Equity (CenterPoint Energy) (Details) $ / shares in Units, $ in Millions																	12 Months Ended
	Dec. 10, 2020 USD ($) $ / shares	Oct. 29, 2020 USD ($) $ / shares	Jul. 29, 2020 USD ($) $ / shares	May 06, 2020 USD ($) $ / shares shares	Apr. 24, 2020 USD ($) $ / shares	Apr. 01, 2020 $ / shares	Feb. 03, 2020 USD ($) $ / shares	Oct. 17, 2019 USD ($) $ / shares	Jul. 31, 2019 USD ($) $ / shares	Apr. 25, 2019 USD ($) $ / shares	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. 31, 2020 USD ($) day $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Nov. 27, 2020 shares	Nov. 06, 2020 shares	Nov. 02, 2020 shares	Jun. 01, 2020 shares
Income allocated to preferred shareholders																	$ 144	$ 117	$ 35
Proceeds from the issuance of Series A Preferred Stock, net																	723	0	1,740
Proceeds from issuance of common stock																	672	0	1,844
Amortization of Beneficial Conversion Feature																	32	0	0
Income allocated to preferred shareholders																	176	117	35
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance																	(98)	(108)
Reclassified to earnings																	0	1	0
Other comprehensive loss from unconsolidated affiliates																	(2)	(1)
Prior service cost (2)																	0	1
Actuarial losses (2)																	7	8
Reclassification of net deferred loss from cash flow hedges (3)																	19	0
Tax benefit (expense)																	(4)	(3)
Net current period other comprehensive income (loss)																	8	10	(25)
Ending Balance																	(90)	(98)	$ (108)
Common Stock, Capital Shares Reserved for Future Issuance | shares																							58,051,121
Enable Midstream Partners [Member]
Undistributed earnings from equity method investments included in retained earnings																	$ 0	$ 0
Common Stock [Member]
Declaration Date	Dec. 10, 2020	Oct. 29, 2020						Oct. 17, 2019	Jul. 31, 2019	Apr. 25, 2019	Dec. 12, 2018	Oct. 23, 2018			Jul. 26, 2018	Apr. 26, 2018
Record Date	Feb. 18, 2021	Nov. 19, 2020						Nov. 21, 2019	Aug. 15, 2019	May 16, 2019	Feb. 21, 2019	Nov. 15, 2018			Aug. 16, 2018	May 17, 2018
Payment Date	Mar. 11, 2021	Dec. 10, 2020						Dec. 12, 2019	Sep. 12, 2019	Jun. 13, 2019	Mar. 14, 2019	Dec. 13, 2018			Sep. 13, 2018	Jun. 14, 2018
Dividends declared per share | $ / shares	$ 0.1600	$ 0.1500	$ 0.1500		$ 0.1500		$ 0.2900	$ 0.2875	$ 0.2875	$ 0.2875	$ 0.2875	$ 0.2775			$ 0.2775	$ 0.2775	$ 0.9000	$ 0.8625	$ 1.1200
Dividends declared	$ 88	$ 83						$ 144	$ 145	$ 144	$ 144	$ 139			$ 120	$ 120	$ 480	$ 433	$ 523
Stock issued (in shares) | shares				41,977,612
Common stock issued per share price | $ / shares				$ 16.08
Proceeds from issuance of common stock				$ 673
SharesIssuedUponConversion | shares																				3,064	6,531,677
Common Stock [Member] | Previous Dividend or Distribution [Member]
Dividends declared per share | $ / shares						$ 0.2900
Common Stock [Member] | Revised Dividend or Distribution [Member]
Dividends declared per share | $ / shares						$ 0.1500
Common Stock [Member] | First Quarter 2020 [Member]
Declaration Date							Feb. 03, 2020
Record Date							Feb. 20, 2020
Payment Date							Mar. 12, 2020
Dividends declared							$ 145
Common Stock [Member] | Second Quarter 2020 [Member]
Declaration Date					Apr. 24, 2020
Record Date					May 21, 2020
Payment Date					Jun. 11, 2020
Dividends declared					$ 82
Common Stock [Member] | Third Quarter 2020 [Member]
Declaration Date			Jul. 29, 2020
Record Date			Aug. 20, 2020
Payment Date			Sep. 10, 2020
Dividends declared			$ 82
Series A Preferred Stock [Member]
Declaration Date									Jul. 31, 2019		Dec. 12, 2018
Record Date									Aug. 15, 2019		Feb. 15, 2019
Payment Date									Sep. 03, 2019		Mar. 01, 2019
Dividends declared per share | $ / shares	$ 30.6250		$ 30.6250				$ 30.6250		$ 30.6250		$ 32.1563						$ 91.8750	$ 30.6250	$ 32.1563
Dividends declared									$ 24		$ 26						$ 73	$ 24	$ 26
Income allocated to preferred shareholders																	$ 49	$ 49	$ 18
Preferred stock par value (in dollars per share) | $ / shares																	$ 0.01	$ 0.01	$ 0.01
Preferred stock liquidation preference														$ 800			$ 800	$ 800
Preferred stock liquidation preference (per share) | $ / shares														$ 1,000			$ 1,000
Preferred stock convertible threshold (in days) | day																	120
Proceeds from the issuance of Series B Preferred Stock, net														$ 790
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Preferred Stock, Shares Issued | shares														800,000
