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Investments (Tables) | 9 Months Ended
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Sep. 30, 2021
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
| 2021 |  | 2020 |  | 2021 |  | 2020
ATC Holdings | ($12) |  | ($11) |  | ($34) |  | ($36)
Other | (1) |  | (4) |  | (13) |  | (10)
| ($13) |  | ($15) |  | ($47) |  | ($46)

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