Equity Securities and Indexed Debt Securities (ZENS) (CenterPoint Energy) - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 1999
Debt and Equity Securities, FV-NI [Line Items]
Unrealized gains (losses)	$ 49	$ (206)	$ 56	$ (370)
Subordinated Debt ZENS
Debt and Equity Securities, FV-NI [Line Items]
Debt instrument, face amount	$ 828		$ 828		$ 1,000
Subordinated note cash exchangeable percentage of fair value (as a percent)			95.00%
ZENS annual interest rate (as a percent)	2.00%		2.00%
Target annual yield on reference shares (as a percent)	2.309%		2.309%
Contingent principal amount of ZENS	$ 20		$ 20