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Fair Value Measurements - Schedule of Estimated Fair Value of Financial Instruments (Details) - USD ($)
$ in Millions
Dec. 31, 2024
Dec. 31, 2023
Carrying amount    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Long-term debt, fair value $ 20,961 $ 18,609
Carrying amount | Houston Electric    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Long-term debt, fair value 8,822 7,587
Carrying amount | CERC    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Long-term debt, fair value 5,184 4,670
Fair value    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Long-term debt, fair value 19,597 17,804
Fair value | Houston Electric    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Long-term debt, fair value 7,746 6,917
Fair value | CERC    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Long-term debt, fair value $ 5,032 $ 4,627