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Fair Value Measurements Fair Value Measurements, Textual (Details) (USD $) In Millions, unless otherwise specified | 9 Months Ended |  |
--- | --- | --- | ---
Sep. 30, 2014 Minimum | Sep. 30, 2014 Maximum | Sep. 30, 2014 Derivative | Dec. 31, 2013 Derivative
Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Fair Value, Net Asset (Liability) |  |  | $ (0.7) | $ (4.3)
Short-term investment maturity period | 34 days | 18 months |  |

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- Definition Short-Term Investment Maturity Period + References No definition available. + Details
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Namespace Prefix: | kalu_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- Definition Fair value of asset after deduction of liability. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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