v3.25.3

Common Equity (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		5 Months Ended	9 Months Ended		44 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2028
Common Equity [Line Items]
Proceeds from issuance of common stock, net	$ 6	$ 6		$ 18	$ 18
At-The-Market Offering Program 2025-2028 [Member]
Common Equity [Line Items]
Forward contract, total shares borrowed and sold (in shares)	7,851,080			10,764,103
Aggregate gross sales price of common stock borrowed or sold	$ 508			$ 686
Fees and commissions from issuance of common stock	$ 4			$ 5
Forward contract, weighted-average forward price, net of commissions (in dollars per share)			$ 63.46
Forward contract, shares that could have settled under outstanding forward sale agreements with physical delivery (in shares)	10,764,103		10,764,103	10,764,103
Forward contract, net cash proceeds upon settlement	$ 683		$ 683	$ 683
Shares included in diluted earnings per share (in shares)				199,923
At-The-Market Offering Program 2025-2028 [Member] \| Forecast [Member]
Common Equity [Line Items]
Proceeds from issuance of common stock, net						$ 1,300

Aggregate Gross Sales Price Of Common Stock [Member]

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Common Equity [Line Items]

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- Definition

The per share price of the Company's stock at which the contract holder of the freestanding contract has the right to purchase or sell the Company's stock at a future date.

+ References

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Amount that would be paid upon settlement of forward contract indexed to equity.

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Number of shares as a settlement alternative for each freestanding forward contract.

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Maximum number of shares that could be issued to settle forward contract indexed to equity.

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Additional shared included in the calculation of diluted EPS as a result of the potentially dilutive effect of equity forward arrangements using the reverse treasury stock method.

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The cash inflow from the additional capital contribution to the entity.

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ALLIANT ENERGY CORP 10-Q