Fair Value Measurements - Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2025	Dec. 31, 2024
Debt securities
Liabilities:
Debt, weighted average interest rate	4.14%	3.99%
Decommissioning fund investments, debt securities average maturities	8 years	7 years
Decommissioning fund investments, debt maturities, one through five years, fair value	$ 783
Decommissioning fund investments, debt maturities, five through ten years, fair value	1,074
Decommissioning fund investments, debt maturities, after ten years, fair value	453
Fair Value, Recurring
Assets:
Sub-total	28	$ 5
Liabilities:
Total liabilities	28	5
Fair Value, Recurring \| Equity securities
Assets:
Assets measured at net asset value	850	821
Fair Value, Recurring \| Debt securities
Assets:
Assets measured at net asset value	323	0
Fair Value, Recurring \| Commodity Contracts
Assets:
Assets	28	5
Liabilities:
Derivative liabilities	28	5
Fair Value, Recurring \| Interest Rate Swaps
Assets:
Assets	0	0
Liabilities:
Derivative liabilities	0	0
Fair Value, Recurring \| Total
Assets:
Sub-total	6,994	6,946
Total assets	8,167	7,767
Liabilities:
Total liabilities	4,998	4,718
Fair Value, Recurring \| Total \| Equity securities
Assets:
Nuclear decommissioning trust, fair value	1,769	1,560
Fair Value, Recurring \| Total \| Debt securities
Assets:
Nuclear decommissioning trust, fair value	1,987	2,059
Fair Value, Recurring \| Total \| Commodity Contracts
Assets:
Assets	3,218	3,231
Liabilities:
Derivative liabilities	4,962	4,691
Fair Value, Recurring \| Total \| Interest Rate Swaps
Assets:
Assets	20	96
Liabilities:
Derivative liabilities	36	27
Level 1 \| Fair Value, Recurring
Assets:
Sub-total	3,926	3,566
Liabilities:
Total liabilities	2,574	2,118
Level 1 \| Fair Value, Recurring \| Equity securities
Assets:
Nuclear decommissioning trust, fair value	1,769	1,560
Level 1 \| Fair Value, Recurring \| Debt securities
Assets:
Nuclear decommissioning trust, fair value	110	83
Level 1 \| Fair Value, Recurring \| Commodity Contracts
Assets:
Assets	2,047	1,923
Liabilities:
Derivative liabilities	2,574	2,118
Level 1 \| Fair Value, Recurring \| Interest Rate Swaps
Assets:
Assets	0	0
Liabilities:
Derivative liabilities	0	0
Level 2 \| Fair Value, Recurring
Assets:
Sub-total	2,313	2,534
Liabilities:
Total liabilities	722	1,002
Level 2 \| Fair Value, Recurring \| Equity securities
Assets:
Nuclear decommissioning trust, fair value	0	0
Level 2 \| Fair Value, Recurring \| Debt securities
Assets:
Nuclear decommissioning trust, fair value	1,877	1,976
Level 2 \| Fair Value, Recurring \| Commodity Contracts
Assets:
Assets	416	462
Liabilities:
Derivative liabilities	686	975
Level 2 \| Fair Value, Recurring \| Interest Rate Swaps
Assets:
Assets	20	96
Liabilities:
Derivative liabilities	36	27
Level 3
Assets:
Assets	727	841
Liabilities:
Derivative liabilities	1,674	1,593
Level 3 \| Fair Value, Recurring
Assets:
Sub-total	727	841
Liabilities:
Total liabilities	1,674	1,593
Level 3 \| Fair Value, Recurring \| Equity securities
Assets:
Nuclear decommissioning trust, fair value	0	0
Level 3 \| Fair Value, Recurring \| Debt securities
Assets:
Nuclear decommissioning trust, fair value	0	0
Level 3 \| Fair Value, Recurring \| Commodity Contracts
Assets:
Assets	727	841
Liabilities:
Derivative liabilities	1,674	1,593
Level 3 \| Fair Value, Recurring \| Interest Rate Swaps
Assets:
Assets	0	0
Liabilities:
Derivative liabilities	$ 0	$ 0

Vistra Corp. 10-Q