Earnings Per Share (CenterPoint Energy) (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Numerator:
Income (loss) available to common shareholders - basic		$ 165	$ (75)	$ 305	$ 90
Preferred stock dividend requirement		30	0	59	0
Net Income (Loss) Available to Common Stockholders, Diluted		$ 165	$ (75)	$ 305	$ 90
Denominator:
Weighted average common shares outstanding - basic		502,200,000	431,523,000	501,862,000	431,378,000
Weighted average common shares outstanding - diluted		504,831,000	431,523,000	504,493,000	434,407,000
Earnings per common share:
Basic earnings (loss) per common share		$ 0.33	$ (0.17)	$ 0.61	$ 0.21
Diluted earnings (loss) per common share		$ 0.33	$ (0.17)	$ 0.61	$ 0.21
Restricted Stock [Member]
Denominator:
Restricted stock (1)	[1]	2,631,000	0	2,631,000	3,029,000
Common Stock [Member]
Earnings per common share:
Amount of antidilutive shares excluded from computation of earnings per share			3,029,000
Series B Preferred Stock [Member]
Numerator:
Preferred stock dividend requirement		$ 0	$ 0	$ 0	$ 0
Denominator:
Series B Preferred Stock (2)	[2]	0	0	0	0
Earnings per common share:
Amount of antidilutive shares excluded from computation of earnings per share		32,121,000		32,121,000

[1] The potentially dilutive impact from restricted stock awards applies the treasury stock method. Under this method, an increase in the average fair market value of Common Stock can result in a greater dilutive impact from these securities. 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.

[2] The potentially dilutive impact from Series B Preferred Stock applies the if-converted method in calculating diluted earnings per common share. Under this method, diluted earnings per common share is adjusted for the more dilutive effect of the Series B Preferred Stock as a result of either its accumulated dividend for the period in the numerator or the assumed-converted common share equivalent in the denominator. The computation of diluted earnings per common share outstanding for the three and six months ended June 30, 2019 excludes 32,121,000 and 32,121,000 potentially dilutive shares, respectively, because to include them would be anti-dilutive. However, these shares could be potentially dilutive in the future.