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Income Taxes (Summary Of Tax Credit Carryforwards) (Details) $ in Millions | Dec. 31, 2015 USD ($)
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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

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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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