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Asset Retirement Obligations | 12 Months Ended
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Dec. 31, 2018
Schedule of Asset Retirement Obligations [Line Items] |
Asset Retirement Obligations (AROs) | ASSET RETIREMENT OBLIGATIONS Recognized AROs relate to legal obligations for the removal, closure or dismantlement of several assets including, but not limited to, wind farms, ash ponds, active ash landfills, solar generation and above ground storage tanks. Recognized AROs also include legal obligations for the management and final disposition of asbestos and polychlorinated biphenyls. AROs are recorded in “Other current liabilities” and “Other liabilities” on the balance sheets. Refer to Note 2 for information regarding regulatory assets related to AROs. A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2018 |  | 2017 |  | 2018 |  | 2017 |  | 2018 |  | 2017
Balance, January 1 |  | $184.5 |  |  |  | $195.7 |  |  |  | $134.1 |  |  |  | $124.7 |  |  |  | $50.4 |  |  |  | $61.4 |
Revisions in estimated cash flows | (10.1 | ) |  | 4.3 |  |  | (10.1 | ) |  | 7.0 |  |  | — |  |  | (2.7 | )
Liabilities settled | (10.4 | ) |  | (23.5 | ) |  | (9.7 | ) |  | (13.1 | ) |  | (0.7 | ) |  | (10.4 | )
Liabilities incurred | 7.3 |  |  | 2.0 |  |  | — |  |  | 11.7 |  |  | 7.3 |  |  | — |
Accretion expense | 6.2 |  |  | 6.0 |  |  | 4.0 |  |  | 3.8 |  |  | 2.2 |  |  | 2.1 |
Balance, December 31 |  | $177.5 |  |  |  | $184.5 |  |  |  | $118.3 |  |  |  | $134.1 |  |  |  | $59.2 |  |  |  | $50.4 |
IPL [Member] |
Schedule of Asset Retirement Obligations [Line Items] |
Asset Retirement Obligations (AROs) | ASSET RETIREMENT OBLIGATIONS Recognized AROs relate to legal obligations for the removal, closure or dismantlement of several assets including, but not limited to, wind farms, ash ponds, active ash landfills, solar generation and above ground storage tanks. Recognized AROs also include legal obligations for the management and final disposition of asbestos and polychlorinated biphenyls. AROs are recorded in “Other current liabilities” and “Other liabilities” on the balance sheets. Refer to Note 2 for information regarding regulatory assets related to AROs. A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2018 |  | 2017 |  | 2018 |  | 2017 |  | 2018 |  | 2017
Balance, January 1 |  | $184.5 |  |  |  | $195.7 |  |  |  | $134.1 |  |  |  | $124.7 |  |  |  | $50.4 |  |  |  | $61.4 |
Revisions in estimated cash flows | (10.1 | ) |  | 4.3 |  |  | (10.1 | ) |  | 7.0 |  |  | — |  |  | (2.7 | )
Liabilities settled | (10.4 | ) |  | (23.5 | ) |  | (9.7 | ) |  | (13.1 | ) |  | (0.7 | ) |  | (10.4 | )
Liabilities incurred | 7.3 |  |  | 2.0 |  |  | — |  |  | 11.7 |  |  | 7.3 |  |  | — |
Accretion expense | 6.2 |  |  | 6.0 |  |  | 4.0 |  |  | 3.8 |  |  | 2.2 |  |  | 2.1 |
Balance, December 31 |  | $177.5 |  |  |  | $184.5 |  |  |  | $118.3 |  |  |  | $134.1 |  |  |  | $59.2 |  |  |  | $50.4 |
WPL [Member] |
Schedule of Asset Retirement Obligations [Line Items] |
Asset Retirement Obligations (AROs) | ASSET RETIREMENT OBLIGATIONS Recognized AROs relate to legal obligations for the removal, closure or dismantlement of several assets including, but not limited to, wind farms, ash ponds, active ash landfills, solar generation and above ground storage tanks. Recognized AROs also include legal obligations for the management and final disposition of asbestos and polychlorinated biphenyls. AROs are recorded in “Other current liabilities” and “Other liabilities” on the balance sheets. Refer to Note 2 for information regarding regulatory assets related to AROs. A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2018 |  | 2017 |  | 2018 |  | 2017 |  | 2018 |  | 2017
Balance, January 1 |  | $184.5 |  |  |  | $195.7 |  |  |  | $134.1 |  |  |  | $124.7 |  |  |  | $50.4 |  |  |  | $61.4 |
Revisions in estimated cash flows | (10.1 | ) |  | 4.3 |  |  | (10.1 | ) |  | 7.0 |  |  | — |  |  | (2.7 | )
Liabilities settled | (10.4 | ) |  | (23.5 | ) |  | (9.7 | ) |  | (13.1 | ) |  | (0.7 | ) |  | (10.4 | )
Liabilities incurred | 7.3 |  |  | 2.0 |  |  | — |  |  | 11.7 |  |  | 7.3 |  |  | — |
Accretion expense | 6.2 |  |  | 6.0 |  |  | 4.0 |  |  | 3.8 |  |  | 2.2 |  |  | 2.1 |
Balance, December 31 |  | $177.5 |  |  |  | $184.5 |  |  |  | $118.3 |  |  |  | $134.1 |  |  |  | $59.2 |  |  |  | $50.4 |

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- Definition [Line Items] for Schedule of Asset Retirement Obligations [Table] + References No definition available. + Details
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- Definition The entire disclosure for an asset retirement obligation and the associated long-lived asset. An asset retirement obligation is a legal obligation associated with the disposal or retirement from service of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -URI http://asc.fasb.org/subtopic&trid=2175671 + Details
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