Related Party Transactions (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Investments in the Money Pool	$ 0		$ 0		$ 0
CenterPoint Energy [Member] | Operation And Maintenance Expense [Member]
Corporate service charges	30,000,000	$ 31,000,000	93,000,000	$ 90,000,000
CenterPoint Houston [Member] | Operation And Maintenance Expense [Member]
Corporate service charges	3,000,000	4,000,000	11,000,000	11,000,000
Billings to Houston Electric for services provided	$ (2,000,000)	$ (2,000,000)	$ (5,000,000)	$ (5,000,000)