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Income Taxes (Summary Of Tax Credit Carryforwards) (Details) $ in Millions	Dec. 31, 2015 USD ($)
Deferred tax assets, net operating losses	$ 525
IPL [Member]
Deferred tax assets, net operating losses	196
WPL [Member]
Deferred tax assets, net operating losses	205
Federal [Member]
Tax carryforwards, net operating losses	732
Deferred tax assets, net operating losses	251
Tax carryforwards, tax credits	240
Deferred tax assets, tax credits	236
Federal [Member] | IPL [Member]
Tax carryforwards, net operating losses	336
Deferred tax assets, net operating losses	113
Tax carryforwards, tax credits	85
Deferred tax assets, tax credits	82
Federal [Member] | WPL [Member]
Tax carryforwards, net operating losses	300
Deferred tax assets, net operating losses	105
Tax carryforwards, tax credits	96
Deferred tax assets, tax credits	96
State [Member]
Tax carryforwards, net operating losses	766
Deferred tax assets, net operating losses	38
State [Member] | IPL [Member]
Tax carryforwards, net operating losses	20
Deferred tax assets, net operating losses	1
State [Member] | WPL [Member]
Tax carryforwards, net operating losses	76
Deferred tax assets, net operating losses	$ 4

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
-Topic 740
-SubTopic 10
-Section 25
-Paragraph 20
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=29652012&loc=d3e28680-109314

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32621-109319

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32632-109319

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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=6907707&loc=d3e32559-109319

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X

- 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=6907707&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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X

- Definition

Amount of deferred tax asset, before valuation allowance, attributable to deductible other tax carryforwards.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32537-109319

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 30
-Paragraph 5
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=6907311&loc=d3e30536-109315

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