Divestitures (CenterPoint Energy and CERC) (Details) - USD ($) $ / shares in Units, $ in Millions				3 Months Ended	12 Months Ended
	Jun. 01, 2020	Apr. 09, 2020	Feb. 01, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jan. 31, 2021
Discontinued Operation, Additional Disclosures [Abstract]
Cash proceeds from sale					$ 1,215	$ 0	$ 0
Disposal Group, Including Discontinued Operation, Balance Sheet Disclosures [Abstract]
Receivables, net						637
Accrued unbilled revenues						117
Natural gas inventory						67
Materials and supplies						6
Non-trading derivative assets						136
Other						39
Total current assets held for sale					0	1,002
Property, plant and equipment, net						321
Goodwill						282
Non-trading derivative assets						58
Other						301
Total non-current assets held for sale					0	962
Total assets held for sale						1,964
Accounts payable						344
Taxes accrued						2
Non-trading derivative liabilities						44
Other						65
Total current liabilities held for sale					0	455
Non-trading derivative liabilities						14
Benefit obligations						4
Other						25
Total non-current liabilities held for sale					0	43
Total liabilities held for sale						498
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Revenues					1,417	4,957	4,503
Non-utility cost of revenues					1,158	3,906	4,459
Operation and maintenance					218	782	66
Depreciation and amortization					0	62	13
Taxes other than income taxes					4	4	2
Goodwill, Impairment Loss					185	0	0
Goodwill impairment					0	48	0
Total					1,380	4,802	4,540
Income (loss) from Discontinued Operations before income taxes					37	155	(37)
Loss on classification to held for sale, net (2)					(198)	0	0
Income tax expense (benefit)					21	46	(9)
Net income (loss) from Discontinued Operations					(182)	109	(28)
Discontinued Operation, Alternative Cash Flow Information [Abstract]
Depreciation and amortization on assets held for sale					0	62	13
Discontinued Operation, Continuing Involvement [Abstract]
Amortization of intangible assets in Non-utility cost of revenues					2	24	0
Goodwill					4,697	4,882
Cost of Sales [Member]
Discontinued Operation, Continuing Involvement [Abstract]
Amortization of intangible assets in Non-utility cost of revenues					2	4	0
Depreciation and amortization expense [Member]
Discontinued Operation, Continuing Involvement [Abstract]
Amortization of intangible assets in Non-utility cost of revenues					6	5	0
Vectren [Member]
Discontinued Operation, Continuing Involvement [Abstract]
Cash paid to acquire Vectren			$ 6,000			$ 5,982
Cash paid per share of Vectren common stock at closing of the Merger						$ 72.00
Goodwill						$ 4,339
Identifiable intangibles						297
Vectren [Member] | Operation And Maintenance Expense [Member]
Discontinued Operation, Continuing Involvement [Abstract]
Severance expense related to the Merger				$ 61		102
Integration costs					83
Vectren [Member] | Cost of Sales [Member] | Operation and maintenance agreements and construction backlog [Member]
Discontinued Operation, Continuing Involvement [Abstract]
Amortization of intangible assets in Non-utility cost of revenues						24
Vectren [Member] | Depreciation and amortization expense [Member]
Discontinued Operation, Continuing Involvement [Abstract]
Amortization of intangible assets in Non-utility cost of revenues					5
Vectren [Member] | Depreciation and amortization expense [Member] | Customer relationships and trade names [Member]
Discontinued Operation, Continuing Involvement [Abstract]
Amortization of intangible assets in Non-utility cost of revenues						$ 16
Vectren [Member] | Stub period [Member]
Discontinued Operation, Continuing Involvement [Abstract]
Common Stock, Dividends, Per Share, Declared						$ 0.41145
Vectren acquisition [Member]
Discontinued Operation, Continuing Involvement [Abstract]
Cash payments towards outstanding share-based awards						$ 78
Other non-qualified plans benefit obligations deferred compensation						41
Incremental share-based awards expense recorded						37
Utility pipeline construction company [Member]
Discontinued Operation, Continuing Involvement [Abstract]
Cash paid to acquire Vectren					25
Goodwill					6
Identifiable intangibles					8
CERC Corp [Member]
Discontinued Operation, Additional Disclosures [Abstract]
Cash proceeds from sale					365
Disposal Group, Including Discontinued Operation, Balance Sheet Disclosures [Abstract]
Total current assets held for sale					0	691
Total non-current assets held for sale					0	213
Total current liabilities held for sale					0	368
Total non-current liabilities held for sale					0	27
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Income tax expense (benefit)					(2)	17	37
Net income (loss) from Discontinued Operations					(66)	23	110
Discontinued Operation, Alternative Cash Flow Information [Abstract]
Depreciation and amortization on assets held for sale					0	12	13
Discontinued Operation, Continuing Involvement [Abstract]
Goodwill					757	757
CERC Corp [Member] | Discontinued Operations, Disposed of by Means Other than Sale, Spinoff [Member]
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Equity in earnings of unconsolidated affiliate, net							184
Infrastructure Services Disposal Group [Member]
Discontinued Operation, Additional Disclosures [Abstract]
Sales price of outstanding equity interests					850
Cash proceeds from sale		$ 850			854
Net deferred tax liabilities on sale recognized as deferred income tax benefit by CenterPoint Energy					129
Cost to sell					14
Pre-tax gain on sale					6
Maximum contractual exposure under Securities Purchase Agreement					21
Disposal Group, Including Discontinued Operation, Balance Sheet Disclosures [Abstract]
Receivables, net						192
Accrued unbilled revenues						109
Natural gas inventory						0
Materials and supplies						6
Non-trading derivative assets						0
Other						4
Total current assets held for sale						311
Property, plant and equipment, net						295
Goodwill						220
Non-trading derivative assets						0
Other						234
Total non-current assets held for sale						749
Total assets held for sale						1,060
Accounts payable						45
Taxes accrued						2
Non-trading derivative liabilities						0
Other						40
Total current liabilities held for sale						87
Non-trading derivative liabilities						0
Benefit obligations						0
Other						16
Total non-current liabilities held for sale						16
Total liabilities held for sale						103
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Revenues					250	1,190
Non-utility cost of revenues					50	309
Operation and maintenance					184	714
Depreciation and amortization					0	50
Taxes other than income taxes					1	2
Goodwill, Impairment Loss					82
Goodwill impairment					0	0
Total					235	1,075
Income (loss) from Discontinued Operations before income taxes					15	115
Loss on classification to held for sale, net (2)					(102)	0
Income tax expense (benefit)					24	29
Net income (loss) from Discontinued Operations					(111)	86
Discontinued Operation, Alternative Cash Flow Information [Abstract]
Depreciation and amortization on assets held for sale					0	50
Amortization of intangible assets in Non-utility cost of revenues					0	19
Write-down of natural gas inventory					0	0
Capital expenditures					18	67
Accounts payable related to capital expenditures					0	0
Discontinued Operation, Continuing Involvement [Abstract]
Pipeline construction and repair services capitalized					34	162
Pipeline construction and repair service charges in operations and maintenance expense					1	4
Current tax expense (benefit) of cash taxes payable upon sale					158
Infrastructure Services Disposal Group [Member] | Subsequent Event [Member]
Discontinued Operation, Additional Disclosures [Abstract]
Receivable from sale of disposal group								$ 4
Infrastructure Services Disposal Group [Member] | CERC Corp [Member]
Discontinued Operation, Continuing Involvement [Abstract]
Pipeline construction and repair services capitalized					0	20
Pipeline construction and repair service charges in operations and maintenance expense					1	4
Energy Services Disposal Group [Member]
Discontinued Operation, Additional Disclosures [Abstract]
Sales price of outstanding equity interests					400
Cash proceeds from sale	$ 286
Net deferred tax liabilities on sale recognized as deferred income tax benefit by CenterPoint Energy					4
Current tax expense (benefit) of cash taxes payable upon sale					(4)
Cost to sell					6
Receivable from sale of disposal group					79
Loss from reclassification to held for sale					31
Outstanding obligation related to AMAs					24	0
