XML 65 R42.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Receivables (Receivables Sold Under The Agreement) (Details) - USD ($) $ in Millions | Mar. 31, 2018 | Dec. 31, 2017
--- | --- | ---
Receivables [Line Items] |  |
Fair value of deferred proceeds | $ 120.9 | $ 222.1
IPL [Member] |  |
Receivables [Line Items] |  |
Fair value of deferred proceeds | 120.9 | 222.1
Receivables Sold [Member] | IPL [Member] |  |
Receivables [Line Items] |  |
Customer accounts receivable | 156.1 | 133.8
Unbilled utility revenues | 93.2 | 112.7
Other receivables | 0.3 | 0.3
Receivables sold to third party | 249.6 | 246.8
Less: cash proceeds | 116.0 | 12.0
Deferred proceeds | 133.6 | 234.8
Less: allowance for doubtful accounts | 12.7 | 12.7
Fair value of deferred proceeds | $ 120.9 | $ 222.1

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 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

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=lnt_ReceivablesSoldMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |