Property, Plant and Equipment	9 Months Ended
Property, Plant and Equipment	Sep. 30, 2014
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	PROPERTY, PLANT AND EQUIPMENT Emission Controls Projects - IPL’s George Neal Unit 3 - Construction of the scrubber and baghouse at George Neal Unit 3 was completed in May 2014, which resulted in a transfer of the capitalized project costs from “Construction work in progress” to “Electric plant” on Alliant Energy’s and IPL’s balance sheets in 2014. As of September 30, 2014, the capitalized project costs consisted of capital expenditures of $59 million and AFUDC of $4 million for IPL’s allocated portion of the George Neal Unit 3 scrubber and baghouse. IPL’s Ottumwa Unit 1 - IPL is currently constructing a scrubber and baghouse at Ottumwa Unit 1 to reduce SO2 and mercury emissions at the EGU. Construction began in 2012 and is expected to be completed in 2014. As of September 30, 2014, Alliant Energy and IPL recorded capitalized expenditures of $151 million and AFUDC of $18 million for IPL’s allocated portion of the scrubber and baghouse in “Construction work in progress” on their balance sheets. WPL’s Columbia Units 1 and 2 - Construction of the scrubbers and baghouses at Columbia Units 1 and 2 was completed in July 2014 and April 2014, respectively, which resulted in a transfer of the capitalized project costs from “Construction work in progress” to “Electric plant” on Alliant Energy’s and WPL’s balance sheets in 2014. As of September 30, 2014, the capitalized project costs consisted of capital expenditures of $272 million and AFUDC of $15 million for WPL’s allocated portion of the Columbia Units 1 and 2 scrubbers and baghouses. WPL’s Edgewater Unit 5 - WPL is currently constructing a scrubber and baghouse at Edgewater Unit 5 to reduce SO2 and mercury emissions at the EGU. Construction began in 2014 and is expected to be completed in 2016. As of September 30, 2014, Alliant Energy and WPL recorded capitalized expenditures of $67 million and AFUDC of $2 million for the scrubber and baghouse in “Construction work in progress” on their balance sheets. Natural Gas-Fired Generation Project - IPL’s Marshalltown Generating Station - IPL is currently constructing Marshalltown, an approximate 650 MW natural gas-fired combined-cycle EGU. Construction began in 2014 and is expected to be completed in 2017. As of September 30, 2014, Alliant Energy and IPL recorded capitalized expenditures of $120 million and AFUDC of $2 million for Marshalltown in “Construction work in progress” on their balance sheets. Anticipated Sale of IPL’s Minnesota Natural Gas Distribution Assets - In November 2014, the MPUC issued an oral decision approving the proposed sale of IPL’s Minnesota natural gas distribution assets. IPL currently expects to complete the sale by March 31, 2015 pending receipt of a final order from the MPUC and completion of various other contingencies. Proceeds from the sale of the natural gas distribution assets, which approximate the carrying value of such assets, are expected to be approximately $10 million, subject to customary closing adjustments. As of September 30, 2014, IPL’s assets and liabilities included in the sale agreement did not meet the criteria to be classified as held for sale due to uncertainties in the regulatory approval process that existed on such date. The operating results of IPL’s Minnesota natural gas distribution business also did not qualify as discontinued operations as of September 30, 2014.
IPL [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	PROPERTY, PLANT AND EQUIPMENT Emission Controls Projects - IPL’s George Neal Unit 3 - Construction of the scrubber and baghouse at George Neal Unit 3 was completed in May 2014, which resulted in a transfer of the capitalized project costs from “Construction work in progress” to “Electric plant” on Alliant Energy’s and IPL’s balance sheets in 2014. As of September 30, 2014, the capitalized project costs consisted of capital expenditures of $59 million and AFUDC of $4 million for IPL’s allocated portion of the George Neal Unit 3 scrubber and baghouse. IPL’s Ottumwa Unit 1 - IPL is currently constructing a scrubber and baghouse at Ottumwa Unit 1 to reduce SO2 and mercury emissions at the EGU. Construction began in 2012 and is expected to be completed in 2014. As of September 30, 2014, Alliant Energy and IPL recorded capitalized expenditures of $151 million and AFUDC of $18 million for IPL’s allocated portion of the scrubber and baghouse in “Construction work in progress” on their balance sheets. WPL’s Columbia Units 1 and 2 - Construction of the scrubbers and baghouses at Columbia Units 1 and 2 was completed in July 2014 and April 2014, respectively, which resulted in a transfer of the capitalized project costs from “Construction work in progress” to “Electric plant” on Alliant Energy’s and WPL’s balance sheets in 2014. As of September 30, 2014, the capitalized project costs consisted of capital expenditures of $272 million and AFUDC of $15 million for WPL’s allocated portion of the Columbia Units 1 and 2 scrubbers and baghouses. WPL’s Edgewater Unit 5 - WPL is currently constructing a scrubber and baghouse at Edgewater Unit 5 to reduce SO2 and mercury emissions at the EGU. Construction began in 2014 and is expected to be completed in 2016. As of September 30, 2014, Alliant Energy and WPL recorded capitalized expenditures of $67 million and AFUDC of $2 million for the scrubber and baghouse in “Construction work in progress” on their balance sheets. Natural Gas-Fired Generation Project - IPL’s Marshalltown Generating Station - IPL is currently constructing Marshalltown, an approximate 650 MW natural gas-fired combined-cycle EGU. Construction began in 2014 and is expected to be completed in 2017. As of September 30, 2014, Alliant Energy and IPL recorded capitalized expenditures of $120 million and AFUDC of $2 million for Marshalltown in “Construction work in progress” on their balance sheets. Anticipated Sale of IPL’s Minnesota Natural Gas Distribution Assets - In November 2014, the MPUC issued an oral decision approving the proposed sale of IPL’s Minnesota natural gas distribution assets. IPL currently expects to complete the sale by March 31, 2015 pending receipt of a final order from the MPUC and completion of various other contingencies. Proceeds from the sale of the natural gas distribution assets, which approximate the carrying value of such assets, are expected to be approximately $10 million, subject to customary closing adjustments. As of September 30, 2014, IPL’s assets and liabilities included in the sale agreement did not meet the criteria to be classified as held for sale due to uncertainties in the regulatory approval process that existed on such date. The operating results of IPL’s Minnesota natural gas distribution business also did not qualify as discontinued operations as of September 30, 2014.
