Related Parties (Net Intercompany Payables) (Details) - Corporate Services [Member] - Related Party [Member] - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
IPL [Member]
Related Party Transaction [Line Items]
Net amounts owed	$ 135	$ 135
WPL [Member]
Related Party Transaction [Line Items]
Net amounts owed	$ 84	$ 64

Amount of liabilities classified as other.

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+ Details

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

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+ Details

ALLIANT ENERGY CORP 10-K