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Regulatory Matters (Regulatory Assets) (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Regulatory Assets [Line Items]
Regulatory assets	$ 1,919	$ 1,940
Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	949	934
Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	453	462
Asset retirement obligations [Member]
Regulatory Assets [Line Items]
Regulatory assets	134	128
Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	88	92
IPL's DAEC PPA amendment [Member]
Regulatory Assets [Line Items]
Regulatory assets	84	90
WPL's Western Wisconsin gas distribution expansion investments [Member]
Regulatory Assets [Line Items]
Regulatory assets	50	52
Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	42	42
Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	119	140
IPL [Member]
Regulatory Assets [Line Items]
Regulatory assets	1,432	1,443
IPL [Member] | Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	896	884
IPL [Member] | Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	224	228
IPL [Member] | Asset retirement obligations [Member]
Regulatory Assets [Line Items]
Regulatory assets	94	89
IPL [Member] | Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	64	66
IPL [Member] | IPL's DAEC PPA amendment [Member]
Regulatory Assets [Line Items]
Regulatory assets	84	90
IPL [Member] | Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	2	2
IPL [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	68	84
WPL [Member]
Regulatory Assets [Line Items]
Regulatory assets	487	497
WPL [Member] | Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	53	50
WPL [Member] | Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	229	234
WPL [Member] | Asset retirement obligations [Member]
Regulatory Assets [Line Items]
Regulatory assets	40	39
WPL [Member] | Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	24	26
WPL [Member] | WPL's Western Wisconsin gas distribution expansion investments [Member]
Regulatory Assets [Line Items]
Regulatory assets	50	52
WPL [Member] | Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	40	40
WPL [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	$ 51	$ 56

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- Definition

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.

+ 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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 340
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382

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