XML 50 R39.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Employee Benefits, Defined Benefit Plans Narrative (Details) - USD ($) $ in Millions | 3 Months Ended |
--- | --- | ---
Mar. 31, 2018 | Mar. 31, 2017 | Dec. 31, 2017
VEBA Postretirement Medical Obligations |  |  |
Payment for Other Postretirement Benefits | $ 15.7 | $ 20.0 |
Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring [Member] |  |  |
VEBA Postretirement Medical Obligations |  |  |
Fair value of deferred compensation assets | 9.9 |  | $ 9.8
Voluntary Employees' beneficiary Association (VEBA) | Union VEBA |  |  |
VEBA Postretirement Medical Obligations |  |  |
Maximum contribution threshold | 12.8 |  |
Voluntary Employees' beneficiary Association (VEBA) | Salaried VEBA |  |  |
VEBA Postretirement Medical Obligations |  |  |
Maximum contribution threshold | 2.9 |  |
Payment for Other Postretirement Benefits | $ 2.9 |  |

X
- Definition Defined Benefit Plan, Maximum Annual Employer Contributions, Amount + References No definition available. + Details
Name: | kalu_DefinedBenefitPlanMaximumPeriodicEmployerContributionsAmount
Namespace Prefix: | kalu_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Carrying amount as of the balance sheet date of assets held under deferred compensation agreements. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.17) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_DeferredCompensationPlanAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of payment for other postretirement benefits. Excludes pension benefits. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 25 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3536-108585 + Details
Name: | us-gaap_OtherPostretirementBenefitsPayments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_PostretirementMedicalPlansWithPrescriptionDrugBenefitsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember
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: |

X
- Details
Name: | us-gaap_RetirementPlanNameAxis=kalu_UnionVebaMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RetirementPlanNameAxis=kalu_SalariedVebaMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |