Subsequent Events (CenterPoint Energy) (Details) - USD ($) $ / shares in Units, $ in Millions				3 Months Ended		9 Months Ended
		Nov. 03, 2020	Oct. 29, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Nov. 06, 2020	Nov. 02, 2020	Dec. 31, 2019
Subsequent Event [Line Items]
Dividends declared per share				$ 0.1500	$ 0.2875	$ 0.5900	$ 0.8625
Expected cash distribution from equity method investment						$ 109	$ 226
Series A Preferred Stock [Member]
Subsequent Event [Line Items]
Preferred stock dividends declared				$ 30.6250	30.6250	$ 61.2500	$ 62.7813
Preferred stock outstanding (in shares)				800,000		800,000				800,000
Series B Preferred Stock [Member]
Subsequent Event [Line Items]
Preferred stock dividends declared				$ 17.5000	$ 17.5000	$ 52.5000	$ 52.5000
Preferred stock outstanding (in shares)				977,500		977,500				977,500
Series C Preferred Stock [Member]
Subsequent Event [Line Items]
Preferred stock dividends declared				$ 0.1500		$ 0.3000
Preferred stock outstanding (in shares)				725,000		725,000				725,000
Subsequent Event [Member] | Common Stock [Member]
Subsequent Event [Line Items]
Dividends Payable, Date Declared			Oct. 29, 2020
Dividends Payable, Date of Record			Nov. 19, 2020
Dividends Payable, Date to be Paid			Dec. 10, 2020
Dividends declared per share			$ 0.1500
SharesIssuedUponConversion								6,531,677
Subsequent Event [Member] | Series B Preferred Stock [Member]
Subsequent Event [Line Items]
Dividends Payable, Date Declared			Oct. 29, 2020
Dividends Payable, Date of Record			Nov. 13, 2020
Dividends Payable, Date to be Paid			Dec. 01, 2020
Preferred stock dividends declared			$ 17.5000
Subsequent Event [Member] | Series C Preferred Stock [Member]
Subsequent Event [Line Items]
Dividends Payable, Date Declared	[1]		Oct. 29, 2020
Dividends Payable, Date of Record	[1]		Nov. 19, 2020
Dividends Payable, Date to be Paid	[1]		Dec. 10, 2020
Preferred stock dividends declared	[1]		$ 0.1500
Preferred stock outstanding (in shares)								625,000
PreferredStockSharesToBeConvertedToCommon									100,000
Common Units [Member] | Subsequent Event [Member] | Enable Midstream Partners [Member]
Subsequent Event [Line Items]
Quarterly cash distribution, declaration date		Nov. 03, 2020
Quarterly cash distribution, date of record		Nov. 17, 2020
Quarterly cash distribution, distribution date		Nov. 24, 2020
Quarterly cash distribution declared per share		$ 0.16525
Expected cash distribution from equity method investment		$ 39
Series A Preferred Units [Member] | Subsequent Event [Member] | Enable Midstream Partners [Member]
Subsequent Event [Line Items]
Quarterly cash distribution, declaration date		Nov. 03, 2020
Quarterly cash distribution, date of record		Nov. 03, 2020
Quarterly cash distribution, distribution date		Nov. 13, 2020
Quarterly cash distribution declared per share		$ 0.62500
Expected cash distribution from cost method investment		$ 9

[1] The Series C Preferred Stock is entitled to participate in any dividend or distribution (excluding those payable in Common Stock) with the Common Stock on a pari passu, pro rata, as-converted basis. The per share amount reflects the dividend per share of Common Stock as if the Series C Preferred Stock were converted into Common Stock.