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Income Taxes (Summary Of Tax Credit Carryforwards) (Details) (USD $) In Millions, unless otherwise specified | Mar. 31, 2014
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Operating Loss Carryforwards [Line Items] |
Net operating losses, deferred tax assets | $ 451
IPL [Member] |
Operating Loss Carryforwards [Line Items] |
Net operating losses, deferred tax assets | 170
WPL [Member] |
Operating Loss Carryforwards [Line Items] |
Net operating losses, deferred tax assets | 170
Federal [Member] |
Operating Loss Carryforwards [Line Items] |
Net operating losses, carryforward amount | 697
Net operating losses, deferred tax assets | 239
Tax credits, carryforward amount | 181
Tax credits, deferred tax assets | 178
Federal [Member] | IPL [Member] |
Operating Loss Carryforwards [Line Items] |
Net operating losses, carryforward amount | 303
Net operating losses, deferred tax assets | 104
Tax credits, carryforward amount | 59
Tax credits, deferred tax assets | 58
Federal [Member] | WPL [Member] |
Operating Loss Carryforwards [Line Items] |
Net operating losses, carryforward amount | 302
Net operating losses, deferred tax assets | 103
Tax credits, carryforward amount | 64
Tax credits, deferred tax assets | 62
State [Member] |
Operating Loss Carryforwards [Line Items] |
Net operating losses, carryforward amount | 681
Net operating losses, deferred tax assets | 34
State [Member] | IPL [Member] |
Operating Loss Carryforwards [Line Items] |
Net operating losses, carryforward amount | 172
Net operating losses, deferred tax assets | 8
State [Member] | WPL [Member] |
Operating Loss Carryforwards [Line Items] |
Net operating losses, carryforward amount | 96
Net operating losses, deferred tax assets | $ 5

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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 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32621-109319 Reference 2: 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 Reference 3: 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 + 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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