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Fair Value Measurements (Tables) | 6 Months Ended
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Jun. 30, 2020
Statement [Line Items] |
Fair Value Measurements | Carrying amounts and related estimated fair values of other financial instruments were as follows (in millions):
Alliant Energy | June 30, 2020 |  | December 31, 2019
|  |  | Fair Value |  |  |  | Fair Value
| Carrying |  | Level |  | Level |  | Level |  |  |  | Carrying |  | Level |  | Level |  | Level |  |
| Amount |  | 1 |  | 2 |  | 3 |  | Total |  | Amount |  | 1 |  | 2 |  | 3 |  | Total
Assets: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Money market fund investments |  | $198.3 |  |  |  | $198.3 |  |  |  | $— |  |  |  | $— |  |  |  | $198.3 |  |  |  | $5.4 |  |  |  | $5.4 |  |  |  | $— |  |  |  | $— |  |  |  | $5.4 |
Derivatives | 42.4 |  |  | — |  |  | 4.6 |  |  | 37.8 |  |  | 42.4 |  |  | 26.8 |  |  | — |  |  | 4.8 |  |  | 22.0 |  |  | 26.8 |
Deferred proceeds | 194.1 |  |  | — |  |  | — |  |  | 194.1 |  |  | 194.1 |  |  | 187.7 |  |  | — |  |  | — |  |  | 187.7 |  |  | 187.7 |
Liabilities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivatives | 46.2 |  |  | — |  |  | 44.8 |  |  | 1.4 |  |  | 46.2 |  |  | 37.6 |  |  | — |  |  | 36.8 |  |  | 0.8 |  |  | 37.6 |
Long-term debt (incl. current maturities) | 6,579.8 |  |  | — |  |  | 7,768.1 |  |  | 1.7 |  |  | 7,769.8 |  |  | 6,190.2 |  |  | — |  |  | 6,917.9 |  |  | 2.0 |  |  | 6,919.9 |
IPL | June 30, 2020 |  | December 31, 2019
|  |  | Fair Value |  |  |  | Fair Value
| Carrying |  | Level |  | Level |  | Level |  |  |  | Carrying |  | Level |  | Level |  | Level |  |
| Amount |  | 1 |  | 2 |  | 3 |  | Total |  | Amount |  | 1 |  | 2 |  | 3 |  | Total
Assets: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Money market fund investments |  | $198.3 |  |  |  | $198.3 |  |  |  | $— |  |  |  | $— |  |  |  | $198.3 |  |  |  | $5.4 |  |  |  | $5.4 |  |  |  | $— |  |  |  | $— |  |  |  | $5.4 |
Derivatives | 37.0 |  |  | — |  |  | 3.3 |  |  | 33.7 |  |  | 37.0 |  |  | 22.3 |  |  | — |  |  | 2.8 |  |  | 19.5 |  |  | 22.3 |
Deferred proceeds | 194.1 |  |  | — |  |  | — |  |  | 194.1 |  |  | 194.1 |  |  | 187.7 |  |  | — |  |  | — |  |  | 187.7 |  |  | 187.7 |
Liabilities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivatives | 20.3 |  |  | — |  |  | 19.0 |  |  | 1.3 |  |  | 20.3 |  |  | 17.4 |  |  | — |  |  | 16.6 |  |  | 0.8 |  |  | 17.4 |
Long-term debt (incl. current maturities) | 3,343.5 |  |  | — |  |  | 3,924.7 |  |  | — |  |  | 3,924.7 |  |  | 3,147.3 |  |  | — |  |  | 3,489.1 |  |  | — |  |  | 3,489.1 |
WPL | June 30, 2020 |  | December 31, 2019
|  |  | Fair Value |  |  |  | Fair Value
| Carrying |  | Level |  | Level |  | Level |  |  |  | Carrying |  | Level |  | Level |  | Level |  |
| Amount |  | 1 |  | 2 |  | 3 |  | Total |  | Amount |  | 1 |  | 2 |  | 3 |  | Total
Assets: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivatives |  | $5.4 |  |  |  | $— |  |  |  | $1.3 |  |  |  | $4.1 |  |  |  | $5.4 |  |  |  | $4.5 |  |  |  | $— |  |  |  | $2.0 |  |  |  | $2.5 |  |  |  | $4.5 |
Liabilities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivatives | 25.9 |  |  | — |  |  | 25.8 |  |  | 0.1 |  |  | 25.9 |  |  | 20.2 |  |  | — |  |  | 20.2 |  |  | — |  |  | 20.2 |
Long-term debt (incl. current maturities) | 2,129.4 |  |  | — |  |  | 2,657.2 |  |  | — |  |  | 2,657.2 |  |  | 1,932.7 |  |  | — |  |  | 2,268.2 |  |  | — |  |  | 2,268.2 |
Fair Value Measurements Using Significant Unobservable Inputs | Information for Alliant Energy’s and IPL’s fair value measurements using significant unobservable inputs (Level 3 inputs) was as follows (in millions). Such amounts for WPL were not material.
