v3.3.1.900
Document and Entity Information - USD ($)
$ in Billions
12 Months Ended
Dec. 31, 2015
Feb. 12, 2016
Jun. 30, 2015
Document and Entity Information [Abstract]      
Entity Registrant Name Kaiser Aluminum Corp    
Entity Central Index Key 0000811596    
Current Fiscal Year End Date --12-31    
Entity Filer Category Large Accelerated Filer    
Document Type 10-K    
Document Period End Date Dec. 31, 2015    
Document Fiscal Year Focus 2015    
Document Fiscal Period Focus FY    
Amendment Flag false    
Entity Common Stock, Shares Outstanding   17,995,363  
Entity Well Known Seasoned Issuer Yes    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Public Float     $ 1.4