XML 65 R45.htm IDEA: XBRL DOCUMENT
v3.4.0.3

Receivables (Additional Attributes Of Receivables Sold Under The Agreement) (Details) - IPL [Member] - USD ($) $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2016 | Mar. 31, 2015
Receivables [Line Items] |  |
Collections reinvested in receivables | $ 440.2 | $ 505.9
Credit losses, net of recoveries | $ 0.4 | $ 1.0

X
- Definition Collections reinvested related to sales of accounts receivable program. + References No definition available. + Details
Name: | lnt_CollectionsReinvestedInReceivables
Namespace Prefix: | lnt_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Credit losses, net of recoveries related to sales of accounts receivable program. + References No definition available. + Details
Name: | lnt_CreditLossesNetOfRecoveries
Namespace Prefix: | lnt_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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: |