Document and Entity Infomration	3 Months Ended
	Mar. 29, 2013	Apr. 10, 2013
Entity Information [Line Items]
Entity Registrant Name	ALTERA CORP
Entity Central Index Key	0000768251
Document Type	10-Q
Document Period End Date	Mar. 29, 2013
Amendment Flag	false
Document Fiscal Year	2013
Document Fiscal Period	Q1
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		320,140,393