Related Party Transactions (Houston Electric and CERC) - Schedule of Amounts Charged For Services (Details) - Operation And Maintenance Expense - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Houston Electric
Related Party Transaction [Line Items]
Net affiliate service charges (billings)	$ (7)	$ (16)	$ (8)
CERC Corp
Related Party Transaction [Line Items]
Net affiliate service charges (billings)	7	16	8
CenterPoint Energy | Houston Electric
Related Party Transaction [Line Items]
Corporate service charges	189	197	177
CenterPoint Energy | CERC Corp
Related Party Transaction [Line Items]
Corporate service charges	$ 216	$ 212	$ 141