WPL [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	PROPERTY, PLANT AND EQUIPMENT Emission Controls Projects - IPL’s George Neal Unit 3 - Construction of the scrubber and baghouse at George Neal Unit 3 was completed in May 2014, which resulted in a transfer of the capitalized project costs from “Construction work in progress” to “Electric plant” on Alliant Energy’s and IPL’s balance sheets in 2014. As of September 30, 2014, the capitalized project costs consisted of capital expenditures of $59 million and AFUDC of $4 million for IPL’s allocated portion of the George Neal Unit 3 scrubber and baghouse. IPL’s Ottumwa Unit 1 - IPL is currently constructing a scrubber and baghouse at Ottumwa Unit 1 to reduce SO2 and mercury emissions at the EGU. Construction began in 2012 and is expected to be completed in 2014. As of September 30, 2014, Alliant Energy and IPL recorded capitalized expenditures of $151 million and AFUDC of $18 million for IPL’s allocated portion of the scrubber and baghouse in “Construction work in progress” on their balance sheets. WPL’s Columbia Units 1 and 2 - Construction of the scrubbers and baghouses at Columbia Units 1 and 2 was completed in July 2014 and April 2014, respectively, which resulted in a transfer of the capitalized project costs from “Construction work in progress” to “Electric plant” on Alliant Energy’s and WPL’s balance sheets in 2014. As of September 30, 2014, the capitalized project costs consisted of capital expenditures of $272 million and AFUDC of $15 million for WPL’s allocated portion of the Columbia Units 1 and 2 scrubbers and baghouses. WPL’s Edgewater Unit 5 - WPL is currently constructing a scrubber and baghouse at Edgewater Unit 5 to reduce SO2 and mercury emissions at the EGU. Construction began in 2014 and is expected to be completed in 2016. As of September 30, 2014, Alliant Energy and WPL recorded capitalized expenditures of $67 million and AFUDC of $2 million for the scrubber and baghouse in “Construction work in progress” on their balance sheets. Natural Gas-Fired Generation Project - IPL’s Marshalltown Generating Station - IPL is currently constructing Marshalltown, an approximate 650 MW natural gas-fired combined-cycle EGU. Construction began in 2014 and is expected to be completed in 2017. As of September 30, 2014, Alliant Energy and IPL recorded capitalized expenditures of $120 million and AFUDC of $2 million for Marshalltown in “Construction work in progress” on their balance sheets. Anticipated Sale of IPL’s Minnesota Natural Gas Distribution Assets - In November 2014, the MPUC issued an oral decision approving the proposed sale of IPL’s Minnesota natural gas distribution assets. IPL currently expects to complete the sale by March 31, 2015 pending receipt of a final order from the MPUC and completion of various other contingencies. Proceeds from the sale of the natural gas distribution assets, which approximate the carrying value of such assets, are expected to be approximately $10 million, subject to customary closing adjustments. As of September 30, 2014, IPL’s assets and liabilities included in the sale agreement did not meet the criteria to be classified as held for sale due to uncertainties in the regulatory approval process that existed on such date. The operating results of IPL’s Minnesota natural gas distribution business also did not qualify as discontinued operations as of September 30, 2014.

The entire disclosure for long-lived, physical assets used in the normal conduct of business and not intended for resale. Includes, but is not limited to, accounting policies and methodology, roll forwards, depreciation, depletion and amortization expense, including composite depreciation, accumulated depreciation, depletion and amortization expense, useful lives and method used, income statement disclosures, assets held for sale and public utility disclosures.

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