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Jointly-Owned Electric Utility Plant (Details) (USD $) In Millions, unless otherwise specified | Dec. 31, 2012
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Jointly Owned Utility Plant Interests [Line Items] |
Plant in Service | $ 769.2
Accumulated Provision for Depreciation | 452.0
Construction Work in Progress | 289.8
Cost Of Removal Obligations Included In Regulatory Liabilities | 44.5
IPL [Member] |
Jointly Owned Utility Plant Interests [Line Items] |
Plant in Service | 430.4
Accumulated Provision for Depreciation | 244.9
Construction Work in Progress | 155.9
Cost Of Removal Obligations Included In Regulatory Liabilities | 32.1
WPL [Member] |
Jointly Owned Utility Plant Interests [Line Items] |
Plant in Service | 338.8
Accumulated Provision for Depreciation | 207.1
Construction Work in Progress | 133.9
Cost Of Removal Obligations Included In Regulatory Liabilities | 12.4
Ottumwa Unit 1 [Member] | IPL [Member] |
Jointly Owned Utility Plant Interests [Line Items] |
In-service Dates | 1981
Ownership Interest % | 48.00%
Plant in Service | 239.2
Accumulated Provision for Depreciation | 118.8
Construction Work in Progress | 84.0
Cost Of Removal Obligations Included In Regulatory Liabilities | 12.0
George Neal Unit 4 [Member] | IPL [Member] |
Jointly Owned Utility Plant Interests [Line Items] |
In-service Dates | 1979
Ownership Interest % | 25.70%
Plant in Service | 97.1
Accumulated Provision for Depreciation | 67.8
Construction Work in Progress | 44.5
Cost Of Removal Obligations Included In Regulatory Liabilities | 11.5
George Neal Unit 3 [Member] | IPL [Member] |
Jointly Owned Utility Plant Interests [Line Items] |
In-service Dates | 1975
Ownership Interest % | 28.00%
Plant in Service | 59.1
Accumulated Provision for Depreciation | 39.1
Construction Work in Progress | 27.2
Cost Of Removal Obligations Included In Regulatory Liabilities | 5.6
Louisa Unit 1 [Member] | IPL [Member] |
Jointly Owned Utility Plant Interests [Line Items] |
In-service Dates | 1983
Ownership Interest % | 4.00%
Plant in Service | 35.0
Accumulated Provision for Depreciation | 19.2
Construction Work in Progress | 0.2
Cost Of Removal Obligations Included In Regulatory Liabilities | 3.0
Columbia Units 1-2 [Member] | WPL [Member] |
Jointly Owned Utility Plant Interests [Line Items] |
In-service Dates | 1975-1978
Ownership Interest % | 46.20%
Plant in Service | 247.0
Accumulated Provision for Depreciation | 157.9
Construction Work in Progress | 133.5
Cost Of Removal Obligations Included In Regulatory Liabilities | 10.2
Edgewater Unit 4 [Member] | WPL [Member] |
Jointly Owned Utility Plant Interests [Line Items] |
In-service Dates | 1969
Ownership Interest % | 68.20%
Plant in Service | 91.8
Accumulated Provision for Depreciation | 49.2
Construction Work in Progress | 0.4
Cost Of Removal Obligations Included In Regulatory Liabilities | $ 2.2

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- Definition Jointly Owned Utility Plant In-Service Dates + References No definition available. + Details
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- Definition The period end amount owned by the reporting utility of a jointly owned utility plant in service. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 360 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 10.C) -URI http://asc.fasb.org/extlink&oid=6500719&loc=d3e659983-123033 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 10 -Section C + Details
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- Definition The period end amount of construction work in progress at a jointly owned electricity generation plant. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 360 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 10.C) -URI http://asc.fasb.org/extlink&oid=6500719&loc=d3e659983-123033 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 10 -Section C + Details
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- Definition The period end amount of accumulated depreciation in a jointly owned electricity generation plant. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 360 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 10.C) -URI http://asc.fasb.org/extlink&oid=6500719&loc=d3e659983-123033 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 10 -Section C + Details
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- Definition The proportionate share of interest (percent) in a jointly owned utility plant. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 360 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 10.C) -URI http://asc.fasb.org/extlink&oid=6500719&loc=d3e659983-123033 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 10 -Section C + Details
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