Income Taxes (Summary Of Tax Credit Carryforwards) (Details) $ in Millions	Jun. 30, 2020 USD ($)
Federal [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	$ 299
Tax credits, carryforward amount	403
Federal [Member] | IPL [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	276
Tax credits, carryforward amount	212
Federal [Member] | WPL [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	3
Tax credits, carryforward amount	170
State [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	595
State [Member] | IPL [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	9
State [Member] | WPL [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	$ 2