Goodwill and Other Intangibles (CenterPoint Energy and CERC) (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Goodwill [Line Items]
Goodwill		$ 4,697		$ 4,697		$ 4,882
Goodwill, Impairment Loss		0	$ 0	185	$ 0
Finite-Live Intangible Assets [Abstract]
Intangible assets gross carrying amount		68		68		68
Intangible assets accumulated amortization		(16)		(16)		(10)
Net intangible assets		52		52		58
Amortization of Intangible Assets				1	19
Finite-Lived Intangible Assets Amortization Expense Maturity Schedule [Abstract]
Remaining three months of 2020	[1]	2		2
2021	[1]	6		6
2022	[1]	6		6
2023	[1]	6		6
2024	[1]	5		5
2025	[1]	5		5
Indiana Electric Integrated [Member]
Goodwill [Line Items]
Goodwill	[2]	936		936		1,121
Goodwill, Impairment Loss	[2]			185
Fair value of goodwill		936		936
Natural Gas Distribution [Member]
Goodwill [Line Items]
Goodwill		3,312		3,312		3,312
Goodwill, Impairment Loss				0
Corporate and Other [Member]
Goodwill [Line Items]
Goodwill		449		449		449
Goodwill, Impairment Loss				0
Customer Relationships [Member]
Finite-Live Intangible Assets [Abstract]
Intangible assets gross carrying amount		33		33		33
Intangible assets accumulated amortization		(7)		(7)		(4)
Net intangible assets		26		26		29
Trade Names [Member]
Finite-Live Intangible Assets [Abstract]
Intangible assets gross carrying amount		16		16		16
Intangible assets accumulated amortization		(3)		(3)		(1)
Net intangible assets		13		13		15
Construction Backlog [Member]
Finite-Live Intangible Assets [Abstract]
Intangible assets gross carrying amount	[3]	5		5		5
Intangible assets accumulated amortization	[3]	(4)		(4)		(4)
Net intangible assets	[3]	1		1		1
Operation and maintenance agreements [Member]
Finite-Live Intangible Assets [Abstract]
Intangible assets gross carrying amount	[3]	12		12		12
Intangible assets accumulated amortization	[3]	(1)		(1)		0
Net intangible assets	[3]	11		11		12
Other [Member]
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 [Member]
Goodwill [Line Items]
Goodwill		757		757		757
CERC Corp [Member] | Natural Gas Distribution [Member]
Goodwill [Line Items]
Goodwill		746		746		746
CERC Corp [Member] | Corporate and Other [Member]
Goodwill [Line Items]
Goodwill		11		11		$ 11
Depreciation and amortization expense [Member]
Finite-Live Intangible Assets [Abstract]
Amortization of Intangible Assets	[4]	2	1	5	2
Non-utility cost of revenues [Member]
Finite-Live Intangible Assets [Abstract]
Amortization of Intangible Assets	[4]	$ 0	$ 1	1	$ 4
Continuing Operations [Member]
Goodwill [Line Items]
Goodwill, Impairment Loss				$ 185

[1] Assets held for sale are not amortized. The table reflects amortization on continuing operations. For further information on discontinued operations, see Note 3.

[2] CenterPoint Energy recognized a non-cash goodwill impairment charge as a result of the March 31, 2020 goodwill impairment test.

[3] Amortization expense related to the operation and maintenance agreements and construction backlog is included in Non-utility cost of revenues, including natural gas on CenterPoint Energy’s Condensed Statements of Consolidated Income.

[4] Assets held for sale are not amortized. The table reflects amortization on continuing operations. For further information on discontinued operations, see Note 3.