Property, Plant, and Equipment, Net - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	1 Months Ended
Jan. 31, 2010 Property
Property, Plant and Equipment [Line Items]
Number of purchased buildings	3
Capitalized acquisition costs included in Buildings and building equipment and land and improvements	$ 31,569

Amount of capitalized asset costs included in buildings and building equipment and land and improvements.

No definition available.

Name:	ment_CapitalizedAssetCosts
Namespace Prefix:	ment_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration