Earnings Per Share (CenterPoint Energy) (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Beneficial Conversion Feature				$ 32	$ 0
Amortization of Beneficial Conversion Feature		$ 16	$ 0	25	0
Continuing Operations Numerator:
Income (loss) from continuing operations		127	251	(791)	545
Preferred stock dividend requirement		36	29	102	88
Amortization of Beneficial Conversion Feature		16	0	25	0
Undistributed earnings allocated to preferred shareholders (1)	[1]	0	0	0	0
Income (loss) available to common shareholders from continuing operations - basic and diluted		69	241	(1,100)	546
Net income (loss) from Discontinued Operations		$ (6)	$ 19	$ (182)	$ 89
Denominator:
Weighted average common shares outstanding - basic		544,811,000	502,228,000	525,160,000	501,986,000
Weighted average common shares outstanding - diluted		548,188,000	505,080,000	525,160,000	504,838,000
Earnings (loss) per common share:
Basic earnings (loss) per common share - continuing operations		$ 0.14	$ 0.44	$ (1.75)	$ 0.91
Basic earnings (loss) per common share - discontinued operations		(0.01)	0.04	(0.35)	0.18
Basic Earnings (Loss) Per Common Share		0.13	0.48	(2.10)	1.09
Diluted Earnings (Loss) Per Common Share
Diluted earnings (loss) per common share - continuing operations		0.14	0.44	(1.75)	0.91
Diluted earnings (loss) per common share - discontinued operations		(0.01)	0.03	(0.35)	0.17
Diluted Earnings (Loss) Per Common Share		$ 0.13	$ 0.47	$ (2.10)	$ 1.08
Restricted Stock [Member]
Denominator:
Restricted stock (4)	[2]	3,377,000	2,852,000	0	2,852,000
Common Stock [Member]
Amount of antidilutive shares excluded from computation of earnings per share				3,377,000
Series B Preferred Stock [Member]
Amount of antidilutive shares excluded from computation of earnings per share		35,940,000	33,537,000	35,923,000	33,537,000
Continuing Operations Numerator:
Preferred stock dividend requirement		$ 17	$ 17	$ 51	$ 51
Denominator:
Preferred Stock	[3]	0	0	0	0
Series C Preferred Stock [Member]
Amount of antidilutive shares excluded from computation of earnings per share		47,355,000		25,578,000
Continuing Operations Numerator:
Preferred stock dividend requirement		$ 7	$ 0	$ 14	$ 0
Denominator:
Preferred Stock	[4]	0	0	0	0
Continuing Operations [Member]
Continuing Operations Numerator:
Income (loss) available to common shareholders from continuing operations - basic and diluted		$ 75	$ 222	$ (918)	$ 457

[1] There were no undistributed earnings to be allocated to participating securities for the three and nine months ended September 30, 2020.

[2] 3,377,000 incremental common shares from assumed conversions of restricted stock have not been included in the computation of diluted earnings (loss) per share for the nine months ended September 30, 2020, respectively, as their inclusion would be anti-dilutive.

[3] The computation of diluted earnings per common share outstanding for the three and nine months ended September 30, 2020 excludes 35,940,000 and 35,923,000 potentially dilutive shares from the denominator, respectively, because the shares would be anti-dilutive. The computation of diluted earnings per common share outstanding for the three and nine months ended September 30, 2019 excludes 33,537,000 and 33,537,000 potentially dilutive shares from the denominator, respectively, because the shares would be anti-dilutive.

[4] The computation of diluted earnings per common share outstanding for the three and nine months ended September 30, 2020 excludes 47,355,000 and 25,578,000 potentially dilutive shares, respectively, of Series C Preferred Stock from the denominator because the shares would be anti-dilutive.