Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2015	Oct. 19, 2015
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, 2015
Amendment Flag	false
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		17,739,189