Document and Entity Information	9 Months Ended
	Oct. 31, 2014	Dec. 02, 2014
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Oct. 31, 2014
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q3
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		115,101,672