 Account Type [Axis] Account Type [Axis] Account Type [Axis] Vesting [Domain] Vesting [Domain] Interest expense Interest Expense Uncertain tax benefits reconciliation Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward] Schedule of Capitalization [Table] Schedule of Capitalization [Table] Depreciation and amortization Depreciation, Depletion and Amortization Short-term investment fund Short-term Investments [Member] Income tax provision from continuing operations Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] Discontinued Operations Discontinued Operations [Member] Product and Service [Axis] Product and Service [Axis] Delaware Trust [Member] Delaware Trust [Member] Delaware Trust Debt Redemption Debt Instrument Redemption [Table Text Block] Medicare prescription drug reimbursements Defined Benefit Plan, Postretirement Medical Plan with Prescription Drug Benefits [Abstract] Counterparty credit exposure, excluding credit risk exposure under certain long term agreements Amount Of Credit Exposure To Significant Portion Of All Counterparties The amount of credit exposure to a significant portion of all counterparties. Weighted Average Recognition Period Remaining (In years) Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition 2022 Long-Term Debt, Maturity, Year Two XOOM Energy, LLC XOOM Energy, LLC [Member] XOOM Energy, LLC [Member] Difference between carrying value and underlying net assets Equity Method Investment, Difference Between Carrying Amount and Underlying Equity Position [Domain] Position [Domain] Revenue recognized Contract with Customer, Liability, Revenue Recognized Redemption Period Prior to January 15, 2023 Redemption Period Prior to January 15, 2023 [Member] Redemption Period Prior to January 15, 2023 [Member] Alternative minimum tax ("AMT") refundable credit Effective Income Tax Rate Reconciliation, AMT Refundable Credit Effective Income Tax Rate Reconciliation, AMT Refundable Credit Spending for current obligations Asset Retirement Obligation, Liabilities Settled Lease expense Operating Lease, Expense 2023 Defined Benefit Plan, Expected Future Prescription Drug Subsidy Receipt, Year Three Land and improvements Land and Land Improvements [Member] Commitments and Contingencies Commitment and Contingency [Line Items] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value, Recurring and Nonrecurring [Table] Accounts payable Increase (Decrease) in Accounts Payable Purchases under coal, gas and transportation arrangement Purchases under power contracts Long-term Purchase Commitment Period Expense The amount the entity spent under long-term purchase commitments during the reporting period. Derivative revenue Total unrealized (losses)/gains Unrealized Gain (Loss) on Derivatives Income/(loss) from discontinued operations per weighted average common share — basic (in usd per share) Discontinued Operation, Income (Loss) from Discontinued Operation, Net of Tax, Per Basic Share Realized gains Debt Securities, Available-for-sale, Realized Gain Dividends paid per share (in usd per share) Common Stock, Dividends, Per Share, Cash Paid Annual dividend growth rate, percentage Common Stock, Annual Dividend Growth Rate Common Stock, Annual Dividend Growth Rate Debt Instrument [Axis] Debt Instrument [Axis] Asset Retirement Obligations Asset Retirement Obligation Disclosure [Text Block] Derivative Fair Value Meaurements and Concentration of Credit Risk Fair Value, Concentration of Risk, Financial Statement Captions [Line Items] Credit Derivatives Contract Type [Domain] Credit Derivatives Contract Type [Domain] Debt Basket Debt Basket [Member] Debt Basket GenOn GenOn [Member] Entity which is a party in merger. Revolving Credit Facility new tranche Credit Facility New Tranche [Member] Credit Facility New Tranche Operating Segments Operating Segments [Member] May 15, 2022 to May 14, 2023 Redemption Period From 15 May 2022 to 14 May 2023 [Member] Redemption Period From 15 May 2022 to 14 May 2023 [Member] Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Share repurchases Treasury Stock, Value, Acquired, Cost Method Changes in nuclear decommissioning trust liability Changes in Nuclear Decommissioning Trust Liability The net change during the reporting period in the nuclear decommissioning trust liability, representing amounts collected, through rates or other authorized charges to electric utility customers, which are designated for funding the Company's portioning of the decommissioning of its nuclear facilities. Following the completion of the decommissioning, if surplus funds remain in the decommissioning trusts, any excess will be refunded to the respective rate payers. Senior Secured First Lien Notes, due 2029 Senior Secured First Lien Notes, Due 2029 Senior Secured First Lien Notes, Due 2029 [Member] Senior Secured First Lien Notes, Due 2029 [Member] Unbilled revenues (included within Accounts receivable, net - Contracts with customers) Unbilled Contracts Receivable Adjustments to reconcile net income to net cash provided by operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Litigation Case [Axis] Litigation Case [Axis] Stream Energy Stream Energy Acquisition [Member] Stream Energy Acquisition [Member] Revenue from Contract with Customer [Abstract] Inventory obsolescence Deferred Tax Assets, Inventory Accumulated depreciation Public Utilities, Property, Plant and Equipment, Accumulated Depreciation Variable lease cost Variable Lease, Cost State taxes Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount Current taxes receivable Income Taxes Receivable Cottonwood Cottonwood [Member] Cottonwood Loss Contingency Nature [Axis] Loss Contingency Nature [Axis] Development costs Research and Development Expense Power Contracts Power Contracts [Member] Power Contracts [Member] Impairment losses, other assets Other Asset Impairment Charges Subsequent Event Subsequent Event [Member] Operating costs and expenses Disposal Group, Including Discontinued Operation, Operating Expense Federal Tax Authority Domestic Tax Authority [Member] Reclassifications Reclassification, Comparability Adjustment [Policy Text Block] Letter of credit Letters of Credit Outstanding, Amount Concentration Risk Type [Axis] Concentration Risk Type [Axis] Dunkirk Dunkirk [Member] Dunkirk [Member] Summary of Proceeds From Sales of Available-For-Sale securities and the related realized gains and losses Schedule of Realized Gain (Loss) [Table Text Block] NRG LTIP NRG LTIP [Member] NRG LTIP [Member] Restructuring Plan [Domain] Restructuring Plan [Domain] Current portion of long-term debt and finance lease Less current maturities Long-term Debt and Lease Obligation, Current Initial Application Period Cumulative Effect Transition [Domain] Initial Application Period Cumulative Effect Transition [Domain] Nuclear Event Nuclear Event [Member] Nuclear Event [Member] Retail Business Acquisitions Retail Business Acquisitions [Member] Retail Business Acquisitions Fair Value Estimate of Fair Value Measurement [Member] Other derivative revenue Products And Services, Other Derivative Revenue [Member] Products and Services, Other Derivative Revenue [Member] Net gain on sale of assets and disposal of assets Gain (Loss) on Disposition of Assets Non-current operating lease liabilities Operating Lease, Liability, Noncurrent 2024 Finite-Lived Intangible Asset, Expected Amortization, Year Four Other intangible assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles Defined benefit plans, net of income tax Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax Financial Institutions Financial Institutions [Member] Represents the information pertaining to the financial institutions. Summary of maximum potential exposure that can be estimated by NRG's guarantees, indemnity, and other contingent liability Schedule of Guarantor Obligations [Table Text Block] Current Assets Assets, Current [Abstract] Revolving Credit Facility Credit Agreement Credit Agreement [Member] Credit Agreement [Member] Equity contracts Investments, Fair Value Disclosure Fair Value, Option, Quantitative Disclosures [Line Items] Fair Value, Option, Quantitative Disclosures [Line Items] Comprehensive Income Attributable to NRG Energy, Inc. Comprehensive Income (Loss), Net of Tax, Attributable to Parent Transition Services Agreement Transition Services Agreement [Member] Transition Services Agreement Balance outstanding at the beginning of the period (in shares) Balance outstanding at the end of the period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested Number The number of fully vested deferred stock units outstanding as of the balance sheet date under the terms of the award. Senior Secured First Lien Notes, due 2024 Senior Secured First Lien Notes, Due 2024 Senior Secured First Lien Notes, Due 2024 [Member] Senior Secured First Lien Notes, Due 2024 [Member] July 15, 2021 to July 14, 2022 Redemption Period From 15 July 2021 to 14 July 2022 [Member] Redemption Period From 15 July 2021 to 14 July 2022 [Member] U.S. government and federal agency obligations US Government-sponsored Enterprises Debt Securities [Member] Documents Incorporated by Reference Documents Incorporated by Reference [Text Block] Reconciliation of the U.S. federal statutory rate to NRG's effective rate Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] 2021 Long-Term Debt, Maturity, Year One Rate of compensation increase Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase Oil lower of cost or market adjustment Inventory lower of cost or market adjustment Oil Inventory Lower of Cost or Market Adjustment Oil Inventory Lower of Cost or Market Adjustment Deductions SEC Schedule, 12-09, Valuation Allowances and Reserves, Deduction Proceeds from sale of assets, net of cash disposed and sale of discontinued operations, net of fees Proceeds from Sale of Other Productive Assets Legal Entity [Axis] Legal Entity [Axis] City Area Code City Area Code Reversal of previously recognized unrealized (gains) on settled positions related to economic hedges Reversal Previously Recognized, Unrealized Gains (Losses) Settled Positions, Economic Hedges Amount reversed into entity's statement of operations for previously recognized unrealized (gains) losses on settled positions related to economic hedges. Settlement payment Payments To Affiliate, Settlement Agreement Payments To Affiliate, Settlement Agreement Income Tax Authority [Axis] Income Tax Authority [Axis] Document Period End Date Document Period End Date Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] Measured using net asset value practical expedient: Measured Using Net Asset Value Practical Expedient [Abstract] Measured Using Net Asset Value Practical Expedient Finite-lived Intangible Assets [Roll Forward] Finite-lived Intangible Assets [Roll Forward] 2023 Unrecorded Unconditional Purchase Obligation, to be Paid, Year Three Stock repurchase program, authorized amount Stock Repurchase Program, Authorized Amount Net Income Net Income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Disaggregation of Revenue Disaggregation of Revenue [Table Text Block] Asset Impairments Impairment or Disposal of Long-Lived Assets, Policy [Policy Text Block] Weighted Average Grant Date Fair Value per Unit Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options Vested, Weighted Average Grant Date Fair Value [Abstract] Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options Vested, Weighted Average Grant Date Fair Value [Abstract] Increase in revolving commitments and letters of credit Line of Credit Facility, Maximum Borrowing Capacity, Increase Line of Credit Facility, Maximum Borrowing Capacity, Increase Renewables Energy Certificates Renewable Energy Certificates [Member] Renewable Energy Certificates [Member] Cash provided/(used) by changes in other working capital, net of acquisition and disposition effects: Cash Provided Used by Changes in Other Working Capital [Abstract] Aggregate intrinsic value for DSUs outstanding Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested, Aggregate Intrinsic Value As of the balance sheet date, the total dollar difference between fair values of the underlying shares reserved for issuance and exercise prices of fully vested equity awards other than options. Amounts paid for shares and share equivalents purchased (in millions) Stock Repurchased During Period, Value Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Amortization of unearned equity compensation Share-based Payment Arrangement, Noncash Expense Proceeds distributed to Company Proceeds from Contributions from Affiliates Difference between book and tax basis of property Deferred Tax Assets, Property, Plant and Equipment Other Proceeds from (Payments for) Other Financing Activities Assignment Of Historical Claims Against REMA Assignment Of Historical Claims Against REMA [Member] Assignment Of Historical Claims Against REMA [Member] Cover [Abstract] Production tax credits ("PTC") Effective Income Tax Rate Reconciliation, Tax Credit, Other, Amount Recourse Debt Recourse Debt Recourse Debt [Member] Recourse Debt [Member] Aggregate intrinsic values for DSUs converted to common stock during the period Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Conversions, Aggregate Intrinsic Value The total accumulated difference between fair values of underlying shares on dates of conversion and conversion price on units which were converted into shares during the reporting period under the plan. Distribution received Proceeds from Equity Method Investment, Distribution 2022 Defined Benefit Plan, Expected Future Prescription Drug Subsidy Receipt, Year Two Accounts payable Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accounts Payable Maximum assessment, administrative fee (as percent) Nuclear Insurance Financial Protection Pool, Maximum Assessment, Administrative Fee, As A Percent Nuclear Insurance Financial Protection Pool, Maximum Assessment, Administrative Fee, As a Percent Domestic and foreign components of income/(loss) before income tax (benefit)/expense Schedule of Income before Income Tax, Domestic and Foreign [Table Text Block] Asset Impairment Charges [Abstract] Asset Impairment Charges [Abstract] Debt discount amortization period Debt Instrument, Convertible, Remaining Discount Amortization Period Long-term debt Long-term