Goodwill and Other Intangibles (CenterPoint Energy and CERC) (Details) - USD ($)	3 Months Ended			12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Goodwill [Line Items]
Goodwill				$ 4,294,000,000	$ 4,697,000,000
Held for Sale				398,000,000
Disposals				5,000,000
Goodwill impairment	$ 0	$ 0		0	185,000,000	$ 0
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount				63,000,000	68,000,000
Accumulated Amortization				(19,000,000)	(18,000,000)
Net Balance				44,000,000	50,000,000
2022				6,000,000
2023				6,000,000
2024				5,000,000
2025				5,000,000
2026				5,000,000
Indiana Electric Integrated
Goodwill [Line Items]
Goodwill impairment			$ 185,000,000		185,000,000
Fair value of goodwill			$ 936,000,000
Customer Relationships
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount				33,000,000	33,000,000
Accumulated Amortization				(12,000,000)	(8,000,000)
Net Balance				21,000,000	25,000,000
Trade Names
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount				16,000,000	16,000,000
Accumulated Amortization				(5,000,000)	(3,000,000)
Net Balance				11,000,000	13,000,000
Construction backlog
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount				0	5,000,000
Accumulated Amortization				0	(5,000,000)
Net Balance				0	0
Operation and maintenance agreements
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount				12,000,000	12,000,000
Accumulated Amortization				(1,000,000)	(1,000,000)
Net Balance				11,000,000	11,000,000
Other
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount				2,000,000	2,000,000
Accumulated Amortization				(1,000,000)	(1,000,000)
Net Balance				1,000,000	1,000,000
Electric
Goodwill [Line Items]
Goodwill				936,000,000	936,000,000
Held for Sale				0
Disposals				0
Accumulated goodwill impairment charge					185,000,000
Natural Gas
Goodwill [Line Items]
Goodwill				2,920,000,000	3,323,000,000
Held for Sale				398,000,000
Disposals				5,000,000
Corporate and Other
Goodwill [Line Items]
Goodwill				438,000,000	438,000,000
Held for Sale				0
Disposals				0
CERC Corp
Goodwill [Line Items]
Goodwill				611,000,000	757,000,000
Held for Sale				144,000,000
Disposals				2,000,000
Depreciation and amortization expense
Finite-Lived Intangible Assets, Net [Abstract]
Amortization of intangible assets in Non-utility cost of revenues				6,000,000	6,000,000	5,000,000
Non-utility cost of revenues
Finite-Lived Intangible Assets, Net [Abstract]
Amortization of intangible assets in Non-utility cost of revenues				$ 1,000,000	$ 2,000,000	4,000,000
Vectren | Depreciation and amortization expense
Finite-Lived Intangible Assets, Net [Abstract]
Amortization of intangible assets in Non-utility cost of revenues						$ 5,000,000