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Investments (Tables) | 9 Months Ended
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Sep. 30, 2017
Schedule of Investments [Line Items] |
Unconsolidated Equity Investments | Equity (income) loss from unconsolidated investments accounted for under the equity method of accounting for the three and nine months ended September 30 was as follows (in millions):
| Alliant Energy |  | WPL
| Three Months |  | Nine Months |  | Three Months |  | Nine Months
| 2017 |  | 2016 |  | 2017 |  | 2016 |  | 2017 |  | 2016 |  | 2017 |  | 2016
ATC Investment |  | ($10.1 | ) |  |  | ($9.1 | ) |  |  | ($32.7 | ) |  |  | ($28.6 | ) |  |  | $— |  |  |  | ($9.1 | ) |  |  | $— |  |  |  | ($28.6 | )
Other | — |  |  | (0.1 | ) |  | (0.2 | ) |  | (0.2 | ) |  | (0.2 | ) |  | (0.2 | ) |  | (0.4 | ) |  | (0.4 | )
|  | ($10.1 | ) |  |  | ($9.2 | ) |  |  | ($32.9 | ) |  |  | ($28.8 | ) |  |  | ($0.2 | ) |  |  | ($9.3 | ) |  |  | ($0.4 | ) |  |  | ($29.0 | )
WPL [Member] |
Schedule of Investments [Line Items] |
Unconsolidated Equity Investments | Equity (income) loss from unconsolidated investments accounted for under the equity method of accounting for the three and nine months ended September 30 was as follows (in millions):
| Alliant Energy |  | WPL
| Three Months |  | Nine Months |  | Three Months |  | Nine Months
| 2017 |  | 2016 |  | 2017 |  | 2016 |  | 2017 |  | 2016 |  | 2017 |  | 2016
ATC Investment |  | ($10.1 | ) |  |  | ($9.1 | ) |  |  | ($32.7 | ) |  |  | ($28.6 | ) |  |  | $— |  |  |  | ($9.1 | ) |  |  | $— |  |  |  | ($28.6 | )
Other | — |  |  | (0.1 | ) |  | (0.2 | ) |  | (0.2 | ) |  | (0.2 | ) |  | (0.2 | ) |  | (0.4 | ) |  | (0.4 | )
|  | ($10.1 | ) |  |  | ($9.2 | ) |  |  | ($32.9 | ) |  |  | ($28.8 | ) |  |  | ($0.2 | ) |  |  | ($9.3 | ) |  |  | ($0.4 | ) |  |  | ($29.0 | )

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- Definition Line items represent reporting 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 Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 12 -Sentence Column A + Details
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- Definition Tabular disclosure of equity method investments including, but not limited to, name of each investee or group of investments, percentage ownership, difference between recorded amount of an investment and the value of the underlying equity in the net assets, and summarized financial information. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=66011266&loc=d3e33918-111571 + Details
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