Benefit Plans (Employees Participate In Defined Contribution Retirement Plans) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
401(k) costs	$ 22.5		$ 19.2		$ 18.5
IPL [Member]
401(k) costs	11.1	[1]	9.9	[1]	9.6	[1]
WPL [Member]
401(k) costs	$ 10.5	[1]	$ 8.5	[1]	$ 8.1	[1]

[1] IPL’s and WPL’s amounts include allocated costs associated with Corporate Services employees.