Income Taxes (Summary Of Tax Credit Carryforwards) (Details) $ in Millions	Mar. 31, 2023 USD ($)
State [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	$ 535
Federal [Member]
Carryforwards [Line Items]
Tax credits, carryforward amount	698
IPL [Member] | State [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	12
IPL [Member] | Federal [Member]
Carryforwards [Line Items]
Tax credits, carryforward amount	468
WPL [Member] | State [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	1
WPL [Member] | Federal [Member]
Carryforwards [Line Items]
Tax credits, carryforward amount	$ 218