Income Taxes (Summary Of Tax Credit Carryforwards) (Details) $ in Millions	Dec. 31, 2019 USD ($)
Federal [Member]
Tax carryforwards, net operating losses	$ 297
Tax carryforwards, tax credits	355
Federal [Member] | IPL [Member]
Tax carryforwards, net operating losses	276
Tax carryforwards, tax credits	175
Federal [Member] | WPL [Member]
Tax carryforwards, net operating losses	2
Tax carryforwards, tax credits	160
State [Member]
Tax carryforwards, net operating losses	615
State [Member] | IPL [Member]
Tax carryforwards, net operating losses	9
State [Member] | WPL [Member]
Tax carryforwards, net operating losses	$ 2