Long-term Contract for Purchase of Electric Power, Buyout Payment

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- Definition

Long-term Contract for Purchase of Electric Power, Contract Term Amendment

+ References

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- Definition

Regulatory Matters [Line Items]

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- Definition

Amount of public utility's approved rate increase (decrease) by regulatory agency.

+ References

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- Definition

The amount of regulated power revenues recognized during the period.

+ References

No definition available.

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- Definition

The amount for the individual regulatory asset as itemized in a table of regulatory assets as of the end of the period.

+ References

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- Definition

The amount for the individual regulatory liability as itemized in a table of regulatory liabilities as of the end of the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 980
-SubTopic 405
-Name Accounting Standards Codification
-Section 25
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481854/980-405-25-1

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- Definition

Remaining balance of regulatory assets for which no return on investment during recovery is provided. In some cases, a regulator may permit an enterprise to include a cost that would be charged to expense by an unregulated enterprise as an allowable cost over a period of time by amortizing that cost for rate-making purposes, but the regulator does not include the unrecovered amount in the rate base.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 980
-SubTopic 340
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481878/980-340-50-1

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-Topic 980
-SubTopic 340
-Section 55
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481849/980-340-55-2

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Regulatory Matters (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Regulatory Matters [Line Items]
Regulatory assets			$ 2,261	$ 2,046
Collected from retail electric customers			3,345	3,421	$ 3,081
Regulatory liabilities			1,130	1,324
IPL [Member]
Regulatory Matters [Line Items]
Regulatory assets not earning a return			74
Regulatory assets			1,577	1,386
Collected from retail electric customers			1,761	1,859	1,752
Regulatory liabilities			644	754
WPL [Member]
Regulatory Matters [Line Items]
Regulatory assets not earning a return			32
Regulatory assets			684	660
Collected from retail electric customers			1,584	1,562	$ 1,329
Regulatory liabilities			486	570
2021 Test Period Fuel-related Costs [Member] \| WPL [Member]
Regulatory Matters [Line Items]
Regulatory assets				37
2022 Test Period Fuel-related Costs [Member] \| WPL [Member]
Regulatory Matters [Line Items]
Regulatory assets				117
Collected from retail electric customers			12
2023 Test Period Fuel-related Costs \| WPL [Member]
Regulatory Matters [Line Items]
Regulatory liabilities			34
2022 Test Period Retail Electric [Member] \| WPL [Member]
Regulatory Matters [Line Items]
Authorized increase (decrease) in final rates, amount				114
2022 Test Period Retail Gas [Member] \| WPL [Member]
Regulatory Matters [Line Items]
Authorized increase (decrease) in final rates, amount				$ 15
2023 Test Period Retail Gas [Member] \| WPL [Member]
Regulatory Matters [Line Items]
Authorized increase (decrease) in final rates, amount			$ 9
DAEC PPA [Member]
Regulatory Matters [Line Items]
Buyout payment						$ 110
PPA term amendment			5 years
Forecast [Member] \| 2024 Test Period Retail Electric [Member] \| WPL [Member]
Regulatory Matters [Line Items]
Authorized increase (decrease) in final rates, amount		$ 49
Forecast [Member] \| 2024 Test Period Retail Gas [Member] \| WPL [Member]
Regulatory Matters [Line Items]
Authorized increase (decrease) in final rates, amount		$ 13
Forecast [Member] \| 2025 Test Period Retail Electric [Member] \| WPL [Member]
Regulatory Matters [Line Items]
Authorized increase (decrease) in final rates, amount	$ 60