XML 161 R129.htm IDEA: XBRL DOCUMENT
v2.4.1.9

Fair Value Measurements (Recurring Fair Value Measurements) (Details) (USD $) In Millions, unless otherwise specified | Dec. 31, 2014 | Dec. 31, 2013
--- | --- | ---
Assets: |  |
Derivative assets | $ 33.0 us-gaap_DerivativeAssets | $ 23.5 us-gaap_DerivativeAssets
Deferred proceeds | 177.2 lnt_FairValueOfDeferredProceedsOfReceivablesSold | 203.5 lnt_FairValueOfDeferredProceedsOfReceivablesSold
Capitalization and liabilities: |  |
Long-term debt (including current maturities) | 4,418.2 us-gaap_DebtInstrumentFairValue | 3,712.3 us-gaap_DebtInstrumentFairValue
Cumulative preferred stock | 200.2 lnt_PreferredStockFairValue | 167.0 lnt_PreferredStockFairValue
Derivative liabilities | 32.0 us-gaap_DerivativeLiabilities | 17.6 us-gaap_DerivativeLiabilities
IPL [Member] |  |
Assets: |  |
Derivative assets | 24.7 us-gaap_DerivativeAssets / dei_LegalEntityAxis = lnt_IplMember | 19.5 us-gaap_DerivativeAssets / dei_LegalEntityAxis = lnt_IplMember
Deferred proceeds | 177.2 lnt_FairValueOfDeferredProceedsOfReceivablesSold / dei_LegalEntityAxis = lnt_IplMember | 203.5 lnt_FairValueOfDeferredProceedsOfReceivablesSold / dei_LegalEntityAxis = lnt_IplMember
Capitalization and liabilities: |  |
Long-term debt (including current maturities) | 2,053.0 us-gaap_DebtInstrumentFairValue / dei_LegalEntityAxis = lnt_IplMember | 1,726.4 us-gaap_DebtInstrumentFairValue / dei_LegalEntityAxis = lnt_IplMember
Cumulative preferred stock | 200.2 lnt_PreferredStockFairValue / dei_LegalEntityAxis = lnt_IplMember | 167.0 lnt_PreferredStockFairValue / dei_LegalEntityAxis = lnt_IplMember
Derivative liabilities | 16.2 us-gaap_DerivativeLiabilities / dei_LegalEntityAxis = lnt_IplMember | 3.6 us-gaap_DerivativeLiabilities / dei_LegalEntityAxis = lnt_IplMember
WPL [Member] |  |
Assets: |  |
Derivative assets | 8.3 us-gaap_DerivativeAssets / dei_LegalEntityAxis = lnt_WplMember | 4.0 us-gaap_DerivativeAssets / dei_LegalEntityAxis = lnt_WplMember
Capitalization and liabilities: |  |
Long-term debt (including current maturities) | 1,908.9 us-gaap_DebtInstrumentFairValue / dei_LegalEntityAxis = lnt_WplMember | 1,532.9 us-gaap_DebtInstrumentFairValue / dei_LegalEntityAxis = lnt_WplMember
Derivative liabilities | 15.8 us-gaap_DerivativeLiabilities / dei_LegalEntityAxis = lnt_WplMember | 14.0 us-gaap_DerivativeLiabilities / dei_LegalEntityAxis = lnt_WplMember
Commodity Contracts [Member] |  |
Assets: |  |
Derivative assets | 38.6 us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember | 26.7 us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember
Capitalization and liabilities: |  |
Derivative liabilities | 37.6 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember | 20.8 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember
Commodity Contracts [Member] | IPL [Member] |  |
Assets: |  |
Derivative assets | 28.0 us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / dei_LegalEntityAxis = lnt_IplMember | 21.1 us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / dei_LegalEntityAxis = lnt_IplMember
Capitalization and liabilities: |  |
Derivative liabilities | 19.5 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / dei_LegalEntityAxis = lnt_IplMember | 5.2 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / dei_LegalEntityAxis = lnt_IplMember
Commodity Contracts [Member] | WPL [Member] |  |
Assets: |  |
Derivative assets | 10.6 us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / dei_LegalEntityAxis = lnt_WplMember | 5.6 us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / dei_LegalEntityAxis = lnt_WplMember
Capitalization and liabilities: |  |
Derivative liabilities | 18.1 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / dei_LegalEntityAxis = lnt_WplMember | 15.6 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / dei_LegalEntityAxis = lnt_WplMember
Level 1 [Member] |  |
Assets: |  |
Deferred proceeds | 0 lnt_FairValueOfDeferredProceedsOfReceivablesSold / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member | 0 lnt_FairValueOfDeferredProceedsOfReceivablesSold / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member
Capitalization and liabilities: |  |
Long-term debt (including current maturities) | 0 us-gaap_DebtInstrumentFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member | 0 us-gaap_DebtInstrumentFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member
Cumulative preferred stock | 200.2 lnt_PreferredStockFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member | 167.0 lnt_PreferredStockFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member
Level 1 [Member] | IPL [Member] |  |
Assets: |  |
Deferred proceeds | 0 lnt_FairValueOfDeferredProceedsOfReceivablesSold / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / dei_LegalEntityAxis = lnt_IplMember | 0 lnt_FairValueOfDeferredProceedsOfReceivablesSold / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / dei_LegalEntityAxis = lnt_IplMember