Alliant Energy | Commodity Contract Derivative |  |
| Assets and (Liabilities), net |  | Deferred Proceeds
Three Months Ended June 30 | 2020 |  | 2019 |  | 2020 |  | 2019
Beginning balance, April 1 |  | $14.2 |  |  |  | $0.4 |  |  |  | $188.0 |  |  |  | $178.3 |
Total net gains (losses) included in changes in net assets (realized/unrealized) | 12.0 |  |  | (0.1 | ) |  | — |  |  | — |
Transfers out of Level 3 | — |  |  | 3.9 |  |  | — |  |  | — |
Purchases | 14.0 |  |  | 13.8 |  |  | — |  |  | — |
Sales | (0.1 | ) |  | — |  |  | — |  |  | — |
Settlements (a) | (3.7 | ) |  | (4.8 | ) |  | 6.1 |  |  | 36.3 |
Ending balance, June 30 |  | $36.4 |  |  |  | $13.2 |  |  |  | $194.1 |  |  |  | $214.6 |
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at June 30 |  | $11.9 |  |  |  | $— |  |  |  | $— |  |  |  | $— |
Alliant Energy | Commodity Contract Derivative |  |
| Assets and (Liabilities), net |  | Deferred Proceeds
Six Months Ended June 30 | 2020 |  | 2019 |  | 2020 |  | 2019
Beginning balance, January 1 |  | $21.2 |  |  |  | $12.2 |  |  |  | $187.7 |  |  |  | $119.4 |
Total net gains (losses) included in changes in net assets (realized/unrealized) | 9.0 |  |  | (5.7 | ) |  | — |  |  | — |
Transfers out of Level 3 | — |  |  | 3.9 |  |  | — |  |  | — |
Purchases | 14.0 |  |  | 13.8 |  |  | — |  |  | — |
Sales | (0.2 | ) |  | (0.2 | ) |  | — |  |  | — |
Settlements (a) | (7.6 | ) |  | (10.8 | ) |  | 6.4 |  |  | 95.2 |
Ending balance, June 30 |  | $36.4 |  |  |  | $13.2 |  |  |  | $194.1 |  |  |  | $214.6 |
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30 |  | $9.0 |  |  |  | ($2.6 | ) |  |  | $— |  |  |  | $— |
IPL | Commodity Contract Derivative |  |
| Assets and (Liabilities), net |  | Deferred Proceeds
Three Months Ended June 30 | 2020 |  | 2019 |  | 2020 |  | 2019
Beginning balance, April 1 |  | $13.5 |  |  |  | $0.6 |  |  |  | $188.0 |  |  |  | $178.3 |
Total net gains included in changes in net assets (realized/unrealized) | 11.0 |  |  | 0.4 |  |  | — |  |  | — |
Transfers out of Level 3 | — |  |  | 2.5 |  |  | — |  |  | — |
Purchases | 10.7 |  |  | 9.5 |  |  | — |  |  | — |
Sales | (0.1 | ) |  | — |  |  | — |  |  | — |
Settlements (a) | (2.7 | ) |  | (3.7 | ) |  | 6.1 |  |  | 36.3 |
Ending balance, June 30 |  | $32.4 |  |  |  | $9.3 |  |  |  | $194.1 |  |  |  | $214.6 |
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at June 30 |  | $11.0 |  |  |  | $0.5 |  |  |  | $— |  |  |  | $— |
IPL | Commodity Contract Derivative |  |
| Assets and (Liabilities), net |  | Deferred Proceeds
Six Months Ended June 30 | 2020 |  | 2019 |  | 2020 |  | 2019
Beginning balance, January 1 |  | $18.7 |  |  |  | $9.0 |  |  |  | $187.7 |  |  |  | $119.4 |
Total net gains (losses) included in changes in net assets (realized/unrealized) | 8.8 |  |  | (2.8 | ) |  | — |  |  | — |
Transfers out of Level 3 | — |  |  | 2.5 |  |  | — |  |  | — |
Purchases | 10.7 |  |  | 9.5 |  |  | — |  |  | — |
Sales | (0.2 | ) |  | (0.1 | ) |  | — |  |  | — |
Settlements (a) | (5.6 | ) |  | (8.8 | ) |  | 6.4 |  |  | 95.2 |
Ending balance, June 30 |  | $32.4 |  |  |  | $9.3 |  |  |  | $194.1 |  |  |  | $214.6 |
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30 |  | $8.8 |  |  |  | ($0.9 | ) |  |  | $— |  |  |  | $— |
(a) | Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for doubtful accounts associated with the receivables sold and cash amounts received from the receivables sold.
Fair Value Of Net Derivative Assets | The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| Excluding FTRs |  | FTRs |  | Excluding FTRs |  | FTRs |  | Excluding FTRs |  | FTRs
June 30, 2020 |  | $19.3 |  |  |  | $17.1 |  |  |  | $18.6 |  |  |  | $13.8 |  |  |  | $0.7 |  |  |  | $3.3 |
December 31, 2019 | 14.6 |  |  | 6.6 |  |  | 13.6 |  |  | 5.1 |  |  | 1.0 |  |  | 1.5 |
IPL [Member] |
Statement [Line Items] |
Fair Value Measurements | Carrying amounts and related estimated fair values of other financial instruments were as follows (in millions):
Alliant Energy | June 30, 2020 |  | December 31, 2019
|  |  | Fair Value |  |  |  | Fair Value
| Carrying |  | Level |  | Level |  | Level |  |  |  | Carrying |  | Level |  | Level |  | Level |  |
| Amount |  | 1 |  | 2 |  | 3 |  | Total |  | Amount |  | 1 |  | 2 |  | 3 |  | Total
Assets: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Money market fund investments |  | $198.3 |  |  |  | $198.3 |  |  |  | $— |  |  |  | $— |  |  |  | $198.3 |  |  |  | $5.4 |  |  |  | $5.4 |  |  |  | $— |  |  |  | $— |  |  |  | $5.4 |
Derivatives | 42.4 |  |  | — |  |  | 4.6 |  |  | 37.8 |  |  | 42.4 |  |  | 26.8 |  |  | — |  |  | 4.8 |  |  | 22.0 |  |  | 26.8 |
Deferred proceeds | 194.1 |  |  | — |  |  | — |  |  | 194.1 |  |  | 194.1 |  |  | 187.7 |  |  | — |  |  | — |  |  | 187.7 |  |  | 187.7 |
Liabilities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivatives | 46.2 |  |  | — |  |  | 44.8 |  |  | 1.4 |  |  | 46.2 |  |  | 37.6 |  |  | — |  |  | 36.8 |  |  | 0.8 |  |  | 37.6 |
Long-term debt (incl. current maturities) | 6,579.8 |  |  | — |  |  | 7,768.1 |  |  | 1.7 |  |  | 7,769.8 |  |  | 6,190.2 |  |  | — |  |  | 6,917.9 |  |  | 2.0 |  |  | 6,919.9 |
IPL | June 30, 2020 |  | December 31, 2019
|  |  | Fair Value |  |  |  | Fair Value
| Carrying |  | Level |  | Level |  | Level |  |  |  | Carrying |  | Level |  | Level |  | Level |  |
| Amount |  | 1 |  | 2 |  | 3 |  | Total |  | Amount |  | 1 |  | 2 |  | 3 |  | Total
Assets: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Money market fund investments |  | $198.3 |  |  |  | $198.3 |  |  |  | $— |  |  |  | $— |  |  |  | $198.3 |  |  |  | $5.4 |  |  |  | $5.4 |  |  |  | $— |  |  |  | $— |  |  |  | $5.4 |
Derivatives | 37.0 |  |  | — |  |  | 3.3 |  |  | 33.7 |  |  | 37.0 |  |  | 22.3 |  |  | — |  |  | 2.8 |  |  | 19.5 |  |  | 22.3 |
Deferred proceeds | 194.1 |  |  | — |  |  | — |  |  | 194.1 |  |  | 194.1 |  |  | 187.7 |  |  | — |  |  | — |  |  | 187.7 |  |  | 187.7 |
Liabilities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivatives | 20.3 |  |  | — |  |  | 19.0 |  |  | 1.3 |  |  | 20.3 |  |  | 17.4 |  |  | — |  |  | 16.6 |  |  | 0.8 |  |  | 17.4 |
Long-term debt (incl. current maturities) | 3,343.5 |  |  | — |  |  | 3,924.7 |  |  | — |  |  | 3,924.7 |  |  | 3,147.3 |  |  | — |  |  | 3,489.1 |  |  | — |  |  | 3,489.1 |
