Benefit Plans (Employees Participate In Defined Contribution Retirement Plans) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
401(k) costs	$ 4.7		$ 4.4		$ 14.7		$ 14.1
IPL [Member]
401(k) costs	2.4	[1]	2.4	[1]	7.6	[1]	7.4	[1]
WPL [Member]
401(k) costs	$ 2.1	[1]	$ 2.0	[1]	$ 6.5	[1]	$ 6.2	[1]

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