CONDENSED STATEMENTS OF CONSOLIDATED CHANGES IN EQUITY - USD ($) $ in Millions	Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [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]	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]
Balance, beginning of period at Dec. 31, 2017		0
Balance, end of period at Mar. 31, 2018		0
Balance, beginning of period at Dec. 31, 2017			431,000,000					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, 2018			431,000,000					1,000					1,000
Balance, beginning of period at Dec. 31, 2017		$ 0	$ 4	$ 4,209	$ 543	$ (68)		$ 0	$ 1,696	$ 673	$ 0		$ 0	$ 2,528	$ 574	$ 6
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances related to benefit and investment plans			0	(1)
Contribution From Parent									0
Other									1					(1)
Net income	$ 165				165		$ 52			52		$ 130			130
Dividend to parent										(32)					(86)
Other comprehensive income (loss)						5					4
Balance, end of period at Mar. 31, 2018	$ 4,857	$ 0	$ 4	4,208	708	(63)	2,394	$ 0	1,697	693	4	3,151	$ 0	2,527	618	6
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	501,197,784		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	502,168,182		502,000,000					1,000					1,000
Balance, beginning of period at Dec. 31, 2018	$ 8,058	$ 1,740	$ 5	6,072	349	(108)	2,682	$ 0	1,896	800	(14)	2,443	$ 0	2,015	423	5
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances related to benefit and investment plans			0	(12)
Contribution From Parent									590
Other									0					0
Net income	169				169		27			27		138			138
Dividend to parent										(24)					(20)
Other comprehensive income (loss)						1					(1)
Balance, end of period at Mar. 31, 2019	$ 8,216	$ 1,740	$ 5	$ 6,060	$ 518	$ (107)	$ 3,274	$ 0	$ 2,486	$ 803	$ (15)	$ 2,561	$ 0	$ 2,015	$ 541	$ 5