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.

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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/1943274/2147477571/980-405-25-1

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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/1943274/2147478742/980-340-50-1

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-Topic 980
-SubTopic 340
-Section 55
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478098/980-340-55-2

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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, 2020
Regulatory Matters [Line Items]
Regulatory assets		$ 2,274	$ 2,261
Collected from retail electric customers		3,372	3,345	$ 3,421
Regulatory liabilities		1,028	1,130
IPL [Member]
Regulatory Matters [Line Items]
Regulatory assets not earning a return		199
Regulatory assets		1,586	1,577
Collected from retail electric customers		1,747	1,761	1,859
Regulatory liabilities		546	644
WPL [Member]
Regulatory Matters [Line Items]
Regulatory assets not earning a return		23
Regulatory assets		688	684
Collected from retail electric customers		1,625	1,584	1,562
Regulatory liabilities		482	486
2022 Test Period Fuel-related Costs [Member] \| WPL [Member]
Regulatory Matters [Line Items]
Regulatory assets				$ 117
Collected from retail electric customers		50	12
2023 Test Period Fuel-related Costs \| WPL [Member]
Regulatory Matters [Line Items]
Regulatory liabilities			34
2024 Test Period Retail Electric [Member] \| WPL [Member]
Regulatory Matters [Line Items]
Authorized increase (decrease) in final rates, amount		49
2024 Test Period Retail Gas [Member] \| WPL [Member]
Regulatory Matters [Line Items]
Authorized increase (decrease) in final rates, amount		13
2021 Test Period Fuel-related Costs [Member] \| WPL [Member]
Regulatory Matters [Line Items]
Collected from retail electric customers			$ 37
October 2024 Through September 2025 Test Period Retail Electric [Member] \| IPL [Member]
Regulatory Matters [Line Items]
Authorized increase (decrease) in final rates, amount		185
October 2024 Through September 2025 Test Period Retail Gas [Member] \| IPL [Member]
Regulatory Matters [Line Items]
Authorized increase (decrease) in final rates, amount		$ 10
DAEC PPA [Member]
Regulatory Matters [Line Items]
Buyout payment					$ 110
PPA term amendment					5 years
Forecast [Member] \| 2025 Test Period Retail Electric [Member] \| WPL [Member]
Regulatory Matters [Line Items]
Authorized increase (decrease) in final rates, amount	$ 60