Commitments and Contingencies - Narrative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2022 USD ($) a warrantyObligation ashPond lawsuit gasManufacturingAndStorageSite suretyBond	Jan. 31, 2022 MW	Dec. 31, 2021 USD ($)	Feb. 09, 2021 MW
Loss Contingencies [Line Items]
Number of surety bond obligations outstanding | suretyBond	53
Performance guarantee obligations outstanding face amount	$ 527
Percentage of work yet to be completed on projects with open surety bonds	39.00%
Number of warranty obligations outstanding | warrantyObligation	37
Warranty obligations outstanding face amount	$ 549
Energy savings commitments not guaranteed	1,200
Guarantor obligations, maximum exposure, undiscounted	$ 511
Pending lawsuits | lawsuit	5
Number of owned coal ash ponds | ashPond	3
Loss from Catastrophes | February 2021 Winter Storm Event
Loss Contingencies [Line Items]
Pending lawsuits | lawsuit	100
F.B. Culley
Loss Contingencies [Line Items]
Number of owned coal ash ponds | ashPond	2
A.B. Brown
Loss Contingencies [Line Items]
Number of owned coal ash ponds | ashPond	1
F.B. Culley East
Loss Contingencies [Line Items]
Number of owned coal ash ponds | ashPond	1
Number of acres | a	10
Indiana Gas Service Territory
Loss Contingencies [Line Items]
Environmental remediation number of sites with potential remedial responsibility | gasManufacturingAndStorageSite	26
SIGECO
Loss Contingencies [Line Items]
Environmental remediation number of sites with potential remedial responsibility | gasManufacturingAndStorageSite	5
Houston Electric | Loss from Catastrophes | February 2021 Winter Storm Event
Loss Contingencies [Line Items]
Pending lawsuits | lawsuit	100
Indiana Electric
Loss Contingencies [Line Items]
Asset retirement obligation	$ 90
Indiana Electric | Minimum
Loss Contingencies [Line Items]
Estimated capital expenditure to clean ash ponds	60
Indiana Electric | Maximum
Loss Contingencies [Line Items]
Estimated capital expenditure to clean ash ponds	80
Energy Services Disposal Group
Loss Contingencies [Line Items]
Guarantor obligation, current carrying value	$ 0		$ 0
Energy Services Disposal Group | CERC Corp
Loss Contingencies [Line Items]
Exposure period after closing	90 days
Annualized fee received for retained CES guarantee exposure	3.00%
Quarterly increase of fee received for retained CES guarantee exposure	1.00%
Exposure period until increased fee	3 months
Estimated remaining exposure	$ 6
Guarantor obligation, current carrying value	0		$ 0
ESG
Loss Contingencies [Line Items]
Fair value of guarantees	$ 0
Posey Solar
Loss Contingencies [Line Items]
Solar array generating capacity (in MW) | MW		200		300