debt Long-term debt Long-term Debt Leases Lessee, Operating Leases [Text Block] Senior Secured First Lien Notes, due 2025 2.000% Senior Secured Notes Due 2025 [Member] 2.000% Senior Secured Notes Due 2025 Asset Impairments Impaired Long-Lived Assets Held and Used [Line Items] Summary of Significant Accounting Policies [Table] Summary of Significant Accounting Policies [Table] Summary of Significant Accounting Policies [Table] Employee and retiree contributions Defined Benefit Plan, Benefit Obligation, Contributions by Plan Participant Service cost benefits earned Service cost Defined Benefit Plan, Service Cost Debt Securities Debt Securities [Member] Customer Relationships Customer Relationships [Member] Business Solutions customers Business Solutions Customers [Member] Business Solutions Customers [Member] Lease, Cost [Abstract] Lease, Cost [Abstract] Income from discontinued operations, net of income tax Income/(loss) from discontinued operations, net of income tax Income/(loss) from discontinued operations, net of income tax Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent Total operating costs and expenses Total operating cost and expenses Costs and Expenses Award Date [Domain] Award Date [Domain] Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations [Member] Equity Components [Axis] Equity Components [Axis] Equity Components [Axis] Number of class action lawsuits Loss Contingency, Pending Claims, Number Letters of credit and surety bonds Letters Of Credit And Surety Bonds [Member] The entity's estimated total guarantee under letters of credit and surety bonds combined. Funds Deposited by Counterparties Funds Deposited by Counterparties [Policy Text Block] Describes the entity's accounting policy for its funds deposited by counterparties. 2026-2030 Defined Benefit Plan, Expected Future Prescription Drug Subsidy Receipt, after Year Five Asset Retirement Obligations Asset Retirement Obligation [Policy Text Block] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Net proceeds of Revolving Credit Facility Proceeds from (Repayments of) Lines of Credit Total deferred tax assets Deferred Tax Assets, Gross Low Minimum Minimum [Member] Total assets acquired Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets Balance Sheet Location [Domain] Balance Sheet Location [Domain] Impairment loss Impairment losses on equity method investments Equity Method Investment, Other than Temporary Impairment Cash paid for amounts included in the measurement of lease liabilities: Cash Flow, Lessee [Abstract] Cash Flow, Lessee Award Date [Axis] Award Date [Axis] Reconciliation of cash, cash equivalents, and restricted cash and cash equivalents Details of supplemental disclosures of cash flow and non-cash investing and financing information Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Defined Benefit Plan, Plan Assets, Category [Domain] Defined Benefit Plan, Plan Assets, Category [Domain] Redeemable noncontrolling interest in subsidiaries Balance at beginning of period Balance at end of period Redeemable Noncontrolling Interest, Equity, Other, Carrying Amount Less: Net income attributable to noncontrolling interest and redeemable interests Less: Net income attributable to noncontrolling interests and redeemable noncontrolling interests Net Income (Loss) Attributable to Noncontrolling Interest Deferred compensation, accrued vacation and other reserves Deferred Tax Assets, Tax Deferred Expense Compensation and Benefits Deferred Compensation, Accrued Vacation and Other Reserves The tax effect as of the balance sheet date of the amount of the estimated future tax deductions arising from deferred compensation, accrued vacation and other reserves, which can only be deducted for tax purposes when actual costs are incurred, and which can only be realized if sufficient tax-basis income is generated in future periods to enable the deduction to be taken. Equity Method Investments and Joint Ventures [Abstract] Equity Method Investments and Joint Ventures [Abstract] Convertible Senior Notes Due 2048 Convertible Senior Notes Due 2048 [Member] Convertible Senior Notes due 2048 [Member] Amortization of unrecognized net loss Amortization of net actuarial (gain) Defined Benefit Plan, Amortization of Gain (Loss) Development Costs and Capitalized Interest Property, Plant and Equipment, Project Development Costs and Interest Capitalization [Policy Text Block] Describes an entity's accounting policy for project development costs and interest on funds borrowed to finance capital projects. Schedule of Amounts Recognized in Balance Sheet Schedule of Amounts Recognized in Balance Sheet [Table Text Block] Gain on sale of assets (Loss)/gain on sale of assets Gain (Loss) on Disposition of Other Assets Entity Interactive Data Current Entity Interactive Data Current Net periodic benefit (credit)/cost Net periodic benefit credit Defined Benefit Plan, Net Periodic Benefit Cost (Credit) U.S. UNITED STATES Exercised (in usd per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Schedule of Target Allocation of Pension Plan Assets Schedule of Allocation of Plan Assets [Table Text Block] Accrued expenses and other current liabilities Increase (Decrease) Accrued Expenses and Other Current Liabilities Operating The sum of the net change during the reporting period of accrued expenses and other current liabilities. Accrued expenses is the net change during the reporting period in the aggregate amount of expenses incurred but not yet paid. Other current liabilities is the net change during the reporting period in other expenses incurred but not yet paid. Operating Revenues Revenues [Abstract] Cash Flows from Operating Activities Net Cash Provided by (Used in) Operating Activities [Abstract] Capital Structure Stockholders' Equity Note Disclosure [Text Block] Summary of Company's NQSO activity, and changes during the year Share-based Payment Arrangement, Option, Activity [Table Text Block] Emissions allowances Deferred Tax Liabilities, Emissions Allowances The amount as of the balance sheet date of the estimated future tax effects arising on emissions allowances. Company's deferred tax assets and liabilities Components of Deferred Tax Assets and Liabilities [Abstract] Commodity contracts Commodity Contract [Member] Annual facility fees, percentage Line of Credit Facility, Commitment Fee Percentage Stock-Based Compensation Share-based Payment Arrangement [Policy Text Block] Income tax valuation allowance, deducted from deferred tax assets SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward] Exercise price as a percentage of fair value (as a percent) Employee Stock Purchase Plan, Exercise Price as Percentage of Fair Value This element represents the exercise price under employee stock purchase plan as a percentage of fair value. Foreign Current Foreign Tax Expense (Benefit) February 15, 2028 to February 14, 2029 Redemption Period February 15, 2028 to February 14, 2029 [Member] Redemption Period February 15, 2028 to February 14, 2029 Civil penalty Litigation Settlement, Amount Awarded to Other Party Derivative [Table] Derivative [Table] Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Schedule