v3.8.0.1
Document and Entity Information - shares
9 Months Ended
Sep. 30, 2017
Oct. 16, 2017
Document Information [Line Items]    
Entity Registrant Name Kaiser Aluminum Corp  
Entity Central Index Key 0000811596  
Document Type 10-Q  
Document Period End Date Sep. 30, 2017  
Amendment Flag false  
Document Fiscal Year Focus 2017  
Document Fiscal Period Focus Q3  
Current Fiscal Year End Date --12-31  
Entity Filer Category Large Accelerated Filer  
Entity Common Stock, Shares Outstanding   16,903,791