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Commitments And Contingencies (Narrative) (Details) (USD $) In Millions, unless otherwise specified | 3 Months Ended
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Mar. 31, 2014 site
Long-term Purchase Commitment [Line Items] |
Performance guarantees outstanding | $ 347
Present value abandonment obligation | 32
IPL [Member] |
Long-term Purchase Commitment [Line Items] |
Number of sites monitoring and remediating (in sites) | 27
WPL [Member] |
Long-term Purchase Commitment [Line Items] |
Number of sites monitoring and remediating (in sites) | 5
Indemnifications [Member] | RMT [Member] |
Long-term Purchase Commitment [Line Items] |
Loss contingency, estimate of possible loss | 3
Performance guarantees outstanding, 2014 [Member] |
Long-term Purchase Commitment [Line Items] |
Performance guarantees outstanding | 246
Performance guarantees outstanding, 2015 [Member] |
Long-term Purchase Commitment [Line Items] |
Performance guarantees outstanding | 53
Performance guarantees outstanding, 2016 [Member] |
Long-term Purchase Commitment [Line Items] |
Performance guarantees outstanding | 48
Scenario, Forecast [Member] |
Long-term Purchase Commitment [Line Items] |
Minimum future commitments | 2,518
Scenario, Forecast [Member] | IPL [Member] |
Long-term Purchase Commitment [Line Items] |
Minimum future commitments | 1,955
Scenario, Forecast [Member] | WPL [Member] |
Long-term Purchase Commitment [Line Items] |
Minimum future commitments | 560
Scenario, Forecast [Member] | Capital Purchase Obligation [Member] | Alliant Energy and IPL [Member] |
Long-term Purchase Commitment [Line Items] |
Minimum future commitments | 35
Environmental Issue [Member] | WPL [Member] |
Long-term Purchase Commitment [Line Items] |
Loss contingency, damages awarded, value | $ 7
Minimum [Member] |
Long-term Purchase Commitment [Line Items] |
Warranty period | 12 months
Maximum [Member] |
Long-term Purchase Commitment [Line Items] |
Warranty period | 60 months
Workforce Subject to Collective Bargaining Arrangements [Member] |
Long-term Purchase Commitment [Line Items] |
Concentration risk | 57.00%
Workforce Subject to Collective Bargaining Arrangements [Member] | IPL [Member] |
Long-term Purchase Commitment [Line Items] |
Concentration risk | 66.00%
Workforce Subject to Collective Bargaining Arrangements [Member] | WPL [Member] |
Long-term Purchase Commitment [Line Items] |
Concentration risk | 80.00%
Workforce Subject to Collective Bargaining Arrangements Expiring within One Year [Member] |
Long-term Purchase Commitment [Line Items] |
Concentration risk | 26.00%
Workforce Subject to Collective Bargaining Arrangements Expiring within One Year [Member] | WPL [Member] |
Long-term Purchase Commitment [Line Items] |
Concentration risk | 80.00%

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- Definition For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 21 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=28364263&loc=d3e13537-108611 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 275 -SubTopic 10 -Section 50 -Paragraph 20 -URI http://asc.fasb.org/extlink&oid=6927468&loc=d3e6404-108592 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 20 -URI http://asc.fasb.org/extlink&oid=28364263&loc=d3e13531-108611 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 275 -SubTopic 10 -Section 50 -Paragraph 18 -URI http://asc.fasb.org/extlink&oid=6927468&loc=d3e6351-108592 + Details
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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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