Preferred stock dividend rate																	6.125%
Preferred stock redemption price (per share) | $ / shares																	$ 1,000
Series A Preferred Stock [Member] | First Quarter 2020 [Member]
Declaration Date							Feb. 03, 2020
Record Date							Feb. 14, 2020
Payment Date							Mar. 02, 2020
Dividends declared							$ 25
Series A Preferred Stock [Member] | Third Quarter 2020 [Member]
Declaration Date	Dec. 10, 2020		Jul. 29, 2020
Record Date	Feb. 15, 2021		Aug. 14, 2020
Payment Date	Mar. 01, 2021		Sep. 01, 2020
Dividends declared	$ 24		$ 24
Series B Preferred Stock [Member]
Declaration Date	Dec. 10, 2020	Oct. 29, 2020						Oct. 17, 2019	Jul. 31, 2019	Apr. 25, 2019	Dec. 12, 2018	Oct. 23, 2018
Record Date	Feb. 15, 2021	Nov. 13, 2020						Nov. 15, 2019	Aug. 15, 2019	May 15, 2019	Feb. 15, 2019	Nov. 15, 2018
Payment Date	Mar. 01, 2021	Dec. 01, 2020						Dec. 02, 2019	Sep. 03, 2019	Jun. 03, 2019	Mar. 01, 2019	Dec. 01, 2018
Dividends declared per share | $ / shares	$ 17.5000	$ 17.5000						$ 17.5000	$ 17.5000	$ 17.5000	$ 17.5000	$ 11.6667						$ 52.5000	$ 29.1667
Dividends declared	$ 17	$ 17						$ 17	$ 17	$ 17	$ 17	$ 11					$ 85	$ 51	$ 28
Preferred Stock, Dividends, Per Share, Cash Paid | $ / shares																	$ 87.5000
Income allocated to preferred shareholders																	$ 68	$ 68	$ 17
Stock issued (in shares) | shares													2,550,000
Preferred stock par value (in dollars per share) | $ / shares																	$ 0.01	$ 0.01	$ 0.01
Preferred stock liquidation preference													$ 978				$ 977	$ 977
Preferred stock liquidation preference (per share) | $ / shares													$ 1,000				$ 1,000
Proceeds from the issuance of Series B Preferred Stock, net													$ 950
Preferred Stock, Convertible, Conversion Price | $ / shares																	$ 1,000
Preferred stock threshold consecutive calendar days | day																	20
PreferredStockSharesToBeConvertedToCommon | shares																				2,000
Income allocated to preferred shareholders																	$ 144	117	$ 35
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Preferred stock dividend rate																	7.00%
Series B Preferred Stock [Member] | Minimum [Member]
Conversion rate per share | shares																	30.5820
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Preferred Stock, Convertible, Stock Price Trigger | $ / shares																	$ 27.2494
Series B Preferred Stock [Member] | Maximum [Member]
Conversion rate per share | shares																	36.6980
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Preferred Stock, Convertible, Stock Price Trigger | $ / shares																	$ 32.6990
Series B Preferred Stock [Member] | First Quarter 2020 [Member]
Declaration Date					Apr. 24, 2020		Feb. 03, 2020
Record Date							Feb. 14, 2020
Payment Date							Mar. 02, 2020
Dividends declared per share | $ / shares							$ 17.5000
Dividends declared							$ 17
Series B Preferred Stock [Member] | Second Quarter 2020 [Member]
Record Date					May 15, 2020
Payment Date					Jun. 01, 2020
Dividends declared per share | $ / shares					$ 17.5000
Dividends declared					$ 17
Series B Preferred Stock [Member] | Third Quarter 2020 [Member]
Declaration Date			Jul. 29, 2020
Record Date			Aug. 14, 2020
Payment Date			Sep. 01, 2020
Dividends declared per share | $ / shares			$ 17.5000
Dividends declared			$ 17
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
Depositary Share [Member] | Minimum [Member]
Conversion rate per share | shares																	1.5291
Depositary Share [Member] | Maximum [Member]
Conversion rate per share | shares																	1.8349
Series C Preferred Stock [Member]
Declaration Date	Dec. 10, 2020	Oct. 29, 2020
Record Date	Feb. 18, 2021	Nov. 19, 2020
Payment Date	Mar. 11, 2021	Dec. 10, 2020
Dividends declared per share | $ / shares																	$ 0.6100
Dividends declared	$ 7	$ 6															$ 27
Preferred Stock, Dividends, Per Share, Cash Paid | $ / shares	$ 0.1600	$ 0.1500
Income allocated to preferred shareholders																	$ 27	$ 0	$ 0
Preferred stock par value (in dollars per share) | $ / shares																	$ 0.01	$ 0.01	$ 0.01
Preferred stock liquidation preference																	$ 625
Preferred stock liquidation preference (per share) | $ / shares				$ 1,000
Proceeds from the issuance of Series B Preferred Stock, net				$ 724
Conversion rate per share | shares				47,354,670
Preferred Stock, Convertible, Conversion Price | $ / shares				$ 15.31
