Benefit Plans (Recognized Compensation Expense And Income Tax Benefits) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Compensation expense	$ 3.2	$ 3.1
Income tax benefits	1.3	1.3
IPL [Member]
Compensation expense	1.7	1.7
Income tax benefits	0.7	0.7
WPL [Member]
Compensation expense	1.4	1.3
Income tax benefits	$ 0.6	$ 0.5