XML 91 R33.htm IDEA: XBRL DOCUMENT
v3.19.3

Derivative Instruments (Tables) | 9 Months Ended
--- | ---
Sep. 30, 2019
Derivative Instruments [Line Items] |
Notional Amounts Of Derivative Instruments | As of September 30, 2019, 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):
| FTRs |  | Natural Gas |  | Coal |  | Diesel Fuel
| MWhs |  | Years |  | Dths |  | Years |  | Tons |  | Years |  | Gallons |  | Years
Alliant Energy | 18,141 |  |  | 2019-2020 |  | 184,007 |  |  | 2019-2026 |  | 7,620 |  |  | 2019-2021 |  | 5,796 |  |  | 2019-2021
IPL | 8,630 |  |  | 2019-2020 |  | 101,579 |  |  | 2019-2026 |  | 3,311 |  |  | 2019-2021 |  | — |  |  | —
WPL | 9,511 |  |  | 2019-2020 |  | 82,428 |  |  | 2019-2026 |  | 4,309 |  |  | 2019-2021 |  | 5,796 |  |  | 2019-2021
Fair Value Of Financial Instruments | Derivative instruments are recorded at fair value each reporting date on the balance sheets as assets or liabilities as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| September 30, 2019 |  | December 31, 2018 |  | September 30, 2019 |  | December 31, 2018 |  | September 30, 2019 |  | December 31, 2018
Current derivative assets |  | $18.6 |  |  |  | $24.6 |  |  |  | $12.8 |  |  |  | $16.1 |  |  |  | $5.8 |  |  |  | $8.5 |
Non-current derivative assets | 11.7 |  |  | 3.7 |  |  | 10.5 |  |  | 1.6 |  |  | 1.2 |  |  | 2.1 |
Current derivative liabilities | 13.4 |  |  | 5.6 |  |  | 5.6 |  |  | 3.1 |  |  | 7.8 |  |  | 2.5 |
Non-current derivative liabilities | 18.4 |  |  | 17.7 |  |  | 7.8 |  |  | 8.1 |  |  | 10.6 |  |  | 9.6 |
IPL [Member] |
Derivative Instruments [Line Items] |
Notional Amounts Of Derivative Instruments | As of September 30, 2019, 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):
| FTRs |  | Natural Gas |  | Coal |  | Diesel Fuel
| MWhs |  | Years |  | Dths |  | Years |  | Tons |  | Years |  | Gallons |  | Years
Alliant Energy | 18,141 |  |  | 2019-2020 |  | 184,007 |  |  | 2019-2026 |  | 7,620 |  |  | 2019-2021 |  | 5,796 |  |  | 2019-2021
IPL | 8,630 |  |  | 2019-2020 |  | 101,579 |  |  | 2019-2026 |  | 3,311 |  |  | 2019-2021 |  | — |  |  | —
WPL | 9,511 |  |  | 2019-2020 |  | 82,428 |  |  | 2019-2026 |  | 4,309 |  |  | 2019-2021 |  | 5,796 |  |  | 2019-2021
Fair Value Of Financial Instruments | Derivative instruments are recorded at fair value each reporting date on the balance sheets as assets or liabilities as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| September 30, 2019 |  | December 31, 2018 |  | September 30, 2019 |  | December 31, 2018 |  | September 30, 2019 |  | December 31, 2018
Current derivative assets |  | $18.6 |  |  |  | $24.6 |  |  |  | $12.8 |  |  |  | $16.1 |  |  |  | $5.8 |  |  |  | $8.5 |
Non-current derivative assets | 11.7 |  |  | 3.7 |  |  | 10.5 |  |  | 1.6 |  |  | 1.2 |  |  | 2.1 |
Current derivative liabilities | 13.4 |  |  | 5.6 |  |  | 5.6 |  |  | 3.1 |  |  | 7.8 |  |  | 2.5 |
Non-current derivative liabilities | 18.4 |  |  | 17.7 |  |  | 7.8 |  |  | 8.1 |  |  | 10.6 |  |  | 9.6 |
WPL [Member] |
Derivative Instruments [Line Items] |
Notional Amounts Of Derivative Instruments | As of September 30, 2019, 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):
| FTRs |  | Natural Gas |  | Coal |  | Diesel Fuel
| MWhs |  | Years |  | Dths |  | Years |  | Tons |  | Years |  | Gallons |  | Years
Alliant Energy | 18,141 |  |  | 2019-2020 |  | 184,007 |  |  | 2019-2026 |  | 7,620 |  |  | 2019-2021 |  | 5,796 |  |  | 2019-2021
IPL | 8,630 |  |  | 2019-2020 |  | 101,579 |  |  | 2019-2026 |  | 3,311 |  |  | 2019-2021 |  | — |  |  | —
WPL | 9,511 |  |  | 2019-2020 |  | 82,428 |  |  | 2019-2026 |  | 4,309 |  |  | 2019-2021 |  | 5,796 |  |  | 2019-2021
Fair Value Of Financial Instruments | Derivative instruments are recorded at fair value each reporting date on the balance sheets as assets or liabilities as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| September 30, 2019 |  | December 31, 2018 |  | September 30, 2019 |  | December 31, 2018 |  | September 30, 2019 |  | December 31, 2018
Current derivative assets |  | $18.6 |  |  |  | $24.6 |  |  |  | $12.8 |  |  |  | $16.1 |  |  |  | $5.8 |  |  |  | $8.5 |
Non-current derivative assets | 11.7 |  |  | 3.7 |  |  | 10.5 |  |  | 1.6 |  |  | 1.2 |  |  | 2.1 |
Current derivative liabilities | 13.4 |  |  | 5.6 |  |  | 5.6 |  |  | 3.1 |  |  | 7.8 |  |  | 2.5 |
Non-current derivative liabilities | 18.4 |  |  | 17.7 |  |  | 7.8 |  |  | 8.1 |  |  | 10.6 |  |  | 9.6 |

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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4B -URI http://asc.fasb.org/extlink&oid=109980867&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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=109980867&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: |