Document and Entity Information - shares	9 Months Ended
	Sep. 25, 2015	Oct. 09, 2015
Document and Entity Information [Abstract]
Entity Registrant Name	ALTERA CORP
Entity Central Index Key	0000768251
Document Type	10-Q
Document Period End Date	Sep. 25, 2015
Amendment Flag	false
Document Fiscal Year	2015
Document Fiscal Period	Q3
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		302,857,381