Benefit Plans (Accumulated Benefit Obligations) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligations	$ 1,214	$ 1,305
Plans with accumulated benefit obligations in excess of plan assets:
Accumulated benefit obligations	1,214	1,305
Fair value of plan assets	1,011	984
Plans with projected benefit obligations in excess of plan assets:
Projected benefit obligations	1,251	1,351
Fair value of plan assets	1,011	984
Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligations	210	227
Plans with accumulated benefit obligations in excess of plan assets:
Accumulated benefit obligations	210	227
Fair value of plan assets	106	108
IPL [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligations	546	589
Plans with accumulated benefit obligations in excess of plan assets:
Accumulated benefit obligations	546	589
Fair value of plan assets	462	453
Plans with projected benefit obligations in excess of plan assets:
Projected benefit obligations	567	615
Fair value of plan assets	462	453
IPL [Member] | Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligations	84	91
Plans with accumulated benefit obligations in excess of plan assets:
Accumulated benefit obligations	84	91
Fair value of plan assets	74	74
WPL [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligations	532	573
Plans with accumulated benefit obligations in excess of plan assets:
Accumulated benefit obligations	532	573
Fair value of plan assets	450	436
Plans with projected benefit obligations in excess of plan assets:
Projected benefit obligations	546	588
Fair value of plan assets	450	436
WPL [Member] | Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligations	81	89
Plans with accumulated benefit obligations in excess of plan assets:
Accumulated benefit obligations	81	89
Fair value of plan assets	$ 17	$ 18