Benefit Plans (Employees Participate In Defined Contribution Retirement Plans) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
401(k) costs	$ 23.6	$ 24.9	$ 22.5
IPL [Member]
401(k) costs	12.0	12.7	11.1
WPL [Member]
401(k) costs	$ 10.7	$ 11.2	$ 10.5