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Investments (Tables) | 12 Months Ended
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Dec. 31, 2020
Investment [Line Items] |
Unconsolidated Equity Investments | Alliant Energy’s unconsolidated investments accounted for under the equity method of accounting are as follows (in millions):
| Ownership Interest at |  | Carrying Value at December 31, |  | Equity (Income) / Loss
| December 31, 2020 |  | 2020 |  | 2019 |  | 2020 |  | 2019 |  | 2018
ATC Holdings | 16%, 20% |  | $331 |  | $320 |  | ($47) |  | ($45) |  | ($38)
Non-utility wind farm in Oklahoma | 50% |  | 103 |  | 105 |  | (8) |  | (5) |  | (16)
Other | Various |  | 42 |  | 33 |  | (6) |  | (3) |  | (1)
|  |  | $476 |  | $458 |  | ($61) |  | ($53) |  | ($55)
Summary Financial Information | Summary aggregate financial information from the financial statements of these holdings is as follows (in millions):
| Alliant Energy |  |
| 2020 |  | 2019 |  | 2018 |  |  |  |  |  |
Revenues | $801 |  |  | $783 |  |  | $724 |  |  |  |  |  |  |
Operating income | 376 |  |  | 359 |  |  | 325 |  |  |  |  |  |  |
Net income | 343 |  |  | 340 |  |  | 217 |  |  |  |  |  |  |
As of December 31: |  |  |  |  |  |  |  |  |  |  |
Current assets | 121 |  |  | 139 |  |  |  |  |  |  |  |  |
Non-current assets | 6,388 |  |  | 5,964 |  |  |  |  |  |  |  |  |
Current liabilities | 317 |  |  | 507 |  |  |  |  |  |  |  |  |
Non-current liabilities | 2,997 |  |  | 2,659 |  |  |  |  |  |  |  |  |
Noncontrolling interest | 192 |  |  | 208 |  |  |  |  |  |  |  |  |

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