Earnings Per Share (CenterPoint Energy) (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Preferred Stock Dividends, Income Statement Impact		$ 29	$ 5	$ 88	$ 5
Numerator:
Income available to common shareholders - basic		241	153	546	243
Preferred stock dividend requirement		29	5	88	5
Net Income (Loss) Available to Common Stockholders, Diluted		$ 241	$ 153	$ 546	$ 243
Denominator:
Weighted average common shares outstanding - basic		502,228,000	431,554,000	501,986,000	431,437,000
Weighted average common shares outstanding - diluted		505,080,000	434,891,000	504,838,000	434,774,000
Earnings per common share:
Basic earnings per common share		$ 0.48	$ 0.35	$ 1.09	$ 0.56
Diluted earnings per common share		$ 0.47	$ 0.35	$ 1.08	$ 0.56
Restricted Stock [Member]
Denominator:
Restricted stock		2,852,000	3,337,000	2,852,000	3,337,000
Series B Preferred Stock [Member]
Preferred Stock Dividends, Income Statement Impact		$ 17	$ 0	$ 51	$ 0
Numerator:
Preferred stock dividend requirement		$ 0	$ 0	$ 0	$ 0
Denominator:
Series B Preferred Stock (1)	[1]	0	0	0	0
Earnings per common share:
Amount of antidilutive shares excluded from computation of earnings per share		33,537,000		33,537,000

[1] 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 nine months ended September 30, 2019 excludes Series B Preferred Stock dividends of $17 million and $51 million, respectively, and 33,537,000 and 33,537,000 potentially dilutive shares, respectively, because to include them would be anti-dilutive. However, these could be potentially dilutive in the future.