Benefit Plans (Recognized Compensation Expense And Income Tax Benefits) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Compensation expense	$ 7.1	$ 2.3	$ 12.4	$ 5.5
Income tax benefits	2.9	0.9	5.1	2.2
IPL [Member]
Compensation expense	3.7	1.2	6.5	2.9
Income tax benefits	1.6	0.5	2.7	1.2
WPL [Member]
Compensation expense	3.1	1.0	5.4	2.4
Income tax benefits	$ 1.3	$ 0.4	$ 2.2	$ 1.0