Earnings Per Share (CenterPoint Energy) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Beneficial Conversion Feature	$ 32	$ 0	$ 0
Numerator:
Income (loss) from continuing operations	(591)	682	396
Less: Preferred stock dividend requirement (Note 13)	176	117	35
Less: Amortization of Beneficial Conversion Feature	32	0	0
Less: Undistributed earnings allocated to preferred shareholders (1)	0	0	0
Income (loss) available to common shareholders from continuing operations - basic and diluted	(949)	674	333
Income (Loss) from Discontinued Operations	$ (182)	$ 109	$ (28)
Denominator:
Weighted average common shares outstanding - basic	531,031,000	502,050,000	448,829,000
Weighted average common shares outstanding - diluted	531,031,000	505,157,000	452,465,000
Earnings Per Share, Basic [Abstract]
Basic earnings (loss) per common share - continuing operations	$ (1.45)	$ 1.12	$ 0.80
Basic earnings (loss) per common share - discontinued operations	(0.34)	0.22	(0.06)
Earnings Per Share, Basic	(1.79)	1.34	0.74
Earnings Per Share, Diluted [Abstract]
Diluted earnings (loss) per common share - continuing operations	(1.45)	1.12	0.80
Diluted earnings (loss) per common share - discontinued operations	(0.34)	0.21	(0.06)
Diluted Earnings (Loss) Per Common Share	$ (1.79)	$ 1.33	$ 0.74
Continuing Operations [Member]
Numerator:
Income (loss) available to common shareholders from continuing operations - basic and diluted	$ (767)	$ 565	$ 361
Restricted Stock [Member]
Denominator:
Restricted stock (2)	0	3,107,000	3,636,000
Series B Preferred Stock [Member]
Amount of antidilutive securities excluded from computation of earnings per share	35,922,000	34,354,000	8,885,000
Numerator:
Less: Preferred stock dividend requirement (Note 13)	$ 144	$ 117	$ 35
Denominator:
Preferred Stock	0	0	0
Series C Preferred Stock [Member]
Amount of antidilutive securities excluded from computation of earnings per share	23,807,000
Denominator:
Preferred Stock	0	0	0
Restricted Stock [Member]
Amount of antidilutive securities excluded from computation of earnings per share	3,690,000