STATEMENTS OF CONSOLIDATED SHAREHOLDERS' EQUITY - USD ($) $ in Millions	Total	Series A Preferred Stock [Member]	Series B Preferred Stock [Member]	Preferred Stock [Member]	Preferred Stock [Member] Series A Preferred Stock [Member]	Preferred Stock [Member] Series B Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] Common Stock [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]	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 year at Dec. 31, 2015				0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances of stock					0	0	0
Balance, end of year at Dec. 31, 2016				0
Balance, beginning of year at Dec. 31, 2015							430,000,000								1,000					1,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances related to benefit and investment plans							1,000,000
Balance, end of year at Dec. 31, 2016							431,000,000								1,000					1,000
Balance, beginning of year at Dec. 31, 2015				$ 0			$ 4	$ 4,180		$ (657)			$ (66)		$ 0	$ 1,322	$ 279	$ 0		$ 0	$ 2,417	$ 828	$ 9
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances related to benefit and investment plans							0	15
Issuances of stock					$ 0	$ 0	0		$ 0
Contribution From Parent																374					72
Capital distribution associated with the Internal Spin	$ 0													$ 0					$ 0		0
Other																					0
Net income	432									432				276			276		245			245
Common Stock dividends declared ($1.12, $1.3475 and $1.03 per share, respectively)										(443)
Preferred stock dividends declared											$ 0	$ 0
Dividend to parent																	(135)					(643)
Other comprehensive income (loss)													(5)					1					(6)
Balance, end of year at Dec. 31, 2016	$ 3,460			$ 0			$ 4	4,195		(668)			(71)	2,117	$ 0	1,696	420	1	2,922	$ 0	2,489	430	3
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of ASU 2018-02 | Adjustments for New Accounting Principle, Early Adoption [Member]										0			0									0	0
Issuances of stock					0	0	0
Balance, end of year at Dec. 31, 2017		0	0	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances related to benefit and investment plans							0
Balance, end of year at Dec. 31, 2017	431,044,845						431,000,000								1,000					1,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances related to benefit and investment plans							$ 0	14
Issuances of stock					$ 0	$ 0	0		0
Contribution From Parent																0					38
Capital distribution associated with the Internal Spin	$ 0													0					0		0
Other																					1
Net income	1,792									1,792				433			433		745			745
Common Stock dividends declared ($1.12, $1.3475 and $1.03 per share, respectively)										(581)
Preferred stock dividends declared											0	0
Dividend to parent																	(180)					(601)
Other comprehensive income (loss)													3					(1)					3
Balance, end of year at Dec. 31, 2017	$ 4,688			$ 0			$ 4	4,209		543			(68)	2,369	$ 0	1,696	673	0	3,108	$ 0	2,528	574	6
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of ASU 2018-02 | Adjustments for New Accounting Principle, Early Adoption [Member]										0			0									0	0
Issuances of stock					1,000,000	1,000,000	70,000,000
Balance, end of year at Dec. 31, 2018		800,000	977,500	2,000,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances related to benefit and investment plans							0
Balance, end of year 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							$ 0	19
Issuances of stock					$ 790	$ 950	1		$ 1,844
Contribution From Parent																200					960
Capital distribution associated with the Internal Spin	$ 0													0					(1,473)		(1,473)
Other																					0
Net income	368									368				336			336		208			208
Common Stock dividends declared ($1.12, $1.3475 and $1.03 per share, respectively)										(523)
Preferred stock dividends declared		$ (26)	$ (28)								$ (26)	$ (28)
Dividend to parent																	(209)					(360)
Other comprehensive income (loss)													(25)					(14)					0
Balance, end of year 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
Balance, end of year (Adjustments for New Accounting Principle, Early Adoption [Member]) at Dec. 31, 2018																							2,443
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of ASU 2018-02 | Adjustments for New Accounting Principle, Early Adoption [Member]										$ 15			$ (15)									$ 1	$ (1)