Benefit Plans (Estimated Future Funding) (Details) - Forecast [Member] $ in Millions	Dec. 31, 2025 USD ($)
Defined Benefit Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated funding for calendar year 2025	$ 20
Defined Benefit Pension Plans [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated funding for calendar year 2025	1
Defined Benefit Pension Plans [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated funding for calendar year 2025	14
Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated funding for calendar year 2025	7
Other Postretirement Benefits Plans [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated funding for calendar year 2025	1
Other Postretirement Benefits Plans [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated funding for calendar year 2025	$ 6