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Investments | 6 Months Ended
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Jun. 30, 2013
Schedule of Equity Method Investments [Line Items] |
Investments | INVESTMENTS Unconsolidated Equity Investments - Equity (income) loss from Alliant Energy’s and WPL’s unconsolidated investments accounted for under the equity method of accounting for the three and six months ended June 30 was as follows (in millions):
| Alliant Energy |  | WPL
| Three Months |  | Six Months |  | Three Months |  | Six Months
| 2013 |  | 2012 |  | 2013 |  | 2012 |  | 2013 |  | 2012 |  | 2013 |  | 2012
American Transmission Company LLC (ATC) |  | ($10.6 | ) |  |  | ($10.3 | ) |  |  | ($20.9 | ) |  |  | ($20.2 | ) |  |  | ($10.6 | ) |  |  | ($10.3 | ) |  |  | ($20.9 | ) |  |  | ($20.2 | )
Other | (0.3 | ) |  | (0.3 | ) |  | (0.7 | ) |  | 0.2 |  |  | (0.2 | ) |  | (0.3 | ) |  | (0.7 | ) |  | (0.5 | )
|  | ($10.9 | ) |  |  | ($10.6 | ) |  |  | ($21.6 | ) |  |  | ($20.0 | ) |  |  | ($10.8 | ) |  |  | ($10.6 | ) |  |  | ($21.6 | ) |  |  | ($20.7 | )
Summary financial information from the unaudited financial statements of ATC for the three and six months ended June 30 was as follows (in millions):
| Three Months |  | Six Months
| 2013 |  | 2012 |  | 2013 |  | 2012
Operating revenues |  | $152.2 |  |  |  | $152.1 |  |  |  | $303.9 |  |  |  | $299.8 |
Operating income | 82.2 |  |  | 80.4 |  |  | 164.2 |  |  | 158.5 |
Net income | 61.3 |  |  | 59.3 |  |  | 121.8 |  |  | 117.4 |
WPL [Member] |
Schedule of Equity Method Investments [Line Items] |
Investments | INVESTMENTS Unconsolidated Equity Investments - Equity (income) loss from Alliant Energy’s and WPL’s unconsolidated investments accounted for under the equity method of accounting for the three and six months ended June 30 was as follows (in millions):
| Alliant Energy |  | WPL
| Three Months |  | Six Months |  | Three Months |  | Six Months
| 2013 |  | 2012 |  | 2013 |  | 2012 |  | 2013 |  | 2012 |  | 2013 |  | 2012
American Transmission Company LLC (ATC) |  | ($10.6 | ) |  |  | ($10.3 | ) |  |  | ($20.9 | ) |  |  | ($20.2 | ) |  |  | ($10.6 | ) |  |  | ($10.3 | ) |  |  | ($20.9 | ) |  |  | ($20.2 | )
Other | (0.3 | ) |  | (0.3 | ) |  | (0.7 | ) |  | 0.2 |  |  | (0.2 | ) |  | (0.3 | ) |  | (0.7 | ) |  | (0.5 | )
|  | ($10.9 | ) |  |  | ($10.6 | ) |  |  | ($21.6 | ) |  |  | ($20.0 | ) |  |  | ($10.8 | ) |  |  | ($10.6 | ) |  |  | ($21.6 | ) |  |  | ($20.7 | )
Summary financial information from the unaudited financial statements of ATC for the three and six months ended June 30 was as follows (in millions):
| Three Months |  | Six Months
| 2013 |  | 2012 |  | 2013 |  | 2012
Operating revenues |  | $152.2 |  |  |  | $152.1 |  |  |  | $303.9 |  |  |  | $299.8 |
Operating income | 82.2 |  |  | 80.4 |  |  | 164.2 |  |  | 158.5 |
Net income | 61.3 |  |  | 59.3 |  |  | 121.8 |  |  | 117.4 |

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