Goodwill and Other Intangibles (CenterPoint Energy and CERC) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021	Dec. 31, 2020
Goodwill [Line Items]
Goodwill	$ 4,294		$ 4,294
Finite-Live Intangible Assets [Abstract]
Gross Carrying Amount	63		63
Accumulated Amortization	(20)		(19)
Net Balance	43		44
Finite-Lived Intangible Assets Amortization Expense Maturity Schedule [Abstract]
Remaining nine months of 2022	5
2023	6
2024	5
2025	5
2026	5
2027	4
Electric
Goodwill [Line Items]
Goodwill	936		936
Goodwill, Impaired, Accumulated Impairment Loss [Abstract]
Accumulated goodwill impairment charge				$ 185
Natural Gas
Goodwill [Line Items]
Goodwill	2,920		2,920
Held for sale	398
Corporate and Other
Goodwill [Line Items]
Goodwill	438		438
Customer Relationships
Finite-Live Intangible Assets [Abstract]
Gross Carrying Amount	33		33
Accumulated Amortization	(13)		(12)
Net Balance	20		21
Trade Names
Finite-Live Intangible Assets [Abstract]
Gross Carrying Amount	16		16
Accumulated Amortization	(5)		(5)
Net Balance	11		11
Operation and maintenance agreements
Finite-Live Intangible Assets [Abstract]
Gross Carrying Amount	12		12
Accumulated Amortization	(1)		(1)
Net Balance	11		11
Other
Finite-Live Intangible Assets [Abstract]
Gross Carrying Amount	2		2
Accumulated Amortization	(1)		(1)
Net Balance	1		1
CERC Corp
Goodwill [Line Items]
Goodwill	611		$ 611
CERC Corp | Natural Gas
Goodwill [Line Items]
Held for sale	144
Depreciation and amortization expense
Finite-Live Intangible Assets [Abstract]
Amortization expense of intangible assets recorded in Depreciation and amortization	$ 1	$ 1