Goodwill and Other Intangibles (CenterPoint Energy and CERC) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Goodwill [Line Items]
Goodwill	$ 4,697		$ 4,697
Finite-Live Intangible Assets [Abstract]
Intangible assets gross carrying amount	68		68
Intangible assets accumulated amortization	(19)		(18)
Net intangible assets	49		50
Finite-Lived Intangible Assets Amortization Expense Maturity Schedule [Abstract]
Remaining nine months of 2021	5
2022	6
2023	6
2024	5
2025	5
2026	5
Electric [Member]
Goodwill [Line Items]
Goodwill	936		936
Goodwill, Impaired, Accumulated Impairment Loss [Abstract]
Accumulated goodwill impairment charge			185
Natural Gas [Member]
Goodwill [Line Items]
Goodwill	3,323		3,323
Corporate and Other [Member]
Goodwill [Line Items]
Goodwill	438		438
Customer Relationships [Member]
Finite-Live Intangible Assets [Abstract]
Intangible assets gross carrying amount	33		33
Intangible assets accumulated amortization	(9)		(8)
Net intangible assets	24		25
Trade Names [Member]
Finite-Live Intangible Assets [Abstract]
Intangible assets gross carrying amount	16		16
Intangible assets accumulated amortization	(3)		(3)
Net intangible assets	13		13
Construction Backlog [Member]
Finite-Live Intangible Assets [Abstract]
Intangible assets gross carrying amount	5		5
Intangible assets accumulated amortization	(5)		(5)
Net intangible assets	0		0
Operation and maintenance agreements [Member]
Finite-Live Intangible Assets [Abstract]
Intangible assets gross carrying amount	12		12
Intangible assets accumulated amortization	(1)		(1)
Net intangible assets	11		11
Other [Member]
Finite-Live Intangible Assets [Abstract]
Intangible assets gross carrying amount	2		2
Intangible assets accumulated amortization	(1)		(1)
Net intangible assets	1		1
CERC Corp [Member]
Goodwill [Line Items]
Goodwill	757		$ 757
Depreciation and amortization expense [Member]
Finite-Live Intangible Assets [Abstract]
Amortization of Intangible Assets	1	$ 1
Non-utility cost of revenues [Member]
Finite-Live Intangible Assets [Abstract]
Amortization of Intangible Assets	$ 0	$ 1