Equity Securities and Indexed Debt Securities (ZENS) (CenterPoint Energy) - Schedule of Securities Classified as Trading (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Debt and Equity Securities, FV-NI [Line Items]
Carrying Value	$ 720	$ 1,439
AT&T Common
Debt and Equity Securities, FV-NI [Line Items]
Balance of investment owned (in shares)	10,212,945	10,212,945
Carrying Value	$ 241	$ 251
Charter Common
Debt and Equity Securities, FV-NI [Line Items]
Balance of investment owned (in shares)	872,503	872,503
Carrying Value	$ 476	$ 569
Energy Transfer Common Units
Debt and Equity Securities, FV-NI [Line Items]
Balance of investment owned (in shares)	0	50,999,768
Carrying Value	$ 0	$ 420
Energy Transfer Series G Preferred Units
Debt and Equity Securities, FV-NI [Line Items]
Balance of investment owned (in shares)	0	192,390
Carrying Value	$ 0	$ 196
Other
Debt and Equity Securities, FV-NI [Line Items]
Carrying Value	$ 3	$ 3