Equity (CenterPoint Energy) (Details)					3 Months Ended		9 Months Ended
	Oct. 23, 2018 $ / shares	Oct. 01, 2018 USD ($) day $ / shares shares	Aug. 22, 2018 USD ($) day $ / shares shares	Dec. 13, 2017 $ / shares	Sep. 30, 2018 USD ($) $ / shares	Sep. 30, 2017 $ / shares	Sep. 30, 2018 USD ($) $ / shares		Sep. 30, 2017 USD ($) $ / shares	Dec. 31, 2017 USD ($) $ / shares
Class of Stock [Line Items]
Dividends Declared Per Share				$ 0.2775	$ 0.2775	$ 0.2675	$ 0.5550	[1]	$ 0.8025
Proceeds from issuance of Series A Preferred Stock, net | $							$ 790,000,000		$ 0
Series A Preferred Stock [Member]
Class of Stock [Line Items]
Stock issued (in shares) | shares			800,000
Preferred stock par value (in dollars per share)			$ 1,000		$ 0.01		$ 0.01			$ 0
Preferred stock liquidation preference | $			$ 800,000,000		$ 800,000		$ 800,000			$ 0
Preferred stock liquidation preference (per share)			$ 1,000
Preferred stock dividend rate			6.125%
Preferred stock redemption price (per share)			$ 1,000
Preferred stock convertible threshold (in days) | day			120
Subsequent Event [Member] | Series B Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock liquidation preference | $		$ 978,000,000
Preferred stock liquidation preference (per share)		$ 1,000
Preferred Stock, Convertible, Conversion Price		$ 1,000
Preferred stock dividend rate		7.00%
Proceeds from issuance of Series B Preferred Stock | $		$ 950,000,000
Conversion rate per share		0.05
Preferred Stock, Convertible, Threshold Consecutive Calendar Days | day		20
Subsequent Event [Member] | Depositary Share [Member]
Class of Stock [Line Items]
Stock issued (in shares) | shares		19,550,000
Number of depositary shares eligible for conversion (in shares) | shares		20
Preferred Stock, Convertible, Conversion Price		$ 50
Subsequent Event [Member] | Common Stock [Member]
Class of Stock [Line Items]
Dividends Declared Per Share	$ 0.2775
Stock issued (in shares) | shares		69,633,027
Common stock issued per share price		$ 27.25
Proceeds from issuance of common stock | $		$ 1,844,000,000
Plus LIBOR Spread [Member] | Series A Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock dividend rate			3.27%
Minimum [Member] | Subsequent Event [Member] | Series B Preferred Stock [Member]
Class of Stock [Line Items]
Convertible Preferred Stock, Shares Issued upon Conversion | shares		30.5820
Preferred Stock, Convertible, Stock Price Trigger		$ 27.2494
Minimum [Member] | Subsequent Event [Member] | Series B Depositary Shares [Member]
Class of Stock [Line Items]
Preferred Stock, Convertible, Stock Price Trigger		$ 27.2494
Minimum [Member] | Subsequent Event [Member] | Depositary Share [Member]
Class of Stock [Line Items]
Convertible Preferred Stock, Shares Issued upon Conversion | shares		1.5291
Maximum [Member] | Subsequent Event [Member] | Series B Preferred Stock [Member]
Class of Stock [Line Items]
Convertible Preferred Stock, Shares Issued upon Conversion | shares		36.6980
Preferred Stock, Convertible, Stock Price Trigger		$ 32.6990
Maximum [Member] | Subsequent Event [Member] | Series B Depositary Shares [Member]
Class of Stock [Line Items]
Preferred Stock, Convertible, Stock Price Trigger		$ 32.6990
Maximum [Member] | Subsequent Event [Member] | Depositary Share [Member]
Class of Stock [Line Items]
Convertible Preferred Stock, Shares Issued upon Conversion | shares		1.8349
Over-Allotment Option [Member] | Subsequent Event [Member] | Series B Depositary Shares [Member]
Class of Stock [Line Items]
Stock issued (in shares) | shares		2,550,000
Over-Allotment Option [Member] | Subsequent Event [Member] | Common Stock [Member]
Class of Stock [Line Items]
Stock issued (in shares) | shares		9,082,568
120 Days After Conclusion of Review or Appeal [Member] | Series A Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock redemption price (per share)			$ 1,020
Preferred stock redemption percentage of liquidation value			102.00%

[1] On December 13, 2017, CenterPoint Energy’s Board of Directors declared a regular quarterly cash dividend of $0.2775 per share of Common Stock, payable on March 8, 2018 to shareholders of record as of the close of business on February 15, 2018.