Capitalization and liabilities: |  |
Long-term debt (including current maturities) | 0 us-gaap_DebtInstrumentFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / dei_LegalEntityAxis = lnt_IplMember | 0 us-gaap_DebtInstrumentFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / dei_LegalEntityAxis = lnt_IplMember
Cumulative preferred stock | 200.2 lnt_PreferredStockFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / dei_LegalEntityAxis = lnt_IplMember | 167.0 lnt_PreferredStockFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / dei_LegalEntityAxis = lnt_IplMember
Level 1 [Member] | WPL [Member] |  |
Capitalization and liabilities: |  |
Long-term debt (including current maturities) | 0 us-gaap_DebtInstrumentFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / dei_LegalEntityAxis = lnt_WplMember | 0 us-gaap_DebtInstrumentFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / dei_LegalEntityAxis = lnt_WplMember
Level 1 [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivative assets | 0 us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member | 0 us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member
Capitalization and liabilities: |  |
Derivative liabilities | 0 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member | 0 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member
Level 1 [Member] | Commodity Contracts [Member] | IPL [Member] |  |
Assets: |  |
Derivative assets | 0 us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / dei_LegalEntityAxis = lnt_IplMember | 0 us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / dei_LegalEntityAxis = lnt_IplMember
Capitalization and liabilities: |  |
Derivative liabilities | 0 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / dei_LegalEntityAxis = lnt_IplMember | 0 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / dei_LegalEntityAxis = lnt_IplMember
Level 1 [Member] | Commodity Contracts [Member] | WPL [Member] |  |
Assets: |  |
Derivative assets | 0 us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / dei_LegalEntityAxis = lnt_WplMember | 0 us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / dei_LegalEntityAxis = lnt_WplMember
Capitalization and liabilities: |  |
Derivative liabilities | 0 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / dei_LegalEntityAxis = lnt_WplMember | 0 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / dei_LegalEntityAxis = lnt_WplMember
Level 2 [Member] |  |
Assets: |  |
Deferred proceeds | 0 lnt_FairValueOfDeferredProceedsOfReceivablesSold / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member | 0 lnt_FairValueOfDeferredProceedsOfReceivablesSold / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member
Capitalization and liabilities: |  |
Long-term debt (including current maturities) | 4,414.9 us-gaap_DebtInstrumentFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member | 3,711.8 us-gaap_DebtInstrumentFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member
Cumulative preferred stock | 0 lnt_PreferredStockFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member | 0 lnt_PreferredStockFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member
Level 2 [Member] | IPL [Member] |  |
Assets: |  |
Deferred proceeds | 0 lnt_FairValueOfDeferredProceedsOfReceivablesSold / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / dei_LegalEntityAxis = lnt_IplMember | 0 lnt_FairValueOfDeferredProceedsOfReceivablesSold / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / dei_LegalEntityAxis = lnt_IplMember
Capitalization and liabilities: |  |
Long-term debt (including current maturities) | 2,053.0 us-gaap_DebtInstrumentFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / dei_LegalEntityAxis = lnt_IplMember | 1,726.4 us-gaap_DebtInstrumentFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / dei_LegalEntityAxis = lnt_IplMember
Cumulative preferred stock | 0 lnt_PreferredStockFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / dei_LegalEntityAxis = lnt_IplMember | 0 lnt_PreferredStockFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / dei_LegalEntityAxis = lnt_IplMember
Level 2 [Member] | WPL [Member] |  |
Capitalization and liabilities: |  |
Long-term debt (including current maturities) | 1,908.9 us-gaap_DebtInstrumentFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / dei_LegalEntityAxis = lnt_WplMember | 1,532.9 us-gaap_DebtInstrumentFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / dei_LegalEntityAxis = lnt_WplMember
Level 2 [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivative assets | 2.6 us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member | 4.7 us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member
Capitalization and liabilities: |  |
Derivative liabilities | 19.5 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member | 3.2 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member
