v2.4.0.6

Derivative Instruments (Notional Amounts Of Derivative Instruments) (Details) (Commodity [Member]) | Dec. 31, 2012 MWh
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Electricity (MWhs) [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 7,676,000
Electricity (MWhs) [Member] | IPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 2,758,000
Electricity (MWhs) [Member] | WPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 4,918,000
FTRs (MWs) [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 28,000
FTRs (MWs) [Member] | IPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 15,000
FTRs (MWs) [Member] | WPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 13,000
Natural Gas (Dths) [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 80,302,000
Natural Gas (Dths) [Member] | IPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 61,491,000
Natural Gas (Dths) [Member] | WPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 18,811,000
Coal (Tons) [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 2,439,000
Coal (Tons) [Member] | WPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 2,439,000
2013 [Member] | Electricity (MWhs) [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 4,130,000
2013 [Member] | Electricity (MWhs) [Member] | IPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 2,209,000
2013 [Member] | Electricity (MWhs) [Member] | WPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 1,921,000
2013 [Member] | FTRs (MWs) [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 28,000
2013 [Member] | FTRs (MWs) [Member] | IPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 15,000
2013 [Member] | FTRs (MWs) [Member] | WPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 13,000
2013 [Member] | Natural Gas (Dths) [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 72,105,000
2013 [Member] | Natural Gas (Dths) [Member] | IPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 57,731,000
2013 [Member] | Natural Gas (Dths) [Member] | WPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 14,374,000
2013 [Member] | Coal (Tons) [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 896,000
2013 [Member] | Coal (Tons) [Member] | WPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 896,000
2014 [Member] | Electricity (MWhs) [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 2,670,000
2014 [Member] | Electricity (MWhs) [Member] | IPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 549,000
2014 [Member] | Electricity (MWhs) [Member] | WPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 2,121,000
2014 [Member] | FTRs (MWs) [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 0
2014 [Member] | FTRs (MWs) [Member] | IPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 0
2014 [Member] | FTRs (MWs) [Member] | WPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 0
2014 [Member] | Natural Gas (Dths) [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 7,747,000
2014 [Member] | Natural Gas (Dths) [Member] | IPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 3,535,000
2014 [Member] | Natural Gas (Dths) [Member] | WPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 4,212,000
2014 [Member] | Coal (Tons) [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 981,000
2014 [Member] | Coal (Tons) [Member] | WPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 981,000
2015 [Member] | Electricity (MWhs) [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 876,000
2015 [Member] | Electricity (MWhs) [Member] | IPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 0
2015 [Member] | Electricity (MWhs) [Member] | WPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 876,000
2015 [Member] | FTRs (MWs) [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 0
2015 [Member] | FTRs (MWs) [Member] | IPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 0
2015 [Member] | FTRs (MWs) [Member] | WPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 0
2015 [Member] | Natural Gas (Dths) [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 450,000
2015 [Member] | Natural Gas (Dths) [Member] | IPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 225,000
2015 [Member] | Natural Gas (Dths) [Member] | WPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 225,000
2015 [Member] | Coal (Tons) [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 562,000
2015 [Member] | Coal (Tons) [Member] | WPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/MWs/Dths/tons) | 562,000

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- Definition Aggregate notional amount of derivative expressed in nonmonetary units. For example, the number of barrels specified in a fuel oil forward purchase contract. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
Name: | invest_DerivativeNonmonetaryNotionalAmount
Namespace Prefix: | invest_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | instant

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- Details
Name: | lnt_NotionalAmountOfDerivativesLineItems
Namespace Prefix: | lnt_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration