XML 38 R15.htm IDEA: XBRL DOCUMENT
v3.20.2

Asset Retirement Obligations | 6 Months Ended
--- | ---
Jun. 30, 2020
Asset Retirement Obligations [Line Items] |
Asset Retirement Obligations | ASSET RETIREMENT OBLIGATIONS A reconciliation of the changes in asset retirement obligations associated with long-lived assets for the six months ended June 30, 2020 is as follows (in millions):
| Alliant Energy |  | IPL
Balance, January 1 |  | $196.3 |  |  |  | $133.9 |
Revisions in estimated cash flows | 0.9 |  |  | — |
Liabilities settled | (3.5 | ) |  | (2.8 | )
Liabilities incurred (a) | 27.6 |  |  | 27.6 |
Accretion expense | 3.5 |  |  | 2.5 |
Balance, June 30 |  | $224.8 |  |  |  | $161.2 |
(a) During the six months ended June 30, 2020, Alliant Energy and IPL recognized additional asset retirement obligations related to IPL’s newly constructed Whispering Willow North and Golden Plains wind sites. The increases in asset retirement obligations resulted in corresponding increases in property, plant and equipment, net on the respective balance sheets.
IPL [Member] |
Asset Retirement Obligations [Line Items] |
Asset Retirement Obligations | ASSET RETIREMENT OBLIGATIONS A reconciliation of the changes in asset retirement obligations associated with long-lived assets for the six months ended June 30, 2020 is as follows (in millions):
| Alliant Energy |  | IPL
Balance, January 1 |  | $196.3 |  |  |  | $133.9 |
Revisions in estimated cash flows | 0.9 |  |  | — |
Liabilities settled | (3.5 | ) |  | (2.8 | )
Liabilities incurred (a) | 27.6 |  |  | 27.6 |
Accretion expense | 3.5 |  |  | 2.5 |
Balance, June 30 |  | $224.8 |  |  |  | $161.2 |
(a) During the six months ended June 30, 2020, Alliant Energy and IPL recognized additional asset retirement obligations related to IPL’s newly constructed Whispering Willow North and Golden Plains wind sites. The increases in asset retirement obligations resulted in corresponding increases in property, plant and equipment, net on the respective balance sheets.

X
- Definition Asset Retirement Obligations [Line Items] + References No definition available. + Details
Name: | lnt_AssetRetirementObligationsLineItems
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: |