XML 84 R64.htm IDEA: XBRL DOCUMENT
v3.24.1.u1

Commitments And Contingencies (Narrative) (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2024 | Dec. 31, 2020 | Dec. 31, 2019
Commitments and Contingencies [Line Items] |  |  |
Minimum future commitments | $ 1,098 |  |
IPL [Member] |  |  |
Commitments and Contingencies [Line Items] |  |  |
Minimum future commitments | 497 |  |
WPL [Member] |  |  |
Commitments and Contingencies [Line Items] |  |  |
Minimum future commitments | 554 |  |
Capital Purchase Commitment [Member] |  |  |
Commitments and Contingencies [Line Items] |  |  |
Minimum future commitments | 191 |  |
Capital Purchase Commitment [Member] | IPL [Member] |  |  |
Commitments and Contingencies [Line Items] |  |  |
Minimum future commitments | 80 |  |
Capital Purchase Commitment [Member] | WPL [Member] |  |  |
Commitments and Contingencies [Line Items] |  |  |
Minimum future commitments | 111 |  |
Indemnification Agreement [Member] |  |  |
Commitments and Contingencies [Line Items] |  |  |
Obligations, maximum | 51 |  |
Indemnification Agreement [Member] | Purchased Power [Member] |  |  |
Commitments and Contingencies [Line Items] |  |  |
Obligations, maximum | 17 |  |
Indemnification Agreement [Member] | Renewable Tax Credits Transferred [Member] | IPL [Member] |  |  |
Commitments and Contingencies [Line Items] |  |  |
Indemnifications, renewable tax credit transfers | 76 |  |
Indemnification Agreement [Member] | Renewable Tax Credits Transferred [Member] | WPL [Member] |  |  |
Commitments and Contingencies [Line Items] |  |  |
Indemnifications, renewable tax credit transfers | $ 22 |  |
Workforce Subject to Collective Bargaining Arrangements [Member] |  |  |
Commitments and Contingencies [Line Items] |  |  |
Employees covered by collective bargaining agreement, percentage | 53.00% |  |
Workforce Subject to Collective Bargaining Arrangements [Member] | IPL [Member] |  |  |
Commitments and Contingencies [Line Items] |  |  |
Employees covered by collective bargaining agreement, percentage | 70.00% |  |
Workforce Subject to Collective Bargaining Arrangements [Member] | WPL [Member] |  |  |
Commitments and Contingencies [Line Items] |  |  |
Employees covered by collective bargaining agreement, percentage | 83.00% |  |
Workforce Subject to Collective Bargaining Arrangements Expiring within One Year [Member] |  |  |
Commitments and Contingencies [Line Items] |  |  |
Employees covered by collective bargaining agreement, percentage | 18.00% |  |
Workforce Subject to Collective Bargaining Arrangements Expiring within One Year [Member] | IPL [Member] |  |  |
Commitments and Contingencies [Line Items] |  |  |
Employees covered by collective bargaining agreement, percentage | 53.00% |  |
Whiting Petroleum Affiliate [Member] |  |  |
Commitments and Contingencies [Line Items] |  |  |
Partnership share, percent | 6.00% |  |
Obligations, maximum | $ 49 |  |
Federal Energy Regulatory Commission [Member] |  |  |
Commitments and Contingencies [Line Items] |  |  |
MISO base return on equity, percentage |  | 10.02% | 9.88%

X
- Definition Concentration Risk Threshold Percentage + References No definition available. + Details
Name: | lnt_ConcentrationRiskThresholdPercentage
Namespace Prefix: | lnt_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Indicates, if estimable, the approximate extent to which the proceeds from liquidation of any assets held either as collateral or by third parties would be expected to cover the maximum potential amount of future payments under the guarantee or each group of similar guarantees. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 460 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Subparagraph (f) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482425/460-10-50-4 + Details
Name: | us-gaap_GuaranteeObligationsLiquidationProceeds
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 460 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Subparagraph (b)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482425/460-10-50-4 + Details
Name: | us-gaap_GuaranteeObligationsMaximumExposure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Percentage investment held by members or limited partners of limited liability company (LLC) or limited partnership (LP). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 272 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482987/272-10-50-3 + Details
Name: | us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPMembersOrLimitedPartnersOwnershipInterest
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition The minimum amount the entity agreed to spend under the long-term purchase commitment. + References No definition available. + Details
Name: | us-gaap_LongTermPurchaseCommitmentAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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_LongTermPurchaseCommitmentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of public utility's approved return on equity. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesApprovedReturnOnEquityPercentage
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
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: |

X
- Details
Name: | us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis=lnt_CapitalPurchaseObligationMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_GuaranteeObligationsByNatureAxis=us-gaap_IndemnificationGuaranteeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis=lnt_PurchasedPowerMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis=lnt_RenewableTaxCreditsTransferredMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ConcentrationRiskByBenchmarkAxis=us-gaap_WorkforceSubjectToCollectiveBargainingArrangementsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ConcentrationRiskByBenchmarkAxis=us-gaap_WorkforceSubjectToCollectiveBargainingArrangementsExpiringWithinOneYearMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_OwnershipAxis=lnt_WhitingPetroleumCorporationMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAgencyAxis=lnt_FederalEnergyRegulatoryCommissionMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |