Income Taxes (Summary Of Tax Credit Carryforwards) (Details) $ in Millions	Dec. 31, 2025 USD ($)
Iowa State [Member]
Income Tax [Line Items]
Tax carryforwards, net operating losses	$ 311
Iowa State [Member] | IPL [Member]
Income Tax [Line Items]
Tax carryforwards, net operating losses	7
Iowa State [Member] | WPL [Member]
Income Tax [Line Items]
Tax carryforwards, net operating losses	1
Federal [Member]
Income Tax [Line Items]
Tax carryforwards, tax credits	669
Federal [Member] | IPL [Member]
Income Tax [Line Items]
Tax carryforwards, tax credits	455
Federal [Member] | WPL [Member]
Income Tax [Line Items]
Tax carryforwards, tax credits	$ 199