Earnings Per Share (CenterPoint Energy) (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended																12 Months Ended
		Dec. 31, 2019		Sep. 30, 2019		Jun. 30, 2019		Mar. 31, 2019		Dec. 31, 2018		Sep. 30, 2018		Jun. 30, 2018		Mar. 31, 2018		Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Net income																		$ 791		$ 368		$ 1,792
Numerator:
Income available to common shareholders - basic (1)		$ 128		$ 241		$ 165		$ 140		$ 90		$ 153		$ (75)		$ 165		674	[1]	333	[1]	1,792	[1]
Add back: Series B Preferred Stock dividend																		117		35		0
Income available to common shareholders - diluted (1)	[1]																	$ 674		$ 333		$ 1,792
Denominator:
Weighted average common shares outstanding - basic																		502,050,000		448,829,000		430,964,000
Plus: Incremental shares from assumed conversions:
Weighted average common shares outstanding - diluted																		505,157,000		452,465,000		434,308,000
Basic Earnings Per Common Share		$ 0.25	[2]	$ 0.48	[2]	$ 0.33	[2]	$ 0.28	[2]	$ 0.18	[2]	$ 0.35	[2]	$ (0.17)	[2]	$ 0.38	[2]	$ 1.34		$ 0.74		$ 4.16
Diluted Earnings Per Common Share		$ 0.25	[2]	$ 0.47	[2]	$ 0.33	[2]	$ 0.28	[2]	$ 0.18	[2]	$ 0.35	[2]	$ (0.17)	[2]	$ 0.38	[2]	$ 1.33		$ 0.74		$ 4.13
Reduction in income taxes due to tax reform																		$ 0		$ 0		$ 1,113	[3]
Preferred Stock Dividends, Income Statement Impact																		$ 117		$ 35		$ 0
Restricted Stock [Member]
Plus: Incremental shares from assumed conversions:
Restricted stock (3)	[4]																	3,107,000		3,636,000		3,344,000
Series B Preferred Stock [Member]
Numerator:
Add back: Series B Preferred Stock dividend	[5]																	$ 0		$ 0		$ 0
Plus: Incremental shares from assumed conversions:
Series B Preferred Stock (2)	[5]																	0		0		0
Preferred Stock Dividends, Income Statement Impact																		$ 68		$ 17		$ 0
Amount of antidilutive securities excluded from computation of earnings per share																		34,354,000		8,885,000
Vectren [Member]
Net income																		$ 190

[1] Income available to common shareholders for the year ended December 31, 2019 includes net income from businesses acquired in the Merger of $190 million. See Note 4. Income available to common shareholders for the year ended December 31, 2017 includes a reduction in income tax expense of $1,113 million due to tax reform. See Note 15 for further discussion of the impacts of the TCJA.

[2] Quarterly earnings (loss) per common share are based on the weighted average number of shares outstanding during the quarter, and the sum of the quarters may not equal annual earnings (loss) per common share.

[3] Recognized a $1.1 billion deferred tax benefit from the remeasurement of CenterPoint Energy’s ADFIT liability as a result of the enactment of the TCJA on December 22, 2017, which reduced the U.S. corporate income tax rate from 35% to 21%.

[4] The potentially dilutive impact from restricted stock awards applies the treasury stock method. Under this method, an increase in the average fair market value of Common Stock can result in a greater dilutive impact from these securities.

[5] The potentially dilutive impact from Series B Preferred Stock applies the if-converted method in calculating diluted earnings per common share. Under this method, diluted earnings per common share is adjusted for the more dilutive effect of the Series B Preferred Stock as a result of either its accumulated dividend for the period in the numerator or the assumed-converted common share equivalent in the denominator. The computation of diluted earnings per common share outstanding for the year ended December 31, 2019 and December 31, 2018 excludes Series B Stock Dividends of $68 million and $17 million, respectively, and 34,354,000 and 8,885,000 potentially dilutive shares, respectively, because to include them would be anti-dilutive. However, these shares could be potentially dilutive in the future.