Income Taxes (Summary Of Tax Credit Carryforwards) (Details) $ in Millions	Sep. 30, 2023 USD ($)
State [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	$ 431
Federal [Member]
Carryforwards [Line Items]
Tax credits, carryforward amount	737
IPL [Member] | State [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	6
IPL [Member] | Federal [Member]
Carryforwards [Line Items]
Tax credits, carryforward amount	520
WPL [Member] | State [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	1
WPL [Member] | Federal [Member]
Carryforwards [Line Items]
Tax credits, carryforward amount	$ 208