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Pension and Other Postretirement Employee Benefits (OPEB) Plans (Tables) | 12 Months Ended
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Dec. 31, 2023
Compensation and Retirement Benefits Disclosures [Abstract] |
Schedule of Pension and OPEB Costs | Pension and OPEB Costs
| Year Ended December 31,
| 2023 |  | 2022 |  | 2021
Pension costs | $ | 9 |  |  | $ | 2 |  |  | $ | 6 |
OPEB costs | 5 |  |  | 4 |  |  | 8 |
Total benefit costs recognized as expense | $ | 14 |  |  | $ | 6 |  |  | $ | 14 |
Schedule of Defined Benefit Plans Disclosures | The following information is based on a December 31, 2023, 2022 and 2021 measurement dates:
| Retirement Plan |  | OPEB Plans
| Year Ended December 31, |  | Year Ended December 31,
| 2023 |  | 2022 |  | 2021 |  | 2023 |  | 2022 |  | 2021
Assumptions Used to Determine Net Periodic Pension and Benefit Cost: |  |  |  |  |  |  |  |  |  |  |
Discount rate | 5.16 | % |  | 2.84 | % |  | 2.50 | % |  | 5.18 | % |  | 2.87 | % |  | 2.51 | %
Expected rate of compensation increase | 3.79 | % |  | 3.49 | % |  | 3.41 | % |  |  |  |  |  |
Interest crediting rate for cash balance | 3.00 | % |  | 3.00 | % |  | 3.00 | % |  |  |  |  |  |
Expected return on plan assets (Vistra Plan) | 5.85 | % |  | 4.24 | % |  | 3.77 | % |  |  |  |  |  |
Expected return on plan assets (Dynegy Plan) | 5.85 | % |  | 4.77 | % |  | 4.42 | % |  |  |  |  |  |
Expected return on plan assets (EEI Plan) | — | % |  | 4.92 | % |  | 4.72 | % |  |  |  |  |  |
Expected return on plan assets (EEI Union) |  |  |  |  |  |  | 3.89 | % |  | 3.92 | % |  | 6.79 | %
Expected return on plan assets (EEI Salaried) |  |  |  |  |  |  | 4.85 | % |  | 3.41 | % |  | 2.95 | %
Components of Net Pension and Benefit Cost: |  |  |  |  |  |  |  |  |  |  |
Service cost | $ | 3 |  |  | $ | 4 |  |  | $ | 5 |  |  | $ | 1 |  |  | $ | 1 |  |  | $ | 1 |
Interest cost | 21 |  |  | 17 |  |  | 16 |  |  | 5 |  |  | 4 |  |  | 4 |
Expected return on assets | (18) |  |  | (19) |  |  | (18) |  |  | (1) |  |  | (1) |  |  | (2) |
Amortization of unrecognized amounts, net | 3 |  |  | — |  |  | 3 |  |  | — |  |  | — |  |  | 5 |
Net periodic pension and OPEB cost | $ | 9 |  |  | $ | 2 |  |  | $ | 6 |  |  | $ | 5 |  |  | $ | 4 |  |  | $ | 8 |
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income: |  |  |  |  |  |  |  |  |  |  |
Net (gain) loss | $ | 7 |  |  | $ | (16) |  |  | $ | (27) |  |  | $ | — |  |  | $ | (22) |  |  | $ | (10) |
Prior service (credit) cost | (6) |  |  | 9 |  |  | — |  |  | — |  |  | — |  |  | (2) |
Curtailment and settlements | — |  |  | — |  |  | (2) |  |  | — |  |  | — |  |  | — |
Total recognized in net periodic benefit cost and other comprehensive income | $ | 10 |  |  | $ | (5) |  |  | $ | (23) |  |  | $ | 5 |  |  | $ | (18) |  |  | $ | (4) |
Assumptions Used to Determine Benefit Obligations at Period End: |  |  |  |  |  |  |  |  |  |  |
Discount rate | 4.97 | % |  | 5.16 | % |  | 2.84 | % |  | 4.98 | % |  | 5.18 | % |  | 2.87 | %
Expected rate of compensation increase | 3.64 | % |  | 3.79 | % |  | 3.49 | % |  |  |  |  |  |
Interest crediting rate for cash balance plans | 3.50 | % |  | 3.00 | % |  | 3.00 | % |  |  |  |  |  |
| Retirement Plan |  | OPEB Plans |
| Year Ended December 31, |  | Year Ended December 31, |
| 2023 |  | 2022 |  | 2023 |  | 2022 |
Change in Pension and Postretirement Benefit Obligations: |  |  |  |  |  |  |  |
Projected benefit obligation at beginning of period | $ | 449 |  |  | $ | 605 |  |  | $ | 110 |  |  | $ | 146 |  |
Service cost | 3 |  |  | 4 |  |  | 1 |  |  | 1 |  |
Interest cost | 21 |  |  | 17 |  |  | 5 |  |  | 4 |  |
Participant contributions | — |  |  | — |  |  | 3 |  |  | 2 |  |
Plan amendments | 1 |  |  | 9 |  |  | — |  |  | — |  |
Actuarial (gain) loss | 10 |  |  | (113) |  |  | 1 |  |  | (30) |  |
Benefits paid | (59) |  |  | (73) |  |  | (12) |  |  | (13) |  |
Projected benefit obligation at end of year | $ | 425 |  |  | $ | 449 |  |  | $ | 108 |  |  | $ | 110 |  |
Accumulated benefit obligation at end of year | $ | 422 |  |  | $ | 447 |  |  | $ | — |  |  | $ | — |  |
Change in Plan Assets: |  |  |  |  |  |  |  |
Fair value of assets at beginning of period | $ | 320 |  |  | $ | 470 |  |  | $ | 29 |  |  | $ | 39 |  |
Employer contributions | — |  |  | — |  |  | 9 |  |  | 9 |  |
Participant contributions | — |  |  | — |  |  | 3 |  |  | 2 |  |
Actual gain (loss) on assets | 24 |  |  | (77) |  |  | 2 |  |  | (6) |  |
Transfers | — |  |  | — |  |  | (19) |  |  | (2) |  |
Benefits paid | (59) |  |  | (73) |  |  | (12) |  |  | (13) |  |
Fair value of assets at end of year | $ | 285 |  |  | $ | 320 |  |  | $ | 12 |  |  | $ | 29 |  |
Funded Status: |  |  |  |  |  |  |  |
Projected benefit obligation | $ | (425) |  |  | $ | (449) |  |  | $ | (108) |  |  | $ | (110) |  |
Fair value of assets | 285 |  |  | 320 |  |  | 12 |  |  | 29 |  |
Funded status at end of year | $ | (140) |  |  | $ | (129) |  |  | $ | (96) |  |  | $ | (81) |  |
Amounts Recognized in the Balance Sheet Consist of: |  |  |  |  |  |  |  |
Investments | $ | — |  |  | $ | — |  |  | $ | 3 |  |  | $ | 20 |  |
Other current liabilities | — |  |  | — |  |  | (9) |  |  | (8) |  |
Other noncurrent liabilities | (140) |  |  | (129) |  |  | (90) |  |  | (93) |  |
Net liability recognized | $ | (140) |  |  | $ | (129) |  |  | $ | (96) |  |  | $ | (81) |  |
Amounts Recognized in Accumulated Other Comprehensive Income Consist of: |  |  |  |  |  |  |  |
Net actuarial (gain) loss | $ | 4 |  |  | $ | (4) |  |  | $ | (15) |  |  | $ | (15) |  |
Prior services cost | 3 |  |  | 9 |  |  | 1 |  |  | 1 |  |
Net (income) loss and prior service cost | $ | 7 |  |  | $ | 5 |  |  | $ | (14) |  |  | $ | (14) |  |
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis | Assets and liabilities measured at fair value on a recurring basis consisted of the following at the respective balance sheet dates shown below:
| December 31, 2023 |  | December 31, 2022
| Level 1 |  | Level 2 |  | Level 3 (a) |  | Reclass (b) |  | Total |  | Level 1 |  | Level 2 |  | Level 3 (a) |  | Reclass (b) |  | Total
Assets: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Commodity contracts | $ | 2,886 |  |  | $ | 628 |  |  | $ | 630 |  |  | $ | 14 |  |  | $ | 4,158 |  |  | $ | 3,512 |  |  | $ | 789 |  |  | $ | 791 |  |  | $ | 13 |  |  | $ | 5,105 |
Interest rate swaps | — |  |  | 64 |  |  | — |  |  | — |  |  | 64 |  |  | — |  |  | 135 |  |  | — |  |  | — |  |  | 135 |
Nuclear decommissioning trust – equity securities (c) | 638 |  |  | — |  |  | — |  |  | — |  |  | 638 |  |  | 532 |  |  | — |  |  | — |  |  | — |  |  | 532 |
Nuclear decommissioning trust – debt securities (c) | — |  |  | 734 |  |  | — |  |  | — |  |  | 734 |  |  | — |  |  | 658 |  |  | — |  |  | — |  |  | 658 |
Sub-total | $ | 3,524 |  |  | $ | 1,426 |  |  | $ | 630 |  |  | $ | 14 |  |  | 5,594 |  |  | $ | 4,044 |  |  | $ | 1,582 |  |  | $ | 791 |  |  | $ | 13 |  |  | 6,430 |
Assets measured at net asset value (d): |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Nuclear decommissioning trust – equity securities (c) |  |  |  |  |  |  |  |  | 579 |  |  |  |  |  |  |  |  |  |  | 458 |
Total assets |  |  |  |  |  |  |  |  | $ | 6,173 |  |  |  |  |  |  |  |  |  |  | $ | 6,888 |
Liabilities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Commodity contracts | $ | 3,815 |  |  | $ | 1,395 |  |  | $ | 1,674 |  |  | $ | 14 |  |  | $ | 6,898 |  |  | $ | 5,297 |  |  | $ | 933 |  |  | $ | 2,010 |  |  | $ | 13 |  |  | $ | 8,253 |
Interest rate swaps | — |  |  | 48 |  |  | — |  |  | — |  |  | 48 |  |  | — |  |  | 83 |  |  | — |  |  | — |  |  | 83 |
Total liabilities | $ | 3,815 |  |  | $ | 1,443 |  |  | $ | 1,674 |  |  | $ | 14 |  |  | $ | 6,946 |  |  | $ | 5,297 |  |  | $ | 1,016 |  |  | $ | 2,010 |  |  | $ | 13 |  |  | $ | 8,336 |
____________ (a)See table below for description of Level 3 assets and liabilities. (b)Fair values for each level are determined on a contract basis, but certain contracts are in both an asset and a liability position. This reclassification represents the adjustment needed to reconcile to the gross amounts presented on our consolidated balance sheet. (c)The nuclear decommissioning trust investment is included in the investments line in our consolidated balance sheets. See Note 22. (d)The fair value amounts presented in this line are intended to permit reconciliation of the fair value hierarchy to the amounts presented in our consolidated balance sheets. Certain investments measured at fair value using the net asset value per share (or its equivalent) have not been classified in the fair value hierarchy. Net asset value as a practical expedient is the classification used for assets that do not have readily determinable fair values. As of December 31, 2023 and 2022, all of the Retirement Plan assets were measured at fair value using the net asset value per share (or its equivalent) except as noted and consisted of the following:
| December 31,
| 2023 |  | 2022
Asset Category: |  |  |
Interest-bearing cash (a) | $ | — |  |  | $ | 2 |
Cash commingled trusts | 4 |  |  | 4 |
Equity securities: |  |  |
Global equities | 82 |  |  | 80 |
Fixed income securities: |  |  |
Corporate bonds (b) | 82 |  |  | 107 |
Government bonds | 54 |  |  | 44 |
Other (c) | 18 |  |  | 24 |
Real estate | 28 |  |  | 43 |
Hedge funds | 17 |  |  | 16 |
Total assets measured at net asset value | $ | 285 |  |  | $ | 320 |
___________ (a)Interest -bearing cash is classified as Level 2. (b)Substantially all corporate bonds are rated investment grade by a major ratings agency such as Moody's. (c)Consists primarily of high-yield bonds, emerging market debt, bank loans, securitized bonds and private investment grade fixed income.
Schedule of Accumulated and Projected Benefit Obligations | The following table provides information regarding pension plans with PBO and ABO in excess of the fair value of plan assets.
| December 31,
| 2023 |  | 2022
Pension Plans with PBO and ABO in Excess of Plan Assets: |  |  |
Projected benefit obligations | $ | 425 |  |  | $ | 449 |
Accumulated benefit obligation | $ | 422 |  |  | $ | 447 |
Plan assets | $ | 285 |  |  | $ | 320 |
Schedule of Allocation of Plan Assets | The target asset allocation ranges of pension plan investments by asset category are as follows:
| Target Allocation Ranges
Asset Category: | Vistra Plan |  | Dynegy Plan |  |
Fixed income securities | 50 | % | - | 70% |  | 40 | % | - | 50% |  |  |  |
Global equity securities | 20 | % | - | 28% |  | 28 | % | - | 38% |  |  |  |
Real estate | 6 | % | - | 10% |  | 7 | % | - | 15% |  |  |  |
Credit strategies | 2 | % | - | 6% |  | 4 | % | - | 8% |  |  |  |
Hedge funds | 2 | % | - | 6% |  | 4 | % | - | 8% |  |  |  |
Schedule of Defined Benefit Plan, Assumptions |
| Retirement Plan
| Expected Long-Term Rate of Return
Asset Class: | Vistra Plan |  | Dynegy Plan |  |
Fixed income securities | 5.3 | % |  | 5.1 | % |  |
Global equity securities | 7.4 | % |  | 7.4 | % |  |
Real estate | 5.5 | % |  | 5.5 | % |  |
Credit strategies | 6.5 | % |  | 6.5 | % |  |
Hedge funds | 7.3 | % |  | 7.3 | % |  |
Weighted average | 5.9 | % |  | 6.1 | % |  |
Schedule of Health Care Cost Trend Rates | The following tables provide information regarding the assumed health care cost trend rates.
| December 31,
| 2023 |  | 2022
Assumed Health Care Cost Trend Rates-Not Medicare Eligible: |  |  |
Health care cost trend rate assumed for next year | 7.00 | % |  | 6.80 | %
Rate to which the cost trend is expected to decline (the ultimate trend rate) | 4.50 | % |  | 4.50 | %
Year that the rate reaches the ultimate trend rate | 2033 |  | 2032
Assumed Health Care Cost Trend Rates-Medicare Eligible: |  |  |
Health care cost trend rate assumed for next year (Vistra Plan) | 12.90 | % |  | 10.30 | %
Health care cost trend rate assumed for next year (Split-Participant Plan) | 12.30 | % |  | 10.00 | %
Rate to which the cost trend is expected to decline (the ultimate trend rate) | 4.50 | % |  | 4.50 | %
Year that the rate reaches the ultimate trend rate | 2033 |  | 2032
Schedule of Expected Benefit Payments | Estimated future benefit payments to beneficiaries are as follows:
| 2024 |  | 2025 |  | 2026 |  | 2027 |  | 2028 |  | 2029-2033
Pension benefits | $ | 52 |  |  | $ | 30 |  |  | $ | 36 |  |  | $ | 37 |  |  | $ | 29 |  |  | $ | 142 |
OPEB | $ | 10 |  |  | $ | 9 |  |  | $ | 9 |  |  | $ | 9 |  |  | $ | 8 |  |  | $ | 37 |

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- Definition Tabular disclosure of the major categories of plan assets of pension plans and/or other employee benefit plans. This information may include, but is not limited to, the target allocation of plan assets, the fair value of each major category of plan assets, and the level within the fair value hierarchy in which the fair value measurements fall. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 715 -SubTopic 20 -Subparagraph (d)(5) -Name Accounting Standards Codification -Paragraph 1 -Section 50 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-1 + Details
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