Earnings Per Share (CenterPoint Energy) (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Beneficial Conversion Feature				$ 32
Amortization of Beneficial Conversion Feature		$ 9	$ 0	9	$ 0
Continuing Operations Numerator:
Income (loss) from continuing operations		135	151	(918)	294
Preferred stock dividend requirement		37	30	66	59
Amortization of Beneficial Conversion Feature		9	0	9	0
Undistributed earnings allocated to preferred shareholders (1)	[1]	0	0	0	0
Income (loss) available to common shareholders from continuing operations - basic		59	165	(1,169)	305
Net income (loss) from Discontinued Operations		$ (30)	$ 44	$ (176)	$ 70
Denominator:
Weighted average common shares outstanding - basic		528,066,000	502,200,000	515,227,000	501,862,000
Weighted average common shares outstanding - diluted		530,837,000	504,831,000	515,227,000	504,493,000
Earnings (loss) per common share:
Basic earnings (loss) per common share - continuing operations		$ 0.17	$ 0.24	$ (1.93)	$ 0.47
Basic earnings (loss) per common share - discontinued operations		(0.06)	0.09	(0.34)	0.14
Basic Earnings (Loss) Per Common Share		0.11	0.33	(2.27)	0.61
Diluted Earnings (Loss) Per Common Share
Diluted earnings (loss) per common share - continuing operations		0.17	0.24	(1.93)	0.47
Diluted earnings (loss) per common share - discontinued operations		(0.06)	0.09	(0.34)	0.14
Diluted Earnings (Loss) Per Common Share		$ 0.11	$ 0.33	$ (2.27)	$ 0.61
Restricted Stock [Member]
Denominator:
Restricted stock (4)	[2]	2,771,000	2,631,000	0	2,631,000
Common Stock [Member]
Amount of antidilutive shares excluded from computation of earnings per share				2,771,000
Series B Preferred Stock [Member]
Amount of antidilutive shares excluded from computation of earnings per share		35,940,000	32,121,000	35,923,000	32,121,000
Continuing Operations Numerator:
Preferred stock dividend requirement		$ 17	$ 17	$ 34	$ 34
Add back: Preferred stock dividend requirement	[3]	$ 0	$ 0	$ 0	$ 0
Denominator:
Preferred Stock	[3]	0	0	0	0
Series C Preferred Stock [Member]
Amortization of Beneficial Conversion Feature		$ 9		$ 9
Amount of antidilutive shares excluded from computation of earnings per share		29,465,000		14,571,000
Continuing Operations Numerator:
Preferred stock dividend requirement		$ 7		$ 7
Amortization of Beneficial Conversion Feature		9		9
Add back: Preferred stock dividend requirement	[4]	$ 0	$ 0	$ 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		$ 89	$ 121	$ (993)	$ 235
Income (Loss) available to common shareholders from continuing operations - diluted		$ 89	$ 121	$ (993)	$ 235

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

[2] 2,771,000 incremental common shares from assumed conversions of restricted stock have not been included in the computation of diluted earnings (loss) per share for the six months ended June 30, 2020, respectively, as their inclusion would be anti-dilutive.

[3] The computation of diluted earnings per common share outstanding for the three and six months ended June 30, 2020 includes the reduction for Series B Preferred Stock dividends of $17 million and $34 million, respectively, within the numerator and 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 six months ended June 30, 2019 includes the reduction for Series B Preferred Stock dividends of $17 million and $34 million, within the numerator, respectively, and excludes 32,121,000 and 32,121,000 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 six months ended June 30, 2020 includes the reduction for Series C Preferred Stock dividends of $7 million and $7 million, respectively, including deemed dividends on the Series C Preferred Stock from the beneficial conversion feature of $9 million and $9 million, respectively, within the numerator and excludes 29,465,000 and 14,571,000 potentially dilutive shares, respectively, of Series C Preferred Stock from the denominator because the shares would be anti-dilutive.