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Commitments And Contingencies (Narrative) (Details) - Jun. 30, 2015 $ in Millions | USD ($) site
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Commitments and Contingencies [Line Items] |
Minimum future commitments | $ 2,277
Performance guarantees outstanding | 198
Present value abandonment obligation | 36
IPL [Member] |
Commitments and Contingencies [Line Items] |
Minimum future commitments | $ 1,799
Number of sites monitoring and remediating (in sites) | site | 24
WPL [Member] |
Commitments and Contingencies [Line Items] |
Minimum future commitments | $ 478
Number of sites monitoring and remediating (in sites) | site | 5
Capital Purchase Obligation [Member] | Alliant Energy and WPL [Member] |
Commitments and Contingencies [Line Items] |
Minimum future commitments | $ 30
Performance guarantees outstanding, 2015 [Member] |
Commitments and Contingencies [Line Items] |
Performance guarantees outstanding | 75
Performance guarantees outstanding, 2016 [Member] |
Commitments and Contingencies [Line Items] |
Performance guarantees outstanding | 48
Performance guarantees outstanding, 2017 [Member] |
Commitments and Contingencies [Line Items] |
Performance guarantees outstanding | 75
Civil Penalty [Member] | IPL [Member] |
Commitments and Contingencies [Line Items] |
Environmental mitigation projects to be completed, value | 1
Environmental Issue [Member] | IPL [Member] |
Commitments and Contingencies [Line Items] |
Environmental mitigation projects to be completed, value | 6
Environmental Issue [Member] | WPL [Member] |
Commitments and Contingencies [Line Items] |
Environmental mitigation projects to be completed, value | $ 7
Minimum [Member] |
Commitments and Contingencies [Line Items] |
Warranty period | 12 months
Maximum [Member] |
Commitments and Contingencies [Line Items] |
Warranty period | 60 months

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- Definition Amount of damages awarded to the plaintiff in the legal matter. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14326-108349 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14435-108349 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 9 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14557-108349 + Details
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