Condensed Statements of Consolidated Changes in Equity - USD ($) $ in Millions	Total	Series A Preferred Stock	Series B Preferred Stock	Series C Preferred Stock	Preferred Stock	Preferred Stock Series C Preferred Stock	Common Stock	Additional Paid-in Capital	Retained Earnings	AOCI Attributable to Parent	Houston Electric	Houston Electric Common Stock	Houston Electric Additional Paid-in Capital	Houston Electric Retained Earnings	Houston Electric AOCI Attributable to Parent	CERC Corp	CERC Corp Common Stock	CERC Corp Additional Paid-in Capital	CERC Corp Retained Earnings	CERC Corp AOCI Attributable to Parent	Cumulative Effect, Period of Adoption, Adjustment Retained Earnings	Cumulative Effect, Period of Adoption, Adjustment CERC Corp Retained Earnings
Balance, beginning of period (in shares) at Dec. 31, 2019					2,000,000
Balance, beginning of period at Dec. 31, 2019					$ 1,740		$ 5	$ 6,080	$ 632	$ (98)		$ 0	$ 2,486	$ 780	$ (15)		$ 0	$ 2,116	$ 515	$ 10	$ (7)	$ (5)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock issued (in shares)						1,000,000	42,000,000
Stock issued						$ 701	$ 0	673
Conversion of Series B Preferred Stock and Series C Preferred Stock					$ 0
Balance, end of period (in shares) at Jun. 30, 2020					3,000,000
Balance, beginning of period (in shares) at Dec. 31, 2019							502,000,000					1,000					1,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances related to benefit and investment plans (in shares)							1,000,000
Issuances related to benefit and investment plans							$ 0	16
Recognition of beneficial conversion feature	$ 32							32			$ 0					$ 0
Capital distribution to parent associated with the sale of CES											0					286		(286)
Other																		(1)
Net income (Loss)	(1,094)								(1,094)		120			120		80			80
Common Stock dividends declared (see Note 19)									(227)
Preferred Stock dividends declared (see Note 19)									(66)
Amortization of beneficial conversion feature	(9)								(9)		0					0
Dividend to parent														(405)					(72)
Other comprehensive income (loss)										14					15
Balance, end of period (in shares) at Jun. 30, 2020							545,000,000					1,000					1,000
Balance, end of period at Jun. 30, 2020	8,392				$ 2,441		$ 5	6,801	(771)	(84)	2,981	$ 0	2,486	495	0	2,357	$ 0	1,829	518	10
Balance, beginning of period (in shares) at Mar. 31, 2020					2,000,000
Balance, beginning of period at Mar. 31, 2020					$ 1,740		$ 5	6,086	(761)	(100)		$ 0	2,486	428	(15)		$ 0	2,116	545	10	0	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock issued (in shares)						1,000,000	42,000,000
Stock issued						$ 701	$ 0	673
Conversion of Series B Preferred Stock and Series C Preferred Stock					$ 0
Balance, end of period (in shares) at Jun. 30, 2020					3,000,000
Balance, beginning of period (in shares) 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 (in shares)							1,000,000
Issuances related to benefit and investment plans							$ 0	10
Recognition of beneficial conversion feature								32
Capital distribution to parent associated with the sale of CES											0					286		(286)
Other																		(1)
Net income (Loss)	105								105		87			87		13			13
Common Stock dividends declared (see Note 19)									(82)
Preferred Stock dividends declared (see Note 19)									(24)
Amortization of beneficial conversion feature	(9)								(9)
Dividend to parent														(20)					(40)
Other comprehensive income (loss)										16					15
Balance, end of period (in shares) at Jun. 30, 2020							545,000,000					1,000					1,000
Balance, end of period at Jun. 30, 2020	$ 8,392				$ 2,441		$ 5	6,801	(771)	(84)	2,981	$ 0	2,486	495	0	2,357	$ 0	1,829	518	10
Balance, beginning of period (in shares) at Dec. 31, 2020	2,402,400	800,000	977,400	625,000	3,000,000
Balance, beginning of period at Dec. 31, 2020	$ 8,348				$ 2,363		$ 6	6,914	(845)	(90)	3,111	$ 0	2,548	563	0	2,567	$ 0	2,046	511	10	0	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock issued (in shares)						0	41,000,000
Stock issued						$ 0	$ 0	624
Conversion of Series B Preferred Stock and Series C Preferred Stock					$ (624)
Balance, end of period (in shares) at Jun. 30, 2021	1,775,903	800,000	975,903	0	3,000,000
Balance, beginning of period (in shares) at Dec. 31, 2020	551,355,861						551,000,000					1,000					1,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances related to benefit and investment plans (in shares)							1,000,000
Issuances related to benefit and investment plans							$ 0	15
Recognition of beneficial conversion feature	$ 0							0			0					0
Capital distribution to parent associated with the sale of CES											0					0		0
Other																		0
Net income (Loss)	614								614		156			156		209			209
Common Stock dividends declared (see Note 19)									(95)
Preferred Stock dividends declared (see Note 19)									(17)
Amortization of beneficial conversion feature	$ 0								0		0					0
Dividend to parent														0					0
Other comprehensive income (loss)										5					0
Balance, end of period (in shares) at Jun. 30, 2021	592,852,490						593,000,000					1,000					1,000
Balance, end of period at Jun. 30, 2021	$ 8,870				$ 1,739		$ 6	7,553	(343)	(85)	3,267	$ 0	2,548	719	0	2,776	$ 0	2,046	720	10
Balance, beginning of period (in shares) at Mar. 31, 2021					3,000,000
Balance, beginning of period at Mar. 31, 2021					$ 2,363		$ 6	6,916	(482)	(87)		$ 0	2,548	616	0		$ 0	2,046	662	10	$ 0	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock issued (in shares)						0	41,000,000
Stock issued						$ 0	$ 0	624
Conversion of Series B Preferred Stock and Series C Preferred Stock					$ (624)
Balance, end of period (in shares) at Jun. 30, 2021	1,775,903	800,000	975,903	0	3,000,000
Balance, beginning of period (in shares) at Mar. 31, 2021							552,000,000					1,000					1,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances related to benefit and investment plans (in shares)							0
Issuances related to benefit and investment plans							$ 0	13
Recognition of beneficial conversion feature								0
Capital distribution to parent associated with the sale of CES											0					0		0
Other																		0
Net income (Loss)	$ 251								251		103			103		58			58
Common Stock dividends declared (see Note 19)									(95)
Preferred Stock dividends declared (see Note 19)									(17)
Amortization of beneficial conversion feature	$ 0								0
Dividend to parent														0					0
Other comprehensive income (loss)										2					0
Balance, end of period (in shares) at Jun. 30, 2021	592,852,490						593,000,000					1,000					1,000
Balance, end of period at Jun. 30, 2021	$ 8,870				$ 1,739		$ 6	$ 7,553	$ (343)	$ (85)	$ 3,267	$ 0	$ 2,548	$ 719	$ 0	$ 2,776	$ 0	$ 2,046	$ 720	$ 10