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Benefit Plans (Schedule Of Qualified and Non-qualified Pension And Other Postretirement Benefits Costs (Credits)) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Defined benefit pension plans [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefits costs (credits) associated with Corporate Services employees	$ 0.5	$ 0.5	$ 1.0	$ 1.0
Defined benefit pension plans [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefits costs (credits) associated with Corporate Services employees	0.4	0.3	0.7	0.6
Other Postretirement Benefits Costs (Credits) [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefits costs (credits) associated with Corporate Services employees	0	0.1	(0.1)	0.1
Other Postretirement Benefits Costs (Credits) [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefits costs (credits) associated with Corporate Services employees	$ (0.1)	$ 0	$ (0.1)	$ 0

X

- Definition

Pension and other postretirement benefits plans costs allocated from Corporate Services.

+ References

No definition available.

+ Details

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Balance Type:	debit
Period Type:	duration

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- Details

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Balance Type:	na
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