XML 85 R73.htm IDEA: XBRL DOCUMENT
v3.25.0.1

Employee Benefits - Summary of Total Expense Related to All Postretirement Benefit Plans (Parenthetical) (Details) - USD ($) $ in Millions | 9 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2024 | Dec. 31, 2024
Defined Benefit Plan Disclosure [Line Items] |  |
Multiemployer pension plans excludes charge to restructuring costs |  | $ 4.6
Two Thousand And Twenty Four Restructuring Plan [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Multiemployer pension plans excludes charge to restructuring costs | $ 4.6 |

X
- Definition Restructuring cost, pension obligation expected + References No definition available. + Details
Name: | kalu_RestructuringCostPensionObligationExpected
Namespace Prefix: | kalu_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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_DefinedBenefitPlanDisclosureLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_RestructuringPlanAxis=kalu_TwoThousandAndTwentyFourRestructuringPlanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |