v2.4.0.6

Receivables (Receivables Sold Under The Agreement) (Details) (IPL [Member], USD $) In Millions, unless otherwise specified | Sep. 30, 2012 | Dec. 31, 2011
--- | --- | ---
IPL [Member] |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Customer accounts receivable | $ 137.9 |  | $ 122.4 |
Unbilled utility revenues | 64.7 |  | 65.4 |
Other receivables | 8.3 |  | 7.5 |
Receivables sold | 210.9 |  | 195.3 |
Less: cash proceeds | 55.0 | [1] | 140.0 | [1]
Deferred proceeds | 155.9 |  | 55.3 |
Less: allowance for doubtful accounts | 2.0 |  | 1.6 |
Fair value of deferred proceeds | 153.9 |  | 53.7 |
Outstanding receivables past due | $ 16.6 |  | $ 15.9 |
[1] | Changes in cash proceeds for the nine months ended September 30, 2012 are recorded in “Sales of accounts receivable” in operating activities in Alliant Energy’s and IPL’s Condensed Consolidated Statements of Cash Flows.

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- 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

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- 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

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- 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

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- 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

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- 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

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- Definition Other Receivables Sold Amount + References No definition available. + Details
Name: | lnt_OtherReceivablesSoldAmount
Namespace Prefix: | lnt_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition Outstanding receivables past due + References No definition available. + Details
Name: | lnt_OutstandingReceivablesPastDue
Namespace Prefix: | lnt_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition Receivables sold + References No definition available. + Details
Name: | lnt_ReceivablesSold
Namespace Prefix: | lnt_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- 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

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