Fair Value Measurements - Schedule of Assets and Liabilities Measured On Recurring Basis (Details) - Fair Value, Recurring - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Assets
Equity securities	$ 579	$ 561
Investments, including money market funds	22	22
Total assets	601	583
Liabilities
Total liabilities	635	619
Houston Electric
Assets
Investments, including money market funds	5	5
Total assets	5	5
CERC
Assets
Investments, including money market funds	16	15
Total assets	16	15
Indexed debt securities derivative
Liabilities
Derivative liability	635	619
Level 1
Assets
Equity securities	579	561
Investments, including money market funds	22	22
Total assets	601	583
Liabilities
Total liabilities	0	0
Level 1 \| Houston Electric
Assets
Investments, including money market funds	5	5
Total assets	5	5
Level 1 \| CERC
Assets
Investments, including money market funds	16	15
Total assets	16	15
Level 1 \| Indexed debt securities derivative
Liabilities
Derivative liability	0	0
Level 2
Assets
Equity securities	0	0
Investments, including money market funds	0	0
Total assets	0	0
Liabilities
Total liabilities	635	619
Level 2 \| Houston Electric
Assets
Investments, including money market funds	0	0
Total assets	0	0
Level 2 \| CERC
Assets
Investments, including money market funds	0	0
Total assets	0	0
Level 2 \| Indexed debt securities derivative
Liabilities
Derivative liability	635	619
Level 3
Assets
Equity securities	0	0
Investments, including money market funds	0	0
Total assets	0	0
Liabilities
Total liabilities	0	0
Level 3 \| Houston Electric
Assets
Investments, including money market funds	0	0
Total assets	0	0
Level 3 \| CERC
Assets
Investments, including money market funds	0	0
Total assets	0	0
Level 3 \| Indexed debt securities derivative
Liabilities
Derivative liability	$ 0	$ 0

Fair value portion of asset recognized for present right to economic benefit.

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