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Income Taxes (Summary Of Tax Credit Carryforwards) (Details) $ in Millions | Sep. 30, 2015 USD ($)
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Carryforwards [Line Items] |
Net operating losses, deferred tax assets | $ 441
IPL [Member] |
Carryforwards [Line Items] |
Net operating losses, deferred tax assets | 166
WPL [Member] |
Carryforwards [Line Items] |
Net operating losses, deferred tax assets | 168
Federal [Member] |
Carryforwards [Line Items] |
Net operating losses, carryforward amount | 527
Net operating losses, deferred tax assets | 180
Tax credits, carryforward amount | 227
Tax credits, deferred tax assets | 224
Federal [Member] | IPL [Member] |
Carryforwards [Line Items] |
Net operating losses, carryforward amount | 231
Net operating losses, deferred tax assets | 79
Tax credits, carryforward amount | 80
Tax credits, deferred tax assets | 78
Federal [Member] | WPL [Member] |
Carryforwards [Line Items] |
Net operating losses, carryforward amount | 218
Net operating losses, deferred tax assets | 75
Tax credits, carryforward amount | 89
Tax credits, deferred tax assets | 87
State [Member] |
Carryforwards [Line Items] |
Net operating losses, carryforward amount | 731
Net operating losses, deferred tax assets | 37
State [Member] | IPL [Member] |
Carryforwards [Line Items] |
Net operating losses, carryforward amount | 183
Net operating losses, deferred tax assets | 9
State [Member] | WPL [Member] |
Carryforwards [Line Items] |
Net operating losses, carryforward amount | 126
Net operating losses, deferred tax assets | $ 6

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- 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 + Details
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- 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 + Details
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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=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 + Details
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- 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 + Details
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