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Employee Benefits, Multiemployer Pension Plans (Details) (Multiemployer Pension Plans Member, USD $) | 9 Months Ended
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Sep. 30, 2012
Monthly contributions per hour worked by each bargaining unit employee | $ 1.00
Newark, Ohio and Spokane, Washington facilities |
Monthly contributions per hour worked by each bargaining unit employee | 1.25
Florence, Alabama facility |
Monthly contributions per hour worked by each bargaining unit employee | 1.25
Starting July 2015 | Newark, Ohio and Spokane, Washington facilities |
Monthly contributions per hour worked by each bargaining unit employee | 1.50
Minimum |
Estimated annual contribution to pension and other postretirement benefit plans | 2,000,000
Maximum |
Estimated annual contribution to pension and other postretirement benefit plans | $ 4,000,000

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- Definition Estimated annual contribution to pension and other postretirement benefit plans. + References No definition available. + Details
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Namespace Prefix: | kalu_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Monthly contributions per hour worked by each bargaining unit employee. + References No definition available. + Details
Name: | kalu_MonthlyContributionsPerHourWorkedByEachBargainingUnitEmployee
Namespace Prefix: | kalu_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
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