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Derivative Instruments (Notional Amounts Of Derivative Instruments) (Details) (Commodity [Member]) | Mar. 31, 2015 MWh
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Electricity (MWhs) [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 9,028,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_EnergyAxis = lnt_ElectricityMwhsMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
Electricity (MWhs) [Member] | IPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 2,051,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_EnergyAxis = lnt_ElectricityMwhsMember / dei_LegalEntityAxis = lnt_IplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
Electricity (MWhs) [Member] | WPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 6,977,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_EnergyAxis = lnt_ElectricityMwhsMember / dei_LegalEntityAxis = lnt_WplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
FTRs (MWhs) [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 3,478,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_EnergyAxis = lnt_FtrsMwhsMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
FTRs (MWhs) [Member] | IPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 2,041,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_EnergyAxis = lnt_FtrsMwhsMember / dei_LegalEntityAxis = lnt_IplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
FTRs (MWhs) [Member] | WPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 1,437,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_EnergyAxis = lnt_FtrsMwhsMember / dei_LegalEntityAxis = lnt_WplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
Natural Gas (Dths) [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 77,538,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_EnergyAxis = lnt_NaturalGasDthsMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
Natural Gas (Dths) [Member] | IPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 42,901,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_EnergyAxis = lnt_NaturalGasDthsMember / dei_LegalEntityAxis = lnt_IplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
Natural Gas (Dths) [Member] | WPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 34,637,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_EnergyAxis = lnt_NaturalGasDthsMember / dei_LegalEntityAxis = lnt_WplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
Coal (Tons) [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 5,348,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_EnergyAxis = lnt_CoalTonsMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
Coal (Tons) [Member] | IPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 1,547,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_EnergyAxis = lnt_CoalTonsMember / dei_LegalEntityAxis = lnt_IplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
Coal (Tons) [Member] | WPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 3,801,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_EnergyAxis = lnt_CoalTonsMember / dei_LegalEntityAxis = lnt_WplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2015 [Member] | Electricity (MWhs) [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 3,530,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearOneMember / us-gaap_EnergyAxis = lnt_ElectricityMwhsMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2015 [Member] | Electricity (MWhs) [Member] | IPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 1,612,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearOneMember / us-gaap_EnergyAxis = lnt_ElectricityMwhsMember / dei_LegalEntityAxis = lnt_IplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2015 [Member] | Electricity (MWhs) [Member] | WPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 1,918,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearOneMember / us-gaap_EnergyAxis = lnt_ElectricityMwhsMember / dei_LegalEntityAxis = lnt_WplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2015 [Member] | FTRs (MWhs) [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 3,478,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearOneMember / us-gaap_EnergyAxis = lnt_FtrsMwhsMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2015 [Member] | FTRs (MWhs) [Member] | IPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 2,041,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearOneMember / us-gaap_EnergyAxis = lnt_FtrsMwhsMember / dei_LegalEntityAxis = lnt_IplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2015 [Member] | FTRs (MWhs) [Member] | WPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 1,437,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearOneMember / us-gaap_EnergyAxis = lnt_FtrsMwhsMember / dei_LegalEntityAxis = lnt_WplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2015 [Member] | Natural Gas (Dths) [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 42,989,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearOneMember / us-gaap_EnergyAxis = lnt_NaturalGasDthsMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2015 [Member] | Natural Gas (Dths) [Member] | IPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 26,967,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearOneMember / us-gaap_EnergyAxis = lnt_NaturalGasDthsMember / dei_LegalEntityAxis = lnt_IplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2015 [Member] | Natural Gas (Dths) [Member] | WPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 16,022,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearOneMember / us-gaap_EnergyAxis = lnt_NaturalGasDthsMember / dei_LegalEntityAxis = lnt_WplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2015 [Member] | Coal (Tons) [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 1,118,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearOneMember / us-gaap_EnergyAxis = lnt_CoalTonsMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2015 [Member] | Coal (Tons) [Member] | IPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 56,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearOneMember / us-gaap_EnergyAxis = lnt_CoalTonsMember / dei_LegalEntityAxis = lnt_IplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2015 [Member] | Coal (Tons) [Member] | WPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 1,062,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearOneMember / us-gaap_EnergyAxis = lnt_CoalTonsMember / dei_LegalEntityAxis = lnt_WplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2016 [Member] | Electricity (MWhs) [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 2,870,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearTwoMember / us-gaap_EnergyAxis = lnt_ElectricityMwhsMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2016 [Member] | Electricity (MWhs) [Member] | IPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 439,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearTwoMember / us-gaap_EnergyAxis = lnt_ElectricityMwhsMember / dei_LegalEntityAxis = lnt_IplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2016 [Member] | Electricity (MWhs) [Member] | WPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 2,431,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearTwoMember / us-gaap_EnergyAxis = lnt_ElectricityMwhsMember / dei_LegalEntityAxis = lnt_WplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2016 [Member] | FTRs (MWhs) [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 0 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearTwoMember / us-gaap_EnergyAxis = lnt_FtrsMwhsMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2016 [Member] | FTRs (MWhs) [Member] | IPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 0 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearTwoMember / us-gaap_EnergyAxis = lnt_FtrsMwhsMember / dei_LegalEntityAxis = lnt_IplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2016 [Member] | FTRs (MWhs) [Member] | WPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 0 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearTwoMember / us-gaap_EnergyAxis = lnt_FtrsMwhsMember / dei_LegalEntityAxis = lnt_WplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2016 [Member] | Natural Gas (Dths) [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 27,423,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearTwoMember / us-gaap_EnergyAxis = lnt_NaturalGasDthsMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2016 [Member] | Natural Gas (Dths) [Member] | IPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 13,176,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearTwoMember / us-gaap_EnergyAxis = lnt_NaturalGasDthsMember / dei_LegalEntityAxis = lnt_IplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2016 [Member] | Natural Gas (Dths) [Member] | WPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 14,247,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearTwoMember / us-gaap_EnergyAxis = lnt_NaturalGasDthsMember / dei_LegalEntityAxis = lnt_WplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2016 [Member] | Coal (Tons) [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 2,044,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearTwoMember / us-gaap_EnergyAxis = lnt_CoalTonsMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2016 [Member] | Coal (Tons) [Member] | IPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 830,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearTwoMember / us-gaap_EnergyAxis = lnt_CoalTonsMember / dei_LegalEntityAxis = lnt_IplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2016 [Member] | Coal (Tons) [Member] | WPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 1,214,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearTwoMember / us-gaap_EnergyAxis = lnt_CoalTonsMember / dei_LegalEntityAxis = lnt_WplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2017 [Member] | Electricity (MWhs) [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 1,314,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearThreeMember / us-gaap_EnergyAxis = lnt_ElectricityMwhsMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2017 [Member] | Electricity (MWhs) [Member] | IPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 0 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearThreeMember / us-gaap_EnergyAxis = lnt_ElectricityMwhsMember / dei_LegalEntityAxis = lnt_IplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2017 [Member] | Electricity (MWhs) [Member] | WPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 1,314,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearThreeMember / us-gaap_EnergyAxis = lnt_ElectricityMwhsMember / dei_LegalEntityAxis = lnt_WplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2017 [Member] | FTRs (MWhs) [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 0 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearThreeMember / us-gaap_EnergyAxis = lnt_FtrsMwhsMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2017 [Member] | FTRs (MWhs) [Member] | IPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 0 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearThreeMember / us-gaap_EnergyAxis = lnt_FtrsMwhsMember / dei_LegalEntityAxis = lnt_IplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2017 [Member] | FTRs (MWhs) [Member] | WPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 0 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearThreeMember / us-gaap_EnergyAxis = lnt_FtrsMwhsMember / dei_LegalEntityAxis = lnt_WplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2017 [Member] | Natural Gas (Dths) [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 7,126,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearThreeMember / us-gaap_EnergyAxis = lnt_NaturalGasDthsMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2017 [Member] | Natural Gas (Dths) [Member] | IPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 2,758,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearThreeMember / us-gaap_EnergyAxis = lnt_NaturalGasDthsMember / dei_LegalEntityAxis = lnt_IplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2017 [Member] | Natural Gas (Dths) [Member] | WPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 4,368,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearThreeMember / us-gaap_EnergyAxis = lnt_NaturalGasDthsMember / dei_LegalEntityAxis = lnt_WplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2017 [Member] | Coal (Tons) [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 1,073,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearThreeMember / us-gaap_EnergyAxis = lnt_CoalTonsMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2017 [Member] | Coal (Tons) [Member] | IPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 274,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearThreeMember / us-gaap_EnergyAxis = lnt_CoalTonsMember / dei_LegalEntityAxis = lnt_IplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2017 [Member] | Coal (Tons) [Member] | WPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 799,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearThreeMember / us-gaap_EnergyAxis = lnt_CoalTonsMember / dei_LegalEntityAxis = lnt_WplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2018 [Member] | Electricity (MWhs) [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 1,314,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearFourMember / us-gaap_EnergyAxis = lnt_ElectricityMwhsMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2018 [Member] | Electricity (MWhs) [Member] | IPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 0 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearFourMember / us-gaap_EnergyAxis = lnt_ElectricityMwhsMember / dei_LegalEntityAxis = lnt_IplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2018 [Member] | Electricity (MWhs) [Member] | WPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 1,314,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearFourMember / us-gaap_EnergyAxis = lnt_ElectricityMwhsMember / dei_LegalEntityAxis = lnt_WplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2018 [Member] | FTRs (MWhs) [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 0 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearFourMember / us-gaap_EnergyAxis = lnt_FtrsMwhsMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2018 [Member] | FTRs (MWhs) [Member] | IPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 0 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearFourMember / us-gaap_EnergyAxis = lnt_FtrsMwhsMember / dei_LegalEntityAxis = lnt_IplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2018 [Member] | FTRs (MWhs) [Member] | WPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 0 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearFourMember / us-gaap_EnergyAxis = lnt_FtrsMwhsMember / dei_LegalEntityAxis = lnt_WplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2018 [Member] | Natural Gas (Dths) [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 0 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearFourMember / us-gaap_EnergyAxis = lnt_NaturalGasDthsMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2018 [Member] | Natural Gas (Dths) [Member] | IPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 0 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearFourMember / us-gaap_EnergyAxis = lnt_NaturalGasDthsMember / dei_LegalEntityAxis = lnt_IplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2018 [Member] | Natural Gas (Dths) [Member] | WPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 0 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearFourMember / us-gaap_EnergyAxis = lnt_NaturalGasDthsMember / dei_LegalEntityAxis = lnt_WplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2018 [Member] | Coal (Tons) [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 1,113,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearFourMember / us-gaap_EnergyAxis = lnt_CoalTonsMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2018 [Member] | Coal (Tons) [Member] | IPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 387,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearFourMember / us-gaap_EnergyAxis = lnt_CoalTonsMember / dei_LegalEntityAxis = lnt_IplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember
2018 [Member] | Coal (Tons) [Member] | WPL [Member] |
Notional Amount of Derivatives [Line Items] |
Notional unit amount of derivatives (in MWhs/Dths/Tons) | 726,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = lnt_DerivativeNonMonetaryNotionalAmountYearFourMember / us-gaap_EnergyAxis = lnt_CoalTonsMember / dei_LegalEntityAxis = lnt_WplMember / us-gaap_TradingActivityByTypeAxis = us-gaap_CommodityMember

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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
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