Income Taxes (Summary Of Tax Credit Carryforwards) (Details) $ in Millions	Mar. 31, 2022 USD ($)
Federal [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	$ 94
Tax credits, carryforward amount	589
State [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	578
IPL [Member] | Federal [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	87
Tax credits, carryforward amount	369
IPL [Member] | State [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	13
WPL [Member] | Federal [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	1
Tax credits, carryforward amount	197
WPL [Member] | State [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	$ 2