Benefit Plans (Employees Participate In Defined Contribution Retirement Plans) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
401(k) costs	$ 25.5	$ 25.1	$ 24.8
IPL [Member]
401(k) costs	13.0	13.0	12.8
WPL [Member]
401(k) costs	$ 11.5	$ 11.2	$ 11.1