Goodwill and Other Intangibles (CenterPoint Energy and CERC) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Goodwill [Line Items]
Goodwill	$ 4,294		$ 4,294		$ 4,697
Held for sale	403		403
Finite-Live Intangible Assets [Abstract]
Intangible assets gross carrying amount	68		68		68
Intangible assets accumulated amortization	(21)		(21)		(18)
Net intangible assets	47		47		50
Amortization of Intangible Assets			0	$ 1
Finite-Lived Intangible Assets Amortization Expense Maturity Schedule [Abstract]
Remaining six months of 2021	3		3
2022	6		6
2023	6		6
2024	5		5
2025	5		5
2026	5		5
Electric
Goodwill [Line Items]
Goodwill	936		936		936
Held for sale	0		0
Goodwill, Impaired, Accumulated Impairment Loss [Abstract]
Accumulated goodwill impairment charge					185
Natural Gas
Goodwill [Line Items]
Goodwill	2,920		2,920		3,323
Held for sale	403		403
Corporate and Other, Net
Goodwill [Line Items]
Goodwill	438		438		438
Held for sale	0		0
Customer Relationships
Finite-Live Intangible Assets [Abstract]
Intangible assets gross carrying amount	33		33		33
Intangible assets accumulated amortization	(10)		(10)		(8)
Net intangible assets	23		23		25
Trade Names
Finite-Live Intangible Assets [Abstract]
Intangible assets gross carrying amount	16		16		16
Intangible assets accumulated amortization	(4)		(4)		(3)
Net intangible assets	12		12		13
Construction Backlog
Finite-Live Intangible Assets [Abstract]
Intangible assets gross carrying amount	5		5		5
Intangible assets accumulated amortization	(5)		(5)		(5)
Net intangible assets	0		0		0
Operation and maintenance agreements
Finite-Live Intangible Assets [Abstract]
Intangible assets gross carrying amount	12		12		12
Intangible assets accumulated amortization	(1)		(1)		(1)
Net intangible assets	11		11		11
Other
Finite-Live Intangible Assets [Abstract]
Intangible assets gross carrying amount	2		2		2
Intangible assets accumulated amortization	(1)		(1)		(1)
Net intangible assets	1		1		1
CERC Corp
Goodwill [Line Items]
Goodwill	611		611		$ 757
Held for sale	146		146
Depreciation and amortization expense
Finite-Live Intangible Assets [Abstract]
Amortization of Intangible Assets	2	$ 2	3	3
Non-utility cost of revenues
Finite-Live Intangible Assets [Abstract]
Amortization of Intangible Assets	$ 0	$ 0	$ 0	$ 1