Earnings Per Share (CenterPoint Energy) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2018		Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Net income (loss)	$ (75)		$ 135	$ 90	$ 327
Basic weighted average shares outstanding	431,523,000		430,996,000	431,378,000	430,896,000
Plus: Incremental shares from assumed conversions:
Diluted weighted average shares	431,523,000		433,797,000	434,407,000	433,697,000
Basic earnings (loss) per share
Net income (loss)	$ (0.17)		$ 0.31	$ 0.21	$ 0.76
Diluted earnings (loss) per share
Net income (loss)	$ (0.17)		$ 0.31	$ 0.21	$ 0.75
Restricted Stock [Member]
Anti-dilutive shares excluded from computation of diluted earnings (loss) per share	3,029,000
Plus: Incremental shares from assumed conversions:
Restricted stock (1)	0	[1]	2,801,000	3,029,000	2,801,000

[1] 3,029,000 incremental shares from assumed conversions of restricted stock have not been included in the computation of diluted earnings (loss) per share for the three months ended June 30, 2018 as their inclusion would be anti-dilutive.