Level 2 [Member] | Commodity Contracts [Member] | IPL [Member] |  |
Assets: |  |
Derivative assets | 2.4 us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / dei_LegalEntityAxis = lnt_IplMember | 3.0 us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / dei_LegalEntityAxis = lnt_IplMember
Capitalization and liabilities: |  |
Derivative liabilities | 13.3 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / dei_LegalEntityAxis = lnt_IplMember | 1.7 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / dei_LegalEntityAxis = lnt_IplMember
Level 2 [Member] | Commodity Contracts [Member] | WPL [Member] |  |
Assets: |  |
Derivative assets | 0.2 us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / dei_LegalEntityAxis = lnt_WplMember | 1.7 us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / dei_LegalEntityAxis = lnt_WplMember
Capitalization and liabilities: |  |
Derivative liabilities | 6.2 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / dei_LegalEntityAxis = lnt_WplMember | 1.5 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / dei_LegalEntityAxis = lnt_WplMember
Level 3 [Member] |  |
Assets: |  |
Deferred proceeds | 177.2 lnt_FairValueOfDeferredProceedsOfReceivablesSold / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member | 203.5 lnt_FairValueOfDeferredProceedsOfReceivablesSold / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member
Capitalization and liabilities: |  |
Long-term debt (including current maturities) | 3.3 us-gaap_DebtInstrumentFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member | 0.5 us-gaap_DebtInstrumentFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member
Cumulative preferred stock | 0 lnt_PreferredStockFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member | 0 lnt_PreferredStockFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member
Level 3 [Member] | IPL [Member] |  |
Assets: |  |
Deferred proceeds | 177.2 lnt_FairValueOfDeferredProceedsOfReceivablesSold / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / dei_LegalEntityAxis = lnt_IplMember | 203.5 lnt_FairValueOfDeferredProceedsOfReceivablesSold / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / dei_LegalEntityAxis = lnt_IplMember
Capitalization and liabilities: |  |
Long-term debt (including current maturities) | 0 us-gaap_DebtInstrumentFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / dei_LegalEntityAxis = lnt_IplMember | 0 us-gaap_DebtInstrumentFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / dei_LegalEntityAxis = lnt_IplMember
Cumulative preferred stock | 0 lnt_PreferredStockFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / dei_LegalEntityAxis = lnt_IplMember | 0 lnt_PreferredStockFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / dei_LegalEntityAxis = lnt_IplMember
Level 3 [Member] | WPL [Member] |  |
Capitalization and liabilities: |  |
Long-term debt (including current maturities) | 0 us-gaap_DebtInstrumentFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / dei_LegalEntityAxis = lnt_WplMember | 0 us-gaap_DebtInstrumentFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / dei_LegalEntityAxis = lnt_WplMember
Level 3 [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivative assets | 36.0 us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member | 22.0 us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member
Capitalization and liabilities: |  |
Derivative liabilities | 18.1 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member | 17.6 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member
Level 3 [Member] | Commodity Contracts [Member] | IPL [Member] |  |
Assets: |  |
Derivative assets | 25.6 us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / dei_LegalEntityAxis = lnt_IplMember | 18.1 us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / dei_LegalEntityAxis = lnt_IplMember
Capitalization and liabilities: |  |
Derivative liabilities | 6.2 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / dei_LegalEntityAxis = lnt_IplMember | 3.5 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / dei_LegalEntityAxis = lnt_IplMember
Level 3 [Member] | Commodity Contracts [Member] | WPL [Member] |  |
Assets: |  |
Derivative assets | 10.4 us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / dei_LegalEntityAxis = lnt_WplMember | 3.9 us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / dei_LegalEntityAxis = lnt_WplMember
Capitalization and liabilities: |  |
Derivative liabilities | $ 11.9 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / dei_LegalEntityAxis = lnt_WplMember | $ 14.1 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / dei_LegalEntityAxis = lnt_WplMember

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- Definition Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=35750535&loc=d3e13433-108611 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=35750535&loc=d3e13476-108611 + Details
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