Number of depositary shares eligible for conversion (in shares) | shares																	0	0	0
PreferredStockSharesToBeConvertedToCommon | shares																						100,000
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Preferred Stock, Shares Issued | shares				725,000
Preferred Stock, Convertible, Conversion Limit				4.90%
Preferred Stock, Convertible, Percent Outstanding Shares To Amend				66 2/3%
Series C Preferred Stock [Member] | Second Quarter 2020 [Member]
Declaration Date					Apr. 24, 2020
Record Date					May 21, 2020
Payment Date					Jun. 11, 2020
Dividends declared					$ 7
Preferred Stock, Dividends, Per Share, Cash Paid | $ / shares					$ 0.1500
Series C Preferred Stock [Member] | Third Quarter 2020 [Member]
Declaration Date			Jul. 29, 2020
Record Date			Aug. 20, 2020
Payment Date			Sep. 10, 2020
Dividends declared			$ 7
Preferred Stock, Dividends, Per Share, Cash Paid | $ / shares			$ 0.1500
Series B [Member] | Maximum [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Preferred Stock, Convertible, Stock Price Trigger | $ / shares																	$ 32.6990
120 Days After Conclusion of Review or Appeal [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Preferred stock redemption price (per share) | $ / shares																	$ 1,020
120 Days After Conclusion of Review or Appeal [Member] | Series A Preferred Stock [Member]
Preferred stock redemption percentage liquidation value																	102.00%
London Interbank Offered Rate (LIBOR) [Member] | Series A Preferred Stock [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Preferred Stock, Dividend Payment Rate, Variable																	3.270
Interest Rate Contract [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Remeasurement of pension and other postretirement plans																	$ 0	$ (3)
Deferred loss from interest rate derivatives (1)																	0	(3)
Cash Flow Hedging [Member] | Interest Rate Contract [Member] | Interest Expense [Member]
Gain (loss) reclassified from accumulated OCI into income																	0	1
Houston Electric [Member]
Amortization of Beneficial Conversion Feature																	0	0	$ 0
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance																	(15)	(14)
Reclassified to earnings																	0	0
Other comprehensive loss from unconsolidated affiliates																	0	0
Prior service cost (2)																	0	0
Actuarial losses (2)																	0	0
Reclassification of net deferred loss from cash flow hedges (3)																	19	0
Tax benefit (expense)																	(4)	0
Net current period other comprehensive income (loss)																	15	(1)	(14)
Ending Balance																	0	(15)	(14)
Houston Electric [Member] | Interest Rate Contract [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Remeasurement of pension and other postretirement plans																	0	(1)
Deferred loss from interest rate derivatives (1)																	0	(1)
CERC Corp [Member]
Amortization of Beneficial Conversion Feature																	0	0	0
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance																	10	5
Reclassified to earnings																	0	0
Other comprehensive loss from unconsolidated affiliates																	0	0
Prior service cost (2)																	1	0
Actuarial losses (2)																	0	0
Reclassification of net deferred loss from cash flow hedges (3)																	0	0
Tax benefit (expense)																	(1)	(2)
Net current period other comprehensive income (loss)																	0	5	0
Ending Balance																	10	10	$ 5
CERC Corp [Member] | Interest Rate Contract [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Remeasurement of pension and other postretirement plans																	0	0
Deferred loss from interest rate derivatives (1)																	0	0
Pension and Other Postretirement Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Remeasurement of pension and other postretirement plans																	(12)	7
Deferred loss from interest rate derivatives (1)																	(12)	7
Pension and Other Postretirement Plans [Member] | Houston Electric [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Remeasurement of pension and other postretirement plans																	0	0
Deferred loss from interest rate derivatives (1)																	0	0
Pension and Other Postretirement Plans [Member] | CERC Corp [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Remeasurement of pension and other postretirement plans																	0	7
Deferred loss from interest rate derivatives (1)																	$ 0	$ 7