Income Taxes (Schedule Of Effective Income Tax Rates) (Details)	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Effective Tax Rate [Line Items]
Statutory federal income tax rate	35.00%	35.00%	35.00%
State income taxes, net of federal benefits	5.50%	5.40%	5.20%
Effect of rate-making on property-related differences	(8.50%)	(8.50%)	(6.80%)
Production tax credits	(6.10%)	(7.20%)	(7.20%)
Impact of Tax Reform	(3.40%)	(0.00%)	(0.00%)
Other items, net	(2.40%)	(1.30%)	(0.30%)
Overall income tax rate	12.50%	13.40%	15.30%
IPL [Member]
Effective Tax Rate [Line Items]
Statutory federal income tax rate	35.00%	35.00%	35.00%
State income taxes, net of federal benefits	6.50%	6.40%	6.20%
Effect of rate-making on property-related differences	(19.10%)	(16.20%)	(17.20%)
Production tax credits	(6.70%)	(6.30%)	(8.30%)
Impact of Tax Reform	1.70%	(0.00%)	(0.00%)
Other items, net	(3.70%)	(1.50%)	(0.50%)
Overall income tax rate	(5.00%)	(2.70%)	(13.10%)
WPL [Member]
Effective Tax Rate [Line Items]
Statutory federal income tax rate	35.00%	35.00%	35.00%
State income taxes, net of federal benefits	5.10%	5.10%	5.10%
Effect of rate-making on property-related differences	(1.70%)	(0.70%)	(0.50%)
Production tax credits	(7.10%)	(6.20%)	(7.10%)
Impact of Tax Reform	(5.80%)	(0.00%)	(0.00%)
Other items, net	(0.60%)	(0.60%)	(0.70%)
Overall income tax rate	24.90%	32.60%	31.80%
IPL's tax benefit riders [Member]
Effective Tax Rate [Line Items]
IPL’s tax benefit riders	(7.60%)	(10.00%)	(10.60%)
IPL's tax benefit riders [Member] \| IPL [Member]
Effective Tax Rate [Line Items]
IPL’s tax benefit riders	(18.70%)	(20.10%)	(28.30%)

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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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Percentage of the difference, between reported income tax expense (benefit) and the expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations, that is attributable to tax exempt income, equity in earnings (loss) of an unconsolidated subsidiary, minority interest income (expense), tax holiday, disposition of a business, disposition of an asset, repatriation of foreign earnings, repatriation of foreign earnings jobs creation act of 2004, change in enacted tax rate, prior year income taxes, change in deferred tax asset valuation allowance, and other adjustments.

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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 applicable to state and local income tax expense (benefit), net of federal tax expense (benefit).

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