Document and Entity Information - shares	6 Months Ended
	Jul. 31, 2015	Aug. 27, 2015
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jul. 31, 2015
Document Fiscal Year Focus	2016
Document Fiscal Period Focus	Q2
Trading Symbol	MENT
Entity Registrant Name	MENTOR GRAPHICS CORP
Entity Central Index Key	0000701811
Current Fiscal Year End Date	--01-31
Entity Filer Category	Large Accelerated Filer
Common Stock, Shares, Outstanding		117,228,814