Property, Plant and Equipment	3 Months Ended
Property, Plant and Equipment	Mar. 31, 2015
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	PROPERTY, PLANT AND EQUIPMENT Utility - Emission Controls Project - 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 March 31, 2015, Alliant Energy and WPL recorded capitalized expenditures for construction work in progress of $110 million and AFUDC of $4 million for the scrubber and baghouse in “Property, plant and equipment, net” 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 March 31, 2015, Alliant Energy and IPL recorded capitalized expenditures of $248 million and AFUDC of $7 million for Marshalltown in “Property, plant and equipment, net” on their balance sheets. Sales of IPL’s Minnesota Electric and Natural Gas Distribution Assets - In April 2015, IPL completed the sale of its Minnesota natural gas distribution assets and received net proceeds of $11 million and a promissory note of $2 million. The proceeds are subject to post-closing adjustments based on the value of the net assets transferred as of the closing date, and will be used for general corporate purposes. Refer to Note 16 for details of the natural gas distribution assets, which qualified as held for sale as of March 31, 2015 and December 31, 2014. In April 2015, the MPUC approved the sale of IPL’s Minnesota electric distribution assets, subject to certain conditions. IPL is currently reviewing the MPUC’s decision. Pending the receipt of remaining regulatory approvals, IPL currently expects the electric transaction to be concluded in the third quarter of 2015. As of March 31, 2015, IPL’s assets and liabilities included in the electric sales 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. Non-regulated and Other - Corporate Services and Other - Corporate Services is implementing a new customer billing and information system for IPL and WPL, which is currently expected to be deployed in 2015. As of March 31, 2015, Alliant Energy recorded capitalized expenditures of $71 million and capitalized interest of $2 million for the system in “Property, plant and equipment, net” on its balance sheet.
IPL [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	PROPERTY, PLANT AND EQUIPMENT Utility - Emission Controls Project - 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 March 31, 2015, Alliant Energy and WPL recorded capitalized expenditures for construction work in progress of $110 million and AFUDC of $4 million for the scrubber and baghouse in “Property, plant and equipment, net” 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 March 31, 2015, Alliant Energy and IPL recorded capitalized expenditures of $248 million and AFUDC of $7 million for Marshalltown in “Property, plant and equipment, net” on their balance sheets. Sales of IPL’s Minnesota Electric and Natural Gas Distribution Assets - In April 2015, IPL completed the sale of its Minnesota natural gas distribution assets and received net proceeds of $11 million and a promissory note of $2 million. The proceeds are subject to post-closing adjustments based on the value of the net assets transferred as of the closing date, and will be used for general corporate purposes. Refer to Note 16 for details of the natural gas distribution assets, which qualified as held for sale as of March 31, 2015 and December 31, 2014. In April 2015, the MPUC approved the sale of IPL’s Minnesota electric distribution assets, subject to certain conditions. IPL is currently reviewing the MPUC’s decision. Pending the receipt of remaining regulatory approvals, IPL currently expects the electric transaction to be concluded in the third quarter of 2015. As of March 31, 2015, IPL’s assets and liabilities included in the electric sales 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.
WPL [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	PROPERTY, PLANT AND EQUIPMENT Utility - Emission Controls Project - 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 March 31, 2015, Alliant Energy and WPL recorded capitalized expenditures for construction work in progress of $110 million and AFUDC of $4 million for the scrubber and baghouse in “Property, plant and equipment, net” on their balance sheets.

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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