Benefit Plans (Recognized Compensation Expense And Income Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Compensation expense	$ 10.7	$ 15.3	$ 12.0
Income tax benefits	4.4	6.2	4.8
IPL [Member]
Compensation expense	5.7	8.3	6.2
Income tax benefits	2.4	3.4	2.5
WPL [Member]
Compensation expense	4.7	6.4	5.2
Income tax benefits	$ 1.9	$ 2.6	$ 2.1