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Jointly-Owned Electric Utility Plant (Details) $ in Millions | Dec. 31, 2015 USD ($)
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Jointly Owned Electric Utility Plant [Line Items] |
Electric Plant | $ 1,526.7
Accumulated Provision for Depreciation | 501.2
Construction Work in Progress | 41.8
IPL [Member] |
Jointly Owned Electric Utility Plant [Line Items] |
Electric Plant | 852.1
Accumulated Provision for Depreciation | 267.5
Construction Work in Progress | 6.9
WPL [Member] |
Jointly Owned Electric Utility Plant [Line Items] |
Electric Plant | 674.6
Accumulated Provision for Depreciation | 233.7
Construction Work in Progress | $ 34.9
Ottumwa Unit 1 [Member] | IPL [Member] |
Jointly Owned Electric Utility Plant [Line Items] |
Ownership Interest % | 48.00%
Electric Plant | $ 481.4
Accumulated Provision for Depreciation | 125.0
Construction Work in Progress | $ 6.5
George Neal Unit 4 [Member] | IPL [Member] |
Jointly Owned Electric Utility Plant [Line Items] |
Ownership Interest % | 25.70%
Electric Plant | $ 184.3
Accumulated Provision for Depreciation | 76.3
Construction Work in Progress | $ 0.2
George Neal Unit 3 [Member] | IPL [Member] |
Jointly Owned Electric Utility Plant [Line Items] |
Ownership Interest % | 28.00%
Electric Plant | $ 150.0
Accumulated Provision for Depreciation | 45.1
Construction Work in Progress | $ 0.1
Louisa Unit 1 [Member] | IPL [Member] |
Jointly Owned Electric Utility Plant [Line Items] |
Ownership Interest % | 4.00%
Electric Plant | $ 36.4
Accumulated Provision for Depreciation | 21.1
Construction Work in Progress | $ 0.1
Columbia Units 1-2 [Member] | WPL [Member] |
Jointly Owned Electric Utility Plant [Line Items] |
Ownership Interest % | 46.20%
Electric Plant | $ 571.9
Accumulated Provision for Depreciation | 175.5
Construction Work in Progress | $ 34.8
Edgewater Unit 4 [Member] | WPL [Member] |
Jointly Owned Electric Utility Plant [Line Items] |
Ownership Interest % | 68.20%
Electric Plant | $ 102.7
Accumulated Provision for Depreciation | 58.2
Construction Work in Progress | $ 0.1

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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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