Related Party Transactions (Houston Electric and CERC) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Houston Electric
Related Party Transaction [Line Items]
Cash dividends paid to parent	$ 37	$ 0
Contribution to parent for sale of Arkansas and Oklahoma Natural Gas businesses	0	0
Contribution from parent	637	0
Non-cash capital contribution from parent in payment for property, plant and equipment below	38	0
Payable to parent for property, plant and equipment below	52	0
Property, plant and equipment from parent	90	0
Houston Electric | Operation and maintenance expense
Related Party Transaction [Line Items]
Net affiliate service charges (billings)	(6)	(1)
Houston Electric | CenterPoint Energy | Operation and maintenance expense
Related Party Transaction [Line Items]
Corporate service charges	39	43
CERC Corp
Related Party Transaction [Line Items]
Cash dividends paid to parent	23	0
Contribution to parent for sale of Arkansas and Oklahoma Natural Gas businesses	720	0
Contribution from parent	0	0
Non-cash capital contribution from parent in payment for property, plant and equipment below	46	0
Payable to parent for property, plant and equipment below	41	0
Property, plant and equipment from parent	87	0
CERC Corp | Operation and maintenance expense
Related Party Transaction [Line Items]
Net affiliate service charges (billings)	6	1
CERC Corp | CenterPoint Energy | Operation and maintenance expense
Related Party Transaction [Line Items]
Corporate service charges	$ 45	$ 50
Investments | Houston Electric
Related Party Transaction [Line Items]
Weighted average interest rate (as a percent)	0.55%		0.34%
Investments | CERC Corp
Related Party Transaction [Line Items]
Weighted average interest rate (as a percent)	0.55%		0.34%
Accounts and notes receivable (payable) - affiliate companies | Houston Electric
Related Party Transaction [Line Items]
Money pool investments (borrowings)	$ 354		$ (512)
Accounts and notes receivable (payable) - affiliate companies | CERC Corp
Related Party Transaction [Line Items]
Money pool investments (borrowings)	$ 0		$ (224)