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Fair Value Measurements Fair Value Measurements, Textual (Details) | Mar. 31, 2013
--- | ---
Minimum |
Schedule of Available-for-sale Securities [Line Items] |
Commercial paper maturity period | 10 days
Maximum |
Schedule of Available-for-sale Securities [Line Items] |
Commercial paper maturity period | 5 months

X
- Definition Commercial paper maturity period + References No definition available. + Details
Name: | kalu_CommercialPaperMaturityPeriod
Namespace Prefix: | kalu_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration