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Derivative Instruments | 3 Months Ended
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Mar. 31, 2018
Derivative Instruments [Line Items] |
Derivative Instruments | DERIVATIVE INSTRUMENTS Commodity Derivatives - Notional Amounts - As of March 31, 2018, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs 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 | 990 |  |  | 2018 |  | 3,370 |  |  | 2018 |  | 156,074 |  |  | 2018-2026 |  | 7,144 |  |  | 2018-2020 |  | 5,670 |  |  | 2018-2019
IPL | — |  |  | — |  | 2,252 |  |  | 2018 |  | 65,541 |  |  | 2018-2026 |  | 2,975 |  |  | 2018-2020 |  | — |  |  | —
WPL | 990 |  |  | 2018 |  | 1,118 |  |  | 2018 |  | 90,533 |  |  | 2018-2026 |  | 4,169 |  |  | 2018-2020 |  | 5,670 |  |  | 2018-2019
Financial Statement Presentation - Derivative instruments are recorded at fair value each reporting date on the balance sheets as assets or liabilities. 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
| March 31, 2018 |  | December 31, 2017 |  | March 31, 2018 |  | December 31, 2017 |  | March 31, 2018 |  | December 31, 2017
Current derivative assets |  | $10.8 |  |  |  | $21.1 |  |  |  | $7.0 |  |  |  | $15.8 |  |  |  | $3.8 |  |  |  | $5.3 |
Non-current derivative assets | 3.3 |  |  | 4.0 |  |  | 0.9 |  |  | 1.3 |  |  | 2.4 |  |  | 2.7 |
Current derivative liabilities | 15.9 |  |  | 18.7 |  |  | 4.8 |  |  | 5.0 |  |  | 11.1 |  |  | 13.7 |
Non-current derivative liabilities | 30.8 |  |  | 23.0 |  |  | 19.9 |  |  | 14.4 |  |  | 10.9 |  |  | 8.6 |
Credit Risk-related Contingent Features - Various agreements contain credit risk-related contingent features, including requirements to maintain certain credit ratings and/or limitations on liability positions under the agreements based on credit ratings. Certain of these agreements with credit risk-related contingency features are accounted for as derivative instruments. In the event of a material change in creditworthiness or if liability positions exceed certain contractual limits, credit support may need to be provided in the form of letters of credit or cash collateral up to the amount of exposure under the contracts, or the contracts may need to be unwound and underlying liability positions paid. At March 31, 2018 and December 31, 2017, the aggregate fair value of all derivative instruments with credit risk-related contingent features in a net liability position was not materially different than amounts that would be required to be posted as credit support to counterparties by Alliant Energy, IPL or WPL if the most restrictive credit risk-related contingent features for derivative agreements in a net liability position were triggered. Balance Sheet Offsetting - The fair value amounts of derivative instruments subject to a master netting arrangement are not netted by counterparty on the balance sheets. However, if the fair value amounts of derivative instruments by counterparty were netted, amounts would not be materially different from gross amounts of derivative assets and derivative liabilities at March 31, 2018 and December 31, 2017. Fair value amounts recognized for the right to reclaim cash collateral (receivable) or the obligation to return cash collateral (payable) are not offset against fair value amounts recognized for derivative instruments executed with the same counterparty under the same master netting arrangement.
IPL [Member] |
Derivative Instruments [Line Items] |
Derivative Instruments | DERIVATIVE INSTRUMENTS Commodity Derivatives - Notional Amounts - As of March 31, 2018, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs 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 | 990 |  |  | 2018 |  | 3,370 |  |  | 2018 |  | 156,074 |  |  | 2018-2026 |  | 7,144 |  |  | 2018-2020 |  | 5,670 |  |  | 2018-2019
IPL | — |  |  | — |  | 2,252 |  |  | 2018 |  | 65,541 |  |  | 2018-2026 |  | 2,975 |  |  | 2018-2020 |  | — |  |  | —
WPL | 990 |  |  | 2018 |  | 1,118 |  |  | 2018 |  | 90,533 |  |  | 2018-2026 |  | 4,169 |  |  | 2018-2020 |  | 5,670 |  |  | 2018-2019
Financial Statement Presentation - Derivative instruments are recorded at fair value each reporting date on the balance sheets as assets or liabilities. 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
| March 31, 2018 |  | December 31, 2017 |  | March 31, 2018 |  | December 31, 2017 |  | March 31, 2018 |  | December 31, 2017
Current derivative assets |  | $10.8 |  |  |  | $21.1 |  |  |  | $7.0 |  |  |  | $15.8 |  |  |  | $3.8 |  |  |  | $5.3 |
Non-current derivative assets | 3.3 |  |  | 4.0 |  |  | 0.9 |  |  | 1.3 |  |  | 2.4 |  |  | 2.7 |
Current derivative liabilities | 15.9 |  |  | 18.7 |  |  | 4.8 |  |  | 5.0 |  |  | 11.1 |  |  | 13.7 |
Non-current derivative liabilities | 30.8 |  |  | 23.0 |  |  | 19.9 |  |  | 14.4 |  |  | 10.9 |  |  | 8.6 |
Credit Risk-related Contingent Features - Various agreements contain credit risk-related contingent features, including requirements to maintain certain credit ratings and/or limitations on liability positions under the agreements based on credit ratings. Certain of these agreements with credit risk-related contingency features are accounted for as derivative instruments. In the event of a material change in creditworthiness or if liability positions exceed certain contractual limits, credit support may need to be provided in the form of letters of credit or cash collateral up to the amount of exposure under the contracts, or the contracts may need to be unwound and underlying liability positions paid. At March 31, 2018 and December 31, 2017, the aggregate fair value of all derivative instruments with credit risk-related contingent features in a net liability position was not materially different than amounts that would be required to be posted as credit support to counterparties by Alliant Energy, IPL or WPL if the most restrictive credit risk-related contingent features for derivative agreements in a net liability position were triggered. Balance Sheet Offsetting - The fair value amounts of derivative instruments subject to a master netting arrangement are not netted by counterparty on the balance sheets. However, if the fair value amounts of derivative instruments by counterparty were netted, amounts would not be materially different from gross amounts of derivative assets and derivative liabilities at March 31, 2018 and December 31, 2017. Fair value amounts recognized for the right to reclaim cash collateral (receivable) or the obligation to return cash collateral (payable) are not offset against fair value amounts recognized for derivative instruments executed with the same counterparty under the same master netting arrangement.
