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Regulatory Matters (Tables) | 6 Months Ended
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Jun. 30, 2021
Regulatory Assets [Line Items] |
Regulatory Assets | Regulatory assets were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| June 30, 2021 |  | December 31, 2020 |  | June 30, 2021 |  | December 31, 2020 |  | June 30, 2021 |  | December 31, 2020
Tax-related | $914 |  | $890 |  | $865 |  | $843 |  | $49 |  | $47
Pension and OPEB costs | 559 |  | 580 |  | 281 |  | 291 |  | 278 |  | 289
Asset retirement obligations | 123 |  | 119 |  | 85 |  | 81 |  | 38 |  | 38
Assets retired early | 103 |  | 113 |  | 72 |  | 77 |  | 31 |  | 36
IPL’s DAEC PPA amendment | 102 |  | 110 |  | 102 |  | 110 |  | — |  | —
WPL’s Western Wisconsin gas distribution expansion investments | 54 |  | 55 |  | — |  | — |  | 54 |  | 55
Derivatives | 3 |  | 26 |  | 2 |  | 13 |  | 1 |  | 13
Other | 137 |  | 117 |  | 81 |  | 68 |  | 56 |  | 49
| $1,995 |  | $2,010 |  | $1,488 |  | $1,483 |  | $507 |  | $527
Regulatory Liabilities | Regulatory liabilities were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| June 30, 2021 |  | December 31, 2020 |  | June 30, 2021 |  | December 31, 2020 |  | June 30, 2021 |  | December 31, 2020
Tax-related | $661 |  | $732 |  | $322 |  | $331 |  | $339 |  | $401
Cost of removal obligations | 373 |  | 367 |  | 245 |  | 238 |  | 128 |  | 129
Derivatives | 81 |  | 28 |  | 40 |  | 25 |  | 41 |  | 3
Electric transmission cost recovery | 48 |  | 68 |  | 23 |  | 39 |  | 25 |  | 29
WPL’s West Riverside liquidated damages | 40 |  | 38 |  | — |  | — |  | 40 |  | 38
Other | 51 |  | 73 |  | 17 |  | 43 |  | 34 |  | 30
| $1,254 |  | $1,306 |  | $647 |  | $676 |  | $607 |  | $630
IPL [Member] |
Regulatory Assets [Line Items] |
Regulatory Assets | Regulatory assets were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| June 30, 2021 |  | December 31, 2020 |  | June 30, 2021 |  | December 31, 2020 |  | June 30, 2021 |  | December 31, 2020
Tax-related | $914 |  | $890 |  | $865 |  | $843 |  | $49 |  | $47
Pension and OPEB costs | 559 |  | 580 |  | 281 |  | 291 |  | 278 |  | 289
Asset retirement obligations | 123 |  | 119 |  | 85 |  | 81 |  | 38 |  | 38
Assets retired early | 103 |  | 113 |  | 72 |  | 77 |  | 31 |  | 36
IPL’s DAEC PPA amendment | 102 |  | 110 |  | 102 |  | 110 |  | — |  | —
WPL’s Western Wisconsin gas distribution expansion investments | 54 |  | 55 |  | — |  | — |  | 54 |  | 55
Derivatives | 3 |  | 26 |  | 2 |  | 13 |  | 1 |  | 13
Other | 137 |  | 117 |  | 81 |  | 68 |  | 56 |  | 49
| $1,995 |  | $2,010 |  | $1,488 |  | $1,483 |  | $507 |  | $527
Regulatory Liabilities | Regulatory liabilities were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| June 30, 2021 |  | December 31, 2020 |  | June 30, 2021 |  | December 31, 2020 |  | June 30, 2021 |  | December 31, 2020
Tax-related | $661 |  | $732 |  | $322 |  | $331 |  | $339 |  | $401
Cost of removal obligations | 373 |  | 367 |  | 245 |  | 238 |  | 128 |  | 129
Derivatives | 81 |  | 28 |  | 40 |  | 25 |  | 41 |  | 3
Electric transmission cost recovery | 48 |  | 68 |  | 23 |  | 39 |  | 25 |  | 29
WPL’s West Riverside liquidated damages | 40 |  | 38 |  | — |  | — |  | 40 |  | 38
Other | 51 |  | 73 |  | 17 |  | 43 |  | 34 |  | 30
| $1,254 |  | $1,306 |  | $647 |  | $676 |  | $607 |  | $630
WPL [Member] |
Regulatory Assets [Line Items] |
Regulatory Assets | Regulatory assets were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| June 30, 2021 |  | December 31, 2020 |  | June 30, 2021 |  | December 31, 2020 |  | June 30, 2021 |  | December 31, 2020
Tax-related | $914 |  | $890 |  | $865 |  | $843 |  | $49 |  | $47
Pension and OPEB costs | 559 |  | 580 |  | 281 |  | 291 |  | 278 |  | 289
Asset retirement obligations | 123 |  | 119 |  | 85 |  | 81 |  | 38 |  | 38
Assets retired early | 103 |  | 113 |  | 72 |  | 77 |  | 31 |  | 36
IPL’s DAEC PPA amendment | 102 |  | 110 |  | 102 |  | 110 |  | — |  | —
WPL’s Western Wisconsin gas distribution expansion investments | 54 |  | 55 |  | — |  | — |  | 54 |  | 55
Derivatives | 3 |  | 26 |  | 2 |  | 13 |  | 1 |  | 13
Other | 137 |  | 117 |  | 81 |  | 68 |  | 56 |  | 49
| $1,995 |  | $2,010 |  | $1,488 |  | $1,483 |  | $507 |  | $527
Regulatory Liabilities | Regulatory liabilities were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| June 30, 2021 |  | December 31, 2020 |  | June 30, 2021 |  | December 31, 2020 |  | June 30, 2021 |  | December 31, 2020
Tax-related | $661 |  | $732 |  | $322 |  | $331 |  | $339 |  | $401
Cost of removal obligations | 373 |  | 367 |  | 245 |  | 238 |  | 128 |  | 129
Derivatives | 81 |  | 28 |  | 40 |  | 25 |  | 41 |  | 3
Electric transmission cost recovery | 48 |  | 68 |  | 23 |  | 39 |  | 25 |  | 29
WPL’s West Riverside liquidated damages | 40 |  | 38 |  | — |  | — |  | 40 |  | 38
Other | 51 |  | 73 |  | 17 |  | 43 |  | 34 |  | 30
| $1,254 |  | $1,306 |  | $647 |  | $676 |  | $607 |  | $630

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