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Investments (Tables) | 12 Months Ended
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Dec. 31, 2015
Investment [Line Items] |
Unconsolidated Equity Investments | Alliant Energy’s and WPL’s unconsolidated investments accounted for under the equity method of accounting are as follows (in millions):
| Ownership |  | Carrying Value at |  |
| Interest at |  | December 31, |  | Equity (Income) / Loss
| December 31, 2015 |  | 2015 |  | 2014 |  | 2015 |  | 2014 |  | 2013
Alliant Energy |  |  |  |  |  |  |  |  |  |  |
ATC (a) | 16% |  |  | $293.3 |  |  |  | $286.5 |  |  |  | ($34.2 | ) |  |  | ($41.9 | ) |  |  | ($42.7 | )
Wisconsin River Power Company | 50% |  | 8.7 |  |  | 7.8 |  |  | (0.9 | ) |  | (0.9 | ) |  | (1.0 | )
Other | Various |  | 0.9 |  |  | 2.3 |  |  | 1.3 |  |  | 2.4 |  |  | — |
|  |  |  | $302.9 |  |  |  | $296.6 |  |  |  | ($33.8 | ) |  |  | ($40.4 | ) |  |  | ($43.7 | )
WPL |  |  |  |  |  |  |  |  |  |  |
ATC (a) | 16% |  |  | $293.3 |  |  |  | $286.5 |  |  |  | ($34.2 | ) |  |  | ($41.9 | ) |  |  | ($42.7 | )
Wisconsin River Power Company | 50% |  | 8.7 |  |  | 7.8 |  |  | (0.9 | ) |  | (0.9 | ) |  | (1.0 | )
|  |  |  | $302.0 |  |  |  | $294.3 |  |  |  | ($35.1 | ) |  |  | ($42.8 | ) |  |  | ($43.7 | )
(a) | Alliant Energy and WPL have the ability to exercise significant influence over ATC’s financial and operating policies through their participation on ATC’s Board of Directors. Refer to Note 18 for information regarding related party transactions with ATC.
Summary Financial Information | Summary aggregate financial information from the financial statements of these investments is as follows (in millions):
| Alliant Energy |  | WPL
| 2015 |  | 2014 |  | 2013 |  | 2015 |  | 2014 |  | 2013
Operating revenues |  | $624 |  |  |  | $643 |  |  |  | $634 |  |  |  | $624 |  |  |  | $643 |  |  |  | $634 |
Operating income | 299 |  |  | 330 |  |  | 334 |  |  | 299 |  |  | 330 |  |  | 334 |
Net income | 186 |  |  | 240 |  |  | 248 |  |  | 202 |  |  | 240 |  |  | 250 |
As of December 31: |  |  |  |  |  |  |  |  |  |  |
Current assets | 88 |  |  | 72 |  |  |  |  | 87 |  |  | 70 |  |  |
Non-current assets | 3,987 |  |  | 3,773 |  |  |  |  | 3,977 |  |  | 3,747 |  |  |
Current liabilities | 332 |  |  | 315 |  |  |  |  | 332 |  |  | 315 |  |  |
Non-current liabilities | 2,052 |  |  | 1,871 |  |  |  |  | 2,052 |  |  | 1,870 |  |  |
Cash Surrender Value of Life Insurance Policies | At December 31, the cash surrender value of these investments was as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2015 |  | 2014 |  | 2015 |  | 2014 |  | 2015 |  | 2014
Cash surrender value | $42.3 |  | $47.0 |  | $18.9 |  | $18.1 |  | $6.4 |  | $11.4
IPL [Member] |
Investment [Line Items] |
Cash Surrender Value of Life Insurance Policies | At December 31, the cash surrender value of these investments was as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2015 |  | 2014 |  | 2015 |  | 2014 |  | 2015 |  | 2014
Cash surrender value | $42.3 |  | $47.0 |  | $18.9 |  | $18.1 |  | $6.4 |  | $11.4
WPL [Member] |
Investment [Line Items] |
Unconsolidated Equity Investments | Alliant Energy’s and WPL’s unconsolidated investments accounted for under the equity method of accounting are as follows (in millions):
| Ownership |  | Carrying Value at |  |
| Interest at |  | December 31, |  | Equity (Income) / Loss
| December 31, 2015 |  | 2015 |  | 2014 |  | 2015 |  | 2014 |  | 2013
Alliant Energy |  |  |  |  |  |  |  |  |  |  |
ATC (a) | 16% |  |  | $293.3 |  |  |  | $286.5 |  |  |  | ($34.2 | ) |  |  | ($41.9 | ) |  |  | ($42.7 | )
Wisconsin River Power Company | 50% |  | 8.7 |  |  | 7.8 |  |  | (0.9 | ) |  | (0.9 | ) |  | (1.0 | )
Other | Various |  | 0.9 |  |  | 2.3 |  |  | 1.3 |  |  | 2.4 |  |  | — |
|  |  |  | $302.9 |  |  |  | $296.6 |  |  |  | ($33.8 | ) |  |  | ($40.4 | ) |  |  | ($43.7 | )
WPL |  |  |  |  |  |  |  |  |  |  |
ATC (a) | 16% |  |  | $293.3 |  |  |  | $286.5 |  |  |  | ($34.2 | ) |  |  | ($41.9 | ) |  |  | ($42.7 | )
Wisconsin River Power Company | 50% |  | 8.7 |  |  | 7.8 |  |  | (0.9 | ) |  | (0.9 | ) |  | (1.0 | )
|  |  |  | $302.0 |  |  |  | $294.3 |  |  |  | ($35.1 | ) |  |  | ($42.8 | ) |  |  | ($43.7 | )
(a) | Alliant Energy and WPL have the ability to exercise significant influence over ATC’s financial and operating policies through their participation on ATC’s Board of Directors. Refer to Note 18 for information regarding related party transactions with ATC.
Summary Financial Information | Summary aggregate financial information from the financial statements of these investments is as follows (in millions):
| Alliant Energy |  | WPL
| 2015 |  | 2014 |  | 2013 |  | 2015 |  | 2014 |  | 2013
Operating revenues |  | $624 |  |  |  | $643 |  |  |  | $634 |  |  |  | $624 |  |  |  | $643 |  |  |  | $634 |
Operating income | 299 |  |  | 330 |  |  | 334 |  |  | 299 |  |  | 330 |  |  | 334 |
Net income | 186 |  |  | 240 |  |  | 248 |  |  | 202 |  |  | 240 |  |  | 250 |
As of December 31: |  |  |  |  |  |  |  |  |  |  |
Current assets | 88 |  |  | 72 |  |  |  |  | 87 |  |  | 70 |  |  |
Non-current assets | 3,987 |  |  | 3,773 |  |  |  |  | 3,977 |  |  | 3,747 |  |  |
Current liabilities | 332 |  |  | 315 |  |  |  |  | 332 |  |  | 315 |  |  |
Non-current liabilities | 2,052 |  |  | 1,871 |  |  |  |  | 2,052 |  |  | 1,870 |  |  |
Cash Surrender Value of Life Insurance Policies | At December 31, the cash surrender value of these investments was as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2015 |  | 2014 |  | 2015 |  | 2014 |  | 2015 |  | 2014
Cash surrender value | $42.3 |  | $47.0 |  | $18.9 |  | $18.1 |  | $6.4 |  | $11.4

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