XML 131 R97.htm IDEA: XBRL DOCUMENT
v3.25.0.1

Benefit Plans (Estimated Future Funding) (Details) - Forecast [Member] $ in Millions | Dec. 31, 2025 USD ($)
--- | ---
Defined Benefit Pension Plans [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Estimated funding for calendar year 2025 | $ 20
Defined Benefit Pension Plans [Member] | IPL [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Estimated funding for calendar year 2025 | 1
Defined Benefit Pension Plans [Member] | WPL [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Estimated funding for calendar year 2025 | 14
Other Postretirement Benefits Plans [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Estimated funding for calendar year 2025 | 7
Other Postretirement Benefits Plans [Member] | IPL [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Estimated funding for calendar year 2025 | 1
Other Postretirement Benefits Plans [Member] | WPL [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Estimated funding for calendar year 2025 | $ 6

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

X
- Definition Amount of contribution expected to be received by defined benefit plan from employer in next fiscal year following current fiscal year. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 18 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480482/715-20-55-18 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (g) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 + Details
Name: | us-gaap_DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | srt_StatementScenarioAxis=srt_ScenarioForecastMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RetirementPlanTypeAxis=us-gaap_PensionPlansDefinedBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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_RetirementPlanTypeAxis=us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |