Earnings Per Share (CenterPoint Energy) (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Preferred Stock Dividends, Income Statement Impact		$ 29	$ 29
Continuing Operations Numerator:
Income (loss) from continuing operations		(1,053)	143
Preferred stock dividend requirement		29	29
Income (loss) available to common shareholders - basic		(1,228)	140
Net income (loss) from Discontinued Operations		$ (146)	$ 26
Denominator:
Weighted average common shares outstanding - basic		502,388,000	501,521,000
Weighted average common shares outstanding - diluted		502,388,000	503,944,000
Earnings (loss) per common share:
Basic earnings (loss) per common share - continuing operations		$ (2.15)	$ 0.23
Basic earnings (loss) per common share - discontinued operations		(0.29)	0.05
Basic Earnings (Loss) Per Common Share		(2.44)	0.28
Diluted earnings (loss) per common share - continuing operations		(2.15)	0.23
Diluted earnings (loss) per common share - discontinued operations		(0.29)	0.05
Diluted Earnings (Loss) Per Common Share		$ (2.44)	$ 0.28
Restricted Stock [Member]
Denominator:
Restricted stock (1)	[1]	0	2,423,000
Common Stock [Member]
Amount of antidilutive shares excluded from computation of earnings per share		2,567,000
Series B Preferred Stock [Member]
Amount of antidilutive shares excluded from computation of earnings per share		35,923,000	34,354,000
Preferred Stock Dividends, Income Statement Impact		$ 17	$ 17
Continuing Operations Numerator:
Preferred stock dividend requirement	[2]	$ 0	$ 0
Denominator:
Series B Preferred Stock (2)	[2]	0	0
Continuing Operations [Member]
Continuing Operations Numerator:
Income (loss) available to common shareholders - basic		$ (1,082)	$ 114
Income (Loss) available to common shareholders from continuing operations - diluted		$ (1,082)	$ 114

[1] 2,567,000 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 March 31, 2020, 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 months ended March 31, 2020 and 2019 excludes Series B Preferred Stock dividends of $17 million and $17 million, respectively, and 35,923,000 and 34,354,000 potentially dilutive shares, respectively, because to include them would be anti-dilutive. However, these could be potentially dilutive in the future.