Fair Value Measurements - Schedule of Fair Value of Debt (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Carrying Amount | Long-term debt under the Vistra Operations Credit Facilities | Level 2
Debt Instrument [Line Items]
Debt instrument, fair value disclosure	$ 2,421	$ 2,435
Carrying Amount | BCOP Credit Facility | Level 3
Debt Instrument [Line Items]
Debt instrument, fair value disclosure	774	344
Carrying Amount | Vistra Zero Term Loan B Facility | Level 2
Debt Instrument [Line Items]
Debt instrument, fair value disclosure	687	685
Carrying Amount | Vistra Operations Senior Notes | Level 2
Debt Instrument [Line Items]
Debt instrument, fair value disclosure	11,636	12,366
Carrying Amount | Energy Harbor Revenue Bonds | Level 2
Debt Instrument [Line Items]
Debt instrument, fair value disclosure	415	414
Carrying Amount | Equipment Financing Agreements | Level 3
Debt Instrument [Line Items]
Debt instrument, fair value disclosure	55	54
Carrying Amount | Forward Repurchase Obligation | Level 3
Debt Instrument [Line Items]
Debt instrument, fair value disclosure	1,314	1,335
Fair Value | Long-term debt under the Vistra Operations Credit Facilities | Level 2
Debt Instrument [Line Items]
Debt instrument, fair value disclosure	2,461	2,478
Fair Value | BCOP Credit Facility | Level 3
Debt Instrument [Line Items]
Debt instrument, fair value disclosure	790	367
Fair Value | Vistra Zero Term Loan B Facility | Level 2
Debt Instrument [Line Items]
Debt instrument, fair value disclosure	687	697
Fair Value | Vistra Operations Senior Notes | Level 2
Debt Instrument [Line Items]
Debt instrument, fair value disclosure	11,954	12,428
Fair Value | Energy Harbor Revenue Bonds | Level 2
Debt Instrument [Line Items]
Debt instrument, fair value disclosure	437	431
Fair Value | Equipment Financing Agreements | Level 3
Debt Instrument [Line Items]
Debt instrument, fair value disclosure	55	53
Fair Value | Forward Repurchase Obligation | Level 3
Debt Instrument [Line Items]
Debt instrument, fair value disclosure	$ 1,314	$ 1,335