Income Taxes (Summary Of Tax Credit Carryforwards) (Details) $ in Millions	Mar. 31, 2025 USD ($)
State [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	$ 336
Federal [Member]
Carryforwards [Line Items]
Tax credits, carryforward amount	701
IPL [Member] | State [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	7
IPL [Member] | Federal [Member]
Carryforwards [Line Items]
Tax credits, carryforward amount	473
WPL [Member] | State [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	1
WPL [Member] | Federal [Member]
Carryforwards [Line Items]
Tax credits, carryforward amount	$ 215