Income Taxes (Schedule Of Effective Income Tax Rates) (Details)	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Effective Tax Rate [Line Items]
Statutory federal income tax rate	35.00%	35.00%
IPL's tax benefit riders	(9.90%)	(11.90%)
Production tax credits	(6.20%)	(6.70%)
Effect of rate-making on property-related differences	(6.10%)	(5.30%)
Other items, net	4.30%	4.60%
Overall income tax rate	17.10%	15.70%
IPL [Member]
Effective Tax Rate [Line Items]
Statutory federal income tax rate	35.00%	35.00%
IPL's tax benefit riders	(25.20%)	(31.20%)
Production tax credits	(7.30%)	(8.30%)
Effect of rate-making on property-related differences	(14.60%)	(12.40%)
Other items, net	4.40%	4.70%
Overall income tax rate	(7.70%)	(12.20%)
WPL [Member]
Effective Tax Rate [Line Items]
Statutory federal income tax rate	35.00%	35.00%
Production tax credits	(6.00%)	(6.40%)
Effect of rate-making on property-related differences	(0.60%)	(1.00%)
Other items, net	4.60%	4.80%
Overall income tax rate	33.00%	32.40%

Effective Income Tax Rate Reconciliation Effect Of Rate Making On Property Related Differences

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Effective income tax rate reconciliation tax benefit rider

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to deduction for qualified production activity.

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