Related Party Transactions (Houston Electric and CERC) - Schedule of Money Pool Investments (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Houston Electric | Investments [Member]
Related Party Transaction [Line Items]
Weighted average interest rate	0.34%	0.24%
CERC Corp | Investments [Member]
Related Party Transaction [Line Items]
Weighted average interest rate	0.34%	0.24%
Accounts and notes receivable (payable) - affiliate companies | Houston Electric
Related Party Transaction [Line Items]
Money pool investments (borrowings)	$ (512)	$ (8)
Accounts and notes receivable (payable) - affiliate companies | CERC Corp
Related Party Transaction [Line Items]
Money pool investments (borrowings)	$ (224)	$ 0