of Assumptions used in Fair Value Model Schedule of Share-based Payment Awards, Market Unit Valuation Assumptions [Table Text Block] Schedule of Share-based Payment Awards, Market Unit Valuation Assumptions [Table Text Block] Total deferred tax liabilities Deferred Tax Liabilities, Gross 2021 Defined Benefit Plan, Expected Future Benefit Payment, Year One Accounts Receivable, Allowance for Credit Loss [Roll Forward] Accounts Receivable, Allowance for Credit Loss [Roll Forward] Marketing and Advertising Costs Advertising Cost [Policy Text Block] Debt, Long-term and Short-term, Combined Amount [Abstract] Debt, Long-term and Short-term, Combined Amount [Abstract] Retirement Plan Type [Domain] Retirement Plan Type [Domain] Petra Nova Parish Holdings Petra Nova Parish Holdings [Member] Petra Nova Parish Holdings [Member] Asset Retirement Obligations [Axis] Asset Retirement Obligations [Axis] Asset Retirement Obligations NRG Dunkirk 2020, tax exempt bonds, due 2042 NRG Dunkirk 2020, tax exempt bonds, due 2042 [Member] NRG Dunkirk 2020, tax exempt bonds, due 2042 Charged to Costs and Expenses SEC Schedule, 12-09, Valuation Allowances and Reserves, Additions, Charge to Cost and Expense Schedule of Equity Method Investments [Table] Schedule of Equity Method Investments [Table] Effective rate Debt Instrument, Interest Rate, Effective Percentage Consolidation Items [Axis] Consolidation Items [Axis] Property, plant and equipment, net Net property, plant, and equipment Public Utilities, Property, Plant and Equipment, Net Net actuarial (gain)/loss Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax Customers acquired Business Acquisition, Customers Acquired Business Acquisition, Customers Acquired Not Designated as Hedging Instrument Not Designated as Hedging Instrument [Member] Asset Retirement Obligations [Domain] Asset Retirement Obligations [Domain] Asset Retirement Obligations Derivative instruments Derivative Instruments and Hedges, Assets Equity securities-nuclear trust fund investments Equity Securities-Nuclear Trust Fund [Member] Equity Securities-Nuclear Trust Fund [Member] Accounts receivable, net Accounts receivable, net Accounts Receivable, after Allowance for Credit Loss, Current Total undiscounted lease payments Lessee, Operating Lease, Liability, to be Paid Other Deferred Tax Assets, Other Senior Notes, due 2029 5.25% Senior Notes due 2029 5.25% Senior Notes Due 2029 [Member] 5.25% Senior Notes Due 2029 [Member] Cash provided/(used) by continuing operations Net Cash Provided by (Used in) Financing Activities, Continuing Operations Purchased Energy and Other Cost of Sales for Customer Operations Cost of Goods and Service [Policy Text Block] 2019 Capital Allocation Plan 2019 Capital Allocation Plan [Member] 2019 Capital Allocation Plan Repurchase of partners' equity interest in VIE Adjustments to Additional Paid in Capital, Other Operating lease income Less: Lease revenue Operating Lease, Lease Income Interest crediting rate Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Weighted-Average Interest Crediting Rate Debt Instrument, Redemption, Period [Domain] Debt Instrument, Redemption, Period [Domain] Distributions from and equity in earnings of unconsolidated affiliates Income (Loss) from Equity Method Investments, Net of Dividends or Distributions Foreign Currency Translation and Transaction Gains and Losses Foreign Currency Transactions and Translations Policy [Policy Text Block] Facilities and equipment Facilities And Equipment [Member] Represents long-lived, depreciable assets of facilities and equipment. Changes in deferred income taxes and liability for uncertain tax benefits Increase (Decrease) in Income Taxes Natural Gas Natural Gas [Member] Details pertaining to the natural gas, which is considered as a derivative commodity. Reorganization costs Restructuring Costs Credit Agreement 2019 Credit Agreement 2019 [Member] Credit Agreement 2019 [Member] Beginning balance Ending balance Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs Fair Value Measurement Inputs and Valuation Techniques [Table] Fair Value Measurement Inputs and Valuation Techniques [Table] Services Agreement Services Agreement [Member] Services Agreement [Member] Document Transition Report Document Transition Report Debt Instrument, Redemption, Period [Axis] Debt Instrument, Redemption, Period [Axis] Counterparty credit exposure, net Net Credit Exposure Represents the net exposure of the entity determined as total credit exposure to all counterparties less collateral (cash and letters of credit) held against those positions as of the reporting date. Deferred Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract] Environmental Matters Environmental Loss Contingency Disclosure [Text Block] Spare parts Other Inventories, Spare Parts, Gross Derivative assets Derivative Asset, Fair Value, Gross Asset Accumulated Depreciation Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation June 15, 2026 to June 14, 2027 Redemption Period From 15 June 2026 to 14 June 2027 [Member] Redemption Period From 15 June 2026 to 14 June 2027 Restricted cash Restricted Cash and Cash Equivalents, Current Level 2 Significant Observable Inputs (Level 2) Fair Value, Inputs, Level 2 [Member] Cash consideration Disposal Group, Including Discontinued Operation, Consideration Short Short [Member] Liabilities Liabilities, Fair Value Disclosure [Abstract] Vesting [Axis] Vesting [Axis] Current Current Income Tax Expense (Benefit), Continuing Operations [Abstract] Annual periodic pension cost Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] Net Amount Derivative Asset, Fair Value, Amount Offset Against Collateral Summary of NRG's total compensation expense recognized and total non-vested compensation costs not yet recognized and the period over which this expense is expected to be recognized Schedule of Share-based Payment Compensation, Allocation of Share-based Compensation Costs by Plan Unrecognized Compensation Cost and Weighted-Average Recognition Period [Table Text Block] Disclosure of the amount of total share-based compensation cost, including amounts attributable to each share-based compensation plan and any related tax benefits. Disclosure of the total compensation cost related to nonvested awards not yet recognized and the weighted average period over which it is expected to be recognized. Subsequent Event [Line Items] Subsequent Event [Line Items] Summary of Financial Information for Consolidated VIEs Additional Financial Information Disclosure [Text Block] Cumulative Effect, Period of Adoption [Axis] Cumulative Effect, Period of Adoption [Axis] Asset sales guarantee obligations Asset Sales Guarantee Obligations [Member] The entity's estimated guarantees under asset sales guarantee obligations. Credit Facility [Domain] Credit Facility [Domain] Conversion price per common share (in usd per share) Debt Instrument, Convertible, Conversion Price Discounts Total discounts Debt Instrument, Unamortized Discount (Premium), Net Litigation Case [Domain] Litigation Case [Domain] Net Income per Weighted Average Common Share - Basic (in usd per share) Income/(Loss) per weighted average common share — basic (in usd per share) Earnings Per Share, Basic Agua Caliente Solar Project Agua Caliente Solar Project [Member] Agua Caliente Solar Project [Member] Maximum assessment mandated by Price-Anderson Act per nuclear reactor for a nuclear incident Nuclear Insurance Financial Protection Pool, Maximum Assessment Maximum assessment to be paid per nuclear reactor for a nuclear incident under the financial protection pool mandated by the Price-Anderson Act. This assessment is paid by each United State nuclear reactor operator over multiple years at a limited amount per year in the event of an incident at any US nuclear reactor. Expected term (in years) Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term Entity File Number Entity File Number Other non-current liabilities Liability, Defined Benefit Plan, Noncurrent Curtailment gain Curtailment gain Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Curtailment Rate of compensation increase Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase Weighted average remaining lease term (in years) Operating Lease, Weighted Average Remaining Lease Term Assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets [Abstract] Acquisition of businesses Finite-lived Intangible Assets Acquired Senior Notes, due 2027 6.625% Senior Notes due 2027 Senior Notes due 2027 [Member] Senior Notes due 2027 [Member] Jointly Owned Utility Plant [Domain] Jointly Owned Utility Plant [Domain] Small Book Acquisitions 2018 Small Book Acquisitions 2018 [Member] Small Book Acquisitions 2018 Maximum assessment payment mandated by Price-Anderson Act for a nuclear incident Nuclear Insurance Financial Protection Pool, Maximum Annual Assessment Nuclear Insurance Financial Protection Pool, Maximum Annual Assessment Income/(loss) from discontinued operations, net of tax Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest Summary of Results of Discontinued Operations Disposal Groups, Including Discontinued Operations [Table Text Block] Account Type [Domain] Account Type [Domain] [Domain] for Account Type [Axis] Prior service cost/(credit) Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, Prior Service Cost (Credit), before Tax Fuel oil Energy Related Inventory, Petroleum Debt Instrument, Unamortized Discount [Abstract] Debt Instrument, Unamortized Discount [Abstract] Compensation Expense Share-based Payment Arrangement, Expense Net assets less noncontrolling interests Net Assets Less Noncontrolling Interest Net Assets Less Noncontrolling Interest Balance Sheet Location [Axis] Balance Sheet Location [Axis] Shares reissuance for ESPP Stock Issued During Period, Value, Employee Stock Purchase Plan Goodwill and Intangible Assets Disclosure [Abstract] Goodwill and Intangible Assets Disclosure [Abstract] Disposal Group Name [Axis] Disposal Group Name [Axis] Significant components of NRG's domestic pension plan Significant Components of Defined Benefit Pension Plan [Abstract] Impairment Impairment of Intangible Assets, Finite-lived Net Counterparty Credit Exposure by Industry Sector and by Counterparty Credit Quality Schedule of Net Exposure to Counter Party Credit Exposure [Table Text Block] Disclosure of the net exposure to counterparty credit risk by category. Document Annual Report Document Annual Report Aggregate Intrinsic Value, Exercisable Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value Foreign Currency Translation and Transaction Gains and Losses Foreign Currency Translation and Transaction [Abstract] Tax detriment recognized Share-based Payment Arrangement, Expense, Tax Benefit Long-term Purchase Commitment by Category of Item Purchased Category of Item Purchased [Axis] Gladstone Gladstone Gladstone Power Station [Member] Represents the information pertaining to Gladstone Power Station. Funds Deposited by Counterparties Funds Deposited by Counterparties [Abstract] Position [Axis] Position [Axis] Financial Transmission Rights Financial Transmission Rights [Member] Financial Transmission Rights [Member] Retirement Benefits [Abstract] Retirement Benefits [Abstract] Professional fees Professional Fees Quarterly dividends per share (usd per share) Common Stock, Quarterly Dividends, Per Share, Cash Paid Common Stock, Quarterly Dividends, Per Share, Cash Paid Receivable [Domain] Receivable [Domain] Subsequent Event [Table] Subsequent Event [Table] Shares issued from LTIP (in shares) Shares Issued, Shares, Share-based Payment Arrangement, after Forfeiture Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Purchases Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Purchases Granted (in usd per share) Weighted average grant date fair value (in usd 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 Capacity Capacity [Member] Offsetting of Derivatives by Counterparty Master Agreement Level and Collateral Received Or Paid Schedule of Offsetting Assets and Liabilities [Table Text Block] Schedule of Offsetting Assets and Liabilities [Table Text Block] Deferred revenue from contract with customers Contract with Customer, Liability, Increase For Cash Payments Received Contract with Customer, Liability, Increase For Cash Payments Received Loss on debt extinguishment, net Gains Losses on Extinguishment of Debt, Non Cash Portion Gains Losses on Extinguishment of Debt, Non-cash Portion Equity method investments Deferred Tax Liabilities, Investment in Noncontrolled Affiliates Cash Flows from Investing Activities Net Cash Provided by (Used in) Investing Activities [Abstract] Finite-lived intangible asset retirements Finite-lived Intangible Asset Retirements Finite-lived Intangible Asset Retirements Debt Issuance Costs Debt, Policy [Policy Text Block] Net loss on deconsolidation of Agua Caliente and Ivanpah projects Gain/(loss) on disposal of discontinued operations, net of tax Deconsolidation, Gain (Loss), Amount Common/collective trust investment — U.S. equity Common Trust Investment US Equity Securities [Member] Represents the investments in common/collective trust in U.S. equity securities. Schedule of Defined Benefit Plans Disclosures [Table] Schedule of Defined Benefit Plans Disclosures [Table] Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] Debt extinguished Extinguishment of Debt, Amount Fuel Contracts Fuel Contracts [Member] An asset acquired in a business combination representing an entity's fuel contracts. Coal Energy Related Inventory, Coal Derivative Instruments Derivative Asset, Fair Value, Gross Liability Accounts receivable - trade Increase (Decrease) in Accounts Receivable Statement of Comprehensive Income [Abstract] Statement of Comprehensive Income [Abstract] Concentration Risk Type [Domain] Concentration Risk Type [Domain] Contributions from noncontrolling interests Noncontrolling Interest, Contributions from Noncontrolling Interest Holders Noncontrolling interest, Contributions from Noncontrolling Interests Plan amendments Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment Total Liabilities and Stockholders' Equity Liabilities and Equity Loss Contingencies [Line Items] Loss Contingencies [Line Items] Commitment fee Line of Credit Facility, Commitment Fee