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Regulatory Matters (Tables) | 9 Months Ended
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Sep. 30, 2021
Regulatory Assets [Line Items] |
Regulatory Assets | Regulatory assets were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| September 30, 2021 |  | December 31, 2020 |  | September 30, 2021 |  | December 31, 2020 |  | September 30, 2021 |  | December 31, 2020
Tax-related | $931 |  | $890 |  | $881 |  | $843 |  | $50 |  | $47
Pension and OPEB costs | 549 |  | 580 |  | 276 |  | 291 |  | 273 |  | 289
Asset retirement obligations | 124 |  | 119 |  | 85 |  | 81 |  | 39 |  | 38
Assets retired early | 98 |  | 113 |  | 69 |  | 77 |  | 29 |  | 36
IPL’s DAEC PPA amendment | 96 |  | 110 |  | 96 |  | 110 |  | — |  | —
WPL’s Western Wisconsin gas distribution expansion investments | 53 |  | 55 |  | — |  | — |  | 53 |  | 55
Commodity cost recovery | 32 |  | 4 |  | 17 |  | 1 |  | 15 |  | 3
Derivatives | 4 |  | 26 |  | 4 |  | 13 |  | — |  | 13
Other | 131 |  | 113 |  | 79 |  | 67 |  | 52 |  | 46
| $2,018 |  | $2,010 |  | $1,507 |  | $1,483 |  | $511 |  | $527
Regulatory Liabilities | Regulatory liabilities were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| September 30, 2021 |  | December 31, 2020 |  | September 30, 2021 |  | December 31, 2020 |  | September 30, 2021 |  | December 31, 2020
Tax-related | $611 |  | $732 |  | $313 |  | $331 |  | $298 |  | $401
Cost of removal obligations | 383 |  | 367 |  | 252 |  | 238 |  | 131 |  | 129
Derivatives | 221 |  | 28 |  | 104 |  | 25 |  | 117 |  | 3
Electric transmission cost recovery | 53 |  | 68 |  | 29 |  | 39 |  | 24 |  | 29
WPL’s West Riverside liquidated damages | 40 |  | 38 |  | — |  | — |  | 40 |  | 38
Other | 53 |  | 73 |  | 22 |  | 43 |  | 31 |  | 30
| $1,361 |  | $1,306 |  | $720 |  | $676 |  | $641 |  | $630
IPL [Member] |
Regulatory Assets [Line Items] |
Regulatory Assets | Regulatory assets were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| September 30, 2021 |  | December 31, 2020 |  | September 30, 2021 |  | December 31, 2020 |  | September 30, 2021 |  | December 31, 2020
Tax-related | $931 |  | $890 |  | $881 |  | $843 |  | $50 |  | $47
Pension and OPEB costs | 549 |  | 580 |  | 276 |  | 291 |  | 273 |  | 289
Asset retirement obligations | 124 |  | 119 |  | 85 |  | 81 |  | 39 |  | 38
Assets retired early | 98 |  | 113 |  | 69 |  | 77 |  | 29 |  | 36
IPL’s DAEC PPA amendment | 96 |  | 110 |  | 96 |  | 110 |  | — |  | —
WPL’s Western Wisconsin gas distribution expansion investments | 53 |  | 55 |  | — |  | — |  | 53 |  | 55
Commodity cost recovery | 32 |  | 4 |  | 17 |  | 1 |  | 15 |  | 3
Derivatives | 4 |  | 26 |  | 4 |  | 13 |  | — |  | 13
Other | 131 |  | 113 |  | 79 |  | 67 |  | 52 |  | 46
| $2,018 |  | $2,010 |  | $1,507 |  | $1,483 |  | $511 |  | $527
Regulatory Liabilities | Regulatory liabilities were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| September 30, 2021 |  | December 31, 2020 |  | September 30, 2021 |  | December 31, 2020 |  | September 30, 2021 |  | December 31, 2020
Tax-related | $611 |  | $732 |  | $313 |  | $331 |  | $298 |  | $401
Cost of removal obligations | 383 |  | 367 |  | 252 |  | 238 |  | 131 |  | 129
Derivatives | 221 |  | 28 |  | 104 |  | 25 |  | 117 |  | 3
Electric transmission cost recovery | 53 |  | 68 |  | 29 |  | 39 |  | 24 |  | 29
WPL’s West Riverside liquidated damages | 40 |  | 38 |  | — |  | — |  | 40 |  | 38
Other | 53 |  | 73 |  | 22 |  | 43 |  | 31 |  | 30
| $1,361 |  | $1,306 |  | $720 |  | $676 |  | $641 |  | $630
WPL [Member] |
Regulatory Assets [Line Items] |
Regulatory Assets | Regulatory assets were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| September 30, 2021 |  | December 31, 2020 |  | September 30, 2021 |  | December 31, 2020 |  | September 30, 2021 |  | December 31, 2020
Tax-related | $931 |  | $890 |  | $881 |  | $843 |  | $50 |  | $47
Pension and OPEB costs | 549 |  | 580 |  | 276 |  | 291 |  | 273 |  | 289
Asset retirement obligations | 124 |  | 119 |  | 85 |  | 81 |  | 39 |  | 38
Assets retired early | 98 |  | 113 |  | 69 |  | 77 |  | 29 |  | 36
IPL’s DAEC PPA amendment | 96 |  | 110 |  | 96 |  | 110 |  | — |  | —
WPL’s Western Wisconsin gas distribution expansion investments | 53 |  | 55 |  | — |  | — |  | 53 |  | 55
Commodity cost recovery | 32 |  | 4 |  | 17 |  | 1 |  | 15 |  | 3
Derivatives | 4 |  | 26 |  | 4 |  | 13 |  | — |  | 13
Other | 131 |  | 113 |  | 79 |  | 67 |  | 52 |  | 46
| $2,018 |  | $2,010 |  | $1,507 |  | $1,483 |  | $511 |  | $527
Regulatory Liabilities | Regulatory liabilities were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| September 30, 2021 |  | December 31, 2020 |  | September 30, 2021 |  | December 31, 2020 |  | September 30, 2021 |  | December 31, 2020
Tax-related | $611 |  | $732 |  | $313 |  | $331 |  | $298 |  | $401
Cost of removal obligations | 383 |  | 367 |  | 252 |  | 238 |  | 131 |  | 129
Derivatives | 221 |  | 28 |  | 104 |  | 25 |  | 117 |  | 3
Electric transmission cost recovery | 53 |  | 68 |  | 29 |  | 39 |  | 24 |  | 29
WPL’s West Riverside liquidated damages | 40 |  | 38 |  | — |  | — |  | 40 |  | 38
Other | 53 |  | 73 |  | 22 |  | 43 |  | 31 |  | 30
| $1,361 |  | $1,306 |  | $720 |  | $676 |  | $641 |  | $630

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