Income Taxes (Summary Of Tax Credit Carryforwards) (Details) $ in Millions	Jun. 30, 2019 USD ($)
Federal [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	$ 760
Tax credits, carryforward amount	325
Federal [Member] | IPL [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	550
Tax credits, carryforward amount	152
Federal [Member] | WPL [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	122
Tax credits, carryforward amount	154
State [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	764
State [Member] | IPL [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	13
State [Member] | WPL [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	$ 2