XML 107 R75.htm IDEA: XBRL DOCUMENT
v3.22.0.1

Debt (Other Short-Term Borrowings) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2020
Debt Instrument [Line Items] |  |
Maximum amount outstanding (based on daily outstanding balances) | $ 648 | $ 495
Average amount outstanding (based on daily outstanding balances) | $ 459 | $ 292
Weighted average interest rates | 0.20% | 0.70%
IPL [Member] |  |
Debt Instrument [Line Items] |  |
Maximum amount outstanding (based on daily outstanding balances) | $ 19 | $ 8
Average amount outstanding (based on daily outstanding balances) | $ 0 | $ 0
Weighted average interest rates | 0.20% | 0.50%
WPL [Member] |  |
Debt Instrument [Line Items] |  |
Maximum amount outstanding (based on daily outstanding balances) | $ 320 | $ 266
Average amount outstanding (based on daily outstanding balances) | $ 172 | $ 117
Weighted average interest rates | 0.10% | 0.70%

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_DebtInstrumentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Weighted average interest rate of short-term debt outstanding calculated over time. + References No definition available. + Details
Name: | us-gaap_ShortTermDebtWeightedAverageInterestRateOverTime
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition For the form of debt having an initial term of less than one year or less than the normal operating cycle, if longer, average borrowings during the period. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher SEC -Name Regulation S-K (SK) -Number 229 -Section 1402 -Paragraph (a) Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher SEC -Name Regulation S-K (SK) -Number 229 -Section 1402 -Paragraph (b) -Subparagraph (1) + Details
Name: | us-gaap_ShorttermDebtAverageOutstandingAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition For the form of debt having an initial term of less than one year or less than the normal operating cycle, if longer, the maximum amount borrowed at any time during the period. + References No definition available. + Details
Name: | us-gaap_ShorttermDebtMaximumAmountOutstandingDuringPeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
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: |