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Pension and Other Postretirement Employee Benefits (OPEB) Plans - Schedule of Defined Benefit Plans Disclosures (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Components of Net Pension and Benefit Cost:      
Net periodic pension and OPEB cost $ 14 $ 6 $ 14
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income:      
Net (gain) loss (5) 23 24
Change in Plan Assets:      
Fair value of assets at beginning of period 30    
Fair value of assets at end of year 28 30  
Funded Status:      
Fair value of assets 28 30  
Pension costs      
Components of Net Pension and Benefit Cost:      
Service cost 3 4 5
Interest cost 21 17 16
Expected return on assets (18) (19) (18)
Amortization of unrecognized amounts, net 3 0 3
Net periodic pension and OPEB cost 9 2 6
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income:      
Net (gain) loss 7 (16) (27)
Prior service (credit) cost (6) 9 0
Curtailment and settlements 0 0 (2)
Total recognized in net periodic benefit cost and other comprehensive income 10 (5) (23)
Change in Pension and Postretirement Benefit Obligations:      
Projected benefit obligation at beginning of period 449 605  
Service cost 3 4 5
Interest cost 21 17 16
Participant contributions 0 0  
Plan amendments 1 9  
Actuarial (gain) loss 10 (113)  
Benefits paid (59) (73)  
Projected benefit obligation at end of year 425 449 605
Accumulated benefit obligation at end of year 422 447  
Change in Plan Assets:      
Fair value of assets at beginning of period 320 470  
Employer contributions 0 0 1
Participant contributions 0 0  
Actual gain (loss) on assets 24 (77)  
Transfers 0 0  
Benefits paid (59) (73)  
Fair value of assets at end of year 285 320 470
Funded Status:      
Projected benefit obligation (425) (449) (605)
Fair value of assets 285 320 $ 470
Funded status at end of year (140) (129)  
Amounts Recognized in the Balance Sheet Consist of:      
Investments 0 0  
Other current liabilities 0 0  
Other noncurrent liabilities (140) (129)  
Net liability recognized (140) (129)  
Amounts Recognized in Accumulated Other Comprehensive Income Consist of:      
Net actuarial (gain) loss 4 (4)  
Prior services cost 3 9  
Net (income) loss and prior service cost $ 7 $ 5  
Pension costs | Vistra Plan, Dynegy Plan And EEI Plan      
Assumptions Used to Determine Net Periodic Pension and Benefit Cost:      
Discount rate 5.16% 2.84% 2.50%
Expected rate of compensation increase 3.79% 3.49% 3.41%
Interest crediting rate for cash balance 3.00% 3.00% 3.00%
Assumptions Used to Determine Benefit Obligations at Period End:      
Discount rate 4.97% 5.16% 2.84%
Expected rate of compensation increase 3.64% 3.79% 3.49%
Interest crediting rate for cash balance plans 3.50% 3.00% 3.00%
Pension costs | Expected return on plan assets (Vistra Plan)      
Assumptions Used to Determine Net Periodic Pension and Benefit Cost:      
Expected return on plan assets 5.85% 4.24% 3.77%
Pension costs | Expected return on plan assets (Dynegy Plan)      
Assumptions Used to Determine Net Periodic Pension and Benefit Cost:      
Expected return on plan assets 5.85% 4.77% 4.42%
Pension costs | Expected return on plan assets (EEI Plan)      
Assumptions Used to Determine Net Periodic Pension and Benefit Cost:      
Expected return on plan assets 0.00% 4.92% 4.72%
OPEB costs      
Components of Net Pension and Benefit Cost:      
Service cost $ 1 $ 1 $ 1
Interest cost 5 4 4
Expected return on assets (1) (1) (2)
Amortization of unrecognized amounts, net 0 0 5
Net periodic pension and OPEB cost 5 4 8
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income:      
Net (gain) loss 0 (22) (10)
Prior service (credit) cost 0 0 (2)
Curtailment and settlements 0 0 0
Total recognized in net periodic benefit cost and other comprehensive income 5 (18) (4)
Change in Pension and Postretirement Benefit Obligations:      
Projected benefit obligation at beginning of period 110 146  
Service cost 1 1 1
Interest cost 5 4 4
Participant contributions 3 2  
Plan amendments 0 0  
Actuarial (gain) loss 1 (30)  
Benefits paid (12) (13)  
Projected benefit obligation at end of year 108 110 146
Accumulated benefit obligation at end of year 0 0  
Change in Plan Assets:      
Fair value of assets at beginning of period 29 39  
Employer contributions 9 9 9
Participant contributions 3 2  
Actual gain (loss) on assets 2 (6)  
Transfers (19) (2)  
Benefits paid (12) (13)  
Fair value of assets at end of year 12 29 39
Funded Status:      
Projected benefit obligation (108) (110) (146)
Fair value of assets 12 29 $ 39
Funded status at end of year (96) (81)  
Amounts Recognized in the Balance Sheet Consist of:      
Investments 3 20  
Other current liabilities (9) (8)  
Other noncurrent liabilities (90) (93)  
Net liability recognized (96) (81)  
Amounts Recognized in Accumulated Other Comprehensive Income Consist of:      
Net actuarial (gain) loss (15) (15)  
Prior services cost 1 1  
Net (income) loss and prior service cost $ (14) $ (14)  
OPEB costs | Vistra Plan, Split-Participant Plan And Dynegy Plan      
Assumptions Used to Determine Net Periodic Pension and Benefit Cost:      
Discount rate 5.18% 2.87% 2.51%
Assumptions Used to Determine Benefit Obligations at Period End:      
Discount rate 4.98% 5.18% 2.87%
OPEB costs | Expected return on plan assets (EEI Union)      
Assumptions Used to Determine Net Periodic Pension and Benefit Cost:      
Expected return on plan assets 3.89% 3.92% 6.79%
OPEB costs | Expected return on plan assets (EEI Salaried)      
Assumptions Used to Determine Net Periodic Pension and Benefit Cost:      
Expected return on plan assets 4.85% 3.41% 2.95%