Document and Entity Infomation	6 Months Ended
	Jun. 28, 2013	Jul. 10, 2013
Document and Entity Information [Abstract]
Entity Registrant Name	ALTERA CORP
Entity Central Index Key	0000768251
Document Type	10-Q
Document Period End Date	Jun. 28, 2013
Amendment Flag	false
Document Fiscal Year	2013
Document Fiscal Period	Q2
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		319,472,196