Proposed Merger with Vectren (CenterPoint Energy) (Details) - USD ($) $ / shares in Units, $ in Millions	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Amount of cash to be paid to acquire Vectren	$ 6,000
Cash to be paid per share of Vectren common stock prior to closing of the Merger	$ 72.00
Short-term debt	$ 0	$ 39
Anticipated amount of short and long-term debt at the closing of the Merger	2,500
Vectren [Member]
Short-term debt	248
Long-term debt, including current maturities	2,000
Termination fee	150
CenterPoint Energy [Member]
Termination fee	$ 210