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Summary Of Significant Accounting Policies (Narrative) (Details) $ in Millions | 6 Months Ended
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Jun. 30, 2022 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |
WPL's cash contribution | $ 62
Tax equity partner's cash contribution | 29
Contributed funds paid to WPL for equity interests | $ 88

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- Definition Cash Received for Equity Interests + References No definition available. + Details
Name: | lnt_CashReceivedForEquityInterests
Namespace Prefix: | lnt_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Tax Equity Partner Cash Contribution + References No definition available. + Details
Name: | lnt_TaxEquityPartnerCashContribution
Namespace Prefix: | lnt_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition WPL Cash Contribution + References No definition available. + Details
Name: | lnt_WPLCashContribution
Namespace Prefix: | lnt_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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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. + Details
Name: | us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration