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Income Taxes (Summary Of Tax Credit Carryforwards) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013
Operating Loss Carryforwards [Line Items]
Net operating losses, deferred tax assets	$ 484
IPL [Member]
Operating Loss Carryforwards [Line Items]
Net operating losses, deferred tax assets	191
WPL [Member]
Operating Loss Carryforwards [Line Items]
Net operating losses, deferred tax assets	173
Federal [Member]
Operating Loss Carryforwards [Line Items]
Net operating losses, carryforward amount	841
Net operating losses, deferred tax assets	289
Tax credits, carryforward amount	155
Tax credits, deferred tax asset	153
Federal [Member] | IPL [Member]
Operating Loss Carryforwards [Line Items]
Net operating losses, carryforward amount	385
Net operating losses, deferred tax assets	132
Tax credits, carryforward amount	47
Tax credits, deferred tax asset	46
Federal [Member] | WPL [Member]
Operating Loss Carryforwards [Line Items]
Net operating losses, carryforward amount	342
Net operating losses, deferred tax assets	117
Tax credits, carryforward amount	50
Tax credits, deferred tax asset	49
State [Member]
Operating Loss Carryforwards [Line Items]
Net operating losses, carryforward amount	795
Net operating losses, deferred tax assets	42
State [Member] | IPL [Member]
Operating Loss Carryforwards [Line Items]
Net operating losses, carryforward amount	228
Net operating losses, deferred tax assets	13
State [Member] | WPL [Member]
Operating Loss Carryforwards [Line Items]
Net operating losses, carryforward amount	147
Net operating losses, deferred tax assets	$ 7

X

- Definition

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-Name Statement of Financial Accounting Standard (FAS)

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



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- Definition

The sum of domestic, foreign and state and local operating loss carryforwards, before tax effects, available to reduce future taxable income under enacted tax laws.

+ References

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-Publisher FASB

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- Definition

The amount of the tax credit carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

+ References

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-Publisher FASB

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- Definition

The cumulative amount of future tax effects arising from the unused tax credit carryforward that cannot be utilized on the tax return during a year that may be carried forward to reduce taxable income or taxes payable in a future year; a tax credit carryforward is the amount by which tax credits available for utilization exceed statutory limitations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 109

-Paragraph 43

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



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