Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Debt (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Jan. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Line of credit facility, current borrowing capacity			$ 1,000
Long-term debt			8,143	$ 7,425
Parent Company [Member]
Debt Instrument [Line Items]
Line of credit facility, current borrowing capacity			500
IPL [Member]
Debt Instrument [Line Items]
Line of credit facility, current borrowing capacity			100
Long-term debt			3,675	3,675
WPL [Member]
Debt Instrument [Line Items]
Line of credit facility, current borrowing capacity			400
Long-term debt			$ 2,800	$ 2,450
Alliant Energy Finance, LLC [Member] \| Term loan credit agreement through January 2024 [Member] \| Term Loan Credit Agreement [Member] \| Subsequent Event
Debt Instrument [Line Items]
Long-term debt		$ 50
Forecast [Member] \| Parent Company [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 500
Forecast [Member] \| IPL [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	400
Forecast [Member] \| WPL [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 500