Equity (CenterPoint Energy) (Details)																	12 Months Ended
		Dec. 12, 2018 USD ($) $ / shares	Oct. 23, 2018 USD ($) $ / shares	Oct. 01, 2018 USD ($) $ / shares shares	Aug. 22, 2018 USD ($) $ / shares shares	Jul. 26, 2018 USD ($) $ / shares	Apr. 26, 2018 USD ($) $ / shares	Dec. 13, 2017 USD ($) $ / shares	Oct. 25, 2017 USD ($) $ / shares	Jul. 27, 2017 USD ($) $ / shares	Apr. 27, 2017 USD ($) $ / shares	Jan. 05, 2017 USD ($) $ / shares	Oct. 27, 2016 USD ($) $ / shares	Jul. 28, 2016 USD ($) $ / shares	Apr. 28, 2016 USD ($) $ / shares	Jan. 20, 2016 USD ($) $ / shares	Dec. 31, 2018 USD ($) day $ / shares shares	Dec. 31, 2017 USD ($) $ / shares	Dec. 31, 2016 USD ($) $ / shares
Dividends declared per share | $ / shares																	$ 1.12	$ 1.3475	$ 1.03
Preferred stock dividend requirement																	$ 35,000,000	$ 0	$ 0
Preferred stock par value (in dollars per share) | $ / shares																	$ 0.01	$ 0.01	$ 0.01
Proceeds from the issuance of Series A Preferred Stock, net					$ 790,000,000												$ 1,740,000,000	$ 0	$ 0
Proceeds from issuance of common stock																	1,844,000,000	0	0
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance																	(68,000,000)	(71,000,000)
Prior service cost (2)	[1]																1,000,000	1,000,000
Actuarial losses (2)	[1]																6,000,000	7,000,000
Tax benefit (expense)																	6,000,000	(4,000,000)
Net current period other comprehensive income (loss)																	(25,000,000)	3,000,000	(5,000,000)
Ending Balance																	(108,000,000)	(68,000,000)	$ (71,000,000)
Enable Midstream Partners [Member]
Undistributed earnings from equity method investments included in retained earnings																	$ 31,000,000	$ 0
Common Stock [Member]
Declaration Date		Dec. 12, 2018	Oct. 23, 2018			Jul. 26, 2018	Apr. 26, 2018	Dec. 13, 2017	Oct. 25, 2017	Jul. 27, 2017	Apr. 27, 2017	Jan. 05, 2017	Oct. 27, 2016	Jul. 28, 2016	Apr. 28, 2016	Jan. 20, 2016
Record Date		Feb. 21, 2019	Nov. 15, 2018			Aug. 16, 2018	May 17, 2018	Feb. 15, 2018	Nov. 16, 2017	Aug. 16, 2017	May 16, 2017	Feb. 16, 2017	Nov. 16, 2016	Aug. 16, 2016	May 16, 2016	Feb. 16, 2016
Payment Date		Mar. 14, 2019	Dec. 13, 2018			Sep. 13, 2018	Jun. 14, 2018	Mar. 08, 2018	Dec. 08, 2017	Sep. 08, 2017	Jun. 09, 2017	Mar. 10, 2017	Dec. 09, 2016	Sep. 09, 2016	Jun. 10, 2016	Mar. 10, 2016
Dividends declared per share | $ / shares		$ 0.2875	$ 0.2775			$ 0.2775	$ 0.2775	$ 0.2775	$ 0.2675	$ 0.2675	$ 0.2675	$ 0.2675	$ 0.2575	$ 0.2575	$ 0.2575	$ 0.2575	$ 1.1200	$ 1.3475	$ 1.0300
Dividends declared		$ 144,000,000	$ 139,000,000			$ 120,000,000	$ 120,000,000	$ 120,000,000	$ 116,000,000	$ 115,000,000	$ 115,000,000	$ 115,000,000	$ 111,000,000	$ 111,000,000	$ 111,000,000	$ 110,000,000	$ 523,000,000	$ 581,000,000	$ 443,000,000
Stock issued (in shares) | shares				69,633,027
Common stock issued per share price | $ / shares				$ 27.25
Proceeds from issuance of common stock				$ 1,844,000,000
Series A Preferred Stock [Member]
Declaration Date		Dec. 12, 2018
Record Date		Feb. 15, 2019
Payment Date		Mar. 01, 2019
Dividends declared per share | $ / shares		$ 32.1563															$ 32.1563	$ 0.0000	$ 0.0000
Dividends declared		$ 26,000,000															$ 26,000,000
Preferred stock dividend requirement																	$ 18,000,000	$ 0	$ 0
Stock issued (in shares) | shares					800,000
Preferred stock par value (in dollars per share) | $ / shares					$ 1,000												$ 0.01	$ 0.00
Preferred stock liquidation preference																	$ 800,000,000	$ 0
Preferred stock liquidation preference (per share) | $ / shares																	$ 1,000
Preferred stock dividend rate																	6.125%
Preferred stock redemption price (per share) | $ / shares																	$ 1,000
Preferred stock convertible threshold (in days) | day																	120
Series B Preferred Stock [Member]
Declaration Date		Dec. 12, 2018	Oct. 23, 2018
Record Date		Feb. 15, 2019	Nov. 15, 2018
Payment Date		Mar. 01, 2019	Dec. 01, 2018
Dividends declared per share | $ / shares		$ 17.5000	$ 11.6667														$ 29.1667	$ 0.0000	$ 0.0000
Dividends declared		$ 17,000,000	$ 11,000,000														$ 28,000,000
Preferred stock dividend requirement																	$ 17,000,000	$ 0	$ 0
Preferred stock par value (in dollars per share) | $ / shares																	$ 0.01	$ 0.00
Preferred stock liquidation preference																	$ 977,500,000	$ 0
Preferred stock liquidation preference (per share) | $ / shares																	$ 1,000
Preferred stock dividend rate																	7.00%
Proceeds from the issuance of Series B Preferred Stock, net				$ 950,000,000
Depositary Share, Conversion Ratio																	0.05
Preferred Stock, Convertible, Conversion Price | $ / shares																	$ 1,000
Preferred stock threshold consecutive calendar days | day																	20
Depositary Share [Member]
Stock issued (in shares) | shares				19,550,000
Depositary share par value (in dollars per depositary share) | $ / shares				$ 50													$ 50
Number of depositary shares eligible for conversion (in shares) | shares																	20
120 Days After Conclusion of Review or Appeal [Member] | Series A Preferred Stock [Member]
Preferred stock redemption price (per share) | $ / shares																	$ 1,020
Preferred stock redemption percentage liquidation value																	102.00%
London Interbank Offered Rate (LIBOR) [Member] | Series A Preferred Stock [Member]
Preferred stock dividend rate																	3.27%
Over-Allotment Option [Member] | Common Stock [Member]
Stock issued (in shares) | shares				9,082,568
Over-Allotment Option [Member] | Series B [Member]
Stock issued (in shares) | shares				2,550,000
Minimum [Member] | Series B Preferred Stock [Member]
Preferred Stock, Convertible, Stock Price Trigger | $ / shares																	$ 27.2494
Conversion rate per share | shares																	30.5820
Minimum [Member] | Series B [Member]
Preferred Stock, Convertible, Stock Price Trigger | $ / shares																	$ 27.2494
Minimum [Member] | Depositary Share [Member]
Conversion rate per share | shares																	1.5291
Maximum [Member] | Series B Preferred Stock [Member]
Preferred Stock, Convertible, Stock Price Trigger | $ / shares																	$ 32.6990
Conversion rate per share | shares																	36.6980
Maximum [Member] | Series B [Member]
Preferred Stock, Convertible, Stock Price Trigger | $ / shares																	$ 32.6990
Maximum [Member] | Depositary Share [Member]
Conversion rate per share | shares																	1.8349
Interest Rate Contract [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Other comprehensive income (loss) before reclassifications:	[2]																$ (19,000,000)	(5,000,000)
Cash Flow Hedging [Member] | Interest Rate Contract [Member] | Interest Expense [Member]
Gain (loss) reclassified from accumulated OCI into income																	1,000,000	1,000,000
Houston Electric [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance																	0	1,000,000
Prior service cost (2)	[1]																0	0
Actuarial losses (2)	[1]																0	0
Tax benefit (expense)																	4,000,000	0
Net current period other comprehensive income (loss)																	(14,000,000)	(1,000,000)	1,000,000
Ending Balance																	(14,000,000)	0	1,000,000
Houston Electric [Member] | Interest Rate Contract [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Other comprehensive income (loss) before reclassifications:	[2]																(18,000,000)	(1,000,000)
Houston Electric [Member] | Cash Flow Hedging [Member] | Interest Rate Contract [Member] | Interest Expense [Member]
Gain (loss) reclassified from accumulated OCI into income																	1,000,000	1,000,000
CERC Corp [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance																	6,000,000	3,000,000
Prior service cost (2)	[1]																1,000,000	1,000,000
Actuarial losses (2)	[1]																0	0
Tax benefit (expense)																	(1,000,000)	(3,000,000)
Net current period other comprehensive income (loss)																	0	3,000,000	(6,000,000)
Ending Balance																	5,000,000	6,000,000	$ 3,000,000
CERC Corp [Member] | Interest Rate Contract [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Other comprehensive income (loss) before reclassifications:	[2]																(1,000,000)	(2,000,000)
CERC Corp [Member] | Cash Flow Hedging [Member] | Interest Rate Contract [Member] | Interest Expense [Member]
Gain (loss) reclassified from accumulated OCI into income																	1,000,000	1,000,000
Pension and Other Postretirement Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Other comprehensive income (loss) before reclassifications:																	(19,000,000)	4,000,000
Pension and Other Postretirement Plans [Member] | Houston Electric [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Other comprehensive income (loss) before reclassifications:																	0	0
Pension and Other Postretirement Plans [Member] | CERC Corp [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Other comprehensive income (loss) before reclassifications:																	1,000,000	7,000,000
Adoption of ASU 2018-02 [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Adoption of ASU 2018-02																	(15,000,000)	0
Adoption of ASU 2018-02 [Member] | Houston Electric [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Adoption of ASU 2018-02																	0	0
Adoption of ASU 2018-02 [Member] | CERC Corp [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Adoption of ASU 2018-02																	$ (1,000,000)	$ 0

[1] Amounts are included in the computation of net periodic cost and are reflected in Other, net in each of the Registrants’ respective Statements of Consolidated Income.

[2] Gains and losses are reclassified from Accumulated other comprehensive income into income when the hedged transactions affect earnings. The reclassification amounts are included in Interest and other finance charges in each of the Registrant’s respective Statements of Consolidated Income. Amounts are less than $1 million for each of the years ended December 31, 2018 and 2017, respectively.