Earnings Per Share (CenterPoint Energy) (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended
	May 31, 2020	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Beneficial conversion feature	$ 32			$ 0	$ 32
Continuing Operations Numerator:
Income (loss) from continuing operations		$ 251	$ 135	614	(918)
Less: Preferred stock dividend requirement (Note 19)		30	37	59	66
Amortization of beneficial conversion feature		0	9	0	9
Undistributed earnings allocated to preferred shareholders (1)		0	0	0	0
Income (loss) available to common shareholders from continuing operations - basic		221	89	555	(993)
Add back: Undistributed earnings allocated to preferred shareholders (1)		0	0	0	0
Income (loss) available to common shareholders from continuing operations - diluted		221	89	555	(993)
Loss available to common shareholders from discontinued operations - basic and diluted		0	(30)	0	(176)
Income (loss) available to common shareholders - basic and diluted		221	59	555	(1,169)
Income (loss) available to common shareholders - basic and diluted		$ 221	$ 59	$ 555	$ (1,169)
Weighted Average Number of Shares Outstanding, Basic [Abstract]
Weighted average common shares outstanding - basic		585,720,000	528,066,000	568,728,000	515,227,000
Plus: Incremental shares from assumed conversions:
Weighted average common shares outstanding - diluted		596,330,000	530,837,000	596,130,000	515,227,000
Earnings (Loss) Per Common Share:
Basic earnings (loss) per common share - continuing operations (in dollars per share)		$ 0.38	$ 0.17	$ 0.98	$ (1.93)
Basic earnings (loss) per common share - discontinued operations (in dollars per share)		0	(0.06)	0	(0.34)
Basic Earnings (Loss) Per Common Share (in dollars per share)		0.38	0.11	0.98	(2.27)
Diluted Earnings (Loss) Per Common Share
Diluted earnings (loss) per common share - continuing operations (in dollars per share)		0.37	0.17	0.93	(1.93)
Diluted earnings (loss) per common share - discontinued operations (in dollars per share)		0	(0.06)	0	(0.34)
Diluted Earnings (Loss) Per Common Share (in dollars per share)		$ 0.37	$ 0.11	$ 0.93	$ (2.27)
Restricted Stock
Plus: Incremental shares from assumed conversions:
Restricted stock (2)		3,558,000	2,771,000	3,558,000	0
Common Stock | Restricted Stock
Diluted Earnings (Loss) Per Common Share
Amount of antidilutive shares excluded from computation of earnings per share					2,771,000
Series B Preferred Stock
Continuing Operations Numerator:
Less: Preferred stock dividend requirement (Note 19)		$ 17	$ 17	$ 34	$ 34
Add back: Series B Preferred Stock dividend		$ 0	$ 0	$ 0	$ 0
Plus: Incremental shares from assumed conversions:
Preferred Stock		0	0	0	0
Diluted Earnings (Loss) Per Common Share
Amount of antidilutive shares excluded from computation of earnings per share		35,898,000	35,940,000	35,917,000	35,923,000
Series C Preferred Stock
Continuing Operations Numerator:
Less: Preferred stock dividend requirement (Note 19)		$ 0	$ 7	$ 0	$ 7
Plus: Incremental shares from assumed conversions:
Preferred Stock		7,052,000	0	23,844,000	0
Diluted Earnings (Loss) Per Common Share
Amount of antidilutive shares excluded from computation of earnings per share			29,465,000		14,571,000