Disposal Group, Including Discontinued Operation, Balance Sheet Disclosures [Abstract]
Receivables, net						445
Accrued unbilled revenues						8
Natural gas inventory						67
Materials and supplies						0
Non-trading derivative assets						136
Other						35
Total current assets held for sale						691
Property, plant and equipment, net						26
Goodwill						62
Non-trading derivative assets						58
Other						67
Total non-current assets held for sale						213
Total assets held for sale						904
Accounts payable						299
Taxes accrued						0
Non-trading derivative liabilities						44
Other						25
Total current liabilities held for sale						368
Non-trading derivative liabilities						14
Benefit obligations						4
Other						9
Total non-current liabilities held for sale						27
Total liabilities held for sale						395
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Revenues					1,167	3,767	4,503
Non-utility cost of revenues					1,108	3,597	4,459
Operation and maintenance					34	68	66
Depreciation and amortization					0	12	13
Taxes other than income taxes					3	2	2
Goodwill, Impairment Loss					62
Goodwill impairment					0	48	0
Total					1,145	3,727	4,540
Income (loss) from Discontinued Operations before income taxes					22	40	(37)
Loss on classification to held for sale, net (2)					(96)	0	0
Income tax expense (benefit)					(3)	17	(9)
Net income (loss) from Discontinued Operations					(71)	23	(28)
Discontinued Operation, Alternative Cash Flow Information [Abstract]
Depreciation and amortization on assets held for sale					0	12	13
Amortization of intangible assets in Non-utility cost of revenues					0	0	0
Write-down of natural gas inventory					3	4	2
Capital expenditures					3	12	21
Accounts payable related to capital expenditures					0	2	2
Discontinued Operation, Continuing Involvement [Abstract]
Transportation revenue					34	101	104
Natural gas expense					48	125	107
Energy Services Disposal Group [Member] | CERC Corp [Member]
Discontinued Operation, Additional Disclosures [Abstract]
Net deferred tax liabilities on sale recognized as deferred income tax benefit by CenterPoint Energy					4
Current tax expense (benefit) of cash taxes payable upon sale					(4)
Pre-tax gain on sale					(3)
Outstanding obligation related to AMAs					24	0
Disposal Group, Including Discontinued Operation, Balance Sheet Disclosures [Abstract]
Receivables, net						445
Accrued unbilled revenues						8
Natural gas inventory						67
Materials and supplies						0
Non-trading derivative assets						136
Other						35
Total current assets held for sale						691
Property, plant and equipment, net						26
Goodwill						62
Non-trading derivative assets						58
Other						67
Total non-current assets held for sale						213
Total assets held for sale						904
Accounts payable						299
Taxes accrued						0
Non-trading derivative liabilities						44
Other						25
Total current liabilities held for sale						368
Non-trading derivative liabilities						14
Benefit obligations						4
Other						9
Total non-current liabilities held for sale						27
Total liabilities held for sale						395
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Revenues					1,167	3,767	4,503
Non-utility cost of revenues					1,108	3,597	4,459
Operation and maintenance					34	68	66
Depreciation and amortization					0	12	13
Taxes other than income taxes					3	2	2
Goodwill, Impairment Loss					62
Goodwill impairment					0	48	0
Total					1,145	3,727	4,540
Equity in earnings of unconsolidated affiliate, net					0	0
Income (loss) from Discontinued Operations before income taxes					22	40	147
Loss on classification to held for sale, net (2)					(90)	0	0
Income tax expense (benefit)					(2)	17	37
Net income (loss) from Discontinued Operations					(66)	23	110
Discontinued Operation, Alternative Cash Flow Information [Abstract]
Depreciation and amortization on assets held for sale					0	12	13
Write-down of natural gas inventory					3	4	2
Capital expenditures					3	12	21
Accounts payable related to capital expenditures					0	2	2
Discontinued Operation, Continuing Involvement [Abstract]
Transportation revenue					34	101	104
Natural gas expense					47	$ 124	$ 107
Energy Services [Member]
Discontinued Operation, Additional Disclosures [Abstract]
Cash proceeds from sale					$ 365