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Jointly-Owned Electric Utility Plant (Details) $ in Millions | Dec. 31, 2017 USD ($)
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Jointly Owned Electric Utility Plant [Line Items] |
Electric Plant | $ 1,692.0
Accumulated Provision for Depreciation | 582.7
Construction Work in Progress | 89.0
IPL [Member] |
Jointly Owned Electric Utility Plant [Line Items] |
Electric Plant | 877.4
Accumulated Provision for Depreciation | 305.5
Construction Work in Progress | 42.0
WPL [Member] |
Jointly Owned Electric Utility Plant [Line Items] |
Electric Plant | 814.6
Accumulated Provision for Depreciation | 277.2
Construction Work in Progress | $ 47.0
Ottumwa Unit 1 [Member] | IPL [Member] |
Jointly Owned Electric Utility Plant [Line Items] |
Ownership Interest % | 48.00%
Electric Plant | $ 501.8
Accumulated Provision for Depreciation | 144.9
Construction Work in Progress | $ 37.3
George Neal Unit 4 [Member] | IPL [Member] |
Jointly Owned Electric Utility Plant [Line Items] |
Ownership Interest % | 25.70%
Electric Plant | $ 187.2
Accumulated Provision for Depreciation | 85.2
Construction Work in Progress | $ 0.8
George Neal Unit 3 [Member] | IPL [Member] |
Jointly Owned Electric Utility Plant [Line Items] |
Ownership Interest % | 28.00%
Electric Plant | $ 150.6
Accumulated Provision for Depreciation | 53.0
Construction Work in Progress | $ 2.5
Louisa Unit 1 [Member] | IPL [Member] |
Jointly Owned Electric Utility Plant [Line Items] |
Ownership Interest % | 4.00%
Electric Plant | $ 37.8
Accumulated Provision for Depreciation | 22.4
Construction Work in Progress | $ 1.4
Columbia Units 1-2 [Member] | WPL [Member] |
Jointly Owned Electric Utility Plant [Line Items] |
Ownership Interest % | 50.10%
Electric Plant | $ 714.7
Accumulated Provision for Depreciation | 216.8
Construction Work in Progress | $ 46.9
Edgewater Unit 4 [Member] | WPL [Member] |
Jointly Owned Electric Utility Plant [Line Items] |
Ownership Interest % | 68.20%
Electric Plant | $ 99.9
Accumulated Provision for Depreciation | 60.4
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 + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + 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 + 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 + 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 + Details
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