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Regulatory Matters (Regulatory Liabilities) (Details) - USD ($) $ in Millions | Mar. 31, 2022 | Dec. 31, 2021
--- | --- | ---
Regulatory Liabilities [Line Items] |  |
Regulatory liabilities | $ 1,372 | $ 1,271
Tax-related [Member] |  |
Regulatory Liabilities [Line Items] |  |
Regulatory liabilities | 578 | 585
Cost of removal obligations [Member] |  |
Regulatory Liabilities [Line Items] |  |
Regulatory liabilities | 391 | 384
Derivatives [Member] |  |
Regulatory Liabilities [Line Items] |  |
Regulatory liabilities | 258 | 166
Electric transmission cost recovery [Member] |  |
Regulatory Liabilities [Line Items] |  |
Regulatory liabilities | 50 | 51
WPL's West Riverside liquidated damages [Member] |  |
Regulatory Liabilities [Line Items] |  |
Regulatory liabilities | 35 | 36
Other [Member] |  |
Regulatory Liabilities [Line Items] |  |
Regulatory liabilities | 60 | 49
IPL [Member] |  |
Regulatory Liabilities [Line Items] |  |
Regulatory liabilities | 754 | 691
IPL [Member] | Tax-related [Member] |  |
Regulatory Liabilities [Line Items] |  |
Regulatory liabilities | 310 | 312
IPL [Member] | Cost of removal obligations [Member] |  |
Regulatory Liabilities [Line Items] |  |
Regulatory liabilities | 256 | 252
IPL [Member] | Derivatives [Member] |  |
Regulatory Liabilities [Line Items] |  |
Regulatory liabilities | 125 | 77
IPL [Member] | Electric transmission cost recovery [Member] |  |
Regulatory Liabilities [Line Items] |  |
Regulatory liabilities | 29 | 27
IPL [Member] | Other [Member] |  |
Regulatory Liabilities [Line Items] |  |
Regulatory liabilities | 34 | 23
WPL [Member] |  |
Regulatory Liabilities [Line Items] |  |
Regulatory liabilities | 618 | 580
WPL [Member] | Tax-related [Member] |  |
Regulatory Liabilities [Line Items] |  |
Regulatory liabilities | 268 | 273
WPL [Member] | Cost of removal obligations [Member] |  |
Regulatory Liabilities [Line Items] |  |
Regulatory liabilities | 135 | 132
WPL [Member] | Derivatives [Member] |  |
Regulatory Liabilities [Line Items] |  |
Regulatory liabilities | 133 | 89
WPL [Member] | Electric transmission cost recovery [Member] |  |
Regulatory Liabilities [Line Items] |  |
Regulatory liabilities | 21 | 24
WPL [Member] | WPL's West Riverside liquidated damages [Member] |  |
Regulatory Liabilities [Line Items] |  |
Regulatory liabilities | 35 | 36
WPL [Member] | Other [Member] |  |
Regulatory Liabilities [Line Items] |  |
Regulatory liabilities | $ 26 | $ 26

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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 -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 405 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6500807&loc=d3e48068-110394 + Details
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