Equity (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended		3 Months Ended
	Feb. 28, 2022	Jul. 31, 2021	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021	Jul. 20, 2021
Class of Stock [Line Items]
Preferred stock, outstanding (in shares)			800,000		800,000
Preferred stock			$ 790		$ 790
Preferred Stock Dividends and Other Adjustments [Abstract]
Preferred stock dividend requirement			13	$ 29
Total income allocated to preferred shareholders			13	29
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance			(64)	(90)
Other comprehensive income (loss) from unconsolidated affiliates			0	1
Actuarial losses			1	2
Reclassification of deferred loss from cash flow hedges realized in net income			1	0
Net current period other comprehensive income			2	3
Ending Balance			$ (62)	$ (87)
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 paid per share (in dollars per share)			$ 0.170	$ 0.160
Series A Preferred Stock
Class of Stock [Line Items]
Preferred stock dividends paid per share (in dollars per share)			30.625	$ 30.625
Preferred stock, liquidation preference (per share)			$ 1,000
Preferred stock, outstanding (in shares)			800,000		800,000
Preferred stock			$ 790		$ 790
Preferred Stock Dividends and Other Adjustments [Abstract]
Preferred stock dividend requirement			$ 13	$ 12
Series B Preferred Stock
Class of Stock [Line Items]
Preferred stock dividends paid per share (in dollars per share)			$ 0	$ 17.500
Preferred Stock Dividends and Other Adjustments [Abstract]
Preferred stock dividend requirement			$ 0	$ 17
Series C Preferred Stock
Class of Stock [Line Items]
Preferred stock dividends paid per share (in dollars per share)			$ 0	$ 0.160
Preferred Stock
Class of Stock [Line Items]
Preferred stock, outstanding (in shares)			800,000		800,000
Preferred stock			$ 790		$ 790
Houston Electric
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance			0	$ 0
Other comprehensive income (loss) from unconsolidated affiliates			0	0
Actuarial losses			0	0
Reclassification of deferred loss from cash flow hedges realized in net income			0	0
Net current period other comprehensive income			0	0
Ending Balance			0	0
CERC Corp
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance			10	10
Other comprehensive income (loss) from unconsolidated affiliates			0	0
Actuarial losses			0	0
Reclassification of deferred loss from cash flow hedges realized in net income			0	0
Net current period other comprehensive income			0	0
Ending Balance			$ 10	$ 10