Related Party Transactions (Houston Electric and CERC) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Capital distribution to parent associated with the Internal Spin		$ 0	$ 0	$ 0
Houston Electric [Member]
Related Party Transaction [Line Items]
Cash dividends paid to parent		209	180	135
Cash contribution from parent		200	0	374
Capital distribution to parent associated with the Internal Spin		0	0	0
Houston Electric [Member] | Other, net [Member]
Related Party Transaction [Line Items]
Interest income (expense), net (1)	[1]	1	2	(4)
Houston Electric [Member] | Operation And Maintenance Expense [Member]
Related Party Transaction [Line Items]
Net affiliate service charges (billings)		(17)	(9)	(8)
Houston Electric [Member] | Operation And Maintenance Expense [Member] | CenterPoint Energy [Member]
Related Party Transaction [Line Items]
Corporate service charges		190	188	179
Houston Electric [Member] | Accounts and notes receivable (payable) - affiliate companies [Member]
Related Party Transaction [Line Items]
Money pool investments (borrowings) (1)	[2]	$ (1)	$ (60)
Houston Electric [Member] | Investments [Member]
Related Party Transaction [Line Items]
Weighted average interest rate		2.42%	1.90%
CERC Corp [Member]
Related Party Transaction [Line Items]
Cash dividends paid to parent		$ 360	$ 601	643
Cash contribution from parent		960	38	72
Capital distribution to parent associated with the Internal Spin		1,473	0	0
CERC Corp [Member] | Other, net [Member]
Related Party Transaction [Line Items]
Interest income (expense), net (1)	[1]	0	0	0
CERC Corp [Member] | Operation And Maintenance Expense [Member]
Related Party Transaction [Line Items]
Net affiliate service charges (billings)		17	9	8
CERC Corp [Member] | Operation And Maintenance Expense [Member] | CenterPoint Energy [Member]
Related Party Transaction [Line Items]
Corporate service charges		147	128	$ 125
CERC Corp [Member] | Accounts and notes receivable (payable) - affiliate companies [Member]
Related Party Transaction [Line Items]
Money pool investments (borrowings) (1)	[2]	$ 114	$ (570)
CERC Corp [Member] | Investments [Member]
Related Party Transaction [Line Items]
Weighted average interest rate		2.42%	1.90%

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

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