WPL [Member] |
Derivative Instruments [Line Items] |
Derivative Instruments | DERIVATIVE INSTRUMENTS Commodity Derivatives - Notional Amounts - As of March 31, 2018, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs 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 | 990 |  |  | 2018 |  | 3,370 |  |  | 2018 |  | 156,074 |  |  | 2018-2026 |  | 7,144 |  |  | 2018-2020 |  | 5,670 |  |  | 2018-2019
IPL | — |  |  | — |  | 2,252 |  |  | 2018 |  | 65,541 |  |  | 2018-2026 |  | 2,975 |  |  | 2018-2020 |  | — |  |  | —
WPL | 990 |  |  | 2018 |  | 1,118 |  |  | 2018 |  | 90,533 |  |  | 2018-2026 |  | 4,169 |  |  | 2018-2020 |  | 5,670 |  |  | 2018-2019
Financial Statement Presentation - Derivative instruments are recorded at fair value each reporting date on the balance sheets as assets or liabilities. 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
| March 31, 2018 |  | December 31, 2017 |  | March 31, 2018 |  | December 31, 2017 |  | March 31, 2018 |  | December 31, 2017
Current derivative assets |  | $10.8 |  |  |  | $21.1 |  |  |  | $7.0 |  |  |  | $15.8 |  |  |  | $3.8 |  |  |  | $5.3 |
Non-current derivative assets | 3.3 |  |  | 4.0 |  |  | 0.9 |  |  | 1.3 |  |  | 2.4 |  |  | 2.7 |
Current derivative liabilities | 15.9 |  |  | 18.7 |  |  | 4.8 |  |  | 5.0 |  |  | 11.1 |  |  | 13.7 |
Non-current derivative liabilities | 30.8 |  |  | 23.0 |  |  | 19.9 |  |  | 14.4 |  |  | 10.9 |  |  | 8.6 |
Credit Risk-related Contingent Features - Various agreements contain credit risk-related contingent features, including requirements to maintain certain credit ratings and/or limitations on liability positions under the agreements based on credit ratings. Certain of these agreements with credit risk-related contingency features are accounted for as derivative instruments. In the event of a material change in creditworthiness or if liability positions exceed certain contractual limits, credit support may need to be provided in the form of letters of credit or cash collateral up to the amount of exposure under the contracts, or the contracts may need to be unwound and underlying liability positions paid. At March 31, 2018 and December 31, 2017, the aggregate fair value of all derivative instruments with credit risk-related contingent features in a net liability position was not materially different than amounts that would be required to be posted as credit support to counterparties by Alliant Energy, IPL or WPL if the most restrictive credit risk-related contingent features for derivative agreements in a net liability position were triggered. Balance Sheet Offsetting - The fair value amounts of derivative instruments subject to a master netting arrangement are not netted by counterparty on the balance sheets. However, if the fair value amounts of derivative instruments by counterparty were netted, amounts would not be materially different from gross amounts of derivative assets and derivative liabilities at March 31, 2018 and December 31, 2017. Fair value amounts recognized for the right to reclaim cash collateral (receivable) or the obligation to return cash collateral (payable) are not offset against fair value amounts recognized for derivative instruments executed with the same counterparty under the same master netting arrangement.

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- Definition The entire disclosure for derivative instruments and hedging activities including, but not limited to, risk management strategies, non-hedging derivative instruments, assets, liabilities, revenue and expenses, and methodologies and assumptions used in determining the amounts. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -URI http://asc.fasb.org/topic&trid=2229140 + Details
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- 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
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