XML 87 R45.htm IDEA: XBRL DOCUMENT
v3.6.0.2

Derivative Instruments (Tables) | 12 Months Ended
--- | ---
Dec. 31, 2016
Derivative [Line Items] |
Notional Amounts of Derivative Instruments | As of December 31, 2016, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts, FTRs, coal contracts and diesel fuel contracts that were accounted for as commodity derivative instruments were as follows (units in thousands):
| Electricity |  | FTRs |  | Natural Gas |  | Coal |  | Diesel Fuel
| MWhs |  | Years |  | MWhs |  | Years |  | Dths |  | Years |  | Tons |  | Years |  | Gallons |  | Years
Alliant Energy | 2,628 |  |  | 2017-2018 |  | 8,970 |  |  | 2017 |  | 139,865 |  |  | 2017-2023 |  | 4,239 |  |  | 2017-2019 |  | 6,552 |  |  | 2017-2018
IPL | — |  |  | — |  | 5,465 |  |  | 2017 |  | 56,265 |  |  | 2017-2021 |  | 1,955 |  |  | 2017-2019 |  | — |  |  | —
WPL | 2,628 |  |  | 2017-2018 |  | 3,505 |  |  | 2017 |  | 83,600 |  |  | 2017-2023 |  | 2,284 |  |  | 2017-2018 |  | 6,552 |  |  | 2017-2018
Fair Value of Financial Instruments | At December 31, the fair values of current derivative assets are included in “Other current assets,” non-current derivative assets are included in “Deferred charges and other,” current derivative liabilities are included in “Other current liabilities” and non-current derivative liabilities are included in “Other liabilities” on the balance sheets as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
Commodity contracts | 2016 |  | 2015 |  | 2016 |  | 2015 |  | 2016 |  | 2015
Current derivative assets |  | $29.4 |  |  |  | $15.1 |  |  |  | $19.1 |  |  |  | $13.8 |  |  |  | $10.3 |  |  |  | $1.3 |
Non-current derivative assets | 12.0 |  |  | 3.3 |  |  | 1.7 |  |  | 1.7 |  |  | 10.3 |  |  | 1.6 |
Current derivative liabilities | 13.3 |  |  | 47.3 |  |  | 2.7 |  |  | 18.5 |  |  | 10.6 |  |  | 28.8 |
Non-current derivative liabilities | 15.3 |  |  | 17.3 |  |  | 5.6 |  |  | 4.9 |  |  | 9.7 |  |  | 12.4 |
IPL [Member] |
Derivative [Line Items] |
Notional Amounts of Derivative Instruments | As of December 31, 2016, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts, FTRs, coal contracts and diesel fuel contracts that were accounted for as commodity derivative instruments were as follows (units in thousands):
| Electricity |  | FTRs |  | Natural Gas |  | Coal |  | Diesel Fuel
| MWhs |  | Years |  | MWhs |  | Years |  | Dths |  | Years |  | Tons |  | Years |  | Gallons |  | Years
Alliant Energy | 2,628 |  |  | 2017-2018 |  | 8,970 |  |  | 2017 |  | 139,865 |  |  | 2017-2023 |  | 4,239 |  |  | 2017-2019 |  | 6,552 |  |  | 2017-2018
IPL | — |  |  | — |  | 5,465 |  |  | 2017 |  | 56,265 |  |  | 2017-2021 |  | 1,955 |  |  | 2017-2019 |  | — |  |  | —
WPL | 2,628 |  |  | 2017-2018 |  | 3,505 |  |  | 2017 |  | 83,600 |  |  | 2017-2023 |  | 2,284 |  |  | 2017-2018 |  | 6,552 |  |  | 2017-2018
Fair Value of Financial Instruments | At December 31, the fair values of current derivative assets are included in “Other current assets,” non-current derivative assets are included in “Deferred charges and other,” current derivative liabilities are included in “Other current liabilities” and non-current derivative liabilities are included in “Other liabilities” on the balance sheets as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
Commodity contracts | 2016 |  | 2015 |  | 2016 |  | 2015 |  | 2016 |  | 2015
Current derivative assets |  | $29.4 |  |  |  | $15.1 |  |  |  | $19.1 |  |  |  | $13.8 |  |  |  | $10.3 |  |  |  | $1.3 |
Non-current derivative assets | 12.0 |  |  | 3.3 |  |  | 1.7 |  |  | 1.7 |  |  | 10.3 |  |  | 1.6 |
Current derivative liabilities | 13.3 |  |  | 47.3 |  |  | 2.7 |  |  | 18.5 |  |  | 10.6 |  |  | 28.8 |
Non-current derivative liabilities | 15.3 |  |  | 17.3 |  |  | 5.6 |  |  | 4.9 |  |  | 9.7 |  |  | 12.4 |
WPL [Member] |
Derivative [Line Items] |
Notional Amounts of Derivative Instruments | As of December 31, 2016, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts, FTRs, coal contracts and diesel fuel contracts that were accounted for as commodity derivative instruments were as follows (units in thousands):
| Electricity |  | FTRs |  | Natural Gas |  | Coal |  | Diesel Fuel
| MWhs |  | Years |  | MWhs |  | Years |  | Dths |  | Years |  | Tons |  | Years |  | Gallons |  | Years
Alliant Energy | 2,628 |  |  | 2017-2018 |  | 8,970 |  |  | 2017 |  | 139,865 |  |  | 2017-2023 |  | 4,239 |  |  | 2017-2019 |  | 6,552 |  |  | 2017-2018
IPL | — |  |  | — |  | 5,465 |  |  | 2017 |  | 56,265 |  |  | 2017-2021 |  | 1,955 |  |  | 2017-2019 |  | — |  |  | —
WPL | 2,628 |  |  | 2017-2018 |  | 3,505 |  |  | 2017 |  | 83,600 |  |  | 2017-2023 |  | 2,284 |  |  | 2017-2018 |  | 6,552 |  |  | 2017-2018
Fair Value of Financial Instruments | At December 31, the fair values of current derivative assets are included in “Other current assets,” non-current derivative assets are included in “Deferred charges and other,” current derivative liabilities are included in “Other current liabilities” and non-current derivative liabilities are included in “Other liabilities” on the balance sheets as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
Commodity contracts | 2016 |  | 2015 |  | 2016 |  | 2015 |  | 2016 |  | 2015
Current derivative assets |  | $29.4 |  |  |  | $15.1 |  |  |  | $19.1 |  |  |  | $13.8 |  |  |  | $10.3 |  |  |  | $1.3 |
Non-current derivative assets | 12.0 |  |  | 3.3 |  |  | 1.7 |  |  | 1.7 |  |  | 10.3 |  |  | 1.6 |
Current derivative liabilities | 13.3 |  |  | 47.3 |  |  | 2.7 |  |  | 18.5 |  |  | 10.6 |  |  | 28.8 |
Non-current derivative liabilities | 15.3 |  |  | 17.3 |  |  | 5.6 |  |  | 4.9 |  |  | 9.7 |  |  | 12.4 |

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_DerivativeLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the location and fair value amounts of derivative instruments (and nonderivative instruments that are designated and qualify as hedging instruments) reported in the statement of financial position. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4B -URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624163-113959 + Details
Name: | us-gaap_ScheduleOfDerivativeInstrumentsInStatementOfFinancialPositionFairValueTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the notional amounts of outstanding derivative positions. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5579245-113959 + Details
Name: | us-gaap_ScheduleOfNotionalAmountsOfOutstandingDerivativePositionsTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
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: |