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Investments (Tables) | 9 Months Ended
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Sep. 30, 2025
Schedule of Equity Method Investments [Line Items] |
Unconsolidated Equity Investments | Alliant Energy’s 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):
| Three Months |  | Nine Months
| 2025 |  | 2024 |  | 2025 |  | 2024
ATC Holdings | ($15) |  | ($13) |  | ($43) |  | ($38)
Non-utility wind farm in Oklahoma | (2) |  | (2) |  | (6) |  | (5)
Corporate venture investments | (1) |  | 2 |  | 10 |  | 1
Other | — |  | (1) |  | (2) |  | (2)
| ($18) |  | ($14) |  | ($41) |  | ($44)

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