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Receivables (Receivables Sold Under The Agreement) (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Receivables [Line Items]
Fair value of deferred proceeds	$ 227	$ 214
IPL [Member]
Receivables [Line Items]
Fair value of deferred proceeds	227	214
Receivables Sold [Member] | IPL [Member]
Receivables [Line Items]
Customer accounts receivable	142	125
Unbilled utility revenues	96	104
Receivables sold to third party	238	229
Less: cash proceeds	1	1
Deferred proceeds	237	228
Less: allowance for expected credit losses	10	14
Fair value of deferred proceeds	$ 227	$ 214

X

- Definition

Allowance for Doubtful Accounts Receivable Sold

+ References

No definition available.

+ Details

Name:	lnt_AllowanceForDoubtfulAccountsReceivableSold
Namespace Prefix:	lnt_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Cash Proceeds From Receivables Sold

+ References

No definition available.

+ Details

Name:	lnt_CashProceedsFromReceivablesSold
Namespace Prefix:	lnt_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Customer Accounts Receivable Sold, Amount

+ References

No definition available.

+ Details

Name:	lnt_CustomerAccountsReceivableSoldAmount
Namespace Prefix:	lnt_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Deferred proceeds of receivables sold

+ References

No definition available.

+ Details

Name:	lnt_DeferredProceedsOfReceivablesSold
Namespace Prefix:	lnt_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Fair value of deferred proceeds of receivables sold

+ References

No definition available.

+ Details

Name:	lnt_FairValueOfDeferredProceedsOfReceivablesSold
Namespace Prefix:	lnt_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Receivables sold

+ References

No definition available.

+ Details

Name:	lnt_ReceivablesSold
Namespace Prefix:	lnt_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Unbilled Utility Revenues Sold, Amount

+ References

No definition available.

+ Details

Name:	lnt_UnbilledUtilityRevenuesSoldAmount
Namespace Prefix:	lnt_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- 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_AccountsNotesAndLoansReceivableLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	dei_LegalEntityAxis=lnt_IplMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=us-gaap_FinanceReceivablesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: