Document and Entity Information (USD $)	12 Months Ended
	Jan. 31, 2014	Mar. 13, 2014	Jul. 31, 2013
Document Type	10-K
Amendment Flag	false
Document Period End Date	Jan. 31, 2014
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY
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
Entity Common Stock, Shares Outstanding		115,360,422
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 2,313,193,631