Amount Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax Income Taxes Income Tax Disclosure [Text Block] Total other liabilities Liabilities, Noncurrent Reduction of liabilities due to deconsolidation Increase (Decrease) in Operating Liabilities Present value of note (as percentage) Debt Instrument, Present Value Of Note, Rate Debt Instrument, Present Value Of Note, Rate Portion at Fair Value Measurement Portion at Fair Value Measurement [Member] Senior Secured First Lien Notes due 2025 to 2027 Senior Secured First Lien Notes Due 2025 to 2027 [Member] Senior Secured First Lien Notes Due 2025 to 2027 Purchase price adjustment Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Consideration Transferred Operating lease cost Operating Lease, Cost Direct Energy Purchase Price Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net Total liabilities assumed Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities Deferred tax liabilities: Deferred Tax Liabilities, Gross [Abstract] Fair Value, Concentration of Risk [Table] Fair Value, Concentration of Risk [Table] February 15, 2026 to February 14, 2027 Redemption Period February 15, 2026 to February 14, 2027 [Member] Redemption Period February 15, 2026 to February 14, 2027 Total — current Current Income Tax Expense (Benefit) Property Taxes For Solar Properties Property Taxes For Solar Properties [Member] Property Taxes For Solar Properties [Member] Line of Credit Facility [Line Items] Line of Credit Facility [Line Items] Weighted average remaining lease term (in years) Finance Lease, Weighted Average Remaining Lease Term Change in Cash from discontinued operations Net Cash Provided by (Used in) Discontinued Operations Increase due to current year positions Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions Summary of the total intrinsic value of options exercised and the cash received from the exercises of options Share-based Compensation Arrangements, Schedule of Intrinsic Value of Options Exercised And Cash Received From Options Exercised [Table Text Block] Share-based Compensation Arrangements, Schedule of Intrinsic Value of Options Exercised And Cash Received From Options Exercised Equity Component [Domain] Equity Component [Domain] Bilateral letter of credit facilities Bilateral Letter of Credit Facilities [Member] Bilateral Letter of Credit Facilities Nuclear insurance liability limit per incident Nuclear Insurance Per Incident Coverage Limit Nuclear Insurance Per Incident Coverage Limit Available-for-sale securities, net of income tax OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment and Tax Agua Caliente Agua Caliente [Member] Agua Caliente [Member] Schedule of Expected Benefit Payments Schedule of Expected Benefit Payments [Table Text Block] Net property, plant and equipment Property, Plant and Equipment, Net Entity Tax Identification Number Entity Tax Identification Number Arthur Kill Plant Arthur Kill Plant [Member] Arthur Kill Plant Stock-Based Compensation Share-based Payment Arrangement [Text Block] Release of reserves to fund equity distributions Increase (Decrease) in Restricted Cash Interest rate contracts Interest Rate Contract Interest Rate Contract [Member] Net Income Attributable to NRG Energy, Inc. Net Income/(Loss) Attributable to NRG Energy, Inc. Net Income (Loss) Attributable to Parent Capital Structure Schedule of Capitalization [Line Items] Carrying amount of equity component Debt Instrument, Convertible, Carrying Amount of Equity Component LIBOR London Interbank Offered Rate (LIBOR) [Member] Inventory Inventory Disclosure [Text Block] Schedule of Capitalization, Equity [Table] Schedule of Capitalization, Equity [Table] Credit applied Restructuring and Related Cost, Credit Applied Restructuring and Related Cost, Credit Applied Trade Names Trade Names [Member] Derivative, nonmonetary notional amount, mass (ton) Derivative, Nonmonetary Notional Amount, Mass Current Fiscal Year End Date Current Fiscal Year End Date Finance leases Finance Lease, Liability Conemaugh Conemaugh [Member] This element represents the information pertaining to Conemaugh, New Florence, PA. Membership percentage Disposal Group, Including Discontinued Operation, Ownership Percentage Disposal Group, Including Discontinued Operation, Ownership Percentage Net exposure (as a percent) Credit Derivative, Maximum Net Exposure, Percentage Represents the percentage of net counterparty credit exposure of the entity. Total (losses) — realized/unrealized: Fair Value Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset and Liability, Realized and Unrealized Gain (Loss) [Abstract] Guarantees Guarantees [Text Block] Nuclear financial protection pool mandated by the Price-Anderson Act Nuclear Insurance Financial Protection Pool Value Nuclear Insurance Financial Protection Pool Value NQSO activity and changes Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward] Federal and state tax credit carryforwards Deferred Tax Assets, Tax Credit Carryforwards Liabilities Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract] Credit Derivatives Contract Type [Axis] Credit Derivatives Contract Type [Axis] Indian River Power LLC, tax exempt bonds, due 2045 Indian River Power LLC Tax Exempt Bonds Due 2045 [Member] Represents Indian River Power LLC tax exempt bonds, which are due 2045. Senior Notes, due 2026 7.250% Senior Notes due 2026 Senior Notes due 2026 [Member] Senior Notes due 2026 [Member] Supplemental Cash Flow Information [Abstract] Supplemental Cash Flow Information [Abstract] Fair Value Inputs, Sensitivity Analysis Fair Value Inputs, Sensitivity Analysis [Table Text Block] Fair Value Inputs, Sensitivity Analysis [Table Text Block] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] Reconciliation of the U.S. federal statutory rate to NRG's effective rate from continuing operations Effective Income Tax Rate Reconciliation, Percent [Abstract] Shares issued under ESPP (in shares) Stock Issued During Period, Shares, Employee Stock Purchase Plans Treasury stock reserved for issuance under the ESPP (in shares) Common Stock, Capital Shares Reserved For Employee Stock Purchase Plan Aggregate number of common shares reserved for employee stock purchase plan. Net loss attributable to redeemable noncontrolling interest - discontinued operations Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Noncontrolling Interest Property, Plant and Equipment Property, Plant and Equipment [Line Items] Net income attributable to redeemable noncontrolling interest - continuing operations Net Income (Loss) Attributable to Redeemable Noncontrolling Interest Property, Plant and Equipment, Type [Domain] Long-Lived Tangible Asset [Domain] Allowance for doubtful accounts, deducted from accounts receivable SEC Schedule, 12-09, Allowance, Credit Loss [Member] Benefit payments Defined Benefit Plan, Benefit Obligation, Benefits Paid June 15, 2024 to June 14, 2025 Redemption Period From 15 June 2024 to 14 June 2025 [Member] Redemption Period From 15 June 2024 to 14 June 2025 Inventory [Domain] Inventory [Domain] Accounts receivable, net - Contracts with customers Energy Supply Contract Customer Contracts [Member] NRG's