Benefit Plans (Accumulated Benefit Obligations) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligations	$ 857	$ 857
Plans with accumulated benefit obligations in excess of plan assets:
Accumulated benefit obligations	857	857
Fair value of plan assets	732	706
Plans with projected benefit obligations in excess of plan assets:
Projected benefit obligations	876	875
Fair value of plan assets	732	706
Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligations	160	168
Plans with accumulated benefit obligations in excess of plan assets:
Accumulated benefit obligations	160	168
Fair value of plan assets	83	83
IPL [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligations	377	379
Plans with accumulated benefit obligations in excess of plan assets:
Accumulated benefit obligations	377	379
Fair value of plan assets	352	344
Plans with projected benefit obligations in excess of plan assets:
Projected benefit obligations	387	389
Fair value of plan assets	352	344
IPL [Member] | Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligations	65	68
Plans with accumulated benefit obligations in excess of plan assets:
Accumulated benefit obligations	65	68
Fair value of plan assets	61	58
WPL [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligations	373	373
Plans with accumulated benefit obligations in excess of plan assets:
Accumulated benefit obligations	373	373
Fair value of plan assets	306	291
Plans with projected benefit obligations in excess of plan assets:
Projected benefit obligations	381	381
Fair value of plan assets	306	291
WPL [Member] | Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligations	61	65
Plans with accumulated benefit obligations in excess of plan assets:
Accumulated benefit obligations	61	65
Fair value of plan assets	$ 14	$ 14