Related Party Transactions (Houston Electric and CERC) (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Houston Electric [Member]
Related Party Transaction [Line Items]
Interest income (expense) (1)	[1]	$ 1	$ 3
Cash dividends paid to parent		385	24
Cash contribution from parent		0	590
Houston Electric [Member] | Operation and maintenance expense [Member]
Related Party Transaction [Line Items]
Net affiliate service charges (billings)		(6)	(2)
Houston Electric [Member] | CenterPoint Energy [Member] | Operation and maintenance expense [Member]
Related Party Transaction [Line Items]
Corporate service charges		49	52
CERC Corp [Member]
Related Party Transaction [Line Items]
Interest income (expense) (1)	[1]	0	1
Cash dividends paid to parent		32	20
Cash contribution from parent		0	0
CERC Corp [Member] | Operation and maintenance expense [Member]
Related Party Transaction [Line Items]
Net affiliate service charges (billings)		6	2
CERC Corp [Member] | CenterPoint Energy [Member] | Operation and maintenance expense [Member]
Related Party Transaction [Line Items]
Corporate service charges		$ 55	$ 43
Investments [Member] | Houston Electric [Member]
Related Party Transaction [Line Items]
Weighted average interest rate		1.98%		1.98%
Investments [Member] | CERC Corp [Member]
Related Party Transaction [Line Items]
Weighted average interest rate		1.98%		1.98%
Accounts and notes receivable (payable) - affiliate companies [Member] | Houston Electric [Member]
Related Party Transaction [Line Items]
Money Pool Borrowings	[2]	$ (133)
Money pool investments (borrowings) (1)	[2]			$ 481
Accounts and notes receivable (payable) - affiliate companies [Member] | CERC Corp [Member]
Related Party Transaction [Line Items]
Money pool investments (borrowings) (1)	[2]	$ 0		$ 0

[1] Interest income is included in Other income (expense), net and interest expense is included in Interest and other finance charges on Houston Electric’s and CERC’s respective Condensed Statements of Consolidated Income.

[2] Included in Accounts and notes receivable (payable)–affiliated companies on Houston Electric’s and CERC’s respective Condensed Consolidated Balance Sheets.