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Derivative Instruments | 12 Months Ended
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Dec. 31, 2017
Derivative [Line Items] |
Derivative Instruments | DERIVATIVE INSTRUMENTS Commodity Derivatives - Purpose - Derivative instruments are used for risk management purposes to mitigate exposures to fluctuations in certain commodity prices, transmission congestion costs and rail transportation costs. Refer to Note 14 for detailed discussion of derivative instruments. Notional Amounts - As of December 31, 2017, 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 | 1,314 |  |  | 2018 |  | 8,970 |  |  | 2018 |  | 170,463 |  |  | 2018-2026 |  | 8,177 |  |  | 2018-2020 |  | 6,552 |  |  | 2018-2019
IPL | — |  |  | — |  | 5,886 |  |  | 2018 |  | 72,662 |  |  | 2018-2026 |  | 3,339 |  |  | 2018-2020 |  | — |  |  | —
WPL | 1,314 |  |  | 2018 |  | 3,084 |  |  | 2018 |  | 97,801 |  |  | 2018-2026 |  | 4,838 |  |  | 2018-2020 |  | 6,552 |  |  | 2018-2019
Financial Statement Presentation - Derivative instruments are recorded at fair value each reporting date on the balance sheet as assets or liabilities. 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
| 2017 |  | 2016 |  | 2017 |  | 2016 |  | 2017 |  | 2016
Current derivative assets |  | $21.1 |  |  |  | $29.4 |  |  |  | $15.8 |  |  |  | $19.1 |  |  |  | $5.3 |  |  |  | $10.3 |
Non-current derivative assets | 4.0 |  |  | 12.0 |  |  | 1.3 |  |  | 1.7 |  |  | 2.7 |  |  | 10.3 |
Current derivative liabilities | 18.7 |  |  | 13.3 |  |  | 5.0 |  |  | 2.7 |  |  | 13.7 |  |  | 10.6 |
Non-current derivative liabilities | 23.0 |  |  | 15.3 |  |  | 14.4 |  |  | 5.6 |  |  | 8.6 |  |  | 9.7 |
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 December 31, 2017 and 2016, 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 December 31, 2017 and 2016. 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 [Line Items] |
Derivative Instruments | DERIVATIVE INSTRUMENTS Commodity Derivatives - Purpose - Derivative instruments are used for risk management purposes to mitigate exposures to fluctuations in certain commodity prices, transmission congestion costs and rail transportation costs. Refer to Note 14 for detailed discussion of derivative instruments. Notional Amounts - As of December 31, 2017, 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 | 1,314 |  |  | 2018 |  | 8,970 |  |  | 2018 |  | 170,463 |  |  | 2018-2026 |  | 8,177 |  |  | 2018-2020 |  | 6,552 |  |  | 2018-2019
IPL | — |  |  | — |  | 5,886 |  |  | 2018 |  | 72,662 |  |  | 2018-2026 |  | 3,339 |  |  | 2018-2020 |  | — |  |  | —
WPL | 1,314 |  |  | 2018 |  | 3,084 |  |  | 2018 |  | 97,801 |  |  | 2018-2026 |  | 4,838 |  |  | 2018-2020 |  | 6,552 |  |  | 2018-2019
Financial Statement Presentation - Derivative instruments are recorded at fair value each reporting date on the balance sheet as assets or liabilities. 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
| 2017 |  | 2016 |  | 2017 |  | 2016 |  | 2017 |  | 2016
Current derivative assets |  | $21.1 |  |  |  | $29.4 |  |  |  | $15.8 |  |  |  | $19.1 |  |  |  | $5.3 |  |  |  | $10.3 |
Non-current derivative assets | 4.0 |  |  | 12.0 |  |  | 1.3 |  |  | 1.7 |  |  | 2.7 |  |  | 10.3 |
Current derivative liabilities | 18.7 |  |  | 13.3 |  |  | 5.0 |  |  | 2.7 |  |  | 13.7 |  |  | 10.6 |
Non-current derivative liabilities | 23.0 |  |  | 15.3 |  |  | 14.4 |  |  | 5.6 |  |  | 8.6 |  |  | 9.7 |
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 December 31, 2017 and 2016, 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 December 31, 2017 and 2016. 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 [Line Items] |
Derivative Instruments | DERIVATIVE INSTRUMENTS Commodity Derivatives - Purpose - Derivative instruments are used for risk management purposes to mitigate exposures to fluctuations in certain commodity prices, transmission congestion costs and rail transportation costs. Refer to Note 14 for detailed discussion of derivative instruments. Notional Amounts - As of December 31, 2017, 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 | 1,314 |  |  | 2018 |  | 8,970 |  |  | 2018 |  | 170,463 |  |  | 2018-2026 |  | 8,177 |  |  | 2018-2020 |  | 6,552 |  |  | 2018-2019
IPL | — |  |  | — |  | 5,886 |  |  | 2018 |  | 72,662 |  |  | 2018-2026 |  | 3,339 |  |  | 2018-2020 |  | — |  |  | —
WPL | 1,314 |  |  | 2018 |  | 3,084 |  |  | 2018 |  | 97,801 |  |  | 2018-2026 |  | 4,838 |  |  | 2018-2020 |  | 6,552 |  |  | 2018-2019
Financial Statement Presentation - Derivative instruments are recorded at fair value each reporting date on the balance sheet as assets or liabilities. 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
| 2017 |  | 2016 |  | 2017 |  | 2016 |  | 2017 |  | 2016
Current derivative assets |  | $21.1 |  |  |  | $29.4 |  |  |  | $15.8 |  |  |  | $19.1 |  |  |  | $5.3 |  |  |  | $10.3 |
Non-current derivative assets | 4.0 |  |  | 12.0 |  |  | 1.3 |  |  | 1.7 |  |  | 2.7 |  |  | 10.3 |
Current derivative liabilities | 18.7 |  |  | 13.3 |  |  | 5.0 |  |  | 2.7 |  |  | 13.7 |  |  | 10.6 |
Non-current derivative liabilities | 23.0 |  |  | 15.3 |  |  | 14.4 |  |  | 5.6 |  |  | 8.6 |  |  | 9.7 |
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 December 31, 2017 and 2016, 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 December 31, 2017 and 2016. 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 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6441202&loc=d3e80720-113993 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624171-113959 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=64837297&loc=d3e41620-113959 Reference 4: 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 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5579240-113959 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4D -URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624177-113959 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 30 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=35736893&loc=d3e80784-113994 Reference 8: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=64837297&loc=d3e41641-113959 Reference 9: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5579245-113959 Reference 10: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4H -URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624258-113959 Reference 11: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 30 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=35736893&loc=d3e80748-113994 Reference 12: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4K -URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5708775-113959 Reference 13: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4J -URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5708773-113959 Reference 14: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5618551-113959 Reference 15: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1B -URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5580258-113959 Reference 16: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4E -URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624181-113959 Reference 17: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 25 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6886632&loc=d3e76258-113986 Reference 18: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=64837297&loc=d3e41638-113959 Reference 19: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(n)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 + Details
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