Equity Securities and Indexed Debt Securities (ZENS) (CenterPoint Energy) - Schedule of Securities Classified as Trading (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Debt and Equity Securities, FV-NI [Line Items]
Carrying value	$ 1,439	$ 871
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	$ 251	$ 294
Charter Common
Debt and Equity Securities, FV-NI [Line Items]
Balance of investment owned (in shares)	872,503	872,503
Carrying value	$ 569	$ 577
Energy Transfer Common Units
Debt and Equity Securities, FV-NI [Line Items]
Balance of investment owned (in shares)	50,999,768	0
Carrying value	$ 420	$ 0
Energy Transfer Series G Preferred Units
Debt and Equity Securities, FV-NI [Line Items]
Balance of investment owned (in shares)	192,390	0
Carrying value	$ 196	$ 0
Other
Debt and Equity Securities, FV-NI [Line Items]
Carrying value	$ 3	$ 0