Equity Securities and Indexed Debt Securities (ZENS) (CenterPoint Energy) - Schedule of Gain (Loss) On Equity Securities (CenterPoint Energy) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Debt and Equity Securities, FV-NI [Line Items]
Gain (loss) on equity securities	$ (172)	$ 49	$ 282
AT&T Common
Debt and Equity Securities, FV-NI [Line Items]
Gain (loss) on equity securities	(43)	(105)	108
Charter Common
Debt and Equity Securities, FV-NI [Line Items]
Gain (loss) on equity securities	(8)	154	174
Energy Transfer Common Units
Debt and Equity Securities, FV-NI [Line Items]
Gain (loss) on equity securities	(124)	0	0
Energy Transfer Series G Preferred Units
Debt and Equity Securities, FV-NI [Line Items]
Gain (loss) on equity securities	2	0	0
Other
Debt and Equity Securities, FV-NI [Line Items]
Gain (loss) on equity securities	$ 1	$ 0	$ 0