WPL | June 30, 2020 |  | December 31, 2019
|  |  | Fair Value |  |  |  | Fair Value
| Carrying |  | Level |  | Level |  | Level |  |  |  | Carrying |  | Level |  | Level |  | Level |  |
| Amount |  | 1 |  | 2 |  | 3 |  | Total |  | Amount |  | 1 |  | 2 |  | 3 |  | Total
Assets: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivatives |  | $5.4 |  |  |  | $— |  |  |  | $1.3 |  |  |  | $4.1 |  |  |  | $5.4 |  |  |  | $4.5 |  |  |  | $— |  |  |  | $2.0 |  |  |  | $2.5 |  |  |  | $4.5 |
Liabilities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivatives | 25.9 |  |  | — |  |  | 25.8 |  |  | 0.1 |  |  | 25.9 |  |  | 20.2 |  |  | — |  |  | 20.2 |  |  | — |  |  | 20.2 |
Long-term debt (incl. current maturities) | 2,129.4 |  |  | — |  |  | 2,657.2 |  |  | — |  |  | 2,657.2 |  |  | 1,932.7 |  |  | — |  |  | 2,268.2 |  |  | — |  |  | 2,268.2 |
Fair Value Measurements Using Significant Unobservable Inputs | Information for Alliant Energy’s and IPL’s fair value measurements using significant unobservable inputs (Level 3 inputs) was as follows (in millions). Such amounts for WPL were not material.
Alliant Energy | Commodity Contract Derivative |  |
| Assets and (Liabilities), net |  | Deferred Proceeds
Three Months Ended June 30 | 2020 |  | 2019 |  | 2020 |  | 2019
Beginning balance, April 1 |  | $14.2 |  |  |  | $0.4 |  |  |  | $188.0 |  |  |  | $178.3 |
Total net gains (losses) included in changes in net assets (realized/unrealized) | 12.0 |  |  | (0.1 | ) |  | — |  |  | — |
Transfers out of Level 3 | — |  |  | 3.9 |  |  | — |  |  | — |
Purchases | 14.0 |  |  | 13.8 |  |  | — |  |  | — |
Sales | (0.1 | ) |  | — |  |  | — |  |  | — |
Settlements (a) | (3.7 | ) |  | (4.8 | ) |  | 6.1 |  |  | 36.3 |
Ending balance, June 30 |  | $36.4 |  |  |  | $13.2 |  |  |  | $194.1 |  |  |  | $214.6 |
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at June 30 |  | $11.9 |  |  |  | $— |  |  |  | $— |  |  |  | $— |
Alliant Energy | Commodity Contract Derivative |  |
| Assets and (Liabilities), net |  | Deferred Proceeds
Six Months Ended June 30 | 2020 |  | 2019 |  | 2020 |  | 2019
Beginning balance, January 1 |  | $21.2 |  |  |  | $12.2 |  |  |  | $187.7 |  |  |  | $119.4 |
Total net gains (losses) included in changes in net assets (realized/unrealized) | 9.0 |  |  | (5.7 | ) |  | — |  |  | — |
Transfers out of Level 3 | — |  |  | 3.9 |  |  | — |  |  | — |
Purchases | 14.0 |  |  | 13.8 |  |  | — |  |  | — |
Sales | (0.2 | ) |  | (0.2 | ) |  | — |  |  | — |
Settlements (a) | (7.6 | ) |  | (10.8 | ) |  | 6.4 |  |  | 95.2 |
Ending balance, June 30 |  | $36.4 |  |  |  | $13.2 |  |  |  | $194.1 |  |  |  | $214.6 |
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30 |  | $9.0 |  |  |  | ($2.6 | ) |  |  | $— |  |  |  | $— |
IPL | Commodity Contract Derivative |  |
| Assets and (Liabilities), net |  | Deferred Proceeds
Three Months Ended June 30 | 2020 |  | 2019 |  | 2020 |  | 2019
