Equity Securities and Indexed Debt Securities (ZENS) (CenterPoint Energy) - Schedule of Gain (Loss) On Equity Securities (CenterPoint Energy) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Debt and Equity Securities, FV-NI [Line Items]
Gain (loss) on equity securities	$ (17)	$ (23)
AT&T Common
Debt and Equity Securities, FV-NI [Line Items]
Gain (loss) on equity securities	(10)	15
Charter Common
Debt and Equity Securities, FV-NI [Line Items]
Gain (loss) on equity securities	(93)	(38)
Energy Transfer Common Units
Debt and Equity Securities, FV-NI [Line Items]
Gain (loss) on equity securities	95	0
Energy Transfer Series G Preferred Units
Debt and Equity Securities, FV-NI [Line Items]
Gain (loss) on equity securities	$ (9)	$ 0