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Income Taxes (Summary Of Tax Credit Carryforwards) (Details) $ in Millions	Jun. 30, 2017 USD ($)
Federal [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	$ 736
Tax credits, carryforward amount	292
Federal [Member] | IPL [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	412
Tax credits, carryforward amount	108
Federal [Member] | WPL [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	217
Tax credits, carryforward amount	123
State [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	707
State [Member] | IPL [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	14
State [Member] | WPL [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	$ 2

X

- Definition

Amount of operating loss carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32559-109319

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+ References

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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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32559-109319

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Carryforwards
-URI http://asc.fasb.org/extlink&oid=6506874

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