Goodwill and Other Intangibles (CenterPoint Energy and CERC) (Details) - USD ($)		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Line Items]
Goodwill		$ 867,000,000	$ 867,000,000
Goodwill impairment charge recorded from annual impairment test		0	0
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount		106,000,000	105,000,000
Accumulated Amortization		(41,000,000)	(31,000,000)
Net Balance		65,000,000	74,000,000
Amortization expense of intangible assets (1)	[1]	10,000,000	13,000,000	$ 4,000,000
Estimated amortization expense over next twelve months		11,000,000
Estimated amortization expense in two years		6,000,000
Estimated amortization expense in three years		6,000,000
Estimated amortization expense in four years		6,000,000
Estimated amortization expense in five years		5,000,000
Customer Relationships [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount		86,000,000	86,000,000
Accumulated Amortization		(27,000,000)	(21,000,000)
Net Balance		59,000,000	65,000,000
Covenants Not To Compete [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount		4,000,000	4,000,000
Accumulated Amortization		(3,000,000)	(2,000,000)
Net Balance		1,000,000	2,000,000
Other Intangible Assets [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount		16,000,000	15,000,000
Accumulated Amortization		(11,000,000)	(8,000,000)
Net Balance		5,000,000	7,000,000
Natural Gas Distribution [Member]
Goodwill [Line Items]
Goodwill		746,000,000	746,000,000
Energy Services [Member]
Goodwill [Line Items]
Goodwill	[2]	110,000,000	110,000,000
Accumulated goodwill impairment charge recorded in 2012		252,000,000	252,000,000
Corporate and Other [Member]
Goodwill [Line Items]
Goodwill		11,000,000	11,000,000
CERC Corp [Member]
Goodwill [Line Items]
Goodwill		867,000,000	867,000,000
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount		106,000,000	105,000,000
Accumulated Amortization		(41,000,000)	(31,000,000)
Net Balance		65,000,000	74,000,000
Amortization expense of intangible assets (1)	[1]	10,000,000	13,000,000	$ 4,000,000
Estimated amortization expense over next twelve months		11,000,000
Estimated amortization expense in two years		6,000,000
Estimated amortization expense in three years		6,000,000
Estimated amortization expense in four years		6,000,000
Estimated amortization expense in five years		5,000,000
CERC Corp [Member] | Customer Relationships [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount		86,000,000	86,000,000
Accumulated Amortization		(27,000,000)	(21,000,000)
Net Balance		59,000,000	65,000,000
CERC Corp [Member] | Covenants Not To Compete [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount		4,000,000	4,000,000
Accumulated Amortization		(3,000,000)	(2,000,000)
Net Balance		1,000,000	2,000,000
CERC Corp [Member] | Other Intangible Assets [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount		16,000,000	15,000,000
Accumulated Amortization		(11,000,000)	(8,000,000)
Net Balance		5,000,000	7,000,000
CERC Corp [Member] | Natural Gas Distribution [Member]
Goodwill [Line Items]
Goodwill		746,000,000	746,000,000
CERC Corp [Member] | Energy Services [Member]
Goodwill [Line Items]
Goodwill	[2]	110,000,000	110,000,000
Accumulated goodwill impairment charge recorded in 2012		252,000,000	252,000,000
CERC Corp [Member] | Corporate and Other [Member]
Goodwill [Line Items]
Goodwill		$ 11,000,000	$ 11,000,000

[1] Recorded in Depreciation and amortization expenses on CenterPoint Energy’s and CERC’s respective Statements of Consolidated Income.

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