Earnings Per Share (CenterPoint Energy) (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Numerator:
Income available to common shareholders - basic		$ 140	$ 165
Preferred stock dividend requirement		29	0
Net Income (Loss) Available to Common Stockholders, Diluted		$ 140	$ 165
Denominator:
Weighted average common shares outstanding - basic		501,521,000	431,231,000
Weighted average common shares outstanding - diluted		503,944,000	434,008,000
Earnings per common share:
Basic earnings per common share		$ 0.28	$ 0.38
Diluted earnings per common share		$ 0.28	$ 0.38
Restricted Stock [Member]
Denominator:
Restricted stock (1)	[1]	2,423,000	2,777,000
Series B Preferred Stock [Member]
Numerator:
Preferred stock dividend requirement		$ 0	$ 0
Denominator:
Series B Preferred Stock (2)	[2]	0	0
Earnings per common share:
Amount of antidilutive shares excluded from computation of earnings per share		34,354,000

[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.

[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 months ended March 31, 2019 excludes 34,354,000 potentially dilutive shares because to include them would be anti-dilutive. However, these shares could be potentially dilutive in the future.