CONDENSED STATEMENTS OF CONSOLIDATED CHANGES IN EQUITY - USD ($) $ in Millions	Total	Common Stock [Member]	Series A Preferred Stock [Member]	Series B Preferred Stock [Member]	Series C 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]	Retained Earnings [Member] Series C 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
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)
Balance, end of period at Mar. 31, 2019						$ 1,740	$ 5	6,060	518				(107)		$ 0	2,015	541	5		$ 0	2,486	803	(15)
Balance, beginning of period at Dec. 31, 2018						2,000,000
Balance, end of period at Jun. 30, 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 Jun. 30, 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]
Other																0
Issuances related to benefit and investment plans							0	(7)
Contribution From Parent																0					590
Net income (Loss)	$ 364								364					$ 166			166		$ 127			127
Common Stock dividends declared (see Note 19)		$ (288)							(144)
Preferred Stock dividends declared (see Note 19)			$ (26)	$ (34)							$ (17)
Amortization of Beneficial Conversion Feature	0
Dividend to parent																	(103)					(40)
Other comprehensive income (loss)													3										(1)
Balance, end of period at Jun. 30, 2019	8,257					$ 1,740	$ 5	6,065	552				(105)	2,506	$ 0	2,015	486	5	3,358	$ 0	2,486	887	(15)
Balance, beginning of period at Mar. 31, 2019						2,000,000
Balance, end of period at Jun. 30, 2019						2,000,000
Balance, beginning of period at Mar. 31, 2019							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 Jun. 30, 2019							502,000,000								1,000					1,000
Balance, beginning of period at Mar. 31, 2019						$ 1,740	$ 5	6,060	518				(107)		$ 0	2,015	541	5		$ 0	2,486	803	(15)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other																0
Issuances related to benefit and investment plans							0	5
Contribution From Parent																0					0
Net income (Loss)	195								195					28			28		100			100
Common Stock dividends declared (see Note 19)									(144)
Preferred Stock dividends declared (see Note 19)											(17)
Amortization of Beneficial Conversion Feature	0
Dividend to parent																	(83)					(16)
Other comprehensive income (loss)													2										0
Balance, end of period at Jun. 30, 2019	$ 8,257					$ 1,740	$ 5	6,065	552				(105)	2,506	$ 0	2,015	486	5	3,358	$ 0	2,486	887	(15)
Preferred stock par value (in dollars per share)			$ 0.01	$ 0.01
Cumulative preferred stock authorized (in shares)	20,000,000
Common stock par value (in dollars per share)	$ 0.01
Common stock authorized (in shares)	1,000,000,000
Preferred stock par value (in dollars per share)			$ 0.01	$ 0.01
Common stock par value (in dollars per share)	$ 0.01
Common stock authorized (in shares)	1,000,000,000
Balance, beginning of period at Dec. 31, 2019			800,000	977,500		2,000,000
Balance, end of period at Mar. 31, 2020						2,000,000
Balance, beginning of period at Dec. 31, 2019	502,242,061						502,000,000								1,000					1,000
Balance, end of period at Mar. 31, 2020							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)
Balance, end of period at Mar. 31, 2020						$ 1,740	$ 5	6,086	(761)				(100)		$ 0	2,116	545	10		$ 0	2,486	428	(15)
Balance, beginning of period at Dec. 31, 2019			800,000	977,500		2,000,000
Balance, end of period at Jun. 30, 2020			800,000	977,500	725,000	3,000,000
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							1,000,000
Balance, end of period at Jun. 30, 2020	544,709,048						545,000,000								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]
Other																(1)
Issuance of stock, shares		42,000,000				1,000,000
Issuances of stock, net of issuance costs						$ 701		673
Issuances related to benefit and investment plans							0	16
Recognition of beneficial conversion feature	(32)							(32)
Contribution From Parent																286					0
Net income (Loss)	(1,094)								(1,094)					80			80		120			120
Common Stock dividends declared (see Note 19)		$ (227)							(227)
Preferred Stock dividends declared (see Note 19)			$ (25)	$ (34)	$ (7)					$ (25)	(34)	$ (7)
Amortization of Beneficial Conversion Feature	(9)				$ (9)				(9)
Dividend to parent																	(72)					(405)
Adoption of ASU 2016-13 | Accounting Standards Update 2016-13 [Member]									(7)								5
Other comprehensive income (loss)													14										15
Balance, end of period at Jun. 30, 2020	$ 8,392					$ 2,441	$ 5	6,801	(771)				(84)	2,357	$ 0	1,829	518	10	2,981	$ 0	2,486	495	0
Balance, beginning of period at Mar. 31, 2020						2,000,000
Balance, end of period at Jun. 30, 2020			800,000	977,500	725,000	3,000,000
Balance, beginning of period at Mar. 31, 2020							502,000,000								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 Jun. 30, 2020	544,709,048						545,000,000								1,000					1,000
Balance, beginning of period at Mar. 31, 2020						$ 1,740	$ 5	6,086	(761)				(100)		$ 0	2,116	545	10		$ 0	2,486	428	(15)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other																(1)
Issuance of stock, shares		42,000,000				1,000,000
Issuances of stock, net of issuance costs						$ 701		673
Issuances related to benefit and investment plans							0	10
Recognition of beneficial conversion feature								(32)
Contribution From Parent																286					0
Net income (Loss)	$ 105								105					13			13		87			87
Common Stock dividends declared (see Note 19)									(82)
Preferred Stock dividends declared (see Note 19)										$ 0	$ (17)	$ (7)
Amortization of Beneficial Conversion Feature	(9)				$ (9)				(9)
Dividend to parent																	(40)					(20)
Other comprehensive income (loss)													16										15
Balance, end of period at Jun. 30, 2020	$ 8,392					$ 2,441	$ 5	$ 6,801	$ (771)				$ (84)	$ 2,357	$ 0	$ 1,829	$ 518	$ 10	$ 2,981	$ 0	$ 2,486	$ 495	$ 0
Preferred stock par value (in dollars per share)			$ 0.01	$ 0.01	$ 0.01
Cumulative preferred stock authorized (in shares)	20,000,000
Common stock par value (in dollars per share)	$ 0.01
Common stock authorized (in shares)	1,000,000,000