STATEMENTS OF CONSOLIDATED COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Tax benefit (expense) on adjustment related to pension and postretirement plans	$ 2	$ (6)	$ 4
Tax expense (benefit) on net deferred gain (loss) from cash flow hedges	(4)	(2)	0
Tax expense (benefit) on deferred loss from cash flow hedges realized in net income	0	0	1
Houston Electric [Member]
Tax expense (benefit) on net deferred gain (loss) from cash flow hedges	(4)	0	0
CERC Corp [Member]
Tax benefit (expense) on adjustment related to pension and postretirement plans	(1)	(4)	4
Tax expense (benefit) on net deferred gain (loss) from cash flow hedges	$ 0	$ (1)	$ 0