Commitments and Contingencies - Narrative (Details) $ in Millions	6 Months Ended
	Jun. 30, 2022 USD ($) a ashPond lawsuit gasManufacturingAndStorageSite warrantyObligation suretyBond	Jul. 05, 2022 MW	Jan. 31, 2022 MW	Dec. 31, 2021 USD ($)	Feb. 09, 2021 MW
Loss Contingencies [Line Items]
Number of surety bond obligations outstanding | suretyBond	55
Performance guarantee obligations outstanding face amount	$ 595
Percentage of work yet to be completed on projects with open surety bonds (as a percent)	37.00%
Number of warranty obligations outstanding | warrantyObligation	34
Warranty obligations outstanding face amount	$ 541
Energy savings commitments not guaranteed	1,200
Guarantor obligations, maximum exposure, undiscounted	$ 546
Pending lawsuits | lawsuit	5
Number of owned coal ash ponds | ashPond	3
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
February 2021 Winter Storm Event
Loss Contingencies [Line Items]
Pending lawsuits | lawsuit	185
February 2021 Winter Storm Event | Loss from Catastrophes
Loss Contingencies [Line Items]
Pending lawsuits | lawsuit	130
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 (in acres) | a	10
CERC | Indiana Gas Service Territory
Loss Contingencies [Line Items]
Environmental remediation number of sites with potential remedial responsibility | gasManufacturingAndStorageSite	26
Indiana Electric
Loss Contingencies [Line Items]
Asset retirement obligation	$ 91
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
Houston Electric | February 2021 Winter Storm Event | Loss from Catastrophes
Loss Contingencies [Line Items]
Pending lawsuits | lawsuit	130
Energy Services Disposal Group
Loss Contingencies [Line Items]
Guarantor obligation, current carrying value	$ 0			$ 0
Energy Services Disposal Group | CERC
Loss Contingencies [Line Items]
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
Posey Solar | Subsequent Event
Loss Contingencies [Line Items]
Solar array generating capacity (in MW) | MW		130