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Jointly-Owned Electric Utility Plant (Tables) | 12 Months Ended
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Dec. 31, 2017
Jointly Owned Electric Utility Plant [Line Items] |
Components of Jointly-Owned Electric Utility Plants | Information relative to IPL’s and WPL’s ownership interest in these jointly-owned coal-fired EGUs at December 31, 2017 was as follows (dollars in millions):
| Ownership |  | Electric |  | Accumulated Provision |  | Construction
| Interest % |  | Plant |  | for Depreciation |  | Work in Progress
IPL |  |  |  |  |  |  |
Ottumwa Unit 1 | 48.0 | % |  |  | $501.8 |  |  |  | $144.9 |  |  |  | $37.3 |
George Neal Unit 4 | 25.7 | % |  | 187.2 |  |  | 85.2 |  |  | 0.8 |
George Neal Unit 3 | 28.0 | % |  | 150.6 |  |  | 53.0 |  |  | 2.5 |
Louisa Unit 1 | 4.0 | % |  | 37.8 |  |  | 22.4 |  |  | 1.4 |
|  |  | 877.4 |  |  | 305.5 |  |  | 42.0 |
WPL |  |  |  |  |  |  |
Columbia Units 1-2 | 50.1 | % |  | 714.7 |  |  | 216.8 |  |  | 46.9 |
Edgewater Unit 4 | 68.2 | % |  | 99.9 |  |  | 60.4 |  |  | 0.1 |
|  |  | 814.6 |  |  | 277.2 |  |  | 47.0 |
Alliant Energy |  |  |  | $1,692.0 |  |  |  | $582.7 |  |  |  | $89.0 |
IPL [Member] |
Jointly Owned Electric Utility Plant [Line Items] |
Components of Jointly-Owned Electric Utility Plants | Information relative to IPL’s and WPL’s ownership interest in these jointly-owned coal-fired EGUs at December 31, 2017 was as follows (dollars in millions):
| Ownership |  | Electric |  | Accumulated Provision |  | Construction
| Interest % |  | Plant |  | for Depreciation |  | Work in Progress
IPL |  |  |  |  |  |  |
Ottumwa Unit 1 | 48.0 | % |  |  | $501.8 |  |  |  | $144.9 |  |  |  | $37.3 |
George Neal Unit 4 | 25.7 | % |  | 187.2 |  |  | 85.2 |  |  | 0.8 |
George Neal Unit 3 | 28.0 | % |  | 150.6 |  |  | 53.0 |  |  | 2.5 |
Louisa Unit 1 | 4.0 | % |  | 37.8 |  |  | 22.4 |  |  | 1.4 |
|  |  | 877.4 |  |  | 305.5 |  |  | 42.0 |
WPL |  |  |  |  |  |  |
Columbia Units 1-2 | 50.1 | % |  | 714.7 |  |  | 216.8 |  |  | 46.9 |
Edgewater Unit 4 | 68.2 | % |  | 99.9 |  |  | 60.4 |  |  | 0.1 |
|  |  | 814.6 |  |  | 277.2 |  |  | 47.0 |
Alliant Energy |  |  |  | $1,692.0 |  |  |  | $582.7 |  |  |  | $89.0 |
WPL [Member] |
Jointly Owned Electric Utility Plant [Line Items] |
Components of Jointly-Owned Electric Utility Plants | Information relative to IPL’s and WPL’s ownership interest in these jointly-owned coal-fired EGUs at December 31, 2017 was as follows (dollars in millions):
| Ownership |  | Electric |  | Accumulated Provision |  | Construction
| Interest % |  | Plant |  | for Depreciation |  | Work in Progress
IPL |  |  |  |  |  |  |
Ottumwa Unit 1 | 48.0 | % |  |  | $501.8 |  |  |  | $144.9 |  |  |  | $37.3 |
George Neal Unit 4 | 25.7 | % |  | 187.2 |  |  | 85.2 |  |  | 0.8 |
George Neal Unit 3 | 28.0 | % |  | 150.6 |  |  | 53.0 |  |  | 2.5 |
Louisa Unit 1 | 4.0 | % |  | 37.8 |  |  | 22.4 |  |  | 1.4 |
|  |  | 877.4 |  |  | 305.5 |  |  | 42.0 |
WPL |  |  |  |  |  |  |
Columbia Units 1-2 | 50.1 | % |  | 714.7 |  |  | 216.8 |  |  | 46.9 |
Edgewater Unit 4 | 68.2 | % |  | 99.9 |  |  | 60.4 |  |  | 0.1 |
|  |  | 814.6 |  |  | 277.2 |  |  | 47.0 |
Alliant Energy |  |  |  | $1,692.0 |  |  |  | $582.7 |  |  |  | $89.0 |

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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 Tabular disclosure of proportionate interests in jointly owned utility plants. Includes the amount of plants in service, the accumulated provision for depreciation (if available), the amount of plants under construction, and the proportionate share. The amounts presented may be further subdivided to show amounts applicable to plant subcategories (for example, production, transmission, distribution). Includes statements that the amounts represent the utility's share in each joint plant and that it must provide its own financing. Information concerning two or more generating plants on the same site may be combined. States that the utility's share of direct expenses of the joint plants is included in the corresponding operating expenses on its income statement (for example, fuel, maintenance of plant, other operating expense). If the share of direct expenses is charged to purchased power, then disclose the amount so charged and the proportionate amounts charged to specific operating expenses on the records maintained for the joint plants. + 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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