Goodwill and Other Intangibles (CenterPoint Energy and CERC) (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2019		Mar. 31, 2018	Dec. 31, 2018
Goodwill [Line Items]
Goodwill		$ 5,129			$ 867
Goodwill, Acquired During Period		4,262
Finite-Live Intangible Assets [Abstract]
Intangible assets gross carrying amount		516			106
Intangible assets accumulated amortization		(56)			(41)
Net intangible assets		460			65
Amortization of Intangible Assets		9		$ 0
Finite-Lived Intangible Assets Amortization Expense Maturity Schedule [Abstract]
Remaining nine months of 2019		61
2020		39
2021		34
2022		35
2023		36
2024		29
Indiana Electric Integrated [Member]
Goodwill [Line Items]
Goodwill		0			0
Natural Gas Distribution [Member]
Goodwill [Line Items]
Goodwill		746			746
Energy Services [Member]
Goodwill [Line Items]
Goodwill	[1]	110			110
Accumulated goodwill impairment charge recorded in 2012		252			252
Infrastructure Services [Member]
Goodwill [Line Items]
Goodwill		6			0
Goodwill, Acquired During Period		6
Corporate and Other [Member]
Goodwill [Line Items]
Goodwill		11			11
Vectren acquisition [Member]
Goodwill [Line Items]
Goodwill	[2]	4,256			0
Goodwill, Acquired During Period	[2]	4,256
Customer Relationships [Member]
Finite-Live Intangible Assets [Abstract]
Intangible assets gross carrying amount		315	[3]		86
Intangible assets accumulated amortization		(31)	[3]		(27)
Net intangible assets		284	[3]		59
Noncompete Agreements [Member]
Finite-Live Intangible Assets [Abstract]
Intangible assets gross carrying amount		4			4
Intangible assets accumulated amortization		(3)			(3)
Net intangible assets		1			1
Trade Names [Member]
Finite-Live Intangible Assets [Abstract]
Intangible assets gross carrying amount		71	[3]		0
Intangible assets accumulated amortization		(1)	[3]		0
Net intangible assets		70	[3]		0
Construction Backlog [Member]
Finite-Live Intangible Assets [Abstract]
Intangible assets gross carrying amount		54	[3],[4]		0
Intangible assets accumulated amortization		(8)	[3],[4]		0
Net intangible assets		46	[3],[4]		0
Operation and maintenance agreements [Member]
Finite-Live Intangible Assets [Abstract]
Intangible assets gross carrying amount		48	[3],[4]		0
Intangible assets accumulated amortization		(1)	[3],[4]		0
Net intangible assets		47	[3],[4]		0
Other [Member]
Finite-Live Intangible Assets [Abstract]
Intangible assets gross carrying amount		24			16
Intangible assets accumulated amortization		(12)			(11)
Net intangible assets		12			5
CERC Corp [Member]
Goodwill [Line Items]
Goodwill		867			867
Finite-Live Intangible Assets [Abstract]
Intangible assets gross carrying amount		106			106
Intangible assets accumulated amortization		(44)			(41)
Net intangible assets		62			65
Finite-Lived Intangible Assets Amortization Expense Maturity Schedule [Abstract]
Remaining nine months of 2019		8
2020		6
2021		6
2022		6
2023		5
2024		5
CERC Corp [Member] | Natural Gas Distribution [Member]
Goodwill [Line Items]
Goodwill		746			746
CERC Corp [Member] | Energy Services [Member]
Goodwill [Line Items]
Goodwill	[5]	110			110
Accumulated goodwill impairment charge recorded in 2012		252			252
CERC Corp [Member] | Corporate and Other [Member]
Goodwill [Line Items]
Goodwill		11			11
CERC Corp [Member] | Customer Relationships [Member]
Finite-Live Intangible Assets [Abstract]
Intangible assets gross carrying amount		86			86
Intangible assets accumulated amortization		(29)			(27)
Net intangible assets		57			59
CERC Corp [Member] | Noncompete Agreements [Member]
Finite-Live Intangible Assets [Abstract]
Intangible assets gross carrying amount		4			4
Intangible assets accumulated amortization		(3)			(3)
Net intangible assets		1			1
CERC Corp [Member] | Other [Member]
Finite-Live Intangible Assets [Abstract]
Intangible assets gross carrying amount		16			16
Intangible assets accumulated amortization		(12)			(11)
Net intangible assets		4			5
Depreciation and amortization expense [Member]
Finite-Live Intangible Assets [Abstract]
Amortization of Intangible Assets		6	[6]	3
Depreciation and amortization expense [Member] | CERC Corp [Member]
Finite-Live Intangible Assets [Abstract]
Amortization of Intangible Assets		3		3
Operation and maintenance agreements and construction backlog [Member]
Finite-Live Intangible Assets [Abstract]
Amortization of Intangible Assets		9	[7]	$ 0
Vectren [Member]
Goodwill [Line Items]
Goodwill	[8]	4,256			$ 0
Vectren [Member] | Depreciation and amortization expense [Member]
Finite-Live Intangible Assets [Abstract]
Amortization of Intangible Assets	[6]	3
Vectren [Member] | Operation and maintenance agreements and construction backlog [Member]
Finite-Live Intangible Assets [Abstract]
Amortization of Intangible Assets	[7]	$ 9

[1] Amount presented is net of the accumulated goodwill impairment charge of $252 million recorded in 2012.

[2] CenterPoint Energy is currently assessing its reporting units subsequent to the Merger and the allocation of goodwill from the Merger to those reporting units. See Note 3.

[3] The fair value of intangible assets acquired through acquisitions is preliminary and subject to change. See Note 3.

[4] 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.

[5] Amount presented is net of the accumulated goodwill impairment charge of $252 million recorded in 2012.

[6] Includes $3 million of amortization expense related to intangibles acquired in the Merger. The fair value of intangible assets, and related amortization assumptions, acquired through acquisitions during the three months ended March 31, 2019, is preliminary and subject to change. See Note 3.

[7] Includes $9 million of amortization expense related to the operation and maintenance agreements and construction backlog intangibles acquired in the Merger. The fair value of intangible assets, and related amortization assumptions, acquired through acquisitions during the three months ended March 31, 2019, is preliminary and subject to change. See Note 3.

[8] CenterPoint Energy is currently assessing its reporting units subsequent to the Merger and the allocation of goodwill from the Merger to those reporting units. See Note 3.