Condensed Statements of Consolidated Changes in Equity - USD ($) $ in Millions	Total	Common Stock [Member]	Series A Preferred Stock [Member]	Series B Preferred Stock [Member]	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Retained Earnings [Member] Series A Preferred Stock [Member]	Retained Earnings [Member] Series B Preferred Stock [Member]	AOCI Attributable to Parent [Member]	CERC Corp [Member]	CERC Corp [Member] Common Stock [Member]	CERC Corp [Member] Additional Paid-in Capital [Member]	CERC Corp [Member] Retained Earnings [Member]	CERC Corp [Member] AOCI Attributable to Parent [Member]	Houston Electric [Member]	Houston Electric [Member] Common Stock [Member]	Houston Electric [Member] Additional Paid-in Capital [Member]	Houston Electric [Member] Retained Earnings [Member]	Houston Electric [Member] AOCI Attributable to Parent [Member]
Balance, beginning of period at Dec. 31, 2018					2,000,000
Balance, end of period at Mar. 31, 2019					2,000,000
Balance, beginning of period at Dec. 31, 2018						501,000,000							1,000					1,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances related to benefit and investment plans						1,000,000
Balance, end of period at Mar. 31, 2019						502,000,000							1,000					1,000
Balance, beginning of period at Dec. 31, 2018					$ 1,740	$ 5	$ 6,072	$ 349			$ (108)		$ 0	$ 2,015	$ 423	$ 5		$ 0	$ 1,896	$ 800	$ (14)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances related to benefit and investment plans						0	(12)
Contribution From Parent														0					590
Net income (Loss)	$ 169							169				$ 138			138		$ 27			27
Dividends, Common Stock, Cash		$ (144)						0
Dividends, Preferred Stock, Cash			$ (26)	$ (17)
Dividend to parent															(20)					(24)
Other comprehensive income (loss)											1										(1)
Balance, end of period at Mar. 31, 2019	$ 8,216				$ 1,740	$ 5	6,060	518			(107)	2,561	$ 0	2,015	541	5	3,274	$ 0	2,486	803	(15)
Balance, beginning of period at Dec. 31, 2019			800,000	977,500	2,000,000
Balance, end of period at Mar. 31, 2020			800,000	977,500	2,000,000
Balance, beginning of period at Dec. 31, 2019	502,242,061					502,000,000							1,000					1,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances related to benefit and investment plans						0
Balance, end of period at Mar. 31, 2020	502,647,495					502,000,000							1,000					1,000
Balance, beginning of period at Dec. 31, 2019	$ 8,359				$ 1,740	$ 5	6,080	632			(98)	2,641	$ 0	2,116	515	10	3,251	$ 0	2,486	780	(15)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances related to benefit and investment plans						0	6
Contribution From Parent														0					0
Net income (Loss)	(1,199)							(1,199)				67			67		33			33
Dividends, Common Stock, Cash		$ (145)						(145)
Dividends, Preferred Stock, Cash			$ (25)	$ (17)					$ (25)	$ (17)
Dividend to parent															(32)					(385)
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification | Accounting Standards Update 2016-13 [Member]								(7)							(5)
Other comprehensive income (loss)											(2)										0
Balance, end of period at Mar. 31, 2020	$ 6,970				$ 1,740	$ 5	$ 6,086	$ (761)			$ (100)	$ 2,671	$ 0	$ 2,116	$ 545	$ 10	$ 2,899	$ 0	$ 2,486	$ 428	$ (15)