XML 31 R8.htm IDEA: XBRL DOCUMENT
v3.7.0.1

Property, Plant and Equipment | 6 Months Ended
--- | ---
Jun. 30, 2017
Property, Plant and Equipment [Line Items] |
Property, Plant and Equipment | PROPERTY, PLANT AND EQUIPMENT Utility - Natural Gas-Fired Generation Projects - IPL’s Marshalltown Generating Station - IPL’s construction of Marshalltown, an approximate 660 MW natural gas-fired combined-cycle EGU, was completed and the EGU was placed into service in April 2017. As of June 30, 2017, Alliant Energy and IPL recorded total project costs of $640 million and AFUDC of $81 million for Marshalltown in “Property, plant and equipment, net” on their balance sheets. WPL’s West Riverside Energy Center - WPL is currently constructing West Riverside, an approximate 730 MW natural gas-fired combined-cycle EGU. Construction began in 2016 and is currently expected to be completed by early 2020. As of June 30, 2017, Alliant Energy and WPL recorded capitalized expenditures for construction work in progress of $185 million and AFUDC of $5 million for West Riverside in “Property, plant and equipment, net” on their balance sheets. These capital expenditures do not yet reflect any potential impacts from the intent to exercise purchase options by certain WPL electric cooperatives for a partial ownership interest in West Riverside. Wind Generation - Franklin County Wind Farm Transfer - In April 2017, the Franklin County wind farm was transferred from AEF to IPL as approved by a February 2017 FERC order. IPL’s purchase price, including certain transaction-related costs, was $32 million. As of the closing date, the estimated fair values of the assets purchased and liabilities assumed by IPL were as follows (in millions):
Electric plant in service |  | $40 |
Current assets | 2 |
Total assets acquired | 42 |
Other liabilities | 10 |
Net assets acquired |  | $32 |
The final amount to be recovered for IPL’s electric rate-making purposes will be determined by the IUB as part of IPL’s Iowa retail electric base rate review for the 2016 Test Year, which was filed in April 2017. Retirement of IPL’s Sutherland Units 1 and 3 - In June 2017, IPL retired Sutherland Units 1 and 3 and reclassified the remaining net book value of these EGUs from property, plant and equipment to a regulatory asset on Alliant Energy’s and IPL’s balance sheets. Refer to Note 2 for further discussion.
IPL [Member] |
Property, Plant and Equipment [Line Items] |
Property, Plant and Equipment | PROPERTY, PLANT AND EQUIPMENT Utility - Natural Gas-Fired Generation Projects - IPL’s Marshalltown Generating Station - IPL’s construction of Marshalltown, an approximate 660 MW natural gas-fired combined-cycle EGU, was completed and the EGU was placed into service in April 2017. As of June 30, 2017, Alliant Energy and IPL recorded total project costs of $640 million and AFUDC of $81 million for Marshalltown in “Property, plant and equipment, net” on their balance sheets. WPL’s West Riverside Energy Center - WPL is currently constructing West Riverside, an approximate 730 MW natural gas-fired combined-cycle EGU. Construction began in 2016 and is currently expected to be completed by early 2020. As of June 30, 2017, Alliant Energy and WPL recorded capitalized expenditures for construction work in progress of $185 million and AFUDC of $5 million for West Riverside in “Property, plant and equipment, net” on their balance sheets. These capital expenditures do not yet reflect any potential impacts from the intent to exercise purchase options by certain WPL electric cooperatives for a partial ownership interest in West Riverside. Wind Generation - Franklin County Wind Farm Transfer - In April 2017, the Franklin County wind farm was transferred from AEF to IPL as approved by a February 2017 FERC order. IPL’s purchase price, including certain transaction-related costs, was $32 million. As of the closing date, the estimated fair values of the assets purchased and liabilities assumed by IPL were as follows (in millions):
Electric plant in service |  | $40 |
Current assets | 2 |
Total assets acquired | 42 |
Other liabilities | 10 |
Net assets acquired |  | $32 |
The final amount to be recovered for IPL’s electric rate-making purposes will be determined by the IUB as part of IPL’s Iowa retail electric base rate review for the 2016 Test Year, which was filed in April 2017. Retirement of IPL’s Sutherland Units 1 and 3 - In June 2017, IPL retired Sutherland Units 1 and 3 and reclassified the remaining net book value of these EGUs from property, plant and equipment to a regulatory asset on Alliant Energy’s and IPL’s balance sheets. Refer to Note 2 for further discussion.
WPL [Member] |
Property, Plant and Equipment [Line Items] |
Property, Plant and Equipment | PROPERTY, PLANT AND EQUIPMENT Utility - Natural Gas-Fired Generation Projects - IPL’s Marshalltown Generating Station - IPL’s construction of Marshalltown, an approximate 660 MW natural gas-fired combined-cycle EGU, was completed and the EGU was placed into service in April 2017. As of June 30, 2017, Alliant Energy and IPL recorded total project costs of $640 million and AFUDC of $81 million for Marshalltown in “Property, plant and equipment, net” on their balance sheets. WPL’s West Riverside Energy Center - WPL is currently constructing West Riverside, an approximate 730 MW natural gas-fired combined-cycle EGU. Construction began in 2016 and is currently expected to be completed by early 2020. As of June 30, 2017, Alliant Energy and WPL recorded capitalized expenditures for construction work in progress of $185 million and AFUDC of $5 million for West Riverside in “Property, plant and equipment, net” on their balance sheets. These capital expenditures do not yet reflect any potential impacts from the intent to exercise purchase options by certain WPL electric cooperatives for a partial ownership interest in West Riverside.

X
- Definition 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. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.13-14) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=64827811&loc=d3e1361-107760 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=64862545&loc=d3e2921-110230 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229 + Details
Name: | us-gaap_PropertyPlantAndEquipmentDisclosureTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_PropertyPlantAndEquipmentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | dei_LegalEntityAxis=lnt_IplMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=lnt_WplMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |