Earnings Per Share (CenterPoint Energy) (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended
	May 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Beneficial Conversion Feature	$ 32
Continuing Operations Numerator:
Income (loss) from continuing operations		$ 363	$ (1,053)
Income allocated to preferred shareholders		29	29
Undistributed earnings allocated to preferred shareholders		23	0
Income (loss) available to common shareholders from continuing operations - basic		311	(1,082)
Income (loss) available to common shareholders from discontinued operations - basic and diluted		0	(146)
Add back: Series B Preferred Stock dividend		17	0
Add back: Undistributed earnings allocated to preferred shareholders		23	0
Income (Loss) available to common shareholders - diluted		$ 351	$ (1,228)
Weighted Average Number of Shares Outstanding, Basic [Abstract]
Weighted average common shares outstanding - basic		551,546,000	502,388,000
Plus: Incremental shares from assumed conversions:
Weighted average common shares outstanding - diluted		631,420,000	502,388,000
Earnings (Loss) Per Common Share:
Basic earnings (loss) per common share - continuing operations		$ 0.56	$ (2.15)
Basic earnings (loss) per common share - discontinued operations		0	(0.29)
Basic Earnings (Loss) Per Common Share		0.56	(2.44)
Diluted Earnings (Loss) Per Common Share
Diluted earnings (loss) per common share - continuing operations		0.56	(2.15)
Diluted earnings (loss) per common share - discontinued operations		0	(0.29)
Diluted Earnings (Loss) Per Common Share		$ 0.56	$ (2.44)
Restricted Stock [Member]
Plus: Incremental shares from assumed conversions:
Restricted stock (1)		3,114,000	0
Common Stock [Member] | Restricted Stock [Member]
Diluted Earnings (Loss) Per Common Share
Amount of antidilutive shares excluded from computation of earnings per share			2,567,000
Series B Preferred Stock [Member]
Continuing Operations Numerator:
Income allocated to preferred shareholders		$ 17	$ 17
Plus: Incremental shares from assumed conversions:
Preferred Stock		35,937,000	0
Diluted Earnings (Loss) Per Common Share
Amount of antidilutive shares excluded from computation of earnings per share			35,923,000
Series C Preferred Stock [Member]
Plus: Incremental shares from assumed conversions:
Preferred Stock		40,823,000	0