XML 50 R30.htm IDEA: XBRL DOCUMENT
v3.20.2

Asset Retirement Obligations (Tables) | 9 Months Ended
--- | ---
Sep. 30, 2020
Schedule of Asset Retirement Obligations [Line Items] |
Reconciliation of Changes in Asset Retirement Obligations | A reconciliation of the changes in asset retirement obligations associated with long-lived assets for the nine months ended September 30, 2020 is as follows (in millions):
| Alliant Energy |  | IPL
Balance, January 1 |  | $196 |  |  |  | $134 |
Revisions in estimated cash flows | 1 |  |  | — |
Liabilities settled | (7 | ) |  | (5 | )
Liabilities incurred (a) | 38 |  |  | 38 |
Accretion expense | 5 |  |  | 4 |
Balance, September 30 |  | $233 |  |  |  | $171 |
(a) During the nine months ended September 30, 2020, Alliant Energy and IPL recognized additional asset retirement obligations related to IPL’s newly constructed Whispering Willow North, Golden Plains and Richland 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] |
Schedule of Asset Retirement Obligations [Line Items] |
Reconciliation of Changes in Asset Retirement Obligations | A reconciliation of the changes in asset retirement obligations associated with long-lived assets for the nine months ended September 30, 2020 is as follows (in millions):
| Alliant Energy |  | IPL
Balance, January 1 |  | $196 |  |  |  | $134 |
Revisions in estimated cash flows | 1 |  |  | — |
Liabilities settled | (7 | ) |  | (5 | )
Liabilities incurred (a) | 38 |  |  | 38 |
Accretion expense | 5 |  |  | 4 |
Balance, September 30 |  | $233 |  |  |  | $171 |
(a) During the nine months ended September 30, 2020, Alliant Energy and IPL recognized additional asset retirement obligations related to IPL’s newly constructed Whispering Willow North, Golden Plains and Richland 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 [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 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
Name: | us-gaap_ScheduleOfChangeInAssetRetirementObligationTableTextBlock
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: |