Beginning balance, April 1 |  | $13.5 |  |  |  | $0.6 |  |  |  | $188.0 |  |  |  | $178.3 |
Total net gains included in changes in net assets (realized/unrealized) | 11.0 |  |  | 0.4 |  |  | — |  |  | — |
Transfers out of Level 3 | — |  |  | 2.5 |  |  | — |  |  | — |
Purchases | 10.7 |  |  | 9.5 |  |  | — |  |  | — |
Sales | (0.1 | ) |  | — |  |  | — |  |  | — |
Settlements (a) | (2.7 | ) |  | (3.7 | ) |  | 6.1 |  |  | 36.3 |
Ending balance, June 30 |  | $32.4 |  |  |  | $9.3 |  |  |  | $194.1 |  |  |  | $214.6 |
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at June 30 |  | $11.0 |  |  |  | $0.5 |  |  |  | $— |  |  |  | $— |
IPL | Commodity Contract Derivative |  |
| Assets and (Liabilities), net |  | Deferred Proceeds
Six Months Ended June 30 | 2020 |  | 2019 |  | 2020 |  | 2019
Beginning balance, January 1 |  | $18.7 |  |  |  | $9.0 |  |  |  | $187.7 |  |  |  | $119.4 |
Total net gains (losses) included in changes in net assets (realized/unrealized) | 8.8 |  |  | (2.8 | ) |  | — |  |  | — |
Transfers out of Level 3 | — |  |  | 2.5 |  |  | — |  |  | — |
Purchases | 10.7 |  |  | 9.5 |  |  | — |  |  | — |
Sales | (0.2 | ) |  | (0.1 | ) |  | — |  |  | — |
Settlements (a) | (5.6 | ) |  | (8.8 | ) |  | 6.4 |  |  | 95.2 |
Ending balance, June 30 |  | $32.4 |  |  |  | $9.3 |  |  |  | $194.1 |  |  |  | $214.6 |
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30 |  | $8.8 |  |  |  | ($0.9 | ) |  |  | $— |  |  |  | $— |
(a) | Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for doubtful accounts associated with the receivables sold and cash amounts received from the receivables sold.
Fair Value Of Net Derivative Assets | The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| Excluding FTRs |  | FTRs |  | Excluding FTRs |  | FTRs |  | Excluding FTRs |  | FTRs
June 30, 2020 |  | $19.3 |  |  |  | $17.1 |  |  |  | $18.6 |  |  |  | $13.8 |  |  |  | $0.7 |  |  |  | $3.3 |
December 31, 2019 | 14.6 |  |  | 6.6 |  |  | 13.6 |  |  | 5.1 |  |  | 1.0 |  |  | 1.5 |
WPL [Member] |
Statement [Line Items] |
Fair Value Measurements | Carrying amounts and related estimated fair values of other financial instruments were as follows (in millions):
Alliant Energy | June 30, 2020 |  | December 31, 2019
|  |  | Fair Value |  |  |  | Fair Value
| Carrying |  | Level |  | Level |  | Level |  |  |  | Carrying |  | Level |  | Level |  | Level |  |
| Amount |  | 1 |  | 2 |  | 3 |  | Total |  | Amount |  | 1 |  | 2 |  | 3 |  | Total
Assets: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Money market fund investments |  | $198.3 |  |  |  | $198.3 |  |  |  | $— |  |  |  | $— |  |  |  | $198.3 |  |  |  | $5.4 |  |  |  | $5.4 |  |  |  | $— |  |  |  | $— |  |  |  | $5.4 |
Derivatives | 42.4 |  |  | — |  |  | 4.6 |  |  | 37.8 |  |  | 42.4 |  |  | 26.8 |  |  | — |  |  | 4.8 |  |  | 22.0 |  |  | 26.8 |
Deferred proceeds | 194.1 |  |  | — |  |  | — |  |  | 194.1 |  |  | 194.1 |  |  | 187.7 |  |  | — |  |  | — |  |  | 187.7 |  |  | 187.7 |
Liabilities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivatives | 46.2 |  |  | — |  |  | 44.8 |  |  | 1.4 |  |  | 46.2 |  |  | 37.6 |  |  | — |  |  | 36.8 |  |  | 0.8 |  |  | 37.6 |
Long-term debt (incl. current maturities) | 6,579.8 |  |  | — |  |  | 7,768.1 |  |  | 1.7 |  |  | 7,769.8 |  |  | 6,190.2 |  |  | — |  |  | 6,917.9 |  |  | 2.0 |  |  | 6,919.9 |
IPL | June 30, 2020 |  | December 31, 2019
|  |  | Fair Value |  |  |  | Fair Value
| Carrying |  | Level |  | Level |  | Level |  |  |  | Carrying |  | Level |  | Level |  | Level |  |
| Amount |  | 1 |  | 2 |  | 3 |  | Total |  | Amount |  | 1 |  | 2 |  | 3 |  | Total
Assets: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Money market fund investments |  | $198.3 |  |  |  | $198.3 |  |  |  | $— |  |  |  | $— |  |  |  | $198.3 |  |  |  | $5.4 |  |  |  | $5.4 |  |  |  | $— |  |  |  | $— |  |  |  | $5.4 |
Derivatives | 37.0 |  |  | — |  |  | 3.3 |  |  | 33.7 |  |  | 37.0 |  |  | 22.3 |  |  | — |  |  | 2.8 |  |  | 19.5 |  |  | 22.3 |
Deferred proceeds | 194.1 |  |  | — |  |  | — |  |  | 194.1 |  |  | 194.1 |  |  | 187.7 |  |  | — |  |  | — |  |  | 187.7 |  |  | 187.7 |
Liabilities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivatives | 20.3 |  |  | — |  |  | 19.0 |  |  | 1.3 |  |  | 20.3 |  |  | 17.4 |  |  | — |  |  | 16.6 |  |  | 0.8 |  |  | 17.4 |
Long-term debt (incl. current maturities) | 3,343.5 |  |  | — |  |  | 3,924.7 |  |  | — |  |  | 3,924.7 |  |  | 3,147.3 |  |  | — |  |  | 3,489.1 |  |  | — |  |  | 3,489.1 |
WPL | June 30, 2020 |  | December 31, 2019
|  |  | Fair Value |  |  |  | Fair Value
| Carrying |  | Level |  | Level |  | Level |  |  |  | Carrying |  | Level |  | Level |  | Level |  |
| Amount |  | 1 |  | 2 |  | 3 |  | Total |  | Amount |  | 1 |  | 2 |  | 3 |  | Total
Assets: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivatives |  | $5.4 |  |  |  | $— |  |  |  | $1.3 |  |  |  | $4.1 |  |  |  | $5.4 |  |  |  | $4.5 |  |  |  | $— |  |  |  | $2.0 |  |  |  | $2.5 |  |  |  | $4.5 |
Liabilities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivatives | 25.9 |  |  | — |  |  | 25.8 |  |  | 0.1 |  |  | 25.9 |  |  | 20.2 |  |  | — |  |  | 20.2 |  |  | — |  |  | 20.2 |
Long-term debt (incl. current maturities) | 2,129.4 |  |  | — |  |  | 2,657.2 |  |  | — |  |  | 2,657.2 |  |  | 1,932.7 |  |  | — |  |  | 2,268.2 |  |  | — |  |  | 2,268.2 |
Fair Value Of Net Derivative Assets | The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| Excluding FTRs |  | FTRs |  | Excluding FTRs |  | FTRs |  | Excluding FTRs |  | FTRs
June 30, 2020 |  | $19.3 |  |  |  | $17.1 |  |  |  | $18.6 |  |  |  | $13.8 |  |  |  | $0.7 |  |  |  | $3.3 |
December 31, 2019 | 14.6 |  |  | 6.6 |  |  | 13.6 |  |  | 5.1 |  |  | 1.0 |  |  | 1.5 |

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