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Asset Retirement Obligations (Tables) | 12 Months Ended
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Dec. 31, 2020
Schedule of Asset Retirement Obligations [Line Items] |
Reconciliation Of Changes In Asset Retirement Obligations (AROs) | A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2020 |  | 2019 |  | 2020 |  | 2019 |  | 2020 |  | 2019
Balance, January 1 | $196 |  |  | $177 |  |  | $134 |  |  | $118 |  |  | $62 |  |  | $59 |
Revisions in estimated cash flows | 13 |  |  | (6) |  |  | 9 |  |  | (7) |  |  | 4 |  |  | 1 |
Liabilities settled | (13) |  |  | (8) |  |  | (9) |  |  | (8) |  |  | (4) |  |  | — |
Liabilities incurred (a) | 48 |  |  | 26 |  |  | 38 |  |  | 26 |  |  | 10 |  |  | — |
Accretion expense | 7 |  |  | 7 |  |  | 5 |  |  | 5 |  |  | 2 |  |  | 2 |
Balance, December 31 | $251 |  |  | $196 |  |  | $177 |  |  | $134 |  |  | $74 |  |  | $62 |
(a)In 2020, IPL placed in service the Whispering Willow North, Golden Plains and Richland wind sites, and WPL placed in service the Kossuth wind site. As a result, Alliant Energy, IPL and WPL recognized additional AROs in 2020, which resulted in corresponding increases in property, plant and equipment, net on the respective balance sheets.
IPL [Member] |
Schedule of Asset Retirement Obligations [Line Items] |
Reconciliation Of Changes In Asset Retirement Obligations (AROs) | A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2020 |  | 2019 |  | 2020 |  | 2019 |  | 2020 |  | 2019
Balance, January 1 | $196 |  |  | $177 |  |  | $134 |  |  | $118 |  |  | $62 |  |  | $59 |
Revisions in estimated cash flows | 13 |  |  | (6) |  |  | 9 |  |  | (7) |  |  | 4 |  |  | 1 |
Liabilities settled | (13) |  |  | (8) |  |  | (9) |  |  | (8) |  |  | (4) |  |  | — |
Liabilities incurred (a) | 48 |  |  | 26 |  |  | 38 |  |  | 26 |  |  | 10 |  |  | — |
Accretion expense | 7 |  |  | 7 |  |  | 5 |  |  | 5 |  |  | 2 |  |  | 2 |
Balance, December 31 | $251 |  |  | $196 |  |  | $177 |  |  | $134 |  |  | $74 |  |  | $62 |
(a)In 2020, IPL placed in service the Whispering Willow North, Golden Plains and Richland wind sites, and WPL placed in service the Kossuth wind site. As a result, Alliant Energy, IPL and WPL recognized additional AROs in 2020, which resulted in corresponding increases in property, plant and equipment, net on the respective balance sheets.
WPL [Member] |
Schedule of Asset Retirement Obligations [Line Items] |
Reconciliation Of Changes In Asset Retirement Obligations (AROs) | A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2020 |  | 2019 |  | 2020 |  | 2019 |  | 2020 |  | 2019
Balance, January 1 | $196 |  |  | $177 |  |  | $134 |  |  | $118 |  |  | $62 |  |  | $59 |
Revisions in estimated cash flows | 13 |  |  | (6) |  |  | 9 |  |  | (7) |  |  | 4 |  |  | 1 |
Liabilities settled | (13) |  |  | (8) |  |  | (9) |  |  | (8) |  |  | (4) |  |  | — |
Liabilities incurred (a) | 48 |  |  | 26 |  |  | 38 |  |  | 26 |  |  | 10 |  |  | — |
Accretion expense | 7 |  |  | 7 |  |  | 5 |  |  | 5 |  |  | 2 |  |  | 2 |
Balance, December 31 | $251 |  |  | $196 |  |  | $177 |  |  | $134 |  |  | $74 |  |  | $62 |
(a)In 2020, IPL placed in service the Whispering Willow North, Golden Plains and Richland wind sites, and WPL placed in service the Kossuth wind site. As a result, Alliant Energy, IPL and WPL recognized additional AROs in 2020, which resulted in corresponding increases in property, plant and equipment, net on the respective balance sheets.

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- Definition Tabular disclosure of the changes in carrying amount of a liability for asset retirement obligations, for changes such as new obligations, changes in estimates of existing obligations, spending on existing obligations, property dispositions, and foreign currency translation. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 30 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13201-110859 + Details
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