Related Party Transactions (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Investments in the Money Pool	$ 0		$ 0		$ 0
CenterPoint Energy [Member] | Operation And Maintenance Expense [Member]
Corporate service charges	32,000,000	$ 29,000,000	63,000,000	$ 59,000,000
CenterPoint Houston [Member] | Operation And Maintenance Expense [Member]
Corporate service charges	5,000,000	3,000,000	8,000,000	7,000,000
Billings to Houston Electric for services provided	$ (1,000,000)	$ (2,000,000)	$ (3,000,000)	$ (3,000,000)