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Equity Securities and Indexed Debt Securities (ZENS) (CenterPoint Energy) - Narrative (Details) - USD ($)
$ in Millions
9 Months Ended
Sep. 30, 2025
Sep. 30, 1999
Subordinated Debt, ZENS, Due 2029    
Debt and Equity Securities, FV-NI [Line Items]    
Outstanding debt balance $ 828  
Subordinated Debt, ZENS, Due 2029    
Debt and Equity Securities, FV-NI [Line Items]    
Aggregate principal   $ 1,000
Subordinated note cash exchangeable percentage of fair value (as a percent) 95.00%  
ZENS annual interest rate (as a percent) 2.00%  
Target annual yield on reference shares (as a percent) 2.309%  
Contingent principal amount of ZENS $ 2