Commitments and Contingencies (Details)		3 Months Ended	9 Months Ended
Sep. 30, 2020 USD ($) site	Sep. 30, 2020 USD ($) site	Sep. 30, 2020 USD ($) site
Purchase Obligations
Remaining three months of 2020	$ 224,000,000	$ 224,000,000	$ 224,000,000
2021	662,000,000	662,000,000	662,000,000
2022	496,000,000	496,000,000	496,000,000
2023	418,000,000	418,000,000	418,000,000
2024	340,000,000	340,000,000	340,000,000
2025	290,000,000	290,000,000	290,000,000
2026 and beyond	$ 1,817,000,000	$ 1,817,000,000	$ 1,817,000,000
Performance Guarantees & Product Warranties [Abstract]
Number of surety bond obligations outstanding	60	60	60
Performance guarantee obligations outstanding face amount	$ 568,000,000	$ 568,000,000	$ 568,000,000
Percentage of work yet to be completed on projects with open surety bonds			21.00%
Guarantor obligations, maximum exposure, undiscounted	519,000,000	519,000,000	$ 519,000,000
Minnesota and Indiana Gas Service Territories [Member]
Legal, Environmental and Other Matters
Liability recorded for environmental loss contingencies	$ 12,000,000	$ 12,000,000	12,000,000
Minnesota and Indiana Gas Service Territories [Member] \| Minimum [Member]
Legal, Environmental and Other Matters
Estimated remediation costs for the Minnesota sites			$ 7,000,000
Years to resolve contingency			5
Minnesota and Indiana Gas Service Territories [Member] \| Maximum [Member]
Legal, Environmental and Other Matters
Estimated remediation costs for the Minnesota sites			$ 54,000,000
Years to resolve contingency			50
Indiana Gas Service Territory [Member]
Legal, Environmental and Other Matters
Environmental remediation number of sites with potential remedial responsibility \| site	26	26	26
SIGECO [Member]
Legal, Environmental and Other Matters
Environmental remediation number of sites with potential remedial responsibility \| site	5	5	5
CERC Corp [Member]
Purchase Obligations
Remaining three months of 2020	$ 163,000,000	$ 163,000,000	$ 163,000,000
2021	486,000,000	486,000,000	486,000,000
2022	325,000,000	325,000,000	325,000,000
2023	271,000,000	271,000,000	271,000,000
2024	246,000,000	246,000,000	246,000,000
2025	220,000,000	220,000,000	220,000,000
2026 and beyond	$ 1,496,000,000	1,496,000,000	1,496,000,000
CERC Corp [Member] \| CERC Senior notes 4.50% due 2021 [Member]
Legal, Environmental and Other Matters
Debt Instrument, Redemption Price, Percentage	100.00%
CERC Corp [Member] \| Minnesota and Indiana Gas Service Territories [Member]
Legal, Environmental and Other Matters
Liability recorded for environmental loss contingencies	$ 7,000,000	7,000,000	7,000,000
CERC Corp [Member] \| Minnesota and Indiana Gas Service Territories [Member] \| Minimum [Member]
Legal, Environmental and Other Matters
Estimated remediation costs for the Minnesota sites			$ 4,000,000
Years to resolve contingency			30
CERC Corp [Member] \| Minnesota and Indiana Gas Service Territories [Member] \| Maximum [Member]
Legal, Environmental and Other Matters
Estimated remediation costs for the Minnesota sites			$ 32,000,000
Years to resolve contingency			50
Indiana Electric Integrated [Member]
Legal, Environmental and Other Matters
Asset retirement obligation	73,000,000	73,000,000	$ 73,000,000
Indiana Electric Integrated [Member] \| Minimum [Member]
Legal, Environmental and Other Matters
Estimated capital expenditure to clean ash ponds	60,000,000	60,000,000	60,000,000
Indiana Electric Integrated [Member] \| Maximum [Member]
Legal, Environmental and Other Matters
Estimated capital expenditure to clean ash ponds	80,000,000	80,000,000	80,000,000
Minnehaha Academy Gas Explosion [Member]
Legal, Environmental and Other Matters
Contested amount of fines imposed	200,000	200,000	200,000
Minnehaha Academy Gas Explosion [Member] \| CERC Corp [Member]
Legal, Environmental and Other Matters
Contested amount of fines imposed	$ 200,000	$ 200,000	200,000
CES natural gas related transactions [Member] \| CERC Corp [Member]
Performance Guarantees & Product Warranties [Abstract]
Quarterly increase of fee received for retained CES guarantee exposure		3.00%
Quarterly increase of fee received for retained CES guarantee exposure		1.00%
Guarantee exposure replaced by third party			68,000,000
Estimated Remaining Exposure			$ 73,000,000

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Contested amount of fines imposed by the Minnesota Office of Pipeline Safety.

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Number of sites identified where the entity may potentially have some remedial responsibility

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Estimated Remaining Exposure

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Estimated Capital Expenditure to Clean Ash Ponds

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Guarantee exposure replaced by third party

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Quarterly increase of fee received for retained CES guarantee exposure

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Estimate of the reasonably possible loss exposure at an individual site.

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Total costs accrued as of the balance sheet date for environmental loss contingencies.

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Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

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Amount of purchase arrangement to be paid after fifth fiscal year following current fiscal year. Includes, but is not limited to, recorded and unrecorded purchase obligations, long-term purchase commitment, and short-term purchase commitment. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of purchase arrangement to be paid in fifth fiscal year following current fiscal year. Includes, but is not limited to, recorded and unrecorded purchase obligations, long-term purchase commitment, and short-term purchase commitment. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of purchase arrangement to be paid in fourth fiscal year following current fiscal year. Includes, but is not limited to, recorded and unrecorded purchase obligations, long-term purchase commitment, and short-term purchase commitment. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of purchase arrangement to be paid in second fiscal year following current fiscal year. Includes, but is not limited to, recorded and unrecorded purchase obligations, long-term purchase commitment, and short-term purchase commitment. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of purchase arrangement to be paid in third fiscal year following current fiscal year. Includes, but is not limited to, recorded and unrecorded purchase obligations, long-term purchase commitment, and short-term purchase commitment. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of purchase arrangement to be paid in remainder of current fiscal year. Includes, but is not limited to, recorded and unrecorded purchase obligations, long-term purchase commitment, and short-term purchase commitment.

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