Document and Entity Information	3 Months Ended
	Apr. 30, 2015	Jun. 01, 2015
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Apr. 30, 2015
Document Fiscal Year Focus	2016
Document Fiscal Period Focus	Q1
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		116,255,500