Income Taxes (Schedule Of Components Of Income Tax) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Current tax expense (benefit):
Federal	$ 4.4	$ (29.3)	$ 58.6
State	(3.6)	11.6	15.7
Deferred tax expense (benefit):
Federal	123.9	157.8	99.0
State	15.6	23.9	(16.8)
Production tax credits	(31.0)	(24.8)	(27.1)
Investment tax credits	(1.6)	(1.7)	(1.8)
Provision recorded as a change in uncertain tax positions, current	0	8.0	16.3
Provision recorded as a change in uncertain tax positions, deferred	(0.4)	(7.6)	(38.3)
Provision recorded as a change in accrued interest	(0.5)	(0.2)	(0.5)
Income tax expense (benefit)	53.9	89.4	69.2
IPL's tax benefit riders [Member]
Current tax expense (benefit):
IPL's tax benefit riders	(52.9)	(48.3)	(35.9)
IPL [Member]
Current tax expense (benefit):
Federal	11.7	(7.7)	54.5
State	(0.1)	9.1	20.0
Deferred tax expense (benefit):
Federal	20.0	37.4	(11.6)
State	(0.8)	3.2	(16.4)
Production tax credits	(14.4)	(12.5)	(12.3)
Investment tax credits	(0.6)	(0.6)	(0.6)
Provision recorded as a change in uncertain tax positions, current	0	8.1	16.6
Provision recorded as a change in uncertain tax positions, deferred	0	(8.2)	(17.6)
Provision recorded as a change in accrued interest	(0.8)	(0.3)	(0.3)
Income tax expense (benefit)	(37.9)	(19.8)	(3.6)
IPL [Member] | IPL's tax benefit riders [Member]
Current tax expense (benefit):
IPL's tax benefit riders	(52.9)	(48.3)	(35.9)
WPL [Member]
Current tax expense (benefit):
Federal	(5.7)	7.2	(4.3)
State	6.0	(0.9)	(7.1)
Deferred tax expense (benefit):
Federal	92.7	81.1	111.3
State	11.8	20.3	19.0
Production tax credits	(16.6)	(12.3)	(14.8)
Investment tax credits	(1.0)	(1.1)	(1.2)
Provision recorded as a change in uncertain tax positions, current	0	(0.1)	(0.3)
Provision recorded as a change in uncertain tax positions, deferred	(0.4)	0.6	(20.7)
Provision recorded as a change in accrued interest	0.4	(0.2)	0
Income tax expense (benefit)	$ 87.2	$ 94.6	$ 81.9