Equity (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended		3 Months Ended		6 Months Ended
	Feb. 28, 2022	Jul. 31, 2021	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021	Jul. 20, 2021
Class of Stock [Line Items]
Preferred stock, outstanding (in shares)			800,000		800,000		800,000
Preferred stock			$ 790		$ 790		$ 790
Preferred Stock Dividends and Other Adjustments [Abstract]
Preferred stock dividend requirement			11	$ 30	24	$ 59
Total income allocated to preferred shareholders			11	30	24	59
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance		$ (85)	(62)	(87)	(64)	(90)
Other comprehensive income (loss) from unconsolidated affiliates			0	1	0	2
Prior service cost			1	0	1	0
Actuarial losses			1	2	2	4
Settlement			13	0	13	0
Reclassification of deferred loss from cash flow hedges realized in net income					1	0
Tax expense			(4)	(1)	(4)	(1)
Net current period other comprehensive income (loss)			(23)	2	(21)	5
Ending Balance			(85)	(85)	(85)	(85)
Other Pension, Postretirement and Supplemental Plans
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Remeasurement of pension and other postretirement plans			(34)	0	(34)	0
Houston Electric
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance		0	0	0	0	0
Other comprehensive income (loss) from unconsolidated affiliates			0	0	0	0
Prior service cost			0	0	0	0
Actuarial losses			0	0	0	0
Settlement			0	0	0	0
Reclassification of deferred loss from cash flow hedges realized in net income					0	0
Tax expense			0	0	0	0
Net current period other comprehensive income (loss)			0	0	0	0
Ending Balance			0	0	0	0
Houston Electric | Other Pension, Postretirement and Supplemental Plans
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Remeasurement of pension and other postretirement plans			0	0	0	0
CERC
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance		$ 10	10	10	10	10
Other comprehensive income (loss) from unconsolidated affiliates			0	0	0	0
Prior service cost			0	0	0	0
Actuarial losses			0	0	0	0
Settlement			0	0	0	0
Reclassification of deferred loss from cash flow hedges realized in net income					0	0
Tax expense			0	0	0	0
Net current period other comprehensive income (loss)			0	0	0	0
Ending Balance			10	10	10	10
CERC | Other Pension, Postretirement and Supplemental Plans
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Remeasurement of pension and other postretirement plans			$ 0	$ 0	$ 0	$ 0
Chief Executive Officer
Preferred Stock Dividends and Other Adjustments [Abstract]
Retention incentive agreement, shares issued								1,000,000
Chief Executive Officer | Restricted Stock Units (RSUs)
Preferred Stock Dividends and Other Adjustments [Abstract]
Restricted stock units granted (in shares)	400,000	400,000
Remaining shares available to be awarded (in shares)		200,000
Common Stock
Class of Stock [Line Items]
Common stock, dividends declared per share (in dollars per share)			$ 0.170	$ 0.160	$ 0.170	$ 0.160
Common Stock dividends paid per share (in dollars per share)			0.170	0.160	0.340	0.320
Series A Preferred Stock
Class of Stock [Line Items]
Preferred stock, dividends declared (in dollars per share)			0	0	0	0
Preferred stock dividends paid per share (in dollars per share)			0	$ 0	30.625	$ 30.625
Preferred stock, liquidation preference (in dollars per share)			$ 1,000		$ 1,000
Preferred stock, outstanding (in shares)			800,000		800,000		800,000
Preferred stock			$ 790		$ 790		$ 790
Preferred Stock Dividends and Other Adjustments [Abstract]
Preferred stock dividend requirement			$ 11	$ 13	$ 24	$ 25
Series B Preferred Stock
Class of Stock [Line Items]
Preferred stock, dividends declared (in dollars per share)			$ 0	$ 17.500	$ 0	$ 17.500
Preferred stock dividends paid per share (in dollars per share)			$ 0	$ 17.500	$ 0	$ 35.000
Preferred Stock Dividends and Other Adjustments [Abstract]
Preferred stock dividend requirement			$ 0	$ 17	$ 0	$ 34
Series C Preferred Stock
Class of Stock [Line Items]
Preferred stock, dividends declared (in dollars per share)			$ 0	$ 0	$ 0	$ 0
Preferred stock dividends paid per share (in dollars per share)			$ 0	$ 0	$ 0	$ 0.160
Preferred Stock
Class of Stock [Line Items]
Preferred stock, outstanding (in shares)			800,000		800,000		800,000
Preferred stock			$ 790		$ 790		$ 790