Major Classes of Property, Plant and Equipment Property, Plant and Equipment [Table Text Block] Net recognized in net periodic pension credit and OCI Defined Benefit Plan, Amount Recognized in Net Periodic Benefit Cost (Credit) and Other Comprehensive (Income) Loss, before Tax Other Commitments [Domain] Other Commitments [Domain] Derivatives, net Deferred Tax Liabilities, Derivatives Revolving commitments available Line of Credit Facility, Remaining Borrowing Capacity Other income Disposal Group, Including Discontinued Operation, Other Income Total derivative assets valued with prices provided by models and other valuation techniques percentage Derivative Asset, Fair Value Determined Using Valuation Techniques, Percentage This element represents the portion of total fair value of all derivative assets, which are valued using various valuation techniques including internal models based on a fundamental analysis of the market and extrapolation of observable market data with similar characteristics. Balance at beginning of period Balance at end of period Finite-Lived Intangible Assets, Gross Total/Net accumulated OCI Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax Finite-Lived Intangible Assets, Net [Abstract] Finite-Lived Intangible Assets, Net [Abstract] Provision for credit losses Accounts Receivable, Credit Loss Expense (Reversal) Share-based Payment Arrangement, Tranche Five Share-based Payment Arrangement, Tranche Five [Member] Share-based Payment Arrangement, Tranche Five Total (losses) — realized/unrealized included in earnings Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Gain (Loss) Included in Earnings Reclassified from accumulated OCI to income: Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net [Abstract] Net loss Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Gain (Loss), before Tax Amounts recognized in accumulated OCI Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax [Abstract] Related Party Transactions [Abstract] Related Party Transactions [Abstract] Increase In credit reserve, primarily in cost of operations Increase In Credit Reserve, Increase In Cost Of Revenue Increase In Credit Reserve, Increase In Cost Of Revenue Schedule of Annual Payments Based on Maturities of Leases Lessee, Operating Lease, Liability, Maturity [Table Text Block] Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Other Effective Income Tax Rate Reconciliation, Other Adjustments, Amount Equity, Class of Treasury Stock [Line Items] Equity, Class of Treasury Stock [Line Items] Weighted average number of common shares outstanding — basic (in shares) Weighted Average Number of Shares Outstanding, Basic Basis spread on variable rate (as a percent) Treasury rate redemption (as percentage) Debt Instrument, Basis Spread on Variable Rate Risk free rate Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate Forfeited (in usd per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price Ownership [Axis] Ownership [Axis] Cash and cash equivalents Cash and Cash Equivalents [Member] Scenario, Plan Scenario, Plan [Member] Loss Contingencies [Table] Loss Contingencies [Table] Share-based Payment Arrangement, Tranche Four Share-based Payment Arrangement, Tranche Four [Member] Share-based Payment Arrangement, Tranche Four Carrying Amount Reported Value Measurement [Member] Plan Name [Domain] Plan Name [Domain] Collateral posted Payments for Advance to Affiliate Entity Well-known Seasoned Issuer Entity Well-known Seasoned Issuer Pension and other postretirement benefits Deferred Tax Assets, Tax Deferred Expense Compensation and Benefits Pensions and Other Postretirement Benefits The tax effect as of the balance sheet date of the amount of the estimated future tax deductions arising from pension and other post retirement costs, which can only be deducted for tax purposes when actual costs are incurred, and which can only be realized if sufficient tax-basis income is generated in future periods to enable the deduction to be taken. Ownership percentage Economic interest in equity method investments (as a percent) Equity Method Investment, Ownership Percentage Revenue Recognition Revenue from Contract with Customer [Text Block] Foreign net operating loss carryforwards Deferred Tax Assets, Operating Loss Carryforwards, Foreign Commitment and Contingency [Table] Commitment and Contingency [Table] Summarization of information required or determined to be disclosed about the commitment and contingencies of the entity. DSUs Deferred Stock Units [Member] Represents details pertaining to deferred stock units. Right-of-use assets obtained in exchange for new operating lease liabilities Right-of-Use Asset Obtained in Exchange for Operating Lease Liability Actuarial loss Actuarial loss Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) Put option agreement, term Put Option Agreement , Term Put Option Agreement , Term Inventory Inventory, Policy [Policy Text Block] Income tax expense/(benefit) Total income tax expense/(benefit) Income Tax Expense (Benefit) Year Health care cost trend rate reaches ultimate trend rate Defined Benefit Plan, Year Health Care Cost Trend Rate Reaches Ultimate Trend Rate Property, Plant and Equipment Property, Plant and Equipment, Policy [Policy Text Block] Annual Payments Based On the Maturities of NRG's Debt Schedule of Maturities of Long-term Debt [Table Text Block] Debt Securities, Available-for-sale [Table] Debt Securities, Available-for-sale [Table] Indefinite-lived Intangible Assets, Major Class Name [Domain] Indefinite-lived Intangible Assets, Major Class Name [Domain] Goodwill and other intangible assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets and Goodwill Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets and Goodwill Recognition of uncertain tax benefits Effective Income Tax Rate Reconciliation, Reversal of Uncertain Tax Positions Reserves Effective Income Tax Rate Reconciliation, Reversal of Uncertain Tax Positions Reserves Common/collective trust investment — non-U.S. equity Common Trust Investment Non US Equity Securities [Member] Represents the investments in common/collective trust in non-US equity securities. Local Phone Number Local Phone Number Cash paid to acquire business Payments to Acquire Businesses, Gross Derivative Instruments and Hedging Activities Disclosure [Abstract] Derivative Instruments and Hedging Activities Disclosure [Abstract] Schedule of Capitalization, Equity [Line Items] Schedule of Capitalization, Equity [Line Items] Counterparty credit exposure, collateral held (cash and letters of credit) against positions Collateral Held Cash and Letters of Credit Carrying amount as of the balance sheet date of cash collateral and letters of credit received by the entity on deposit from third parties in support of energy risk management. Cumulative Effect, Period of Adoption [Domain] Cumulative Effect, Period of Adoption [Domain] Schedule of Amortization and Retirements of Intangible Expense Finite-lived Intangible Assets Amortization Expense [Table Text Block] (Loss)/gain from operations of discontinued components, before tax Disposal Group, Including Discontinued Operation, Operating