Related Party Transactions (Houston Electric and CERC) (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Houston Electric [Member]
Related Party Transaction [Line Items]
Interest income (expense) (1)	[1]	$ (1)	$ 6	$ 0	$ 9
Cash dividends paid to parent		20	16	405	40
Cash contribution from parent		0	0	0	590
Houston Electric [Member] | Operation and maintenance expense [Member]
Related Party Transaction [Line Items]
Net affiliate service charges (billings)		(4)	(2)	(10)	(4)
Houston Electric [Member] | CenterPoint Energy [Member] | Operation and maintenance expense [Member]
Related Party Transaction [Line Items]
Corporate service charges		45	42	94	94
CERC Corp [Member]
Related Party Transaction [Line Items]
Interest income (expense) (1)	[1]	0	1	0	2
Cash dividends paid to parent		40	83	72	103
Cash contribution from parent		0	0	0	0
Capital Distribution to Parent		286	0	286	0
CERC Corp [Member] | Operation and maintenance expense [Member]
Related Party Transaction [Line Items]
Net affiliate service charges (billings)		4	2	10	4
CERC Corp [Member] | CenterPoint Energy [Member] | Operation and maintenance expense [Member]
Related Party Transaction [Line Items]
Corporate service charges		$ 49	$ 32	$ 104	$ 75
Investments [Member] | Houston Electric [Member]
Related Party Transaction [Line Items]
Weighted average interest rate		0.38%		0.38%		1.98%
Investments [Member] | CERC Corp [Member]
Related Party Transaction [Line Items]
Weighted average interest rate		0.38%		0.38%		1.98%
Accounts and notes receivable (payable) - affiliate companies [Member] | Houston Electric [Member]
Related Party Transaction [Line Items]
Money pool investments (borrowings) (1)	[2]	$ 33		$ 33		$ 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		$ 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.