Debt, Credit Facilities and Financings - Schedule of Line of Credit Facilities (Details) - USD ($) $ in Millions	Oct. 31, 2025	Sep. 30, 2025	May 20, 2025
Debt Instrument [Line Items]
Facility Limit		$ 9,134
Cash Borrowings (Long-Term Debt, Including Amounts Due Currently)		3,944
Letters of Credit Outstanding		981
Available Capacity		3,103
Line of Credit
Debt Instrument [Line Items]
Facility Limit		5,896
Cash Borrowings (Long-Term Debt, Including Amounts Due Currently)		2,456
Letters of Credit Outstanding		981
Available Capacity		2,459
Vistra Operations debt
Debt Instrument [Line Items]
Facility Limit		7,646
Cash Borrowings (Long-Term Debt, Including Amounts Due Currently)		2,456
Letters of Credit Outstanding		981
Available Capacity		3,103
Project-level debt
Debt Instrument [Line Items]
Facility Limit		1,488
Cash Borrowings (Long-Term Debt, Including Amounts Due Currently)		1,488
Letters of Credit Outstanding		0
Available Capacity		0
Revolving Credit Facility | Line of Credit
Debt Instrument [Line Items]
Facility Limit		3,440
Cash Borrowings (Long-Term Debt, Including Amounts Due Currently)		0
Letters of Credit Outstanding		981
Available Capacity		2,459
Term Loan B-3 Facility | Line of Credit
Debt Instrument [Line Items]
Facility Limit		2,456
Cash Borrowings (Long-Term Debt, Including Amounts Due Currently)		2,456
Letters of Credit Outstanding		0
Available Capacity		0
Vistra Operations Commodity-Linked Facility | Revolving Credit Facility
Debt Instrument [Line Items]
Facility Limit		1,750
Cash Borrowings (Long-Term Debt, Including Amounts Due Currently)		0
Letters of Credit Outstanding		0
Available Capacity		644
BCOP Credit Facility
Debt Instrument [Line Items]
Facility Limit		791
Cash Borrowings (Long-Term Debt, Including Amounts Due Currently)		791
Letters of Credit Outstanding		0
Available Capacity		0
BCOP Credit Facility | Bridge Loans
Debt Instrument [Line Items]
Facility Limit		367
Cash Borrowings (Long-Term Debt, Including Amounts Due Currently)		367
Letters of Credit Outstanding		0
Available Capacity		0
BCOP Credit Facility | Bridge Loans | Subsequent Event
Debt Instrument [Line Items]
Cash Borrowings (Long-Term Debt, Including Amounts Due Currently)	$ 106
BCOP Credit Facility | Construction / Term Loans
Debt Instrument [Line Items]
Facility Limit		424
Cash Borrowings (Long-Term Debt, Including Amounts Due Currently)		424
Letters of Credit Outstanding		0
Available Capacity		0
BCOP Credit Facility | Term Loan - Due Dec 2029
Debt Instrument [Line Items]
Facility Limit		120
BCOP Credit Facility | Construction Term Loans Converted to Term Loan Due Dec 2029
Debt Instrument [Line Items]
Facility Limit			$ 88
BCOP Credit Facility | Construction Loan Converted to Term Loan Due Dec 2026
Debt Instrument [Line Items]
Facility Limit		216
Vistra Zero Term Loan B Facility | Revolving Credit Facility
Debt Instrument [Line Items]
Facility Limit		697
Cash Borrowings (Long-Term Debt, Including Amounts Due Currently)		697
Letters of Credit Outstanding		0
Available Capacity		$ 0