Benefit Plans (Employees Participate In Defined Contribution Retirement Plans) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
401(k) costs	$ 24.9	$ 22.5	$ 19.2
IPL [Member]
401(k) costs	12.7	11.1	9.9
WPL [Member]
401(k) costs	$ 11.2	$ 10.5	$ 8.5