Document and Entity Information (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Apr. 19, 2013	Jun. 30, 2012
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-Q
Document Period End Date	Mar. 31, 2013
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Common Stock, Shares Outstanding		18,902,523
Entity Public Float			$ 974.3