Income Taxes (Summary Of Tax Credit Carryforwards) (Details) $ in Millions	Mar. 31, 2024 USD ($)
State [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	$ 403
Federal [Member]
Carryforwards [Line Items]
Tax credits, carryforward amount	685
IPL [Member] | State [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	6
IPL [Member] | Federal [Member]
Carryforwards [Line Items]
Tax credits, carryforward amount	462
WPL [Member] | State [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	1
WPL [Member] | Federal [Member]
Carryforwards [Line Items]
Tax credits, carryforward amount	$ 214