Income (Loss) Share-based Payment Arrangement, Tranche One Share-based Payment Arrangement, Tranche One [Member] Total intrinsic value of options exercised Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value Income tax expense Discontinued Operation, Tax Effect of Discontinued Operation Reorganization Costs Costs Associated with Exit or Disposal Activities or Restructurings, Policy [Policy Text Block] Coal, Gas and Transportation Commitments Coal, Gas and Transportation Commitments [Member] Long-term contractual agreements to procure fuel and transportation services for the Company's generation assets. Derivative [Line Items] Derivative [Line Items] Jointly Owned Utility Plant Interests Jointly Owned Utility Plant Interests [Line Items] Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] Variable Interest Entities Disclosure [Abstract] -- None. No documentation exists for this element. -- Deferred revenue Contract with Customer, Liability Related Party Transaction [Domain] Related Party Transaction [Domain] SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS SEC Schedule, 12-09, Schedule of Valuation and Qualifying Accounts Disclosure [Text Block] Carlsbad Energy Holdings LLC Carlsbad Energy Holdings LLC [Member] Carlsbad Energy Holdings LLC [Member] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] Schedule of Finite-Lived Intangible Assets [Table] Schedule of Finite-Lived Intangible Assets [Table] Revolving credit facilities Revolving credit facility Credit facility Line of Credit Facility, Maximum Borrowing Capacity Award Type [Axis] Award Type [Axis] Significant assumptions used to calculate NRG's benefit expense Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract] Weighted Average Grant Date Fair Value per Unit Weighted Average Grant-Date Fair Value per Unit Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Discount rate Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate Revolving Credit Facility Borrowings Revolving Credit Facility Borrowings [Member] Revolving Credit Facility Borrowings [Member] Vested in period, fair value Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value Other non-current assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets Cost To Complete Construction Cost To Complete Construction [Member] Cost To Complete Construction [Member] Accumulated Deficit Retained Earnings [Member] Revisions in estimates for current obligations Asset Retirement Obligation, Revision of Estimate Measurement Basis [Axis] Measurement Basis [Axis] Schedule of Net Benefit Cost (Credit) Related to Pension and Other Postretirement Benefit Plans Components Schedule of Net Benefit Costs [Table Text Block] Summary of Significant Accounting Policies Significant Accounting Policies [Text Block] Net Cash (Used)/Provided by Investing Activities Net Cash Provided by (Used in) Investing Activities Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract] Weighted Average Remaining Contractual Term, Outstanding (in years) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term Share-based Compensation [Abstract] Share-based Payment Arrangement, Noncash Expense [Abstract] Nuclear trust fund investments: Nuclear Trust Fund Investments [Abstract] Nuclear Trust Fund Investments Award Type [Domain] Equity Award [Domain] Award Type [Domain] California property tax indemnity Guarantor Obligations, Current Carrying Value Other current liabilities Liability, Defined Benefit Plan, Current Corporate debt securities Corporate Debt Securities [Member] Revolving credit facility commitment increase Debt Instrument, Increase (Decrease), Net Deconsolidations of Agua Caliente and Ivanpah projects Cash Divested from Deconsolidation Exercisable (in usd per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price June 15, 2025 to June 14, 2026 Redemption Period From 15 June 2025 to 14 June 2026 [Member] Redemption Period From 15 June 2025 to 14 June 2026 Collateral required contracts with credit rating contingent features in a net liability position Derivative, Net Liability Position, Aggregate Fair Value Discontinued Operations and Disposal Groups [Abstract] Discontinued Operations and Disposal Groups [Abstract] Federal benefit on state uncertain tax positions Deferred Tax Assets, Federal Benefit on State Unrecognized Tax Benefits The tax effect as of the balance sheet date of the amount of the estimated future tax reductions attributable to the difference between the tax basis and the generally accepted accounting principles basis of a federal benefit on state unrecognized tax benefits which will decrease future taxable income when such basis difference reverses. Property, Plant and Equipment Property, Plant and Equipment Disclosure [Text Block] Other commitment Other Commitment Term Loan Facility Term Loan Facility Due 2023 [Member] Term Loan Facility Due 2023 [Member] Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Finance leases: Finance Lease [Abstract] Finance Lease Treasury stock, at cost; 178,825,915 and 172,894,601 shares at December 31, 2020 and 2019 Treasury Stock, Value Other revenue Products And Services, Other [Member] Products And Services, Other [Member] Earnings Per Share Earnings Per Share [Text Block] Pension Benefits Pension Benefit Payments Pension Plan [Member] Hardware and office equipment and furnishings Office Equipment [Member] Counterparty Risk by Institution [Domain] Counterparty Risk by Institution [Domain] Represents the counter party risk exposure by institutions involved. Discount rate Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate Cash collateral Cash Collateral Cash Collateral Redeemable noncontrolling interests Redeemable Noncontrolling Interest, Equity, Carrying Amount Current Liabilities Liabilities, Current [Abstract] Summary of NRG's proportionate ownership interest in the company's jointly-owned facilities Schedule of Jointly Owned Utility Plants [Table Text Block] 2017 Granted in 2017 [Member] Granted in 2017 Write-off of fully amortized balances Finite-Lived Intangible Assets, Write-off of Fully Amortized Intangible Assets Write-off of fully amortized intangible assets during the period. Accretion Asset Retirement Obligation, Accretion Expense Guarantor Obligations Guarantor Obligations [Line Items] Renewable Purchased Power Agreements Renewable Purchased Power Agreements [Member] Renewable Purchased Power Agreements Asset Impairments Asset Impairment Charges [Text Block] Schedule Of Contract Assets And Liabilities [Line Items] Schedule Of Contract Assets And Liabilities [Line Items] [Line Items] for Schedule Of Contract Assets And Liabilities [Table] Unrealized Mark To Market Results [Abstract] Unrealized Mark To Market Results [Abstract] -- None. No documentation exists for this element. -- Guarantees and Product Warranties [Abstract] Income Tax Contingency [Table] Income Tax Contingency [Table] Recent Accounting Developments New Accounting Pronouncements, Policy [Policy Text Block] Asset Retirement Obligation [Table] Asset Retirement Obligation [Table] Asset Retirement Obligation Statement of Financial Position [Abstract] Statement of Financial Position [Abstract]