Derivative Instruments (Balance Sheet Offsetting) (Details) - Commodity Contracts [Member] - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Derivative Instruments [Line Items]
Derivative assets, Gross (as reported)	$ 56	$ 88
Derivative assets, Net	26	47
Derivative liabilities, Gross (as reported)	94	98
Derivative liabilities, Net	64	57
IPL [Member]
Derivative Instruments [Line Items]
Derivative assets, Gross (as reported)	34	54
Derivative assets, Net	17	32
Derivative liabilities, Gross (as reported)	30	30
Derivative liabilities, Net	13	8
WPL [Member]
Derivative Instruments [Line Items]
Derivative assets, Gross (as reported)	22	34
Derivative assets, Net	9	15
Derivative liabilities, Gross (as reported)	64	68
Derivative liabilities, Net	$ 51	$ 49

Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

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Fair value, after effect of master netting arrangement and deduction of obligation to return financial collateral not offset and financial instrument subject to master netting arrangement not offset, of financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and contract can be net settled by means outside contract or delivery of asset. Includes derivative not subject to master netting arrangement or similar agreement.

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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.

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