XML 77 R21.htm IDEA: XBRL DOCUMENT
v3.19.3.a.u2

Asset Retirement Obligations | 12 Months Ended
--- | ---
Dec. 31, 2019
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, above ground storage tanks and solar generation. 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
| 2019 |  | 2018 |  | 2019 |  | 2018 |  | 2019 |  | 2018
Balance, January 1 |  | $177.5 |  |  |  | $184.5 |  |  |  | $118.3 |  |  |  | $134.1 |  |  |  | $59.2 |  |  |  | $50.4 |
Revisions in estimated cash flows | (5.5 | ) |  | (10.1 | ) |  | (6.7 | ) |  | (10.1 | ) |  | 1.2 |  |  | — |
Liabilities settled | (8.8 | ) |  | (10.4 | ) |  | (8.4 | ) |  | (9.7 | ) |  | (0.4 | ) |  | (0.7 | )
Liabilities incurred (a) | 26.2 |  |  | 7.3 |  |  | 26.2 |  |  | — |  |  | — |  |  | 7.3 |
Accretion expense | 6.9 |  |  | 6.2 |  |  | 4.5 |  |  | 4.0 |  |  | 2.4 |  |  | 2.2 |
Balance, December 31 |  | $196.3 |  |  |  | $177.5 |  |  |  | $133.9 |  |  |  | $118.3 |  |  |  | $62.4 |  |  |  | $59.2 |
(a) In 2019, Alliant Energy and IPL recognized additional AROs related to IPL’s newly constructed Upland Prairie and English Farms wind sites. The increases in AROs resulted in corresponding increases in property, plant and equipment, net on the respective balance sheets.
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, above ground storage tanks and solar generation. 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
| 2019 |  | 2018 |  | 2019 |  | 2018 |  | 2019 |  | 2018
Balance, January 1 |  | $177.5 |  |  |  | $184.5 |  |  |  | $118.3 |  |  |  | $134.1 |  |  |  | $59.2 |  |  |  | $50.4 |
Revisions in estimated cash flows | (5.5 | ) |  | (10.1 | ) |  | (6.7 | ) |  | (10.1 | ) |  | 1.2 |  |  | — |
Liabilities settled | (8.8 | ) |  | (10.4 | ) |  | (8.4 | ) |  | (9.7 | ) |  | (0.4 | ) |  | (0.7 | )
Liabilities incurred (a) | 26.2 |  |  | 7.3 |  |  | 26.2 |  |  | — |  |  | — |  |  | 7.3 |
Accretion expense | 6.9 |  |  | 6.2 |  |  | 4.5 |  |  | 4.0 |  |  | 2.4 |  |  | 2.2 |
Balance, December 31 |  | $196.3 |  |  |  | $177.5 |  |  |  | $133.9 |  |  |  | $118.3 |  |  |  | $62.4 |  |  |  | $59.2 |
(a) In 2019, Alliant Energy and IPL recognized additional AROs related to IPL’s newly constructed Upland Prairie and English Farms wind sites. The increases in AROs resulted in corresponding increases in property, plant and equipment, net on the respective balance sheets.
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, above ground storage tanks and solar generation. 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
| 2019 |  | 2018 |  | 2019 |  | 2018 |  | 2019 |  | 2018
Balance, January 1 |  | $177.5 |  |  |  | $184.5 |  |  |  | $118.3 |  |  |  | $134.1 |  |  |  | $59.2 |  |  |  | $50.4 |
Revisions in estimated cash flows | (5.5 | ) |  | (10.1 | ) |  | (6.7 | ) |  | (10.1 | ) |  | 1.2 |  |  | — |
Liabilities settled | (8.8 | ) |  | (10.4 | ) |  | (8.4 | ) |  | (9.7 | ) |  | (0.4 | ) |  | (0.7 | )
Liabilities incurred (a) | 26.2 |  |  | 7.3 |  |  | 26.2 |  |  | — |  |  | — |  |  | 7.3 |
Accretion expense | 6.9 |  |  | 6.2 |  |  | 4.5 |  |  | 4.0 |  |  | 2.4 |  |  | 2.2 |
Balance, December 31 |  | $196.3 |  |  |  | $177.5 |  |  |  | $133.9 |  |  |  | $118.3 |  |  |  | $62.4 |  |  |  | $59.2 |
(a) In 2019, Alliant Energy and IPL recognized additional AROs related to IPL’s newly constructed Upland Prairie and English Farms wind sites. The increases in AROs resulted in corresponding increases in property, plant and equipment, net on the respective balance sheets.

X
- Definition [Line Items] for Schedule of Asset Retirement Obligations [Table] + References No definition available. + Details
Name: | lnt_ScheduleOfAssetRetirementObligationsLineItems
Namespace Prefix: | lnt_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- 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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -URI http://asc.fasb.org/subtopic&trid=2175671 + Details
Name: | us-gaap_AssetRetirementObligationDisclosureTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | dei_LegalEntityAxis=lnt_IplMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=lnt_WplMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |